Ok,

I hear a lot about the AF ratios that they should be between 11 and 12 what is exactly right?

Are these in metric, so 12 kgs of air to 1 kg of gas?

Please explain.

regards,
Rogier

 

11:1 = air to fuel ratio

 

No, you need to take your car to a professional tuner to determine the proper air-fuel ratio for your application.

It is a mass ratio. The units make no difference.

Example:

12 kg air : 1 kg fuel = 12:1
12 g air : 1 g fuel = 12:1
12 mg air : 1 mg fuel = 12:1
12 pounds air : 1 pound fuel = 12:1
12 oz air : 1 oz fuel = 12:1

 

I thought it was a mol ration not a mass ratio?

-Marques

 

That also works.

Mol
Definition: [n] the molecular weight of a substance expressed in grams; the basic unit of amount of substance adopted under the System International d'Unites

 

ok thanks for that, but is the ratio for each car different? rx7 I mean than. I got a 3rd gen, and going to a t78 with mild streetport. open exhaust, and well everything on it.

 

1) Every engine is slightly different.
2) Every type and brand of gasoline is slightly different.
3) I assume you are attempting to tune the engine by reading a display from an air-fuel ratio gauge. The gauge may not be calibrated properly, and will give different readings depending on where you place the O2 sensor. You will not ever have a totally reliable reading unless you use special laboratory equipment.
4) Not very many people have the EXACT setup you have, and even if they did your engine would still act differently. See DCrosby's 4th post about this subject here:
https://www.rx7club.com/showthread.p...hreadid=220817

Engine tuning is performed by adjusting trends, not specific numbers.