Engine rebuild questions...
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The car remains awd. We changed the front differential from the stock hydra/friction unit to a RAMP LSD unit. We were able to use the stock Porsche front differential case, gut the internals and fit RAMP internals. The stock differential wasn't limited slip and is only rated for about 50 foot pounds of torque. Our ramp differential is rated for 300 ft lbs. Not great but far better given the confines of the stock Porsche case. The car is fitted with a Porsche GT3 billet RSR LSD in the rear.
I have taken pwdrhound's thread OT again with these questions. I'm sorry. I will be happy to answer questions but please ask them at https://www.6speedonline.com/forums/...aring-259.html so as not to further disrupt this thread.
I have taken pwdrhound's thread OT again with these questions. I'm sorry. I will be happy to answer questions but please ask them at https://www.6speedonline.com/forums/...aring-259.html so as not to further disrupt this thread.
Last edited by cjv; Nov 13, 2013 at 09:53 PM.
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Look at 3.6L 996tt dyno charts for 600 hp motors (stock cams) from let's say 6800 to 7500 rpm's, how much gain in hp do you see in this range? The torque has long since gone into decline! How would spending any time in this range instead of shifting to the next gear make the car quicker? In lower/mid rpm's torque accelerates. In higher rpm's hp accelerates. With the above described motor there would be no torque gain and very little hp gain above 6800 rpm's. When shifting wouldn't one want to shift at a rpm's level where after the shift (bottom of next gear) one would be near or fast approaching peak torque? It's been awhile but wouldn't that be about 3880-4200 rpm's on a stock cam 996tt? Am I missing something?
My desire for a 7500 rpm redline is not for more power but rather for the flexibility the higher redline affords you in a road course situation when in many cases the extra 500 rpm allows you to stay in gear during certain parts of the track where a gear change would upset the balance of the car. If you can delay a shift and keep accelarating throught those parts of the track than you have shaved some time. An extra 500 rpm may not sound like much but if you can avoid or delay a shift 2 or 3 times during a 2 min lap than you are potentially saving over a second or so. That may not seem like much but it's huge. Having the extra 500 rpms to play with in a road course setting is much more benefitial than having an extra 100hp. As it stands, I really can't utilize full throttle anywhere except the long straight aways at most tracks. Having an engine that is operating at a higher RPM also makes the throttle easier to modulate as the turbos are spooled up. The more technical the track with more turns and less straights, the more a higher redline would be beneficial. Being able to operate at a higher RPM also allows you to use the engine more effectively as a breaking source than if you were in a higher gear / lower RPM situation. If you add all of this up you can see how a higher redline holds tangible benefits.
A lot of my questions and considerations are centered around this. The reason I was considering the GT3 crank is the fact that it is lighter. I figured that may be beneficial in allowing the engine to rev more. However, the more I read the more it seems that the stock 996TT crank is just fine. Maybe knife edge it?? I've also read about guys using a GT3 exhaust cam which I believe is a direct bolt of if I'm not mistaken. Would that be of any benefit?? I don't know. Same with the 3.8 pistons/liners. Benefit of those in my mind would be the ability to run slightly lower boost to attain the same power but at $5K are probably not very cost effective. The GT3 pump as you suggested is definitelly on my list along with the rods. Carillos or Pauter? Which would be better for my goals? I'm assuming ligher rods would be more desirable to allow higher revs. I am also very interested in finding out about the Clevite extreme load bearings you mentioned. I am assuming Clevite is an OEM supplier of bearings on these motors?
Ultimately I'm thinking durability here on a motor that I would like to be able to run hard for at least 100 track hrs between rebuids. My definition of running hard is 30 min sessions where the engine is operated in a racing environment with most shift around the 6800/7000 mark and the occasiasional 7500 shift while running in the black group with GT3s, Cups, and other race prepped vehicles. This is how I operate my car now (obviously minus the ability to shift at 7500) but with over 55 hours of track time on the clock I feel that a rebuild/refresh is somewhere in my future maybe at the end of next season. My limit is a max of 650 crank HP (maybe 550 whp) with a goal of a reliable 7500 redline. I guess I'm trying to ascertain if this is a realistic goal/expectation without resorting to some exotic mega dollar rebuild. I'd like to keep the parts cost around $10K or so. So far my engine is running strong without any issues but I would like to have a plan and parts on hand when the time comes for a rebuild. I hope this clarifies my goals and explains why I'd like a higher redline and such. Again thank you for your continued support and input as I'm open to suggestions. I'd like to chat with you sometime via phone if you'd be up for it. Thx...
Last edited by pwdrhound; Nov 14, 2013 at 02:20 AM.
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Chad,
My desire for a 7500 rpm redline is not for more power but rather for the flexibility the higher redline affords you in a road course situation when in many cases the extra 500 rpm allows you to stay in gear during certain parts of the track where a gear change would upset the balance of the car. If you can delay a shift and keep accelarating throught those parts of the track than you have shaved some time. An extra 500 rpm may not sound like much but if you can avoid or delay a shift 2 or 3 times during a 2 min lap than you are potentially saving over a second or so. That may not seem like much but it's huge. Having the extra 500 rpms to play with in a road course setting is much more benefitial than having an extra 100hp. As it stands, I really can't utilize full throttle anywhere except the long straight aways at most tracks. Having an engine that is operating at a higher RPM also makes the throttle easier to modulate as the turbos are spooled up. The more technical the track with more turns and less straights, the more a higher redline would be beneficial. Being able to operate at a higher RPM also allows you to use the engine more effectively as a breaking source than if you were in a higher gear / lower RPM situation. If you add all of this up you can see how a higher redline holds tangible benefits.
A lot of my questions and considerations are centered around this. The reason I was considering the GT3 crank is the fact that it is lighter. I figured that may be beneficial in allowing the engine to rev more. However, the more I read the more it seems that the stock 996TT crank is just fine. Maybe knife edge it?? I've also read about guys using a GT3 exhaust cam which I believe is a direct bolt of if I'm not mistaken. Would that be of any benefit?? I don't know. Same with the 3.8 pistons/liners. Benefit of those in my mind would be the ability to run slightly lower boost to attain the same power but at $5K are probably not very cost effective. The GT3 pump as you suggested is definitelly on my list along with the rods. Carillos or Pauter? Which would be better for my goals? I'm assuming ligher rods would be more desirable to allow higher revs. I am also very interested in finding out about the Clevite extreme load bearings you mentioned. I am assuming Clevite is an OEM supplier of bearings on these motors?
Ultimately I'm thinking durability here on a motor that I would like to be able to run hard for at least 100 track hrs between rebuids. My definition of running hard is 30 min sessions where the engine is operated in a racing environment with most shift around the 6800/7000 mark and the occasiasional 7500 shift while running in the black group with GT3s, Cups, and other race prepped vehicles. This is how I operate my car now (obviously minus the ability to shift at 7500) but with over 55 hours of track time on the clock I feel that a rebuild/refresh is somewhere in my future maybe at the end of next season. My limit is a max of 650 crank HP (maybe 550 whp) with a goal of a reliable 7500 redline. I guess I'm trying to ascertain if this is a realistic goal/expectation without resorting to some exotic mega dollar rebuild. I'd like to keep the parts cost around $10K or so. So far my engine is running strong without any issues but I would like to have a plan and parts on hand when the time comes for a rebuild. I hope this clarifies my goals and explains why I'd like a higher redline and such. Again thank you for your continued support and input as I'm open to suggestions. I'd like to chat with you sometime via phone if you'd be up for it. Thx...
My desire for a 7500 rpm redline is not for more power but rather for the flexibility the higher redline affords you in a road course situation when in many cases the extra 500 rpm allows you to stay in gear during certain parts of the track where a gear change would upset the balance of the car. If you can delay a shift and keep accelarating throught those parts of the track than you have shaved some time. An extra 500 rpm may not sound like much but if you can avoid or delay a shift 2 or 3 times during a 2 min lap than you are potentially saving over a second or so. That may not seem like much but it's huge. Having the extra 500 rpms to play with in a road course setting is much more benefitial than having an extra 100hp. As it stands, I really can't utilize full throttle anywhere except the long straight aways at most tracks. Having an engine that is operating at a higher RPM also makes the throttle easier to modulate as the turbos are spooled up. The more technical the track with more turns and less straights, the more a higher redline would be beneficial. Being able to operate at a higher RPM also allows you to use the engine more effectively as a breaking source than if you were in a higher gear / lower RPM situation. If you add all of this up you can see how a higher redline holds tangible benefits.
A lot of my questions and considerations are centered around this. The reason I was considering the GT3 crank is the fact that it is lighter. I figured that may be beneficial in allowing the engine to rev more. However, the more I read the more it seems that the stock 996TT crank is just fine. Maybe knife edge it?? I've also read about guys using a GT3 exhaust cam which I believe is a direct bolt of if I'm not mistaken. Would that be of any benefit?? I don't know. Same with the 3.8 pistons/liners. Benefit of those in my mind would be the ability to run slightly lower boost to attain the same power but at $5K are probably not very cost effective. The GT3 pump as you suggested is definitelly on my list along with the rods. Carillos or Pauter? Which would be better for my goals? I'm assuming ligher rods would be more desirable to allow higher revs. I am also very interested in finding out about the Clevite extreme load bearings you mentioned. I am assuming Clevite is an OEM supplier of bearings on these motors?
Ultimately I'm thinking durability here on a motor that I would like to be able to run hard for at least 100 track hrs between rebuids. My definition of running hard is 30 min sessions where the engine is operated in a racing environment with most shift around the 6800/7000 mark and the occasiasional 7500 shift while running in the black group with GT3s, Cups, and other race prepped vehicles. This is how I operate my car now (obviously minus the ability to shift at 7500) but with over 55 hours of track time on the clock I feel that a rebuild/refresh is somewhere in my future maybe at the end of next season. My limit is a max of 650 crank HP (maybe 550 whp) with a goal of a reliable 7500 redline. I guess I'm trying to ascertain if this is a realistic goal/expectation without resorting to some exotic mega dollar rebuild. I'd like to keep the parts cost around $10K or so. So far my engine is running strong without any issues but I would like to have a plan and parts on hand when the time comes for a rebuild. I hope this clarifies my goals and explains why I'd like a higher redline and such. Again thank you for your continued support and input as I'm open to suggestions. I'd like to chat with you sometime via phone if you'd be up for it. Thx...
If you have any change left over have the case fitted with larger oil squirters. Probably a $1,000.00 add but motor will lubricate better and allow heat to be removed easier.
If you would like to talk send me a contact number via private message.
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My choice would be to keep the existing crank (forget knife edging the stock crank) and get the better bearing. The Carillo rods are lighter, lose some weight there and don't forget about the lighter harmonic balancer. I believe BBI has a good one and the are not very expensive. I really like the 3.8L for reliability and options. More power, same power less boost and the ability to run on pump gas. The GT3 oil pump is a must.
If you have any change left over have the case fitted with larger oil squirters. Probably a $1,000.00 add but motor will lubricate better and allow heat to be removed easier.
If you would like to talk send me a contact number via private message.
If you have any change left over have the case fitted with larger oil squirters. Probably a $1,000.00 add but motor will lubricate better and allow heat to be removed easier.
If you would like to talk send me a contact number via private message.
Carillo rods
3.8L pistons/liners
Ligher harmonic balancer
GT3 oil pump
Better crankshaft bearings
Larger oil squirters
My car already has the updated 997 lifters that were installed last year. I am assuming a GT3 exhaust cam is of no benefit for my application? PM sent with my contact info.
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Excellent. Thank you. I think I'm getting somewhere now. So I think I'm going to stick with stock crank and go with:
Carillo rods
3.8L pistons/liners
Ligher harmonic balancer
GT3 oil pump
Better crankshaft bearings
Larger oil squirters
My car already has the updated 997 lifters that were installed last year. I am assuming a GT3 exhaust cam is of no benefit for my application? PM sent with my contact info.
Carillo rods
3.8L pistons/liners
Ligher harmonic balancer
GT3 oil pump
Better crankshaft bearings
Larger oil squirters
My car already has the updated 997 lifters that were installed last year. I am assuming a GT3 exhaust cam is of no benefit for my application? PM sent with my contact info.
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One more question. Has anyone during a rebuild upgraded the IMS shaft to the GT3 version which is one piece as opposed to the two piece Turbo version? Is that a simple swap while the engine is out and worth doing?
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My choice would be to keep the existing crank (forget knife edging the stock crank) and get the better bearing. The Carillo rods are lighter, lose some weight there and don't forget about the lighter harmonic balancer. I believe BBI has a good one and the are not very expensive. I really like the 3.8L for reliability and options. More power, same power less boost and the ability to run on pump gas. The GT3 oil pump is a must.
If you have any change left over have the case fitted with larger oil squirters. Probably a $1,000.00 add but motor will lubricate better and allow heat to be removed easier.
If you would like to talk send me a contact number via private message.
If you have any change left over have the case fitted with larger oil squirters. Probably a $1,000.00 add but motor will lubricate better and allow heat to be removed easier.
If you would like to talk send me a contact number via private message.
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I could be wrong so don't quote me but per my conversation with cvj, I believe he said the turbo crank is cast or something along those lines and as such material should not be removed from it. The gt3 crank is forged.
Last edited by pwdrhound; Nov 15, 2013 at 06:05 AM.
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You can. I do not. You would need the latest 997 cup ims, it has the female side of the turbo scavenge pump. The cup uses that pump instead of the two pumps off the cams to scavenge the heads.
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The 996TT and GT3 (same with the GT3 Cup/ GT3R) all use a similar crankshaft (material).
Differences I am aware of are, looking at journals, the GT3 rod journal is smaller vs. thinner (narrower), The rod is 53 mm at the crank and 22mm wrist pin. I believe the width of the journal is 25 mm.
The 996tt has a 55mm journal at the crank and a 23mm wrist pin. So the rod journal diameter is larger than the GT3 crank.
The GT3 crank has wider journals but narrower diameter journal. Probably to reduce reciprocating mass on the high revving GT3.
Another difference in the cranks is internal oil circuits. The 996tt lubricates every 360 degrees while the GT3 lubricates every 180 degrees.
I believe the 996tt crank was used in the racing GT1. I believe these cars base produced 600 hp. .
Last edited by cjv; Nov 15, 2013 at 09:20 AM.