996tt/GT3 READ on a build
996tt/GT3 READ on a build
Found this today and thought i would share it with everyone.
Haven't seen this posted so have a look
Highly modified 996 turbo engine
HEAD
Modified 996 turbo head flows:
in 324CFM / ex 296CFM with 28" of water @ .500" lift and
in 306CFM / ex 280CFM with 25" of water @ .500" lift.
Valves used: in 39mm, ex 34mm. ( Source: Rennlist )
We already have the GT3 Cup heads, lifters, GT3R valve springs, Carrillo rods and GT1 oil pump.The case will be boat tailed and shuffle pinned. The crank will be knifed edged. The heads will be fully ported and polished.Currently looking for some GT3 Cup sized valves that are sodium filled. The stock Cup valves are stainless steel.
Larger valve stems are not a problem. Actually, not sure the sodium filled would hold up to the 8000 RPM'S. The stock GT2 are stainless steel while the turbo's are sodium filled. I may increase radiator and oil cooler size and just go with the GT3 Cup stainless steel valves. I do not know as of yet what older factory turbo's used. Yes, the oil pressue dropped slightly.The motor was warming up at an idle.The cams are from the stock GT3. I don't want too much lift or duration.
GT3 cams should have plenty of duration for a turbo motor. I'd assume that cams for an 8200 rpm NA motor have much more duration than stock turbo cams. I wonder if the hot shot German tuners use the GT3 cams in their high end turbo motors that use GT3 heads? For some reason I thought you were running ported stock turbo heads.
Any idea of the rpm capability of the stock valve train, possibly with stronger valve springs?
*About 6700 rpm's. I have pushed mine to 7400, but it wouldn't last there very long. The Cup's valves, keepers, lifters, springs and cam are different as to design and materials used.
Here are the difference in valve sizes:
Stock 996tt
32.0 mm ex, 37.0 mm in
GT3 Cup Heads
35.5 mm ex, 41.0 mm in
GT3R Heads
36.4 mm ex, 42.0 mm in
As a comparison, the approximate valve size of the stock turbo is 32 mm for the exhaust and 37 mm for the intake. The GT3 Cup heads use approx. 35.5 mm exhaust and 41 mm intake. The valves have 6 mm stems and overall lenght is just under 113 mm. The difference dimension wise is the stock valves are flat on the face while these valves have a dished face.
I was not able, until recently, to find valves that would stand up to the higher temps of the turbo/nitrous application (in the 35.5 and 41 mm with 6mm stem/113 mm overall sizing).
Note the 996tt head between the two banks of valves on the left and right side. These are oil grooves. The Cup heads do not have these grooves. Those sir are for the EGR air system. They pump air from the air pump through the intake port through the head and mix the exhaust port with the air being pushed in to lower the CO level. If you are trying to maintain 50 state legal you are going to need to machine that back in. I would bet the GTIII heads do not have that little port on the top??
996-105-123-52 keepers
996-105-121-94 valve spring retainers
996-105-117-91 bottom retainers
996-105-461-93 shims
I don't know the cost of the GT3 heads. I used GT3 Cup heads which are a little different as to the valve sizes. I bought a few sets before the Euro rose. I believe they were a little over $900.00 US apiece for a bare head.
Changing to GT3 heads on any turbo motor isn't possible without having to make other required changes. First, the turbo motor runs hotter and it is my belief the stock GT3 valves will overheat or burn. The stock turbo valves are a different size (smaller). The cam is different as is the dimensions of the cam housing. The lifters are different as they are designed for higher rpm's. Finally the ports are larger requiring a larger throttle body and intake from the heads to the throttle body.
To accomplish what you are looking for on a more economical basis has been done by TTP. The bare turbo head and the GT3 series head difference appears to be the size of the valve and the ports. TTP has taken a turbo head, ported it and installed larger valves. This avoids special intakes, cam housings, cams (use a regrind)and lifters. They ported the intake and installed a regrind cam. The motor is very strong. Ask EL750.
The other difficulity encountered was the valve length. We are using GT3 Cup heads. We had Manley (exhaust) and Ferrea (intake) make the valves. We sent them the GT3 Cup valves to copy the dimensions. To complicate matters the GT3 uses hydralic lifters while the GT3 Cup uses solid lifters. We have decided to use hydralic lifters which were made to GT3 specifications because with solids we would have to pull the motor to adjust the valves and we didn't want to do that. We had our own made because we wanted a hydralic to redline a bit more than 8100 rpm's. We knew our valves had a slightly wider valve stem, however we were surprised to learn the GT3 valves are about 2 mm longer than the GT3 Cup valves. Thank God S Car Go ordered two GT3 valves for the mock up as the valve train dimensions must be exact. This means we will either use valve caps or make a new set of valves.
One thing I almost forgot to mention. Our Manley and Forrea valves were manufacturered with dishes in the center of the valve. The stock turbo and the GT3 Cup valves are flat on the top. The GT3 valve's are lightened due to a cup being machined in the center by Porsche. Don't understand why Porsche machines the GT3 valves with a cup and leaves the GT3 Cup valves flat.
When we originally ordered the GT3 Cup heads, valves and lifters I thought they were hydralic. What we received was solid. Today we learned they are available both ways. The 2001/2002 GT3 Cup motors used solid lifters. The 2003, 2004 and 2005 GT3 Cup motors use hydralic lifters. By the way the valve lengths are also different in the GT3, GT3 Cup solid and GT3 Cup hydralic. It's really too bad this information isn't available from Porsche.
I just recieved the flow numbers for our heads.
Flowed at 25” water. Inlet bell and Exhaust outlet used.
lift 0.050”, intake 52.3 cfm, exhaust 40.9 cfm
lift 0.100", intake 97.5 cfm, exhaust 92.2 cfm
lift 0.150", intake 144.0 cfm, exhaust 144.7 cfm
lift 0.200", intake 194.0 cfm, exhaust 179.2 cfm
lift 0.250", intake 237.6 cfm, exhaust 204.8 cfm
lift 0.300", intake 272.8 cfm, exhaust 225.3 cfm
lift 0.350", intake 297.3 cfm, exhaust 238.7 cfm
lift 0.400", intake 310.7 cfm, exhaust 250.9 cfm
lift 0.450", intake 320.9 cfm, exhaust 259.2 cfm
lift 0.500", intake 324.5 cfm, exhaust 266.2 cfm
lift 0.550", intake 327.2 cfm, exhaust 272.0 cfm
cfm = cubic feet per minute
note* With a normally asperated motor to find hp:
cfm x .27 x number of cylinders
To find hp for turbo motor:
hp(using NA hp formula) x boost +1 Atmosphere
I have not been able to find anyone who has flowed stock 996tt heads. I just can't believe Porsche doesn't have this information available.
Case in point is the heads. We were satisfied with the exhausts ............ then we learned the relation between the head flow and hp. I was amazed that people don't even know what a stock head flows. Then I found out how some flow people play the same game as some dyno people. The numbers can sound great but how many inches of flow are they using to test and what is a realistic pressure. I have learned 25 psi is the number to use. There are values and formulas assocoated with this number that will accurately predict power output.
CAMSHAFT
The stock turbo and GT3 cams have been sent to a cams "only" specialist. Both cams will be profiled. Yes, after all these years the cam specifications for both of these cams will be available. The cam specialist will then tell us if the pointers of the turbo cam can be imprinted on the GT3 cams. If so, then we will check with the ecu tuner to ensure the vario cam segment of the ecu program can be deleted and the other cam segment be modified to operate through the full rpm range.
Our other option is to grind the turbo cam to the GT3 profile or another profile close to that of the GT3. If this route is followed we would have to go back to the turbo valves made for the GT3 Cup heads. These valves vary from what we are currently using in that the overall valve lenght is a few mm's shorter. Luck has it these were the second set of valves that we made prior to determining that we needed a slightly longer valve for the GT3 cam. Today S Car Go Racing sent these valves (the shorter valve lenght ones) to HP Coating. Don't know if this is the route we will be following .............. but if we do the correct valves will be ready. If we follow this route the cylinder holders will still be GT3 (which is heavier duty) but the cam housing would be from the turbo which is lighter duty.
One other bit of info. The GT3 exhaust cam will fit the turbo cam housing. The GT3 intake cam will not. The GT3 cams are not vario lift cams. The turbo's intake is vario lift, however the exhaust cam is not.
We have decided to utilize the turbo cams. The reason being with the base lift being left untouched passing smog will be a given. Now, we have sent the stock turbo cams and the GT3 cams to a cam manufacturer. They have profiled both cams giving us each cams lift, durantion, etc. We have told the cam maker the turbo's timing and instructed him to weld/grind the second set of lobes so we will make power to 8100 rpm's.
We are having a modified GT3 intake cam (non vario lift) made up with turbo cam markers.
We are suppose to have the cams, gears and cam housings by Monday. This set back has lead to talking to some of the best Porsche minds on the planet. The intake is not vario lift. We are using gear drives. Both intake and exhaust cams have been race proven on turbo's. We are not using either our turbo or GT3 cam housings.
We have received our cams, cam housings, gears, etc. today. We started with variable lift intake cams and variable timing. We then tried non variable lift intake cams with variable timing. We settled on non variable lift intake cams and non variable timing. The exhaust cams were designed to marry with the intakes. The lift and duration is to die for. The power range will start around 2,800 rpm's and peak at 8200 rpm's. Idle will be a little rough, however once out of idle she will purrr.
Here is some information for anyone who is interested about the stock 996tt intake cams.
*Lift is .402" secondary cam lobe .118" ( 0.402 inch = 10.210 8 millimeter, 0.118 inch = 2.997 2 millimeter )
*Duration .040 234 degrees .050 230 degrees
*secondary cam duration .040 128 degrees .050 120 degrees
*cam base circle 1.378
As a side note we have proven these cams will make power to 7500 rpm's
Another item is the cams. It took us three months to figure out what cams would work with the GT3 turbo motor setup. With the help of others and buying three different sets of cams we cracked this barrier only to discover that after all the cams we purchased we arrived at a solution but a new issue cropped up ............. harmonic distortion or in layman's having a cam that rams up smoothly in a turbo application.
A few people have used the GT3 exhaust cams in the turbo motor. To my knowledge no one has changed the intake cams. This is an area where the research is expensive (lift/durantion/head flow/timing/variable vs non variable lift and variable vs non variable timing) and the potential for engine damage can and has proven to be very expensive as in bent intake valves).
We have spent the money and solved the inherent problems. We have discovered the limits to which the intake and exhaust lobes can be taken to in the areas of power and longevity. The turbo and NA cams require different profiles relating to cam design. It has to do with valve train harmonics (how you ramp up to and down from the lift).
Like I said earlier, this work is a big step for the 996tt motors and their power/reponsiveness. Those who are considering opening up their motors will be following once the cat is out of the bag.
How many people know the 06 Cup cams make 20 more hp than the 04 Cup cams?
The cam builder built the cams for the pre 2004 lifters and not the 2004/2005 lifters. Even though we sent the lifters and cam housings. I guess he wasn't aware that Porsche made a change.
The harmonic distortion on the tt, GT3, GT3 Cup and GT3R cams is very bad to say the least. This has nothing to due with knocking, but with smoothiness of the valve train. This was one reason we reprofiled the cams. Second, we learned up to what lift the motor continued to make power and where the power ceased.
As for the ECU, the tt and the GT3's cam markers are in different locations. In addition, the tt and the GT3's run different timing. What we have designed, manufactured and tested is intake/exhaust cams with ultimate lift/duraion, little to no harmonic distortation and markers that are compatable with the tt's ECU. These cams are made in heaven for a tuner.
We have the Titanium Retainers and a new Spring in house for the new Cam
design. As soon as I have further details we will be able to assemble and
ship the heads.
To update you on the 996TT Triggering issue. The 996TT electronics requires a 4 segment wheel which it uses for Cam timing (VTC).
The GT3 Cup cams have only one Trigger point. The issue is 2 fold. The new
cams are single lobe type, the 996TT are the variable lift type, and the
996TT Cams will not fit into the cup cam trays.
I am currently having five sets of intake and exhaust cams for the 996tt being made from billet. These cams will also be gun barrel drill. They will be capable of approx. 8400 rpm's. These cams will have the 996tt marking points and a lift and duration simular to the new Cup cars. These cams will allow a tuner to use them with the 996 ECU providing your pistons have the proper clearance. Pistons would also be available if desired. These cams are made for the GT3 heads and cam housings.
Back to the cams. The farther we go ............ the more we learn. We now have two choices. Both cams (intake and exhaust) will have the same profile abeit a little different. We already have the profile to deliver the max torque and power for the big valve/port heads. I used GT3 heads and VRAlexander (Protomotive) installed larger valves/ports on turbo heads. Our heads flowed within 22 cfm of each other at 25 psi. One of the big differences between the motors will be the cam lift. To really take advantage of these big breathing heads you need more lift. The motor can deliver an additional 10 hp for each additional 10/1000's of lift and 110/1000's is available before the numbers start to drop off. I'm told that when KA idle's the motor will lope. Can you imagine pulling up to a Porrsche 996tt at a light and listening to her lope.
Now to the exiting news. We are making computer grinded billet intake and exhaust cams for the 996tt (vario lift) and the GT3 cam housings (none vario). Both applications will be tunable by the top tuners using the 996tt ecu. These cams will both have the same profile and will be gun barrel drilled when finished for lightness and maximum rpm's.
Markski is using a set a GT3 cams I we sent to him. These cams are not vario lift, but vario timing. They also have the single cam point markers of the GT3 street cams. What this means is Protomotive has to come up with a way for the 996tt ecu to read the pointer markers.
My set up is a little different. We started with the profile of the 2006 GT3 Cup cam and added approx. 30,000ths of lift. In addition we made a gun barreled cam from billet, no variable lift and we are having the cam made with the 3-5 cam markers of the GT3.
How many people realize the GT3 Street, GT3 Cup and GT3R motors all have a different number of cam pointers? Each cam requires different ECU's. Now to make matters worst there are solid and hydralic tappets along with different GT3 year models have different tappets with different overall dimensions and designs. If the above isn't bad enough, try welding metal any one of the above stock Porsche GT3 cams using the required Porsche tappets. Well, it may work for awhile, but the different metals (cam and tappets) will quickly wear down the welded lobes. So what do you do?
All of the people to date who have turbocharged the GT3 heads have used either the stock GT3 street or GT3 Cup cams with the respective tappets. The problem is you don't have a crisp or responsive motor. You have a motor that is fast but far from optimum. You have a turbocharged motor with a normally aspirated cam profile. Not good to say the least. You have to do strange things to the timing and the performance suffers in many areas. Furthermore, you have these huge GT3 heads with a cam that can't make real good use of these monster heads breathing wise. Some people have used stock turbo heads that are ported and valved to GT3 dimensions. This is great ............. but how about the tappets. They simply won't stand up to anywhere near 8500 rpm's. We know of no one prior to S Car Go Racing who has made a turbo cam for the GT3 heads that is compatable with existing tappets and ECU's. The S Car Go turbo cams (intake and exhaust) for the GT3 heads will be proven before the end of the year.
Here are the final specs
.............................Intake.......... Exhaust
Seat Duration..... 296............. 284
0.050’ Duration.. 254............. 243
Gross cam lift.... XXXXXX..... XXXXXX
Hyd Valve Lash..0.004........... 0.004
Net Valve Lift..... XXXXXX..... XXXXXX
The cam specs on the GT3 street cams are:
Duration......... Intake 286.0 Exhaust 285.0
50/1000's Lift.. Intake 235.0 Exhaust 226.6
0 Lash Lift...... Intake 484.0 Exhaust 437.0
FVD 996 Turbo/GT2 Sport Camshafts (4pc Set) 100 105 292
Intake Camshaft 284°, MD 110°, Lift 12.50mm, TDC 2.84
Exhaust Camshaft 272°, MD 110°, Lift 11.45mm, TDC 2.04
BTW, Chad, I was talking about Neil. I was not going to mention his name as I know he keeps who he does business with to himself.
I spoke to him about the parts he designed etc. Its a shame that you will never get to see what they are capable of doing. So many special parts for this engine. A real shame.
For all those who are interested, Crankshafts, Rods, Pistons, Intake and Exhaust Camshafts, Pistons and Liners, Cylinder Heads with very special Valve Train parts, Turbo's, 6 channel CDI Ignition with special CDI Coils, are amongst the parts now available. Chad earlier posts told who did these parts. If anyone is interested email me, m42racer@aol.com and I will forward the contact information.
This all goes back to the cams, springs and o-ringing. Let me start with the cams. As many of you know there has been four views of this issue. Use the Porsche GT3 cams or cam, regrind the upper lobes of the 996tt cams, use the 996tt stock cam or design a new cam. I believe many remember me stating that we found alot of harmonic distortion in the stock cams and cams reground using stock profiles but increasinng the lifts.
Harmonic distortion is such an innocent sounding word. Please bare in mind the following is my opinion based on tests and experience. Some tuners have successfully used the Porsche 996tt stock, GT3 cams, GT3 exhaust cams and hybrids of the Porsche cams. It appears the success was derived through the use of high valve spring pressures. Why you may ask? The answer appears to be to overcome the harmonic distortion found in the Porsche cam profiles when used with hydralic tappets and higher rpm's.
Case in point. Tuner A and B are working together. A is of the school of using Porsche cams with high spring pressures, the B uses engineered cams not requiring the high pressures. B assembles the heads for B based on his philosophy but does not opt for the cams that eliminate the HD. Well, you guessed it. It appears the two mixed philosophies resulted in a motor wiping out all the hydralic tappets. It appears either higher spring pressure or a cam designed to eliminate HD would have eliminated the problem. If B is correct, his theory would be the better way to go because the higher spring pressure just drastically accelerates wear on the valve guides and it appears the high spring pressures only masks an existing problem. On the other hand, B's theory has not been tested on a 996tt to my knowledge. My motor is designed around B's theory. B designed and built the cams and heads while A is assembling the rest of the motor.
I have an inside track on this too. To be fair here this is not the place to trash anyone. It is a place to be sure all the facts are true and correct. I do not know the exacts here either. The engine that Chad talks of losing the lifters, did happen, and the reason is clear, but why the decision to run the stock Cmas is unknown to me. Maybe the customer decided not to spend the money and Tuner A had no other choice. Remember, if you go out and do hotrod things to your engine, you are entering unknown territory often. Thats why its called development.
To clear up a point here, if I understand Tuner A and B to be who I know them to be, Tuner A asked Tuner B to build heads with all trick parts, to run to 8K RPM. Tuner B was given all og the parts including the stock Cams. Tuner B told Tuner A that stock Cams would not work and should not be run to 8K RPM. Tuner B gave Tuner A a quotation to design and build Cams suitable to run thses heads with trck Valve Train to 8K. Either Tuner A or Tuner A's customer decided not to have Tuner B design and make Cams, but to use stock Cams. The heads were built with parts and the setup was done for the parts included to run to 8K RPM. THe parts used in these heads were all lightweight Titanium replacing the heavier stock steel parts. The final setup actually in the end was approx the same as the stock steel setup was.
The engine was run and the lifters all failed as Tuner A was told they would by Tuner B. Tuner B as Chad has said, engineers the setup based upon calculations etc. Both Tuner B and his staff are qualified engine engineers who have long resume's and lots of experience. Tuner B's business has been buiding Porsche 4V water cooled engines since the 80's. I know they know what is required. These race engine run to 8500RPM and make 760+ HP.
The result here is from running a Cam unsuitable for this application. I have been told that the new engines in most new cars are designed and run at the engines limit. Tests have shown that certain engines can run quite happily to 7000RPM but run at 7100RPM go in the toilet. Any redesigning of these new engines should be done by those who know. Not by those who think they do. The new designs will catch out the ignorant.
In Chads engine, the cams were re designed to run at the engine speeds required, eliminating the harmonics found in the stock designs. Cam designing not just about lift and duration. Its about many other factors well beyond my understanding. Any vibrations or harmonics inded into the Valve Train is always from the Cam. It will always happen at the same RPM. Adding Spring pressure dampens the effect, it will never get rid of it. The real issue is at engine speed. As the engine speed increases the open pressure goes to zero,
and the seat pressure is all that controls the Valve. Running Titanium Valves requires a specfic set of rules again. Too much seat pressure and the Titanium Valves are put under too much closing force. Running a Titanium Valve with a Cam design for steel Valves is also a problem. Steel Valves are close against the seat with greater force as the material will take for abuse and force. This is why increasing the seat force on the heads in question is not a real answer to the problem. Add seat force to help dampen the harmonic and the Titanium Valve closing force will destroy the Valves. This is a street engine not a race engine too. Race engines are usually rebuilt at shorter intervals. Telling a street customer that his valves will need to be replace every 60 hours is not a real answer either.
In Chads engine the Cams were engineered for the application, the engine speeds required and the springs set for this use. The setup I'm told is very similar to the 962C engine running almost the same. If it works in that engine, then I'm confident Tuner B has it right. He did prove to Tuner A it would not!!
BLOCK
After all the parts were recieved, I was told why having my heads and liner have takinb so long. Apparaently my Woosner liners are not consentric at the tops like the Porsche liners. Not an issue but for the o-rings.
Well this called for a little engineering that in the long run will save thousands of dollars for those that follow. Along the way we also learned interesting additional things. First, in the past it has cost about $2,500 to machine the heads/liners due to the alignment work involved. The new machine work should cost about $600.00. Second, in the past both Porsche and EVO head gaskets(the only ones I am aware of) slightly overlap the bore or liner ID. This is how the heads seal and really isn't ideal. This will no longer be required with our design. We went to the best head gasket maker in the US, a company called Kinitics to build the gaskets based on our engineering design. Along the way we learned that they build a modified 996tt head gasket for a company called RPM Motorsports (or RPM something) out of Tempe Arizona. I wonder who these gaskets are being made for.
Anyway, the long and the short of it is we have brought down the machining costs. We are engineering the head gaskets, gas sealing o-ring and a T ring. We will have these made to our engineering specs. With this design the bar chosen to be run will not be the weak link as the seal together with the studs should take whatever pressure you choose to throw at it. Wear and tear on the motor should now be the limiting factor together with fuel and timing. As a plus, the machining,the three sets of o-rings and the head gaskets will probably cost less than the old machining costs by itself use to.
CRANKSHAFT
Finally received some hard information on the turbo crankshaft. The GT2 and GT3 share the same crankshaft. The same crank is also shared with the GT1. The turbo has a different crank which is not as strong as the GT1, GT2, GT3 crank.
Well, that is not entirely true. The 996 GTII does not share any difference in the crank as compared to it's AWD brother. The GT3 and GTI do have different ranks. The TT/GTII are the same.
Here are some pics of the crank. The c/s was welded and stroked 1mm. The rod journals were ground to 2.000-1.999 inches. It was knife edged, nitrided, cross drilled, cryo treated, maged and balanced. With 102 mm pistons and 1mm stroke the engines displacement will be 4.0 L.
Actually, there is one other problem besides rods on these motors when you start entering the 600 to 700 rwhp range. The crank wants to move. Shuffle pinning is as important as changing the rods.
Crank is a GT3 RSR crank which has been lightened (knife edged) balanced, stroked, reduced journal sized, nitrated, polished and blue printed to very near zero tolerences.
CONNECTION RODS
Technically speaking, the rod is simply a two-force member. That means, it is not subjected to flexure, only tension and compression. When I look at this, I clearly see a compression buckling failure. What I mean by this is that the force on the rod is applied at the wrist pin and crank bearing. Regardless of where the piston is in the stroke, and hence the angle of the rod, it is still a two force member only subjected to tension or compression. My assessment is that the force of the explosion in the combustion chamber applied to the piston top induced an excessive compression force in the rod that exceeded its buckling yield strength. Forces less than the yield strength of the rod will allow the rod to operate in its elastic range. That means the rod can elongate and shorten under tension and compression loads respectively. The rod can also bow out of plane much like the analogy of pressing on a thin metal yardstick standing upright. It will flex outward within its elastic range but will eventually permanently bend after reaching its yield strength.
This is the wonderful property of steel and its related alloys. The stress strain curve allows for a range of operation in the elastic region with a gradual deformation leading towards ultimate failure. The yield point is where the metal permanently deforms but does not yet break. This is why safety factors are used in Allowable Stress Design and Load Factor Design in steel construction. They allow the element in question to operate in the elastic range without permanent deformation and/or failure.
Now, if you look at the cross section of the rod, you will see it is an I shape. If you orient the rod such that its cross section is like a capital I (as opposed to an H), the strong axis is horizontal. The weak axis is vertical. Clearly, in textbook fashion, the rod yielded about its weak axis. Although impractical, a much better and stronger rod would incorporate a square cross section giving both axes equal buckling resistance.
I was talking to a individual at Porsche Motorsports, about the rod situation.... They are dumping the Titanium rod bolts and are replacing them with ARP's... The big ends are getting hammered/ovaled.. The added heat and stress is causing the bolts to fail... They are recommending the ARP's.. No with the Carrillo's, it's always wise to step up and order the 3/8 carrbolts...
Once we sent them the titanium GT3RS and stock 996tt rods it was discovered the GT3RS rods are .030 longer. To use that design would raise the compression ratio a full point which would be too much even thould our pistons were designed for a slightly lower than stock 9.4-1 compression ratio. In addition the GT3 crank's journals are wider in addition to the radius of the counter weights being shorter.
The new rods using the 996tt case with the GT3 crank will be a special breed 8100 rpm lower end, designed for the 996 turbo application. The rods are being designed for 1000 hp.
So to sum our situation up. We are using Woosner 104 mm pistons with 23 mm wrist pins. We are using the GT3R crank with the smaller radius and wider journals. We are usin Pauter rods sized for the GT3R crank and 23 mm wrist pins for the Woosner pistons. The difference on the different GT3 cranks is the dampener used or not used.
Sorry, just sat back at the computer. Yes, the 993 and the 964 as well as the 996TT is exactly 22.9 mm. In fact even the same circlip that the 993 uses.
Agreed, some people were talking in non descript terms. Now we know the GT3 rods use 22 mm wrist pins while the 996 uses 23 mm pins. We know the GT3 rods are thirty thousands longer than the 996tt rods. We know the rod width on the GT3 is 17.71 mm while the 996tt is 14.68 mm. We know the rod journals on the GT3 are 52.99 mm while the 996tt are 54.96 mm.
To sum it up, most people believed because both motors were 3.6L the parts were readily interchangable. This is hardly the truth. They can be interchanged, with different approaches and it is expensive. Time will tell if was is worth it.
The GT3 crank is stronger and has higher rpm advantages. It also has different dimensions. The journals are wider and narrower. The GT3 rods are .030 shorter. The result is you must have rods with custom dimensions made.
Just another bit of information. The stock turbo rods are about 3 mm longer than the GT3 rods and the GT3 RS rods are about 12.5 mm longer than the GT3 rods. I believe they do this to the racing motors because it changes the angle and allows them to live longer at higher rpm's.
And now the secret sauce. How many tuners are going to give out this kind of information on custom rods/dimensions. In addition these rods are balanced to the assembly and have two oil holes on the wrist pin side to promote lubrication The journal side has been designed to accept NASCAR oval bearings to better tolerate the extreme redline.
I called Rob this morning. He has both of the GT3 rods. He didn't know the exact center to center, so I asked him to wing it using a mm ruler. Using this method, one rod's approx. center to center is 129 mm and the other is 137 mm. I asked Rob if this was for the Cup and the RS motors. He said they are interchangeable and are used on either with the correct pistons. According to him, all of the GT3 motors use one of these two lengths.
The earlier pic is of the longer titanium Pankl rod.
If the above isn't enough ................ while traveling throughout the world talking to all these interesting people, in the know, we happen to meet someone who has designed and manufactured some very interesting titanium rods for the 996tt that will sustain 1000+ hp @ 8200 rpm's with some longevity. These rods are very light, the cost about 1K per rod. These will be the fourth set of rods we have bought.
Here is a sneak peek of our rods. They are special in a lot of ways. They are designed for 1600 hp. They have smaller larger side diameters for the NASCAR oval bearings. The larger side is specially designed and constructed unlike Carillo, Pauter or Porsche rods in that they are designed for limited clearance so as to clear the case and oil pump in conjunction with the stroker crank. They also have the strength to handle the torque loads being generated. In addition, their weight is extremely low (385 grams). Pistons are currently in production. We opted for a 9.0-1 compression ratio. The wrist pin height was raised. The diameter is 105.7 mm. The liners have been made and we should have them delivered in the first week of February.
We have one prototype rod. As soon as the pistons arrive we will mock up the case, crank, pistons and rods to insure not obstructions. The rods will be a reduced clearance rod so as to clear the oil pump, reduced journal size so as to accomadate the NASCAR oval bearings. Direct pressure fed pin oiling (rifle drilling). This is a trick new design to cool rods and provide additional lubrication for liner walls and wrist pins. Rod bolts are extra strong Series 625 quality high tensile.
PISTONS
New 104 mm piston on left, stock 100 mm piston on right. The new piston skirts have been coated with our secret sauce. Now the pistons will be sent out for the tops to be thermal coated.
The stock pistons weigh 558.6 grams each. The Woosner pistons weigh 550.0 grams each. The weight includes the piston, rings and wrist pin. The stock postons are 100 mm diameter (bore/liner) and the Woosner pistons are 102 mm.
As a side note, I was talking (through e-mail) to a fellow member yesterday and was informed Woosner no longer has or sells (wasn't sure judging from the e-mail) liners for their 102 and 104 mm pistons. I believe FVD markets this manufacturer in the US).
The GT3 piston and valve looked very nice. At first look I had a concern as to weather there was enough meat on the Woosner pistons to flycut for the valves pockets. Those GT3 pistons really have some deep cuts. Luckly, the GT3 rods are a few mm's longer than the turbo's rods.
The pistons are coming along great. In the mean time we learned a few more bits of information. I had mentioned earlier that I belived the GT3 Cup motors used hydralic lifters. Well the answer is no and yes.
Side by side. GT3 100 mm, Killer Angel 102 mm. As shown in the pics, the stock GT3's lift is mild by comparison. The stock GT3 valves are also alot smaller.
Killer Angel's final product will have a slight built up slope in the center tapering down to the valve pockets.
OIL PUMP
The 996tt uses a a dry sump with a single index (pickup) pump. The GT3 uses a two index pump. The GT1 uses a three index pump.
Cost of 996tt pump about $500.00, GT3 pump about $1,400.00, GT1 pump about $6,000.00.
The GT2 shares all of the components of the standard 996TT, one can also state that these two cars also share it with the 993TT..
In order to replace the stock oil pump you'd have to tear the engine down and split the case.. Now if you are going to do that, you might as well replace the rods.. And as Chad will find out, he will have to clearance his $6000 oil pump for #2 Carrillo rod.. Has to be done when you use Carrillos... This is going to be a very common proceedure.. with the HP numbers that we are seeing..
THROTTLE BODY
The 996tt and the Boxster share the same throttle body. I believe they are both 66mm. A little over a year ago we experimented with the throttle body of the 996 NA motor. This throttle body is I believe 74 mm and it works. In addition we bored this throttle body about 4 mm to attain an approximate 78 mm throttle body.
A throttle body that matches the area of the intake valves would be ideal. The 78 mm is nice but according to my calculations, not enough. We have found a 90 mm throttle body with the correct Bosch controls to function with the 996tt drive by wire acelerator. In addition we are having a splitter made up to accomadate the 90 mm throttle body. This throttle body will also be bored about 4 mm.
Below are three throttle bodies. The smallest one is stock for the 996tt. The 996tt and the Boxster use the same TB. It is approximately 66 mm and can be honed to approx. 69 mm. The middle size is the one I used on the cjv/ s car go a little over one year ago. I believe it is the same one used on the Gemballa EVO 750 and EVO Stage V. I believe this throttle body is approx. 74 mm and can be honed to 77 mm. I believe it comes from the stock 996 NA motor. The largest throttle body is what is currently being used on the cjv/ s car go. It is 90 mm and we do not know how much it can be honed at this time.
The two smaller ones can be can be bought through a Porsche dealer or call Rob at S Car Go. Any part with the exception of the 85 mm Europipe exhaust is available on an alacarte or package basis. If my 90 mm one tests OK, then my other one and the splitter intake will be available. When you go to the larger TB, you need the enlarged intake pieces. Mine were machined out of aluminum billet by S Car Go Racing. I will have the pieces made from carbon fiber (so as to help eliminate heat sink) if the 90 mm TB works.
This goes to show Todd and Protomotive can solve any problem related to the OBDII ECU.
The new 996 GT3 is using a 82 mm TB. Yes, that is 6 mm larger than the 76 mm currently being used on the GT3 and yes we can use it on our 996's. Unfortunately it is not larger than 90 mm so it is no help to KA, but to everyone else your 76 mm TB's are now obsolete.
INTAKE
I'm not going to spend the money to find out as it won't help me out at all at this point. However, using the formula's and assuming a .8 bar boost producing 415 hp, I figure the stock 996tt intakes would flow approx. 142 cfm per cylinder at 25 psi.
ECU
I have spoken to (blank) and asked him for his advice regarding the requirements of the 996TT ECU/software. It is my understanding after talking to him, that he is unsure of the ability of the ECU to understand anything other than the stock settings. He hopes to know more in a few weeks when he tests another engine.
As there is no way to modify the GT3 sync wheel, we seem to have only 2
choices. The first and less expensive is to hope the 996TT ECU software can
be modified to accept a single Cam sync trigger, and it can be adjusted to
suit another Cam position. If not, we will have to use the single Cam sync
and have that trigger another simulated trigger signal that the 996ECU will
accept. The existing Cam Trigger sensors will input into a module that will
output to the ECU the 4 segment signal. There seem to be no alternatives
here.
I suppose the 3rd choice would be an alternative electronics package.
The simulated signal choice will be expensive with expected and possible
changes required until it is correct. This system will require some testing
to ensure we "fool" the stock ECU. I have no idea of the cost or the time
required. There is no way to estimate this, nor the cost of any testing. It
can only be done on a time and material basis.
If this is the direction we have to go, we need to start the work as soon as
possible, so that we do not hold up the project any longer than necessary.
I suggest we allow (blank) time to find his and the stock ECU's ability to be
changed, and if this proves unsuccessful, we immediately start designing the
trigger simulator.
Rewritting the stock ECU programs, changing certain parameters and shutting off other functions is one option. Fooling the ECU in certain area's is another. Going to a Motec type system is a third.
Since that letter was written, we have been able to locate the pertinent files in the stock ECU program. Example, we know the profile of all the cams and the profile numbers of these cams match up exactly in the stock ECU program ......... bingo. We have been able to make the changes and a motor with the single lobe cams and modified stock ECU will be tested on an engine dyno in about ten days.
I have spoken to Rob @ S Car Go regarding the triggering issue he may
encounter. I have no experience with street engine electronics or the re
programming ability. It is clear that the 996TT Cams are not candidates for
his engine project. We will be using the modified cams which have 1 trigger
point. He has Cup Heads and Cam trays and the 996 Cam will not fit due to
the Trigger wheel. Modifying the Cup Cam for a 4 segment wheel is not
possible, and any attempt on these thin Cams appears to be a poor choice.
Welding and any other sort of fitment is not a good solution. We cannot
afford any problem issue here.
The solution appears to be one of two. I am hoping you can modify the
software to allow the system to accept one sync signal and have this signal
occur anytime between the last and the first cylinder to fire, and if this
will satisfy the ECU, he is free and clear. However, if that cannot be
achieved, then we have to look for an alternative solution. We have an
electronic solution, but this should be selected only after you have no
programming ability to change this parameter.
What have you done in the past when customers have used Cup Heads and Trays? Are they changing Cams, or are all 996 Turbo hot rods using all stock parts?
I look forward to hearing from you and hopefully success on your part to
solve this major problem.
I can manipulate the placement of the triggers, as long as there are 4
of them, but it must be 4.
There are many options for the trigger. You could place it on the front
of the camshaft, or the rear, or we even put another one between cylinders 2 and 3 on another car we did and welded a new pickup into the valve cover.
A mechanical solution may be 20 or so hours of machine work. A software
solution at this point may be months worth of development I could not use
for any other car.
The 996tt's have been changing exhaust cams, not intakes, probably for
this reason, or just simply regrinding the stock intake cams paying close
attention to the lobe/trigger placement.
BUILD/Neil
The following is an estimate for the 80.40mm Crank and the Steel Rods.
The Crank for the 2.000” Clevite Bearing will be a custom crank. Until I check the drawing and discuss with manufacturer the Oil drilling bias, the price the is estimated as,
1 off Custom Crank 80.40mm stroke, 2.00’ Rod Journal and knife edged $ 6750.00 + inbound shipping freight. 12 weeks delivery
1 set Rods, center to center length to be determined $ 2730.00 + inbound shipping freight, 4 week delivery
1 off Crank 80.40mm stroke, 53.00mm Rod Journal “stock” $ 5250.00 + in bound shipping freight, 1 in stock
1 set Rods, standard length, 131.70mm $ 2073.60 + inbound shipping freight, 4 week delivery
Again I need to check the drilling bias to be sure it can be done without a full re engineer. If I know the compression height of your Pistons and their weight, I can calculate the Rod length required and the reciprocation weight at the expected engine high speed limit. If you would require Pistons, I can provide an estimate once I know which Rod length will be used. There will be some difference in the Piston cost due to design above the Pin, if the Pin is at the shortest Compression height. This cost will be the design time to establish the desired Static Compression (dome Volume) and ring packaging above the Pin.
I thought I would send this over to give you some idea of the differences with long and short Rods.
1.55 L/R is not the shortest we have seen. I have Chevy engines out there with 1.52. The typical 350 small block with the off the shelf stroker kit is around 1.52.
There are many variables that the rod length affects. The issue is how much and how important are these. There is a lot of hype attached the Rod ratios. Some put a lot more importance upon it than I think is necessary.
The shorter Rod will have a greater angle at any given Crank position. This increases the side loading of the Piston against the Cylinder wall. Offset Pins in the Piston, and offset bores in the Rod help here.
The shorter rod will not dwell at TDC as long as a longer rod will, but will sit at BDC longer. This helps in the cam timing allowing slightly different Exhaust cam timing. You may run more Ignition timing to obtain the same amount of power.
Some will argue that a longer Rod will give a wider Torque curve. This typically occurs as the engine will rev higher due to many factors. The shorter rod often does lower the RPM where peak torque occurs, but other factors can affect this also. If this was to happen in your case, this would be a good thing. The Piston is in a different position in the Cylinder bore with a shorter Rod. This often changes the negative pressures in the Cylinder, changing the Cylinder’s ability to fill and scavenge. You have to put all factors into play here. You have a Turbocharged engine, so Cylinder filling in time and volume are very different than that of a NA engine. Factor in the your heads ability to flow and your cam design, the blanket statement that one is better than the other is often stretched in order to justify one over the other.
In the real world, you often cannot achieve the perfect design. What works in one engine does not necessarily work another. This topic is quite involved with many variables. Suffice to say, it can get quite technical.
Bottom line here, the shorter length will not hurt you here, but as I told you, I have not built one of these engines with the length we are discussing and therefore cannot tell you what the performance or wear rate is. I do feel that the longer Rod (1.58 +) is the way to go all things being equal, and if we can do this by making the engine slightly wider, this should be the way to go.
The following is what the ratios are.
Stock 127.00/76.40 1.66
Chad 4.2L using existing aftermarket Pistons 125/80.40 1.55
Chad 4.2L using above Pistons with wider engine 127/80.40 1.58
Chad 4.2L using new Pistons with wider engine 129/80.40 1.60
As you can see, there is little difference. I feel comfortable that with the stock length Rod and making the engine wider (all things considered here) the L/R of 1.58 will be just fine.
As an update I decided not to go with the 80.4 mm stroker crank. The reason for the decision was I just didn't feel good about running a L/R ratio of 1.55. I felt even with thicker liners the short rod length would lead to long term troubles.
I sent our 102 mm CP Pistons, one of our Woosner liners along with the two liner housings to Neil at Performance Developments. PD is going to supply a ductle iron piston liners which are thicker than the stock liners. PD will custom fit (hone) each liner to fit the individual pistons. PD will also come up with some tin plated piston rings for our pistons. The case will require some machining for these liners to fit.
Forging X100A
Bore Diameter 3.937
Clearance 0.0015
Compression Height 1.242
Point 0.4" UP 3.9355
Top Groove Width 0.0595
2nd Groove Width 0.07
3rd Groove Width 0.119
Intake Valve Relief -0.215
Exhaust Valve Relief -2.50
Dome Height 0.41
Gram Weight 449
Pin Diameter 0.905
Pin Length 2.25
Lock Type .073 Wire
Cam Profile 10MC6P16
Neil did prototype KA GT3 type cams with the appropiate type cam pointers which to my knowledge no one has done to date. I was not aware he did Todd's cams but if he did then he was the one who took the stock 996tt cams and eliminated the use of the lower lobes and welded and reground the upper lobes. In either case this is leading edge type work with the 996tt motor as I couldn't get any major cam companies to do either about a year ago. They simply could not overcome the obsticles.
Actually it is almost 81.6 mm. The NASCAR oval bearings are smaller than the stock Porsche bearings. While grinding the crank it is offset another .02 mm. Then it is knife edged and lightened, cross drilled, micro polished, nitrated and balanced. The pistons are 105.5 mm.
The final blueprint for KA's motor.
Case: Spanish case, boat tailed, shuffle pinned, machined for GT1 three index oil pump, machined to accept 12mm studs and designed washers, machined to accept 15.7 mm liners.
Crank: Arrow Precision 80.4 mm billet crank stroked 1 mm to 81.4 mm while fitting for NASCAR oval bearings, knife edged, lightened, cross drilled, micro polished balanced, cryo'ed and nitrated.
Oil Pump: Three index, three individual pickups. GT1 friction coating on all gears.
Rods: Pauter titanium rods designed for stroker lenght, oil dispersant coated. 50.8 mm journal size, 23 mm wrist pin size.
Cams: Single lobe billet cams designed by Performance Development, friction coated. I can't give out exact specs, however the intake seat duration is approx. 285 and exhaust is approx. 295. The intake lift is approx. 0.500 and the exhaust is approx. 0.445.
Tappets: Designed by Performance Developments.
Springs: Designed and made by Performance Development, heat dispersant treated. Titanium retainers, keepers and shims.
Heads: GT3 Cup machined for PD dual combustion chamber 0-rings, ceramic coated combustion chambers and exhaust ports, heat dispersant intake ports, ported to flow 360 cfm @ 25 psi. Heads machined to accept 12 mm studs.
Head Gasket: Designed by PD to provide added deck height for longer stroker rod length.
Liners: Designed and honed by PD, built by Arrow Precision. Extra thick steel walls designed for stroker rod angle pressures, o-ringed.
Pistons: 105.5 mm CP manufactured, design by Scargo Racing for valve clearance/lightness/strength, friction coated skirts, ceramic coated domes.
Haven't seen this posted so have a look
Highly modified 996 turbo engine
HEAD
Modified 996 turbo head flows:
in 324CFM / ex 296CFM with 28" of water @ .500" lift and
in 306CFM / ex 280CFM with 25" of water @ .500" lift.
Valves used: in 39mm, ex 34mm. ( Source: Rennlist )
We already have the GT3 Cup heads, lifters, GT3R valve springs, Carrillo rods and GT1 oil pump.The case will be boat tailed and shuffle pinned. The crank will be knifed edged. The heads will be fully ported and polished.Currently looking for some GT3 Cup sized valves that are sodium filled. The stock Cup valves are stainless steel.
Larger valve stems are not a problem. Actually, not sure the sodium filled would hold up to the 8000 RPM'S. The stock GT2 are stainless steel while the turbo's are sodium filled. I may increase radiator and oil cooler size and just go with the GT3 Cup stainless steel valves. I do not know as of yet what older factory turbo's used. Yes, the oil pressue dropped slightly.The motor was warming up at an idle.The cams are from the stock GT3. I don't want too much lift or duration.
GT3 cams should have plenty of duration for a turbo motor. I'd assume that cams for an 8200 rpm NA motor have much more duration than stock turbo cams. I wonder if the hot shot German tuners use the GT3 cams in their high end turbo motors that use GT3 heads? For some reason I thought you were running ported stock turbo heads.
Any idea of the rpm capability of the stock valve train, possibly with stronger valve springs?
*About 6700 rpm's. I have pushed mine to 7400, but it wouldn't last there very long. The Cup's valves, keepers, lifters, springs and cam are different as to design and materials used.
Here are the difference in valve sizes:
Stock 996tt
32.0 mm ex, 37.0 mm in
GT3 Cup Heads
35.5 mm ex, 41.0 mm in
GT3R Heads
36.4 mm ex, 42.0 mm in
As a comparison, the approximate valve size of the stock turbo is 32 mm for the exhaust and 37 mm for the intake. The GT3 Cup heads use approx. 35.5 mm exhaust and 41 mm intake. The valves have 6 mm stems and overall lenght is just under 113 mm. The difference dimension wise is the stock valves are flat on the face while these valves have a dished face.
I was not able, until recently, to find valves that would stand up to the higher temps of the turbo/nitrous application (in the 35.5 and 41 mm with 6mm stem/113 mm overall sizing).
Note the 996tt head between the two banks of valves on the left and right side. These are oil grooves. The Cup heads do not have these grooves. Those sir are for the EGR air system. They pump air from the air pump through the intake port through the head and mix the exhaust port with the air being pushed in to lower the CO level. If you are trying to maintain 50 state legal you are going to need to machine that back in. I would bet the GTIII heads do not have that little port on the top??
996-105-123-52 keepers
996-105-121-94 valve spring retainers
996-105-117-91 bottom retainers
996-105-461-93 shims
I don't know the cost of the GT3 heads. I used GT3 Cup heads which are a little different as to the valve sizes. I bought a few sets before the Euro rose. I believe they were a little over $900.00 US apiece for a bare head.
Changing to GT3 heads on any turbo motor isn't possible without having to make other required changes. First, the turbo motor runs hotter and it is my belief the stock GT3 valves will overheat or burn. The stock turbo valves are a different size (smaller). The cam is different as is the dimensions of the cam housing. The lifters are different as they are designed for higher rpm's. Finally the ports are larger requiring a larger throttle body and intake from the heads to the throttle body.
To accomplish what you are looking for on a more economical basis has been done by TTP. The bare turbo head and the GT3 series head difference appears to be the size of the valve and the ports. TTP has taken a turbo head, ported it and installed larger valves. This avoids special intakes, cam housings, cams (use a regrind)and lifters. They ported the intake and installed a regrind cam. The motor is very strong. Ask EL750.
The other difficulity encountered was the valve length. We are using GT3 Cup heads. We had Manley (exhaust) and Ferrea (intake) make the valves. We sent them the GT3 Cup valves to copy the dimensions. To complicate matters the GT3 uses hydralic lifters while the GT3 Cup uses solid lifters. We have decided to use hydralic lifters which were made to GT3 specifications because with solids we would have to pull the motor to adjust the valves and we didn't want to do that. We had our own made because we wanted a hydralic to redline a bit more than 8100 rpm's. We knew our valves had a slightly wider valve stem, however we were surprised to learn the GT3 valves are about 2 mm longer than the GT3 Cup valves. Thank God S Car Go ordered two GT3 valves for the mock up as the valve train dimensions must be exact. This means we will either use valve caps or make a new set of valves.
One thing I almost forgot to mention. Our Manley and Forrea valves were manufacturered with dishes in the center of the valve. The stock turbo and the GT3 Cup valves are flat on the top. The GT3 valve's are lightened due to a cup being machined in the center by Porsche. Don't understand why Porsche machines the GT3 valves with a cup and leaves the GT3 Cup valves flat.
When we originally ordered the GT3 Cup heads, valves and lifters I thought they were hydralic. What we received was solid. Today we learned they are available both ways. The 2001/2002 GT3 Cup motors used solid lifters. The 2003, 2004 and 2005 GT3 Cup motors use hydralic lifters. By the way the valve lengths are also different in the GT3, GT3 Cup solid and GT3 Cup hydralic. It's really too bad this information isn't available from Porsche.
I just recieved the flow numbers for our heads.
Flowed at 25” water. Inlet bell and Exhaust outlet used.
lift 0.050”, intake 52.3 cfm, exhaust 40.9 cfm
lift 0.100", intake 97.5 cfm, exhaust 92.2 cfm
lift 0.150", intake 144.0 cfm, exhaust 144.7 cfm
lift 0.200", intake 194.0 cfm, exhaust 179.2 cfm
lift 0.250", intake 237.6 cfm, exhaust 204.8 cfm
lift 0.300", intake 272.8 cfm, exhaust 225.3 cfm
lift 0.350", intake 297.3 cfm, exhaust 238.7 cfm
lift 0.400", intake 310.7 cfm, exhaust 250.9 cfm
lift 0.450", intake 320.9 cfm, exhaust 259.2 cfm
lift 0.500", intake 324.5 cfm, exhaust 266.2 cfm
lift 0.550", intake 327.2 cfm, exhaust 272.0 cfm
cfm = cubic feet per minute
note* With a normally asperated motor to find hp:
cfm x .27 x number of cylinders
To find hp for turbo motor:
hp(using NA hp formula) x boost +1 Atmosphere
I have not been able to find anyone who has flowed stock 996tt heads. I just can't believe Porsche doesn't have this information available.
Case in point is the heads. We were satisfied with the exhausts ............ then we learned the relation between the head flow and hp. I was amazed that people don't even know what a stock head flows. Then I found out how some flow people play the same game as some dyno people. The numbers can sound great but how many inches of flow are they using to test and what is a realistic pressure. I have learned 25 psi is the number to use. There are values and formulas assocoated with this number that will accurately predict power output.
CAMSHAFT
The stock turbo and GT3 cams have been sent to a cams "only" specialist. Both cams will be profiled. Yes, after all these years the cam specifications for both of these cams will be available. The cam specialist will then tell us if the pointers of the turbo cam can be imprinted on the GT3 cams. If so, then we will check with the ecu tuner to ensure the vario cam segment of the ecu program can be deleted and the other cam segment be modified to operate through the full rpm range.
Our other option is to grind the turbo cam to the GT3 profile or another profile close to that of the GT3. If this route is followed we would have to go back to the turbo valves made for the GT3 Cup heads. These valves vary from what we are currently using in that the overall valve lenght is a few mm's shorter. Luck has it these were the second set of valves that we made prior to determining that we needed a slightly longer valve for the GT3 cam. Today S Car Go Racing sent these valves (the shorter valve lenght ones) to HP Coating. Don't know if this is the route we will be following .............. but if we do the correct valves will be ready. If we follow this route the cylinder holders will still be GT3 (which is heavier duty) but the cam housing would be from the turbo which is lighter duty.
One other bit of info. The GT3 exhaust cam will fit the turbo cam housing. The GT3 intake cam will not. The GT3 cams are not vario lift cams. The turbo's intake is vario lift, however the exhaust cam is not.
We have decided to utilize the turbo cams. The reason being with the base lift being left untouched passing smog will be a given. Now, we have sent the stock turbo cams and the GT3 cams to a cam manufacturer. They have profiled both cams giving us each cams lift, durantion, etc. We have told the cam maker the turbo's timing and instructed him to weld/grind the second set of lobes so we will make power to 8100 rpm's.
We are having a modified GT3 intake cam (non vario lift) made up with turbo cam markers.
We are suppose to have the cams, gears and cam housings by Monday. This set back has lead to talking to some of the best Porsche minds on the planet. The intake is not vario lift. We are using gear drives. Both intake and exhaust cams have been race proven on turbo's. We are not using either our turbo or GT3 cam housings.
We have received our cams, cam housings, gears, etc. today. We started with variable lift intake cams and variable timing. We then tried non variable lift intake cams with variable timing. We settled on non variable lift intake cams and non variable timing. The exhaust cams were designed to marry with the intakes. The lift and duration is to die for. The power range will start around 2,800 rpm's and peak at 8200 rpm's. Idle will be a little rough, however once out of idle she will purrr.
Here is some information for anyone who is interested about the stock 996tt intake cams.
*Lift is .402" secondary cam lobe .118" ( 0.402 inch = 10.210 8 millimeter, 0.118 inch = 2.997 2 millimeter )
*Duration .040 234 degrees .050 230 degrees
*secondary cam duration .040 128 degrees .050 120 degrees
*cam base circle 1.378
As a side note we have proven these cams will make power to 7500 rpm's
Another item is the cams. It took us three months to figure out what cams would work with the GT3 turbo motor setup. With the help of others and buying three different sets of cams we cracked this barrier only to discover that after all the cams we purchased we arrived at a solution but a new issue cropped up ............. harmonic distortion or in layman's having a cam that rams up smoothly in a turbo application.
A few people have used the GT3 exhaust cams in the turbo motor. To my knowledge no one has changed the intake cams. This is an area where the research is expensive (lift/durantion/head flow/timing/variable vs non variable lift and variable vs non variable timing) and the potential for engine damage can and has proven to be very expensive as in bent intake valves).
We have spent the money and solved the inherent problems. We have discovered the limits to which the intake and exhaust lobes can be taken to in the areas of power and longevity. The turbo and NA cams require different profiles relating to cam design. It has to do with valve train harmonics (how you ramp up to and down from the lift).
Like I said earlier, this work is a big step for the 996tt motors and their power/reponsiveness. Those who are considering opening up their motors will be following once the cat is out of the bag.
How many people know the 06 Cup cams make 20 more hp than the 04 Cup cams?
The cam builder built the cams for the pre 2004 lifters and not the 2004/2005 lifters. Even though we sent the lifters and cam housings. I guess he wasn't aware that Porsche made a change.
The harmonic distortion on the tt, GT3, GT3 Cup and GT3R cams is very bad to say the least. This has nothing to due with knocking, but with smoothiness of the valve train. This was one reason we reprofiled the cams. Second, we learned up to what lift the motor continued to make power and where the power ceased.
As for the ECU, the tt and the GT3's cam markers are in different locations. In addition, the tt and the GT3's run different timing. What we have designed, manufactured and tested is intake/exhaust cams with ultimate lift/duraion, little to no harmonic distortation and markers that are compatable with the tt's ECU. These cams are made in heaven for a tuner.
We have the Titanium Retainers and a new Spring in house for the new Cam
design. As soon as I have further details we will be able to assemble and
ship the heads.
To update you on the 996TT Triggering issue. The 996TT electronics requires a 4 segment wheel which it uses for Cam timing (VTC).
The GT3 Cup cams have only one Trigger point. The issue is 2 fold. The new
cams are single lobe type, the 996TT are the variable lift type, and the
996TT Cams will not fit into the cup cam trays.
I am currently having five sets of intake and exhaust cams for the 996tt being made from billet. These cams will also be gun barrel drill. They will be capable of approx. 8400 rpm's. These cams will have the 996tt marking points and a lift and duration simular to the new Cup cars. These cams will allow a tuner to use them with the 996 ECU providing your pistons have the proper clearance. Pistons would also be available if desired. These cams are made for the GT3 heads and cam housings.
Back to the cams. The farther we go ............ the more we learn. We now have two choices. Both cams (intake and exhaust) will have the same profile abeit a little different. We already have the profile to deliver the max torque and power for the big valve/port heads. I used GT3 heads and VRAlexander (Protomotive) installed larger valves/ports on turbo heads. Our heads flowed within 22 cfm of each other at 25 psi. One of the big differences between the motors will be the cam lift. To really take advantage of these big breathing heads you need more lift. The motor can deliver an additional 10 hp for each additional 10/1000's of lift and 110/1000's is available before the numbers start to drop off. I'm told that when KA idle's the motor will lope. Can you imagine pulling up to a Porrsche 996tt at a light and listening to her lope.
Now to the exiting news. We are making computer grinded billet intake and exhaust cams for the 996tt (vario lift) and the GT3 cam housings (none vario). Both applications will be tunable by the top tuners using the 996tt ecu. These cams will both have the same profile and will be gun barrel drilled when finished for lightness and maximum rpm's.
Markski is using a set a GT3 cams I we sent to him. These cams are not vario lift, but vario timing. They also have the single cam point markers of the GT3 street cams. What this means is Protomotive has to come up with a way for the 996tt ecu to read the pointer markers.
My set up is a little different. We started with the profile of the 2006 GT3 Cup cam and added approx. 30,000ths of lift. In addition we made a gun barreled cam from billet, no variable lift and we are having the cam made with the 3-5 cam markers of the GT3.
How many people realize the GT3 Street, GT3 Cup and GT3R motors all have a different number of cam pointers? Each cam requires different ECU's. Now to make matters worst there are solid and hydralic tappets along with different GT3 year models have different tappets with different overall dimensions and designs. If the above isn't bad enough, try welding metal any one of the above stock Porsche GT3 cams using the required Porsche tappets. Well, it may work for awhile, but the different metals (cam and tappets) will quickly wear down the welded lobes. So what do you do?
All of the people to date who have turbocharged the GT3 heads have used either the stock GT3 street or GT3 Cup cams with the respective tappets. The problem is you don't have a crisp or responsive motor. You have a motor that is fast but far from optimum. You have a turbocharged motor with a normally aspirated cam profile. Not good to say the least. You have to do strange things to the timing and the performance suffers in many areas. Furthermore, you have these huge GT3 heads with a cam that can't make real good use of these monster heads breathing wise. Some people have used stock turbo heads that are ported and valved to GT3 dimensions. This is great ............. but how about the tappets. They simply won't stand up to anywhere near 8500 rpm's. We know of no one prior to S Car Go Racing who has made a turbo cam for the GT3 heads that is compatable with existing tappets and ECU's. The S Car Go turbo cams (intake and exhaust) for the GT3 heads will be proven before the end of the year.
Here are the final specs
.............................Intake.......... Exhaust
Seat Duration..... 296............. 284
0.050’ Duration.. 254............. 243
Gross cam lift.... XXXXXX..... XXXXXX
Hyd Valve Lash..0.004........... 0.004
Net Valve Lift..... XXXXXX..... XXXXXX
The cam specs on the GT3 street cams are:
Duration......... Intake 286.0 Exhaust 285.0
50/1000's Lift.. Intake 235.0 Exhaust 226.6
0 Lash Lift...... Intake 484.0 Exhaust 437.0
FVD 996 Turbo/GT2 Sport Camshafts (4pc Set) 100 105 292
Intake Camshaft 284°, MD 110°, Lift 12.50mm, TDC 2.84
Exhaust Camshaft 272°, MD 110°, Lift 11.45mm, TDC 2.04
BTW, Chad, I was talking about Neil. I was not going to mention his name as I know he keeps who he does business with to himself.
I spoke to him about the parts he designed etc. Its a shame that you will never get to see what they are capable of doing. So many special parts for this engine. A real shame.
For all those who are interested, Crankshafts, Rods, Pistons, Intake and Exhaust Camshafts, Pistons and Liners, Cylinder Heads with very special Valve Train parts, Turbo's, 6 channel CDI Ignition with special CDI Coils, are amongst the parts now available. Chad earlier posts told who did these parts. If anyone is interested email me, m42racer@aol.com and I will forward the contact information.
This all goes back to the cams, springs and o-ringing. Let me start with the cams. As many of you know there has been four views of this issue. Use the Porsche GT3 cams or cam, regrind the upper lobes of the 996tt cams, use the 996tt stock cam or design a new cam. I believe many remember me stating that we found alot of harmonic distortion in the stock cams and cams reground using stock profiles but increasinng the lifts.
Harmonic distortion is such an innocent sounding word. Please bare in mind the following is my opinion based on tests and experience. Some tuners have successfully used the Porsche 996tt stock, GT3 cams, GT3 exhaust cams and hybrids of the Porsche cams. It appears the success was derived through the use of high valve spring pressures. Why you may ask? The answer appears to be to overcome the harmonic distortion found in the Porsche cam profiles when used with hydralic tappets and higher rpm's.
Case in point. Tuner A and B are working together. A is of the school of using Porsche cams with high spring pressures, the B uses engineered cams not requiring the high pressures. B assembles the heads for B based on his philosophy but does not opt for the cams that eliminate the HD. Well, you guessed it. It appears the two mixed philosophies resulted in a motor wiping out all the hydralic tappets. It appears either higher spring pressure or a cam designed to eliminate HD would have eliminated the problem. If B is correct, his theory would be the better way to go because the higher spring pressure just drastically accelerates wear on the valve guides and it appears the high spring pressures only masks an existing problem. On the other hand, B's theory has not been tested on a 996tt to my knowledge. My motor is designed around B's theory. B designed and built the cams and heads while A is assembling the rest of the motor.
I have an inside track on this too. To be fair here this is not the place to trash anyone. It is a place to be sure all the facts are true and correct. I do not know the exacts here either. The engine that Chad talks of losing the lifters, did happen, and the reason is clear, but why the decision to run the stock Cmas is unknown to me. Maybe the customer decided not to spend the money and Tuner A had no other choice. Remember, if you go out and do hotrod things to your engine, you are entering unknown territory often. Thats why its called development.
To clear up a point here, if I understand Tuner A and B to be who I know them to be, Tuner A asked Tuner B to build heads with all trick parts, to run to 8K RPM. Tuner B was given all og the parts including the stock Cams. Tuner B told Tuner A that stock Cams would not work and should not be run to 8K RPM. Tuner B gave Tuner A a quotation to design and build Cams suitable to run thses heads with trck Valve Train to 8K. Either Tuner A or Tuner A's customer decided not to have Tuner B design and make Cams, but to use stock Cams. The heads were built with parts and the setup was done for the parts included to run to 8K RPM. THe parts used in these heads were all lightweight Titanium replacing the heavier stock steel parts. The final setup actually in the end was approx the same as the stock steel setup was.
The engine was run and the lifters all failed as Tuner A was told they would by Tuner B. Tuner B as Chad has said, engineers the setup based upon calculations etc. Both Tuner B and his staff are qualified engine engineers who have long resume's and lots of experience. Tuner B's business has been buiding Porsche 4V water cooled engines since the 80's. I know they know what is required. These race engine run to 8500RPM and make 760+ HP.
The result here is from running a Cam unsuitable for this application. I have been told that the new engines in most new cars are designed and run at the engines limit. Tests have shown that certain engines can run quite happily to 7000RPM but run at 7100RPM go in the toilet. Any redesigning of these new engines should be done by those who know. Not by those who think they do. The new designs will catch out the ignorant.
In Chads engine, the cams were re designed to run at the engine speeds required, eliminating the harmonics found in the stock designs. Cam designing not just about lift and duration. Its about many other factors well beyond my understanding. Any vibrations or harmonics inded into the Valve Train is always from the Cam. It will always happen at the same RPM. Adding Spring pressure dampens the effect, it will never get rid of it. The real issue is at engine speed. As the engine speed increases the open pressure goes to zero,
and the seat pressure is all that controls the Valve. Running Titanium Valves requires a specfic set of rules again. Too much seat pressure and the Titanium Valves are put under too much closing force. Running a Titanium Valve with a Cam design for steel Valves is also a problem. Steel Valves are close against the seat with greater force as the material will take for abuse and force. This is why increasing the seat force on the heads in question is not a real answer to the problem. Add seat force to help dampen the harmonic and the Titanium Valve closing force will destroy the Valves. This is a street engine not a race engine too. Race engines are usually rebuilt at shorter intervals. Telling a street customer that his valves will need to be replace every 60 hours is not a real answer either.
In Chads engine the Cams were engineered for the application, the engine speeds required and the springs set for this use. The setup I'm told is very similar to the 962C engine running almost the same. If it works in that engine, then I'm confident Tuner B has it right. He did prove to Tuner A it would not!!
BLOCK
After all the parts were recieved, I was told why having my heads and liner have takinb so long. Apparaently my Woosner liners are not consentric at the tops like the Porsche liners. Not an issue but for the o-rings.
Well this called for a little engineering that in the long run will save thousands of dollars for those that follow. Along the way we also learned interesting additional things. First, in the past it has cost about $2,500 to machine the heads/liners due to the alignment work involved. The new machine work should cost about $600.00. Second, in the past both Porsche and EVO head gaskets(the only ones I am aware of) slightly overlap the bore or liner ID. This is how the heads seal and really isn't ideal. This will no longer be required with our design. We went to the best head gasket maker in the US, a company called Kinitics to build the gaskets based on our engineering design. Along the way we learned that they build a modified 996tt head gasket for a company called RPM Motorsports (or RPM something) out of Tempe Arizona. I wonder who these gaskets are being made for.
Anyway, the long and the short of it is we have brought down the machining costs. We are engineering the head gaskets, gas sealing o-ring and a T ring. We will have these made to our engineering specs. With this design the bar chosen to be run will not be the weak link as the seal together with the studs should take whatever pressure you choose to throw at it. Wear and tear on the motor should now be the limiting factor together with fuel and timing. As a plus, the machining,the three sets of o-rings and the head gaskets will probably cost less than the old machining costs by itself use to.
CRANKSHAFT
Finally received some hard information on the turbo crankshaft. The GT2 and GT3 share the same crankshaft. The same crank is also shared with the GT1. The turbo has a different crank which is not as strong as the GT1, GT2, GT3 crank.
Well, that is not entirely true. The 996 GTII does not share any difference in the crank as compared to it's AWD brother. The GT3 and GTI do have different ranks. The TT/GTII are the same.
Here are some pics of the crank. The c/s was welded and stroked 1mm. The rod journals were ground to 2.000-1.999 inches. It was knife edged, nitrided, cross drilled, cryo treated, maged and balanced. With 102 mm pistons and 1mm stroke the engines displacement will be 4.0 L.
Actually, there is one other problem besides rods on these motors when you start entering the 600 to 700 rwhp range. The crank wants to move. Shuffle pinning is as important as changing the rods.
Crank is a GT3 RSR crank which has been lightened (knife edged) balanced, stroked, reduced journal sized, nitrated, polished and blue printed to very near zero tolerences.
CONNECTION RODS
Technically speaking, the rod is simply a two-force member. That means, it is not subjected to flexure, only tension and compression. When I look at this, I clearly see a compression buckling failure. What I mean by this is that the force on the rod is applied at the wrist pin and crank bearing. Regardless of where the piston is in the stroke, and hence the angle of the rod, it is still a two force member only subjected to tension or compression. My assessment is that the force of the explosion in the combustion chamber applied to the piston top induced an excessive compression force in the rod that exceeded its buckling yield strength. Forces less than the yield strength of the rod will allow the rod to operate in its elastic range. That means the rod can elongate and shorten under tension and compression loads respectively. The rod can also bow out of plane much like the analogy of pressing on a thin metal yardstick standing upright. It will flex outward within its elastic range but will eventually permanently bend after reaching its yield strength.
This is the wonderful property of steel and its related alloys. The stress strain curve allows for a range of operation in the elastic region with a gradual deformation leading towards ultimate failure. The yield point is where the metal permanently deforms but does not yet break. This is why safety factors are used in Allowable Stress Design and Load Factor Design in steel construction. They allow the element in question to operate in the elastic range without permanent deformation and/or failure.
Now, if you look at the cross section of the rod, you will see it is an I shape. If you orient the rod such that its cross section is like a capital I (as opposed to an H), the strong axis is horizontal. The weak axis is vertical. Clearly, in textbook fashion, the rod yielded about its weak axis. Although impractical, a much better and stronger rod would incorporate a square cross section giving both axes equal buckling resistance.
I was talking to a individual at Porsche Motorsports, about the rod situation.... They are dumping the Titanium rod bolts and are replacing them with ARP's... The big ends are getting hammered/ovaled.. The added heat and stress is causing the bolts to fail... They are recommending the ARP's.. No with the Carrillo's, it's always wise to step up and order the 3/8 carrbolts...
Once we sent them the titanium GT3RS and stock 996tt rods it was discovered the GT3RS rods are .030 longer. To use that design would raise the compression ratio a full point which would be too much even thould our pistons were designed for a slightly lower than stock 9.4-1 compression ratio. In addition the GT3 crank's journals are wider in addition to the radius of the counter weights being shorter.
The new rods using the 996tt case with the GT3 crank will be a special breed 8100 rpm lower end, designed for the 996 turbo application. The rods are being designed for 1000 hp.
So to sum our situation up. We are using Woosner 104 mm pistons with 23 mm wrist pins. We are using the GT3R crank with the smaller radius and wider journals. We are usin Pauter rods sized for the GT3R crank and 23 mm wrist pins for the Woosner pistons. The difference on the different GT3 cranks is the dampener used or not used.
Sorry, just sat back at the computer. Yes, the 993 and the 964 as well as the 996TT is exactly 22.9 mm. In fact even the same circlip that the 993 uses.
Agreed, some people were talking in non descript terms. Now we know the GT3 rods use 22 mm wrist pins while the 996 uses 23 mm pins. We know the GT3 rods are thirty thousands longer than the 996tt rods. We know the rod width on the GT3 is 17.71 mm while the 996tt is 14.68 mm. We know the rod journals on the GT3 are 52.99 mm while the 996tt are 54.96 mm.
To sum it up, most people believed because both motors were 3.6L the parts were readily interchangable. This is hardly the truth. They can be interchanged, with different approaches and it is expensive. Time will tell if was is worth it.
The GT3 crank is stronger and has higher rpm advantages. It also has different dimensions. The journals are wider and narrower. The GT3 rods are .030 shorter. The result is you must have rods with custom dimensions made.
Just another bit of information. The stock turbo rods are about 3 mm longer than the GT3 rods and the GT3 RS rods are about 12.5 mm longer than the GT3 rods. I believe they do this to the racing motors because it changes the angle and allows them to live longer at higher rpm's.
And now the secret sauce. How many tuners are going to give out this kind of information on custom rods/dimensions. In addition these rods are balanced to the assembly and have two oil holes on the wrist pin side to promote lubrication The journal side has been designed to accept NASCAR oval bearings to better tolerate the extreme redline.
I called Rob this morning. He has both of the GT3 rods. He didn't know the exact center to center, so I asked him to wing it using a mm ruler. Using this method, one rod's approx. center to center is 129 mm and the other is 137 mm. I asked Rob if this was for the Cup and the RS motors. He said they are interchangeable and are used on either with the correct pistons. According to him, all of the GT3 motors use one of these two lengths.
The earlier pic is of the longer titanium Pankl rod.
If the above isn't enough ................ while traveling throughout the world talking to all these interesting people, in the know, we happen to meet someone who has designed and manufactured some very interesting titanium rods for the 996tt that will sustain 1000+ hp @ 8200 rpm's with some longevity. These rods are very light, the cost about 1K per rod. These will be the fourth set of rods we have bought.
Here is a sneak peek of our rods. They are special in a lot of ways. They are designed for 1600 hp. They have smaller larger side diameters for the NASCAR oval bearings. The larger side is specially designed and constructed unlike Carillo, Pauter or Porsche rods in that they are designed for limited clearance so as to clear the case and oil pump in conjunction with the stroker crank. They also have the strength to handle the torque loads being generated. In addition, their weight is extremely low (385 grams). Pistons are currently in production. We opted for a 9.0-1 compression ratio. The wrist pin height was raised. The diameter is 105.7 mm. The liners have been made and we should have them delivered in the first week of February.
We have one prototype rod. As soon as the pistons arrive we will mock up the case, crank, pistons and rods to insure not obstructions. The rods will be a reduced clearance rod so as to clear the oil pump, reduced journal size so as to accomadate the NASCAR oval bearings. Direct pressure fed pin oiling (rifle drilling). This is a trick new design to cool rods and provide additional lubrication for liner walls and wrist pins. Rod bolts are extra strong Series 625 quality high tensile.
PISTONS
New 104 mm piston on left, stock 100 mm piston on right. The new piston skirts have been coated with our secret sauce. Now the pistons will be sent out for the tops to be thermal coated.
The stock pistons weigh 558.6 grams each. The Woosner pistons weigh 550.0 grams each. The weight includes the piston, rings and wrist pin. The stock postons are 100 mm diameter (bore/liner) and the Woosner pistons are 102 mm.
As a side note, I was talking (through e-mail) to a fellow member yesterday and was informed Woosner no longer has or sells (wasn't sure judging from the e-mail) liners for their 102 and 104 mm pistons. I believe FVD markets this manufacturer in the US).
The GT3 piston and valve looked very nice. At first look I had a concern as to weather there was enough meat on the Woosner pistons to flycut for the valves pockets. Those GT3 pistons really have some deep cuts. Luckly, the GT3 rods are a few mm's longer than the turbo's rods.
The pistons are coming along great. In the mean time we learned a few more bits of information. I had mentioned earlier that I belived the GT3 Cup motors used hydralic lifters. Well the answer is no and yes.
Side by side. GT3 100 mm, Killer Angel 102 mm. As shown in the pics, the stock GT3's lift is mild by comparison. The stock GT3 valves are also alot smaller.
Killer Angel's final product will have a slight built up slope in the center tapering down to the valve pockets.
OIL PUMP
The 996tt uses a a dry sump with a single index (pickup) pump. The GT3 uses a two index pump. The GT1 uses a three index pump.
Cost of 996tt pump about $500.00, GT3 pump about $1,400.00, GT1 pump about $6,000.00.
The GT2 shares all of the components of the standard 996TT, one can also state that these two cars also share it with the 993TT..
In order to replace the stock oil pump you'd have to tear the engine down and split the case.. Now if you are going to do that, you might as well replace the rods.. And as Chad will find out, he will have to clearance his $6000 oil pump for #2 Carrillo rod.. Has to be done when you use Carrillos... This is going to be a very common proceedure.. with the HP numbers that we are seeing..
THROTTLE BODY
The 996tt and the Boxster share the same throttle body. I believe they are both 66mm. A little over a year ago we experimented with the throttle body of the 996 NA motor. This throttle body is I believe 74 mm and it works. In addition we bored this throttle body about 4 mm to attain an approximate 78 mm throttle body.
A throttle body that matches the area of the intake valves would be ideal. The 78 mm is nice but according to my calculations, not enough. We have found a 90 mm throttle body with the correct Bosch controls to function with the 996tt drive by wire acelerator. In addition we are having a splitter made up to accomadate the 90 mm throttle body. This throttle body will also be bored about 4 mm.
Below are three throttle bodies. The smallest one is stock for the 996tt. The 996tt and the Boxster use the same TB. It is approximately 66 mm and can be honed to approx. 69 mm. The middle size is the one I used on the cjv/ s car go a little over one year ago. I believe it is the same one used on the Gemballa EVO 750 and EVO Stage V. I believe this throttle body is approx. 74 mm and can be honed to 77 mm. I believe it comes from the stock 996 NA motor. The largest throttle body is what is currently being used on the cjv/ s car go. It is 90 mm and we do not know how much it can be honed at this time.
The two smaller ones can be can be bought through a Porsche dealer or call Rob at S Car Go. Any part with the exception of the 85 mm Europipe exhaust is available on an alacarte or package basis. If my 90 mm one tests OK, then my other one and the splitter intake will be available. When you go to the larger TB, you need the enlarged intake pieces. Mine were machined out of aluminum billet by S Car Go Racing. I will have the pieces made from carbon fiber (so as to help eliminate heat sink) if the 90 mm TB works.
This goes to show Todd and Protomotive can solve any problem related to the OBDII ECU.
The new 996 GT3 is using a 82 mm TB. Yes, that is 6 mm larger than the 76 mm currently being used on the GT3 and yes we can use it on our 996's. Unfortunately it is not larger than 90 mm so it is no help to KA, but to everyone else your 76 mm TB's are now obsolete.
INTAKE
I'm not going to spend the money to find out as it won't help me out at all at this point. However, using the formula's and assuming a .8 bar boost producing 415 hp, I figure the stock 996tt intakes would flow approx. 142 cfm per cylinder at 25 psi.
ECU
I have spoken to (blank) and asked him for his advice regarding the requirements of the 996TT ECU/software. It is my understanding after talking to him, that he is unsure of the ability of the ECU to understand anything other than the stock settings. He hopes to know more in a few weeks when he tests another engine.
As there is no way to modify the GT3 sync wheel, we seem to have only 2
choices. The first and less expensive is to hope the 996TT ECU software can
be modified to accept a single Cam sync trigger, and it can be adjusted to
suit another Cam position. If not, we will have to use the single Cam sync
and have that trigger another simulated trigger signal that the 996ECU will
accept. The existing Cam Trigger sensors will input into a module that will
output to the ECU the 4 segment signal. There seem to be no alternatives
here.
I suppose the 3rd choice would be an alternative electronics package.
The simulated signal choice will be expensive with expected and possible
changes required until it is correct. This system will require some testing
to ensure we "fool" the stock ECU. I have no idea of the cost or the time
required. There is no way to estimate this, nor the cost of any testing. It
can only be done on a time and material basis.
If this is the direction we have to go, we need to start the work as soon as
possible, so that we do not hold up the project any longer than necessary.
I suggest we allow (blank) time to find his and the stock ECU's ability to be
changed, and if this proves unsuccessful, we immediately start designing the
trigger simulator.
Rewritting the stock ECU programs, changing certain parameters and shutting off other functions is one option. Fooling the ECU in certain area's is another. Going to a Motec type system is a third.
Since that letter was written, we have been able to locate the pertinent files in the stock ECU program. Example, we know the profile of all the cams and the profile numbers of these cams match up exactly in the stock ECU program ......... bingo. We have been able to make the changes and a motor with the single lobe cams and modified stock ECU will be tested on an engine dyno in about ten days.
I have spoken to Rob @ S Car Go regarding the triggering issue he may
encounter. I have no experience with street engine electronics or the re
programming ability. It is clear that the 996TT Cams are not candidates for
his engine project. We will be using the modified cams which have 1 trigger
point. He has Cup Heads and Cam trays and the 996 Cam will not fit due to
the Trigger wheel. Modifying the Cup Cam for a 4 segment wheel is not
possible, and any attempt on these thin Cams appears to be a poor choice.
Welding and any other sort of fitment is not a good solution. We cannot
afford any problem issue here.
The solution appears to be one of two. I am hoping you can modify the
software to allow the system to accept one sync signal and have this signal
occur anytime between the last and the first cylinder to fire, and if this
will satisfy the ECU, he is free and clear. However, if that cannot be
achieved, then we have to look for an alternative solution. We have an
electronic solution, but this should be selected only after you have no
programming ability to change this parameter.
What have you done in the past when customers have used Cup Heads and Trays? Are they changing Cams, or are all 996 Turbo hot rods using all stock parts?
I look forward to hearing from you and hopefully success on your part to
solve this major problem.
I can manipulate the placement of the triggers, as long as there are 4
of them, but it must be 4.
There are many options for the trigger. You could place it on the front
of the camshaft, or the rear, or we even put another one between cylinders 2 and 3 on another car we did and welded a new pickup into the valve cover.
A mechanical solution may be 20 or so hours of machine work. A software
solution at this point may be months worth of development I could not use
for any other car.
The 996tt's have been changing exhaust cams, not intakes, probably for
this reason, or just simply regrinding the stock intake cams paying close
attention to the lobe/trigger placement.
BUILD/Neil
The following is an estimate for the 80.40mm Crank and the Steel Rods.
The Crank for the 2.000” Clevite Bearing will be a custom crank. Until I check the drawing and discuss with manufacturer the Oil drilling bias, the price the is estimated as,
1 off Custom Crank 80.40mm stroke, 2.00’ Rod Journal and knife edged $ 6750.00 + inbound shipping freight. 12 weeks delivery
1 set Rods, center to center length to be determined $ 2730.00 + inbound shipping freight, 4 week delivery
1 off Crank 80.40mm stroke, 53.00mm Rod Journal “stock” $ 5250.00 + in bound shipping freight, 1 in stock
1 set Rods, standard length, 131.70mm $ 2073.60 + inbound shipping freight, 4 week delivery
Again I need to check the drilling bias to be sure it can be done without a full re engineer. If I know the compression height of your Pistons and their weight, I can calculate the Rod length required and the reciprocation weight at the expected engine high speed limit. If you would require Pistons, I can provide an estimate once I know which Rod length will be used. There will be some difference in the Piston cost due to design above the Pin, if the Pin is at the shortest Compression height. This cost will be the design time to establish the desired Static Compression (dome Volume) and ring packaging above the Pin.
I thought I would send this over to give you some idea of the differences with long and short Rods.
1.55 L/R is not the shortest we have seen. I have Chevy engines out there with 1.52. The typical 350 small block with the off the shelf stroker kit is around 1.52.
There are many variables that the rod length affects. The issue is how much and how important are these. There is a lot of hype attached the Rod ratios. Some put a lot more importance upon it than I think is necessary.
The shorter Rod will have a greater angle at any given Crank position. This increases the side loading of the Piston against the Cylinder wall. Offset Pins in the Piston, and offset bores in the Rod help here.
The shorter rod will not dwell at TDC as long as a longer rod will, but will sit at BDC longer. This helps in the cam timing allowing slightly different Exhaust cam timing. You may run more Ignition timing to obtain the same amount of power.
Some will argue that a longer Rod will give a wider Torque curve. This typically occurs as the engine will rev higher due to many factors. The shorter rod often does lower the RPM where peak torque occurs, but other factors can affect this also. If this was to happen in your case, this would be a good thing. The Piston is in a different position in the Cylinder bore with a shorter Rod. This often changes the negative pressures in the Cylinder, changing the Cylinder’s ability to fill and scavenge. You have to put all factors into play here. You have a Turbocharged engine, so Cylinder filling in time and volume are very different than that of a NA engine. Factor in the your heads ability to flow and your cam design, the blanket statement that one is better than the other is often stretched in order to justify one over the other.
In the real world, you often cannot achieve the perfect design. What works in one engine does not necessarily work another. This topic is quite involved with many variables. Suffice to say, it can get quite technical.
Bottom line here, the shorter length will not hurt you here, but as I told you, I have not built one of these engines with the length we are discussing and therefore cannot tell you what the performance or wear rate is. I do feel that the longer Rod (1.58 +) is the way to go all things being equal, and if we can do this by making the engine slightly wider, this should be the way to go.
The following is what the ratios are.
Stock 127.00/76.40 1.66
Chad 4.2L using existing aftermarket Pistons 125/80.40 1.55
Chad 4.2L using above Pistons with wider engine 127/80.40 1.58
Chad 4.2L using new Pistons with wider engine 129/80.40 1.60
As you can see, there is little difference. I feel comfortable that with the stock length Rod and making the engine wider (all things considered here) the L/R of 1.58 will be just fine.
As an update I decided not to go with the 80.4 mm stroker crank. The reason for the decision was I just didn't feel good about running a L/R ratio of 1.55. I felt even with thicker liners the short rod length would lead to long term troubles.
I sent our 102 mm CP Pistons, one of our Woosner liners along with the two liner housings to Neil at Performance Developments. PD is going to supply a ductle iron piston liners which are thicker than the stock liners. PD will custom fit (hone) each liner to fit the individual pistons. PD will also come up with some tin plated piston rings for our pistons. The case will require some machining for these liners to fit.
Forging X100A
Bore Diameter 3.937
Clearance 0.0015
Compression Height 1.242
Point 0.4" UP 3.9355
Top Groove Width 0.0595
2nd Groove Width 0.07
3rd Groove Width 0.119
Intake Valve Relief -0.215
Exhaust Valve Relief -2.50
Dome Height 0.41
Gram Weight 449
Pin Diameter 0.905
Pin Length 2.25
Lock Type .073 Wire
Cam Profile 10MC6P16
Neil did prototype KA GT3 type cams with the appropiate type cam pointers which to my knowledge no one has done to date. I was not aware he did Todd's cams but if he did then he was the one who took the stock 996tt cams and eliminated the use of the lower lobes and welded and reground the upper lobes. In either case this is leading edge type work with the 996tt motor as I couldn't get any major cam companies to do either about a year ago. They simply could not overcome the obsticles.
Actually it is almost 81.6 mm. The NASCAR oval bearings are smaller than the stock Porsche bearings. While grinding the crank it is offset another .02 mm. Then it is knife edged and lightened, cross drilled, micro polished, nitrated and balanced. The pistons are 105.5 mm.
The final blueprint for KA's motor.
Case: Spanish case, boat tailed, shuffle pinned, machined for GT1 three index oil pump, machined to accept 12mm studs and designed washers, machined to accept 15.7 mm liners.
Crank: Arrow Precision 80.4 mm billet crank stroked 1 mm to 81.4 mm while fitting for NASCAR oval bearings, knife edged, lightened, cross drilled, micro polished balanced, cryo'ed and nitrated.
Oil Pump: Three index, three individual pickups. GT1 friction coating on all gears.
Rods: Pauter titanium rods designed for stroker lenght, oil dispersant coated. 50.8 mm journal size, 23 mm wrist pin size.
Cams: Single lobe billet cams designed by Performance Development, friction coated. I can't give out exact specs, however the intake seat duration is approx. 285 and exhaust is approx. 295. The intake lift is approx. 0.500 and the exhaust is approx. 0.445.
Tappets: Designed by Performance Developments.
Springs: Designed and made by Performance Development, heat dispersant treated. Titanium retainers, keepers and shims.
Heads: GT3 Cup machined for PD dual combustion chamber 0-rings, ceramic coated combustion chambers and exhaust ports, heat dispersant intake ports, ported to flow 360 cfm @ 25 psi. Heads machined to accept 12 mm studs.
Head Gasket: Designed by PD to provide added deck height for longer stroker rod length.
Liners: Designed and honed by PD, built by Arrow Precision. Extra thick steel walls designed for stroker rod angle pressures, o-ringed.
Pistons: 105.5 mm CP manufactured, design by Scargo Racing for valve clearance/lightness/strength, friction coated skirts, ceramic coated domes.
Registered User
Joined: Mar 2009
Posts: 886
From: In my garage
Rep Power: 123
All from this thread:
https://www.6speedonline.com/forums/...-j-maring.html
A good compilation though.
https://www.6speedonline.com/forums/...-j-maring.html
A good compilation though.
Registered User
Joined: Jul 2010
Posts: 3,319
From: Long island NY
Rep Power: 381
thats a build for someone with a race unlimited budget. There is no need for most of what written there. Oil pump?? I am logging crank case psi and using a gt3 oil pump.. 6000 for a gt1 oil pump? How about just logging whats going on and fixing what needs fixing? The head flow I know because I took my junk to a flow bench. I would love to see this project completed. How is Chad doing?
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Joined: Sep 2006
Posts: 7,481
Rep Power: 707
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