Tuning with race gas

[survyor2]

I searched this topic because I thought this would have been a topic covered many times but I'm not having much luck. And the information that I do find is conflicting.

On 93 oct: 7mgte, 440rwhp, 18psi, lexus afm, 550cc, .70 a/r SP61 turbo i shoot for 11.7afr at max psi.

I'm on 110oct leaded now.
What psi is my safe max psi? 24-25?
What afr should I shoot for? I've read: same as 93oct, then 12.0, 12.2, 12.5. I want to get this right.

Thanks,
Dennis

 

[suprahero]

I've never heard of anyone on a boosted car shooting for 12.5... When I use race gas, I still shoot for mid elevens and I ran 24psi on 110 with no problems. I don't know of any set boost levels per octane though since different turbos put out different amounts of air.

Disclaimer: I'm not very smart and I don't pretend to be. This is just what I've done in the past. Good luck.

 

[rumptis]

Disclaimer: I'm not very smart and I don't pretend to be. This is just what I've done in the past. Good luck.

Understatement of the year ^

Funny stuff Jay....at least you are humble.

Thanks for making me laugh!

 

[Fletch124]

I searched this topic because I thought this would have been a topic covered many times but I'm not having much luck. And the information that I do find is conflicting.

On 93 oct: 7mgte, 440rwhp, 18psi, lexus afm, 550cc, .70 a/r SP61 turbo i shoot for 11.7afr at max psi.

I'm on 110oct leaded now.
What psi is my safe max psi? 24-25?
What afr should I shoot for? I've read: same as 93oct, then 12.0, 12.2, 12.5. I want to get this right.

Thanks,
Dennis

First off it will be difficult to get to 24psi on a lex afm and 550s.

 

[suprafanatic]

oh it can be done!! lol.. i hit 30psi one time on accident.. i dont recomend that

 

[survyor2]

I tuned with the 110oct today and here is what I found out.

I hit fuel cut at 24 psi. I backed it off to 23.5 psi and didn't have any issues.

Most of what I read told me to tune for 12.2-12.5 afr. I made an executive decision and set a goal for 12.3 afr while monitoring egts. My max egt is actual 5 degrees cooler at 12.3afr at 23.5psi on 110oct than 11.7afr at 18.5 psi on 93oct.

I was thinking of going with the FCD i have but its not worth it for an extra 1.5psi.

I think I could have run even leaner but I can't control my timing. So there you have it...lower egt with +5psi on race gas. Dyno next weekend to see what I picked up. Maybe I'll hit 500rwhp.

Dennis

 

[IJ.]

Dennis: Biggest benefit with good fuel is knock resistance, this will allow either more boost or more timing or a combination of both if you run out of boost room like you have.

 

[survyor2]

Very true IJ. And a/f ratios have alot to do with knock.

Those who believe in runing 11.* a/f on race fuel, I'm curious what you think of this article:

http://www.innovatemotorsports.com/resources/rich.php

Dennis

 

[IJ.]

I'd tune to the first signs of rattle on the electric ears then back it down 2 degrees and 2psi to keep it safe Dennis.

Every combination is different there's no xx psi for xx octane.