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View Full Version : AFR Why 11 and not 12.2?272 cams Passed Sniffer



mygsx
10-14-2005, 06:50 PM
I know from before afr of 12.0's were supposedly the "optimum" range?Maybe this has been answered before but we need to be at 11.0 afr's is it possibly due to the California octane 91 we have?Enlightenment please :rally:

Side note:I spoke to Bo@SRM performance today and a car they had in had some head work with 272 cams put in on the sniffer.The results were Passing with flying colors. So all you evo's out there with 272's can breath a little better 8)

wilson1
10-14-2005, 09:12 PM
sounds wonderful! :D

earlyapex
10-14-2005, 10:35 PM
You know from before 12.0 AFR is ok? What was before? NA?

You could maybe do 12.0 if you have perfect 91 octane and you know 150% that you will get that exact gas every time.

For safety, I would tune for 11.5 and below on california 91 octane. 100 octane is a whole nother ballgame. :)

mygsx
10-15-2005, 06:00 PM
Oh.......... ok thanks for the info so its really has to do with the octane rating level huh,Sucks to be us Ca octane users. :shock:

EvoVIII
10-16-2005, 08:59 AM
so the higher the better?

mygsx
10-16-2005, 12:17 PM
I guess so :D

earlyapex
10-16-2005, 12:55 PM
so the higher the better?

The higher what the better? Octane? Yes, AFR, no.

bdking57
10-19-2005, 03:58 PM
I only had my car tuned to 11.1 for safety purpose at autox.. I just wanted the added security of bouncing of the rev limiter on 91 octane and not worrying about it.. but i think its running a little to rich and im gonna have a second leaner map dialed in at 11.5 or higher... I would run some 100octane mixed in with that map, and it would be good for just driving around because my car burns the hell out of my eyes as it is now.

TylerO@WORKS
10-20-2005, 10:01 AM
Best power without knock is seen at around 12-12.5 AFR on most turbocharged cars, with perfect gas and good intake air temps. That however leaves no room for safety.

A richer AFR of 11-11.8 AFR provides a good margin of safty and protects you from a bad tank of gas, hot intake temps, and heatsoak... all the kinds of things you will run into with a street car. All this while only loosing a few % power.

earlyapex
10-20-2005, 01:02 PM
Best power without knock is seen at around 12-12.5 AFR on most turbocharged cars, with perfect gas and good intake air temps. That however leaves no room for safety.

A richer AFR of 11-11.8 AFR provides a good margin of safty and protects you from a bad tank of gas, hot intake temps, and heatsoak... all the kinds of things you will run into with a street car. All this while only loosing a few % power.

I agree with this, however, I would emphasize the second paragraph much more about 11 AFR.

12-12.5 AFR is better left to 100octane and above if you want your motor to last.