2.0 or 2.3 for highway runs?
#61
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Originally Posted by Ted B
This is a misconception, and is incorrect. Compression is not a substitute for boost. Increasing boost increases the air mass being processed by the engine. Greater air mass = greater power. Increasing compression does not increase air mass, only how hard the mixture is being squeezed. An increase in compression by one full point (e.g. 9:1 to 10:1) typically increases off boost torque by ~5%, but the tradeoff in the reduced boost pressure the higher compression motor can tolerate creates a much larger reduction in power potential.
Slowboy recently tested a bunch of different turbos on the same motor. They started the testing with a 10/1 compression block. They tested a couple of turbos. Then they got quite a few complaints from people saying that most people would be using the turbos on lower compression setups. So they ditched the 10/1 block for a 8.3/1 compression shortblock. Then they started the turbo testing again.
57 trim turbo with 10/1
15psi 345/309
20psi401/378
27psi 459/???
57trim with 8.3/1
15psi 290/245
20psi 325/320
25psi 361/361
Reported spool difference between the two compressions was 200rpm faster with the 10/1 block.
before John Sheppard switched to alky he ran 11/1 2.0 at 56psi boost. Don't know what compression he switched to for alky but he sold off his spare 11/1 pistons at the time of the swap to alky. Local race team here in tampa has a supra motor running 14/1 on alky. A friend of mine helps out with the car and says he has seen them make passes as high as 71psi boost.
The reasons people have better results with more reasonable compression 8.5-9.0 is because it is easier to map the timing. Especially when the factory maps are based off 8.8/1. Mapping a high compression turbo engine is not easy. But the rewards are there. Porshes turbo 911 has been 9.4/1 from the factory for a few years now.
Last edited by 94AWDcoupe; Jun 16, 2006 at 10:20 PM.
#62
EvoM Guru
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Originally Posted by Blue Evo 8
How much is enough power?
One thing to consider about this swap is your speedo will likely be reading too low by 10%, so one might want to check to the availability of a speedo gear (?) that compensates for the difference in the final drive gearing.
#63
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Originally Posted by 94AWDcoupe
Slowboy recently tested a bunch of different turbos on the same motor. They started the testing with a 10/1 compression block. They tested a couple of turbos. . . . [/i]
Originally Posted by 94AWDcoupe
Before John Sheppard switched to alky he ran 11/1 2.0 at 56psi boost. . . . The reasons people have better results with more reasonable compression 8.5-9.0 is because it is easier to map the timing. Especially when the factory maps are based off 8.8/1. Mapping a high compression turbo engine is not easy. But the rewards are there. Porshes turbo 911 has been 9.4/1 from the factory for a few years now.
I agree completely that assuming competent piston/head design and tuning, a higher compression engine improves evacuation and spool characteristics, but there are tradeoffs, and hence the reason why turbo street engines are most often designed around 8-9:1 CR. As for Porsche, the 9.4:1 CR of that turbo 911 is probably intended to improve spool characteristics with a turbo large enough to produce considerable power (although its power curve shows that it does only very briefly), and it does not appear to offer anywhere near the potential to run a boost pressure of 30-35 psi that has proven possible over the long term with 8.5-8.8:1 EVOs. In fact, that turbo Porsche runs only 1 bar (~15psi), and does so for just a few hundred rpm.
Last edited by Ted B; Jun 17, 2006 at 04:07 PM.
#66
Evolved Member
!!!
A 2.1L is a 4G64 block with 4G63 Crank,Long Rod,Overbore piston.That what Curt Brown use to run 10.5@127MPH on stock turbo and 600whp(BR nightmare dyno) on GT35R(No nitrous).He will hit the track tommorow.
Originally Posted by Derek888
wow I didnt know a 2.1 can rev up to 10k safely.
#67
EvoM Guru
iTrader: (6)
Originally Posted by Derek888
wow I didnt know a 2.1 can rev up to 10k safely.
Revving any configuration to 10k rpm is a great way to break parts in such a manner that repair requires at least a new crankshaft and/or block, much less replacement rod(s) and piston(s), as one forum member recently discovered after a few trips to 10k rpm with a built shortblock.
Want to rev it to 10k? Be prepared to rebuild/replace it during or after a season of racing. Want to drive it daily on the street? Forget 10k rpm.
#68
Evolved Member
iTrader: (40)
Originally Posted by Ted B
Don't bet on it!
Revving any configuration to 10k rpm is a great way to break parts in such a manner that repair requires at least a new crankshaft and/or block, much less replacement rod(s) and piston(s), as one forum member recently discovered after a few trips to 10k rpm with a built shortblock.
Want to rev it to 10k? Be prepared to rebuild/replace it during or after a season of racing. Want to drive it daily on the street? Forget 10k rpm.
Revving any configuration to 10k rpm is a great way to break parts in such a manner that repair requires at least a new crankshaft and/or block, much less replacement rod(s) and piston(s), as one forum member recently discovered after a few trips to 10k rpm with a built shortblock.
Want to rev it to 10k? Be prepared to rebuild/replace it during or after a season of racing. Want to drive it daily on the street? Forget 10k rpm.
I'd guess 8500 RPM limit for a daily driven 2.1L would be good enough?
#69
EvoM Guru
iTrader: (6)
That should be sufficient for any GT35R application, and is a much safer limit than 10k rpm. There is NO reason to rev even a 2.0L to 10k rpm unless one has a turbo larger than a GT35R and a power curve to support it.
Those who dream of revving to 10k rpm for no justifiable reason other than the fact that they think it's cool just end up fulfilling the age old adage about a fool and his money . . .
Those who dream of revving to 10k rpm for no justifiable reason other than the fact that they think it's cool just end up fulfilling the age old adage about a fool and his money . . .
#71
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Originally Posted by Ang Wen Yan
!!!
A 2.1L is a 4G64 block with 4G63 Crank,Long Rod,Overbore piston.That what Curt Brown use to run 10.5@127MPH on stock turbo and 600whp(BR nightmare dyno) on GT35R(No nitrous).He will hit the track tommorow.
A 2.1L is a 4G64 block with 4G63 Crank,Long Rod,Overbore piston.That what Curt Brown use to run 10.5@127MPH on stock turbo and 600whp(BR nightmare dyno) on GT35R(No nitrous).He will hit the track tommorow.
holy crap!!! 10.5 on the stock turbo?!?!?!? was he sprayin???
#72
Evolved Member
Originally Posted by Rcebowl
holy crap!!! 10.5 on the stock turbo?!?!?!? was he sprayin???
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