My GT2 vs Peter's 3.8L monster
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are you speaking of ignition advance? or cam advance? 
I think you are speaking of cam advance which although relevent, doesn't play into our scenario here
The cam home signal might be different between the two forcing you to use a GT3 trigger pattern(hence a reprogram). If there are multiple cam/home triggers because of the variable timing, I can see the need for a change in tuning. This part I am not 100% sure on as I have not set up a TT with GT3 cams yet. I can research it though. Due to the design of the 996TT cams, I would think that there is a physical limitation limiting you to the 30 degrees maximum. With enough time, you can reprogram the DME to do whatever you want(even activate your brake lights over 100mph ) It just involves adding some additional code. With that known, it must be a physical limitation of the cams or actuator.
Justin.
I think you are speaking of cam advance which although relevent, doesn't play into our scenario here
The cam home signal might be different between the two forcing you to use a GT3 trigger pattern(hence a reprogram). If there are multiple cam/home triggers because of the variable timing, I can see the need for a change in tuning. This part I am not 100% sure on as I have not set up a TT with GT3 cams yet. I can research it though. Due to the design of the 996TT cams, I would think that there is a physical limitation limiting you to the 30 degrees maximum. With enough time, you can reprogram the DME to do whatever you want(even activate your brake lights over 100mph ) It just involves adding some additional code. With that known, it must be a physical limitation of the cams or actuator.Justin.
We are running modified GT3 Street sync'ed cams. So are a few others on this board though don't know if the profiles were re designed. The cams on the 996tt are variable lift and timing. The cams on the GT3 Street is variable timing only. The cams on the Cup and RSR have only one sync or cam pointer and do not have variable lift or timing. Some have reground 996tt cams and eliminated the variable lift and installed GT3 cam sync's (very difficult to do). The actuator on the respective build's is the limitation for the timing.
Last edited by cjv; Sep 1, 2010 at 03:10 PM.
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Preignition is result of a hot spot (carbon, etc.) in the combustion chamber that leads to the fuel/air mixture lighting off some time other than when the spark plug fires...not good. Detonation is when the fuel/air mixture explodes and this is where cylinder pressures go through the roof and cause havic and eventual damage to your engine....double no good. If I'm understanding your question Justin (doubtful) I'd say it's a trick question because these, preignition and detonation, are both unintentionally consequances meaning they could happen at varying times semi-independent of the timing map and are more closely related to improper AFRs (fueling).
Detonation is caused when two waves of ignition collide. One wave originates from your plug. Although the causes you mentioned can cause the other wave to start .... this isn't usually the case with our motors. The culprit is usually directly related to the top ring on your piston not being capable of removing generated heat (through the liners quick enough) and reaching temperatures hot enough to ignite fuel in the area located at the top of the piston ring, liner and the top of the piston. When it ignites the fuel, this second wave travels toward the center of the piston dome and when the two waves meet you have what we refer to as detonation.
There are tricks to keep the piston, top piston ring and liner cooler that help prevent this from happening.
Last edited by cjv; Sep 1, 2010 at 04:38 PM.
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I'm happy with a kinda Justin. It's always worked for me with my girlfriend, "Did that feel good, are you happy, do you like this." Kinda................good enough for me lol.
Thanks for the info CJV and Justin. I always enjoy learning more about stuff unless it's related to purses, shoes or shopping.
Thanks for the info CJV and Justin. I always enjoy learning more about stuff unless it's related to purses, shoes or shopping.
I hate you all more every day. Completely off topic but to bring back up my rep I came across this vid of a car I'm looking at!
http://www.youtube.com/watch?v=Fu_tpwJgjQ0
http://www.youtube.com/watch?v=Fu_tpwJgjQ0
I hate you all more every day. Completely off topic but to bring back up my rep I came across this vid of a car I'm looking at!
http://www.youtube.com/watch?v=Fu_tpwJgjQ0
http://www.youtube.com/watch?v=Fu_tpwJgjQ0
Yu looking to buy that??? i don't believe it for a second!
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there are many small upgrades you can do, modify the oiling in the crankshaft as this is the cause of alot of failures chamfer the oil holes and cross drill or add second oiling hole to the #2 rod specifically, Boat tailing of the crankcase webs, New oil pump GT3 has a second pickup is couple hundred more then 996tt pump.
some are usging the Motorsports bearings rather then the oem porsche bearings.(actually they are cheaper)
shuffle pin the crank case halves.
none of these are expensive in themselves but you add them all up and it shoots the cost up quickly.
head gasket has 3 camps
Stock studs stock gasket some over torque stock studs
aftermarket Studs and MLS gaskets
Head O ring/flame ring
there are other things but this alone with rods quickly adds up to 8k over top of standard build costs
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Different tuners have different thoguhts on this: EVOMS and BBi obviously prefer large head studs. Switzer and TPC don't believe in them at all. Protomotive does builds with both, based on what the customer wants.
There are stock cars running larger turbos than mine (and making more power) on stock heads studs at 1.9 BAR without issues. My head studs, while stock, have been overtorqued beyond factory spec.
Considering all of that; I'm honestly not worried about running 1.8 BAR at all.
There are stock cars running larger turbos than mine (and making more power) on stock heads studs at 1.9 BAR without issues. My head studs, while stock, have been overtorqued beyond factory spec.
Considering all of that; I'm honestly not worried about running 1.8 BAR at all.
Robert
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Throwing in my 2 cents on head studs, if you have a good tune then I think you can run safely two bars without going to larger head studs. In my car, I have 8mm APR studs and I have hit 39 pounds of boost on these studs. Not saying that they will last at these levels; however, I have been running my 3.8 liter since 2007 and three years later at two bars and the heads never lifted. They did show signs of lift at 39 pounds so I will be looking at doing 12 mm HS. I hope this helps and thanks Scott for sharing your wealth of knowedge.
Robert
Robert
alot of the head stud issues relate to how they are secured in the block and how they are torqued (design of the head/nut washer)
when you torque down the larger studs you get deformation of the cylidner head casing around the stud one person came up with a fix (an old porsche idea recycled) another company copied it.
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Yes, But the AFR were way off! I am upgrading to 100 pound injectors and a few other goodies and then we will try it again but this time I think we will do it in Arkansas with the mad magician.
Robert
Robert
