EVO Compression Chamber
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EVO Combustion Chamber
Compared to the STi, the evo can run much more boost on the same octane with a higher compression (8.2:1 compared to 8.8:1).
Why?
Why?
Last edited by Austin_; Aug 21, 2003 at 11:10 AM.
I wouldn't go that far. They're both very good engines. The STi motor uses less boost but more displacement. The boxer 4 also can't make as much power and pass emissions because the cat has to be so far downstream from the manifold. The light off time for the cat is much longer on the STi. If emissions were not a consideration it could make as much power as the 4G63.
Honestly you can't go wrong with either car.
Honestly you can't go wrong with either car.
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From: Riverview, FL
Originally posted by IzenGreyEvo7
I wouldn't go that far. They're both very good engines. The STi motor uses less boost but more displacement. The boxer 4 also can't make as much power and pass emissions because the cat has to be so far downstream from the manifold. The light off time for the cat is much longer on the STi. If emissions were not a consideration it could make as much power as the 4G63.
Honestly you can't go wrong with either car.
I wouldn't go that far. They're both very good engines. The STi motor uses less boost but more displacement. The boxer 4 also can't make as much power and pass emissions because the cat has to be so far downstream from the manifold. The light off time for the cat is much longer on the STi. If emissions were not a consideration it could make as much power as the 4G63.
Honestly you can't go wrong with either car.
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From: Riverview, FL
Originally posted by IzenGreyEvo7
Yeah the whole detonation issue must be very embarrasing for Subaru. I'd still wouldn't turn one down though.
Yeah the whole detonation issue must be very embarrasing for Subaru. I'd still wouldn't turn one down though.
I have an EVIL BLACK EVO, though...
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Re: EVO Combustion Chamber
Originally posted by Austin
Compared to the STi, the evo can run much more boost on the same octane with a higher compression (8.2:1 compared to 8.8:1).
Why?
Compared to the STi, the evo can run much more boost on the same octane with a higher compression (8.2:1 compared to 8.8:1).
Why?
Here are my thoughts.
EJ25 or EJ20 have poor intake flow, and the fuel rails systems does not flow equal fuel to the injectors.
Now here is the the really problem the Exhaust pluming is long and the uppipe to the turbo is about 1in away from the number 3 cyl. That number 3 cyl runs lean and you can get to 20psi of boost on 93 oct on a wrx. but you need to mod the hell out of it to do it.
Rails
Inj
FMIC
EM
Bigger turbo
and so on.
Now also you have to understand with the TMIC as the car goes fast the less air inters the hood scoop so you have to tapper boost at higher RPM for it to work. At 24lb of boost on a Stock WRX the valves start to open.
Now see in stock form the WRX motor is weeker (IMHO) but Fully built (sleaved and closed deck) could make as much or even more power at the same displacment as the 4g63 IMHO.
WRX motors are harder to tune and are knock prone because of un-equal fuel delivery and heat transfer.
One other thing when tuning WRXs I have never seen a leaner A/F then 11.2 with out knock on pump gas. With the EVO I have seen 12/1 on pump gas and no knock. (WRXs love gas and plent of it). And they still make power runing so rich that's the up side!
My Best
Eris
Couple things that I would think contribute to detonation in the sti.
1. Top mount intercooler. First thing 2ndgen rx7 turbo guys would do is go to a front mount cause it cuts down on heat soak problems which can lead to detonation if the ecu is not looking at intake temps close enough.
2. Too much ignition advance. If the ecu is running the timing up too far.
3. Running too lean
Not sure how a timing issue would get through Q.C. unless maybee they had to crank it up to get it to pass emmissions or something which could be the case if the intake setup does not create an uniform air/fuel distribution for each cylinder, as in the fuel does not get mixed with the air well enough to give a uniform burn in each cylinder.
Oh and what the last guy just said too.
1. Top mount intercooler. First thing 2ndgen rx7 turbo guys would do is go to a front mount cause it cuts down on heat soak problems which can lead to detonation if the ecu is not looking at intake temps close enough.
2. Too much ignition advance. If the ecu is running the timing up too far.
3. Running too lean
Not sure how a timing issue would get through Q.C. unless maybee they had to crank it up to get it to pass emmissions or something which could be the case if the intake setup does not create an uniform air/fuel distribution for each cylinder, as in the fuel does not get mixed with the air well enough to give a uniform burn in each cylinder.
Oh and what the last guy just said too.
Last edited by Mad_SB; Aug 22, 2003 at 01:53 PM.
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From: Nothern CA
As far as the opposed design is concerned, Turbo Porche Carreras have done well and believe me the old EMPI VW inch pinchers would make my Vette sweat. The WRX Subarus do well too but the sti seems to be an exception. Vishnu has run these cars in a shop with fans to ensure proper cooling and the knock threshold is still embarrassingly low. Perhaps the cylinder head on the 2.5 just isn't a great design or as some of you suggest, maybe it just isn't tunned well. Aren't you glad you have an Evo?