Thread: Why I tune to 12.0:1 A/F ratio (0.82 lambda) and why you should too. (all welcome)

Hey ashtonsser, what are the stock, cast pistons made of?

lolz....

Wait, only around 500 WHP on pump and meth injection? Let me know when you get past 600 WHP on stock internals, maybe then I will be a little bit more inclined to show a little respect. But we can argue about our e-penis's all day.

Payu, you can do whatever you want. If you are making good power running rich, then do it, I don't care.

As for Ben, his only problem is that he is too stubborn to listen to me. I told him to back off some more timing, especially since I knew that he was still knocking due to his timing, and the fact that he was most likely already past MBT.

And you can't compare drag racing to circuit racing. You are at full throttle for less than 12 seconds on a fast car at the strip. At the track, its more like 30 min for the sessions they were running.

The point of this thread was to get people thinking about AFR's. To get people to realize that rich isn't always good/needed. If you think you need to run richer, than do it. But I know from experience that anything lower than 12:1 isn't necessary under almost all conditions.

Also, whenever Ben decides to pony up some more moneys, we can get some good EGT numbers at different AFR to verify or disprove the actual physics of a motor.

i ran across this on another forum i visit and figured i should post it since some of us might run race gas from time to time
Interesting thread by Eric Brooks... - WWW.S197FORUM.COM

here is an interesting thread for understanding power and engines:

Mixed up about fuel mixtures - February 2002 Issue - (Aircraft Maintenance Technology)

Peak power and peak egt happen at different temps.
One reason that peak power happens on the rich side of stoichiometric is that the mixture may be cooler but the volume produced is greater because CO instead of CO2 increases the volume of the gas coming out of the engine.

2CO + O2 => 2CO2, and that means a 30% volume drop...

As for a narrowband, it has no place on a performance car...


I can take a bottle of test gas that corresponds to burnt gasoline 12:1 feed it at various temperatures to a narrowband in a test lab and it could read anywhere between 8:1 and 13.9:1, take your pick...


Mike

I just finally got around to reading this.

The point seems to be that race gas (and pump gas) has varying stoichiometry based on blend, brand, season, etc. Race gas can vary from 13.9 to 15.0 in stoichiometry.



Big whoop.


E85 has a stoichimetric ratio of 9.7:1 and one tunes with it the same exact way they tune with any gasoline using lambda (or Air/Fuel ratio if you prefer). The octane rating of a fuel is much more important. Better yet, the AKI (Anti-Knock Index) is most important.

With E85 one could conceivably tune to leaner lambda values than I recommend for gasoline. You could go as lean as 0.91 lambda or so (13.5:1 as displayed on a typical gasoline calibrated AFR meter), but that is due to it's AKI, not stoichimetric ratio. You might not make any more power going that lean, just saying...

You have to really be careful when referring to AFR. It really is a silly measurement to use, since lambda is a normalized number. That is, .8 lambda in pump gas is .8 lambda in e85.

When you say 13.5:1, are you saying its 13.5/9.7 = 1.39 lambda?

Or are you saying its 13.5/14.7 = .918 lambda which is actually 8.9:1 AFR in e85?

This is why I always prefer to work in lambda.

I didn't even realize I'd done that... Hmmm...
Yes, very confusing I see.

I'll edit it.

lol now your confusing some of the rest of us to