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

Is 11.6 considered, "stupid rich"? I'd give his car amonth.

Sorry Ken, but yes 11.6 is overly rich. I can't tell you how much power difference it will make, without knowing what sort of timing you are running and the type of motor you are running.

Many people in the DSM crowd have got it wrong. There is such a thing as too much timing. There is a point called MBT (Minimum advance for Best Torque) and you can exceed this point without knocking. If you are past this point and are adding fuel and getting more power, you are doing so because a) you started to burn the mixture too soon and b) by adding the extra fuel you have slowed down the flame velocity. You are basically getting back to the point of making best torque.

A slow controlled burn does not make more power. A fast controlled burn makes more power. People turn to race gas for the Octane.

Octane is basically the fuel's resistance to knock. This means higher Octane is related to higher activation energy (amount of energy[heat!] needed to ignite the mixture).

Higher octane does not make more power. With high octane you get to move your timing to MBT which means more power.

Latent heat is the amount of energy released (or absorbed) in a phase change process. So when you vaporize the extra fuel from running stupid rich, you take out some of the energy (heat!) in the charge.

An example of this is:

If you go from 12.5 [about best power] to 11.0 [stupid rich] you extract 3.8 kJ of energy per kg of air in the charge. So your charge air has 3.8 kJ of energy less. The specific heat of air (amount of energy required to change temperature by 1 degree Kelvin) is about 1. So by going from 12.5 to 11.0 you make the air 3.8 degrees Celsius[8.8 deg f] cooler, which is insignificant.

Basically being richer than 12 is useless, being richer than 12.5 is useless, but that is usually the accepted margin to compensate for various external factors.

Here is a hint for those concerned with safety..

Latent heat of Gasoline: 350 kj/kg

Water: 2260 kj/kg


There is a reason why when you let me build/tune a car it will set a records for volumetric efficiency.

Edit: Ben helps too.... sometimes

Thanks for helping me and others here understand this. I did not understand before, but now it makes more sense.

Water injection ftw?

Yes, water/meth injection ftw. And stay the hell away from e85.

But but E85 is made with some corn... so it has to be good... /politician

e85 is some nasty stuff. As soon as you pump it into your gas tank, you magically have the ability to run like 38psi at 14 degrees of timing.

Well I have been contemplating e85, but haven't gotten off my lazy arse and done my homework. I don't know if 550 at 4 bar would be enough for a t28 slightly larger than a disco?

Good thread either way.

Now you will learn why I and many others tune richer than 12.0:1 jejejeje.... I have never melted or closed the gap on spark plugs on my tunes and that its caused because of high EGT combined with some exhaust backpressure but now you will learn jejejeje...

Or it could have something to do with collapsed rocker arm... but hey you can continue your posts that you can't back up with facts or science.

Your posts and attitude make me not believe anything you say... so keep up the bs.

I still have run 12:1 for many years and I haven't melted anything ever either... Does that make me right? No the science does.

i was running a 12.3-5:1 when i had my t25, s4 cam setup on 8psi it was powerful enough to run a 13.0@110 on street tires. But i will say upping the boost on the t25 over 12psi and adding the added heat and backpressure which also keeps heat in the cylinders did not end well at all for the motor.

So yeah many people told me i needed to be 11.3:1-11.6:1 to be optimum on pump gas. With race fuel you can go into the upper 11's. My setup now is held steady at 11.8:1 or so accross the board on 110 octane race fuel. I had no detonation no misfires no melting plugs and you know what ill stay right there where im at cuz i know the tune is good. Ive had bad experiences with running leaner than 11.8:1 and i wont do it again, Dont even say its was a timing issue, Yes it was an issue with overboosting but it was also an issue of being too lean.

This is one of those circumstances where when its running soo strong you know something is gonna go wrong. With volumetric efficiency in an engine comes heat with heat comes detonation. You can be less effecient and make less heat and be safe making a little bit less or you can push the limits which ive done several times and found out the hard way its not always best. And again to those in my other threads saying timing issue, no way, 13-14 deg base timing is plenty of leway. Its a plain and simple fact that i was being as efficient as possible but again with that comes problems. It leaves no room for error