A/F Ratio Numbers

[shey love]

I rescently purchased a Densecharger 6in CAI and changed mufflers. Besides that I'm stock. I was told by John DeMolet that I might run a little lean so on his recommendation I purchased some Denso IT-20 plugs that are 1 heat range colder to help richen it up. I am going to the dyno on Tuesday for the 2nd time to see how these changes affect it over the stock pull. I have not istalled the plugs yet, I want to see what the A/F readings are 1st.

My question is what is a sweet A/F ratio for are cars? Thanks Shey.

 

[03Sssnake]

With Pulley and chip, 11:5-11:9 AF...Without added boost from smaller pulley... I would think somewhere between 12:0-12:5 AF

 

[shey love]

Big D, so is the higher the 1st number getting richer or leaner. Joe

 

[Blue03Cobra]

Originally posted by shey love
Big D, so is the higher the 1st number getting richer or leaner. Joe

Higher 1st number is leaner. 10:1 = pig rich

 

[03Sssnake]

The lower#, is the richer, the higher#, is the leaner....

 

[03Sssnake]

The first number is air, 2nd is fuel (12:1)...12 parts air to 1 part fuel etc.... The more parts air/fuel=leaner.....

 

[shey love]

My 1st dyno run posted a 393.5 rwh but I didn't get an A/F ratio because I thought I was going to leave it stock. That didn't last. So If I am in between 12:0 and 12:5 leave it. If I am in the 11's then change to colder plug correct. What do you think is border line to lean. Shey.

 

[shey love]

Sorry guys I meant if it reads in the high twelves or 13's then switch to colder plug. Shey.

 

[03Sssnake]

If your in the high twelves, mid to low thirteens...Your too lean. A colder plug (shorter insulator will not help) Colder plug will help with misfires and detonation, not AF. You may ultimately require a tuned chip to correct the AF. It is somewhat normal with the factory tune for these cars to be alittle lean at low RPMS and pig rich at high RPMS...I would be concerned with a high AF at the big end, say 3500/4k rpms - 6K Rpms you would want to see the AF around 11:9-12:1 ideally.....

 

[shey love]

Thanks D, I will post a new thread with the new #'s after I get back. Hopefully nothing is to lean and I can just leave it. Thanks for the other related info. Shey.