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Old 09-06-2007, 05:32 PM   #1
Ralliart4
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Location: San AntonioTX/kingston Jamaica
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2002 Impreza WRX RA
PSM

Default High compression 2.0

After seeing the FIA regulation capping the allowed compression ratio for the WRC spec cars i was hit by a moment of inspiration.

How practical is it to do a high compression built block from a ej205?

I have had some good results with the KA24de motor turbocharged and that is by turbo talk fairly high compression being in the mid 9.5 to 9.8:1 area.

Do any of you guys have any ideas or pointers? Rally guys please your input is most appreciated.
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Old 09-06-2007, 08:26 PM   #2
radve
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Default High Compression

I am running my rally engine at 9.45 :1 fitted with a 34mm restrictor on a development turbo as we have found that the exhaust gas back pressure was critical to prevent det and yet keep the low end response ,we have just installed egr type als
We run Sunoco 104 race fuel and 1.85 bar [email protected] 1.1 bar @5900 rpm
The two most critical things we found in preventing det is exhaust gas back pressure and piston crown design
Having ran most of this season in this spec we are looking to increase the comp ratio to around 9.6:1 next season
However this engine is using a closed deck block and special headstuds ,I have not run a ej205 block to those sort of cylinder pressures I think that may be a problem if you are looking to run above 1.5 bar boost

Last edited by radve; 09-06-2007 at 08:32 PM.
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Old 09-06-2007, 09:28 PM   #3
poormansporsche
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Default

I think 9:1 would be the best bet on a EJ20G block Closed desk of course. I dunno about an EJ205. I'm sure it'd take it for a while anyway. Depends on the tune. You'll have to run really high octane gas and probably water injection to prevent det.

cheers

poorman
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Old 09-06-2007, 09:34 PM   #4
Ralliart4
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Quote:
Originally Posted by radve View Post
I am running my rally engine at 9.45 :1 fitted with a 34mm restrictor on a development turbo as we have found that the exhaust gas back pressure was critical to prevent det and yet keep the low end response ,we have just installed egr type als
We run Sunoco 104 race fuel and 1.85 bar [email protected] 1.1 bar @5900 rpm
The two most critical things we found in preventing det is exhaust gas back pressure and piston crown design
Having ran most of this season in this spec we are looking to increase the comp ratio to around 9.6:1 next season
However this engine is using a closed deck block and special headstuds ,I have not run a ej205 block to those sort of cylinder pressures I think that may be a problem if you are looking to run above 1.5 bar boost
Thank you very much for your input. Can I get some more info about your setup either here or by pm?

- Do you think if the car was unrestricted that the exhaust pressure would still be that significant of a problem.
- I probably will not run the car past 1.5bar
- Did this setup require a custom piston or was there an off the shelf product that is available in the US at a reasonable price.
- Have you had more success with the EGR type ALS vs. the usual throttle/ignition stand alone setup?
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Old 09-06-2007, 10:02 PM   #5
radve
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Default high compression

No problem please pm for further specs

Exhaust gas back pressure becomes less of a problem on non restricted engines due to the fact that you can move the power up the rev range allowing larger turbine sizes
If you dont have to run a restrictor ,we have found no real advantage to running above 9.0:1 cr also cp do a off the shelf piston that will acheive 9.0:1 when used with the thin headgaskets as cylinder charging at higher rpm is no longer a problem
What ambient /and charge temps do you run ? looking at your location water /met injection might be a good idea
The egr als is still under development as we are testing a new management system with better controls but egts are lower and we can definately achieve more boost
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