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Fuel vs alcohol

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V6POWER

Senior Member
Joined
May 24, 2001
Messages
2,966
Is it better to use more 93 octane to quench knock or should I turn up the alcohol to quench knock? Right now I am running 41# static fp with alcohol pump on max and 23-24# boost with less than 2* knock on shift. Would I see any gain going to higher fp and lower pump speed? I am running the SMC single nozzle with 100% denatured + MMO.
 
Well if you richen the car, it will knock less but at the expense of making power.

Your options are go to a dual nozzle whereby you can increase the alky volume into the motor, or add octane to your gasoline. when I had my SMC, I ran 11.9's with the kit..on the edge of getting KR. Add some xylene to the tank.. car would go 11.6's on the alky+93. I then made the current setup using the larger pump.. no more xylene ;) So I know what your experiencing first hand.

You want to run the car lean to make power, you only want to run enough alcohol to get rid of the detonation, and you want to run as much timing as you can to make the most power. Figure these three out..car will fly.

HTH
 
Thanks Razor. I've gotten the 11.9 using just 93 + alcohol. Even if I added the xylene I won't see the 11.6 because of traction limitations. :( I will experiment with using more 93 and less alcohol and see what happens. Then I will have to see about adding timing.

When you were using the SMC kit, what were your static fp, alcohol pump speed and timing?
 
FP will be chip dependant. Typically on most chips I run 41-43 line off.

Timing was 20 degrees WOT

Pump speed10 on the SMC controller.

Temps here are pretty hot, the fact I was running a stock IC didnt help.. so pumping in higher volumes of alky..dropped the KR from squeezing the boost up. get the MPH up..the ET will fall..always does. Raising FP will lessen the knock, but slow the car down... sometimes :D
 
Thanks for the very definitive answer. :D
I know, each car is different and we just have to find the correct tune for our car. I will play around with fp and pump speed and see what runs best with an EGT in the 1620-1650 area which seems to be the best for my car.
 
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