air/fuel ratio question!!??

[paco]

I got my s-afc installed yesterday!! Everything seems to be fine I gained 6 hp in the 3000-5000 rpm range and 10 hp in the 5000 up rpm range. Anyways, the question is my a/f ratio was at 12.5-12.8 and they left it at 13.2-13.8, is this good?????

[paco]

I have been reading in other posts and everybody says that the a/f ratio has to be 14.5 or that is the best anyhow. So the fact that I am at 13.2-13.8 is not good??? Is something gonna happen to my car if I keep driving it like this???

[Auto-9]

Eh I dunno if something is going to happen but you're running a bit rich. Not as rich as when I'm at WOT though...at that point my car is at 10.2:1 but it idles at 14.7:1 (optimal is what I hear).

[manybrews]

thats a bit rich unless your at WOT.

it should be about 14.7 to 1 during normal cruise.

[paco]

MAN!! I'm all confused now. I thought mid or high 13s was lean and that 12s was rich. Can somebody please explain.

[HeadAche]

<div class='quotetop'>QUOTE(paco)</div><div class='quotemain'>MAN!! I'm all confused now. Â*I thought mid or high 13s was lean and that 12s was rich. Can somebody please explain. </div>

Your fine dont worry to much about it.. Your safe at 13.2-13.5 if the AFC starts to rise to 14 then you are going to have to turn it back down. my car runs rich just about all the time, thats only because of the internal mods, if i leaned it out, i would lose tons of power threw the band.. I personally wouldnt change the settings..

[manybrews]

the perfect fuel ratio is 14.7 to one. Thats gas' stoichiometric ratio, in which (theoretically) all the fuel will be consumed with all the air.

anything over that (15.0 and up) is lean.

anything under that (14.0 and down) is rich.

generally, a rich ratio is only used on a cold start to aid in starting, and WOT to make sure that 100 percent of the air is used. Running rich also adds a quenching effect to the charge, thereby cooling it. So rich running can prevent detonation.

However, with todays wonderful fuel managment, its not really necessary to run it REALLY rich, like in the good old days. A 13 to 1 ratio is pretty much the norm, whereas a 10 to one would have been the norm in 1971.

[DJ Galant]

Here is what I know, what i learned from professional dyno technicians.
They know their shit about the air /fuel ratio issues.
Chemicaly perfect condition used for best burn of fuel is at 14.7:1 (stoichmetric condition) .
Best performance is at about (12.6:1 toabout 12.8:1) afr. Here is where you potentaialy are making maximum of your hp numbers....
Best fuel economy is at about 15.8:1. (though you can except anything from 5 to 10% lose of power).
Hell of rich, (lost of power about 5%) anything below 10:6:1.
Lean condition, safe, but kind of pushing it is at 16.2:1 (lost of power about 15 %)
Lean condition , ussualy causing detonation starts at 16.7:1. Here is where you defeniatly don't want to go - not only that you loose about 25% of ypour ptentaial max power, but you are risking your engine.
LEAN AND DANGAROUS is at 18.0:1 .You defeniately are going to blow something up....not to mention you lose more than 30% of your max power.Save money for a brand new internals.....
Hope that helps..

[SuperchargedGTZ]

well for FI cars you wanna be BELOW 13% cause detonation is so much easier to accomplish. At my last dyno run I ran 13.7 and they told me that I was running way to lean for my application. for NA cars, you still dont wanna see that, but prob. in the high 13 to low 14. you are ok though

[Gilhuly]

Good Thread!