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CR with E85 on boost?

Posted: Thu Mar 22, 2007 10:32 pm
by SWR
As the meth cars run high CR's with big boost on top, (I searched and found a 1.8-liter Honda running 13.8:1 with 35lbs. on top), I'm now wondering if a higher CR would be benefical on an ethanol fueled car running up to about 25psi?

Ethanol is technically alcohol and has a serious cooling ability,just like methanol,so given that E85 likes about 8:1 AFR (Meth 5:1(?) and gas 12:5.1) would a CR in-between the low 7:1 for gas and the high 13+:1 for meth be benefical? Like 10:1 or so?

Opinions welcome...verbal bashing is not. (I've had a hard day) :)

Posted: Fri Mar 23, 2007 8:42 am
by Doug Schriefer
E85 runs about a 9:1 AFR. With the extra cooling benefit, increasing the compression will help produce more power as long as you don't exceed the capability of the 105 (+/-) octane.

Posted: Fri Mar 23, 2007 11:40 am
by Stevespeed
Need to know the application. For say drag only you could stay lower in the static compression and take better advantage of cylinder filling with more boost. But for a street car, increasing the static compression will limit the amount of boost but provide major benefits in driveability.

Posted: Fri Mar 23, 2007 1:19 pm
by SWR
It's a street/strip Volvo 850,with bias to street use,I reckon 80% so. Being a 600hp+ FWD drivability is an issue... And,we're trying to get the most hp with the least boost,so we'll try to stay below 22 psi... The "norm" here is (for gas) 8:1 or less and 30+ psi boost,we're trying to go for higher static CR due to fairly long cams (high rpm) and restrict the boost somewhat. I'm just curious if close to 10:1 would be considered high with regard to the fuel. I know 10:1 on gas with boost on top is pushing it,but I'm not sure how the ethanol reacts..

Posted: Mon Mar 26, 2007 2:32 pm
by SWR
Just gettin' to the top... :wink: ...still looking for info.

Posted: Tue Mar 27, 2007 1:00 am
by Stevespeed
I think 10:1 would be a good place to start. Maybe try to monitor for detonation with something like a J&S Electronics unit.

Re: CR with E85 on boost?

Posted: Fri Jul 31, 2020 3:46 pm
by pdq67
I'm sorry, another way old thread.


Re: CR with E85 on boost?

Posted: Fri Jul 31, 2020 11:12 pm
by Orr89rocz
Seen 11-11.5:1 work ok. Most run 10.5-11 ish.

Lsx 10.8:1 with 30 lbs boost went 7.17 at 197 at 3280 lbs

My bbc is 10:1 on 19psi so far its Around 1600 whp

Re: CR with E85 on boost?

Posted: Sat Aug 01, 2020 9:23 am
by jed
What happened to SWR???
I always enjoyed reading his posts.