A/F ratio ?

your a/f should stay consistant no matter what gear you are in but I too have noticed at the end of 3rd just as you go into 4th it does richen up so looks normal and yes the air temp will play a role

 

just do it at .5 at a time to be safe

 

If your A/F ratio is richening up with increased temps, look for knock retard. Your computer will richen the mixture if it experiences significant knock. Better chances of getting knock as ambient temps increase.

 

Is that true? It will certainly pull timing but I didn't know it adds fuel for knock.

 

It doesn't add fuel. The PCM just pulls timing.
Another case of misinformation.

J

 

Jeff, I'm not trying to be a smart ass or spread mis-information. We spent HOURS on the dyno and the street with the wide-band O2 sensor in efforts to get the A/F correct on my Jeep. We had our A/F ratio right where we wanted it, but when we got significant knock retard, the computer would start dumping additional fuel and our A/F ratio would get much richer. When we decreased timing and the knock went away, the A/F ratio was back on the money again. If you have a better explanation of what's going on, I'd like to hear it. I can tell you with 100% certainty that it wasn't just timing being pulled alone. That wouldn't explain the dramatic shifts in A/F ratio during knock. My experience has shown that the computer has a richening protocol during knock. I have not been able to find the table in CMR, but that doesn't mean it doesn't exist. There's plenty of torque management tables you can't touch with CMR either.

 

Lets just ask Dave at B&G if anyone knows its him, lets keep it civil guys and provoking comments to yourself.

 

What was the advance in those situations? With knock retard and without knock retard? If the advance was less when knock retarded is it possible you weren't burning the entire charge?

 

In my case, we were aiming for a 12.5:1 A/F ratio and trying to get around 22 degrees of timing. The computer would pull 2 degrees of timing (down to 20 degrees) and the A/F ratio would drop to 11.5:1. When we changed the timing to 20 degrees, we got 0 knock and the A/F ratio stay solid at 12.5:1. I can't explain why 20 degrees of timing with 0 knock would allow the A/F ratio to stay at 12.5:1, but 2 degrees of knock (dropping from 22 degrees down to 20 degrees) would richen up the A/F ratio to 11.5:1. It's not timing that's changing the A/F ratio because the timing advance was the same in both cases. If Blown7 or anyone brighter than me would like to explain why it's richening up the mixture when knock is present, I'm all ears.

 

Dave knows a lot more than me and he will correct us all, but I am pretty sure the PCM only pulls timing and doesn't throw in more fuel....