A/F ratio error?

[loboracing]

Is there anything that would cause FAST to miscalculate A/F? My logs show that the car is running 11:1 at idle and 9:1 WOT and seems to be fat across the range but I pulled my plugs and the insulators is very light tan or white, in fact the passenger rear burned off the side electrode (i hope it didnt chunk off and mess something up).

[loboracing]

wow, no replies:frown: . could a leaking vacuum line under boost cause this? My vacuum lines are a mess and need some attention.

[loboracing]

ok, how about this. What can cause the plugs to be white while still having a rich A/F ratio?

[Farmer]

What was your O2 correction at WOT? I'm new to the FAST system and recently I've had trouble with fuel delivery. When the system was trying to add fuel at WOT the engine couldn't get the fuel (weak pump) and the O2 correction was at 16-20% but the A/F ratio was still reading 10.75-11.25. I don't understand why the A/F wouldn't read lean, like 20% leaner than normal, the plugs were white.

[Ted A.]

What was your O2 correction at WOT? I'm new to the FAST system and recently I've had trouble with fuel delivery. When the system was trying to add fuel at WOT the engine couldn't get the fuel (weak pump) and the O2 correction was at 16-20% but the A/F ratio was still reading 10.75-11.25. I don't understand why the A/F wouldn't read lean, like 20% leaner than normal, the plugs were white.


The FAST is telling you it was adding 16 to 20% fuel to maintain A/F. Either a VE problem or Fuel delivery problem. You system was working correct and the correction kept things in line.

[Ted A.]

Is there anything that would cause FAST to miscalculate A/F? My logs show that the car is running 11:1 at idle and 9:1 WOT and seems to be fat across the range but I pulled my plugs and the insulators is very light tan or white, in fact the passenger rear burned off the side electrode (i hope it didnt chunk off and mess something up).


That does not neccesarily indicate that your A/F in each cylinder is 11:1 and 9:1 WOT. You can run lean in one or more cylinders and still show proper A/F at your WO2.

I am not sure which intake manifold you are running, but if it is stock ported one the DLS power plate works very well at balancing out airflow and little individual correction is needed.

[loboracing]

My o2 correction seems to be pretty much in check. All the plugs seem to be whiter than they should. I was wondering about the power plates, It seems like they would help with air distribution to a point until it starts to restrict airflow....?

[Bruce]

Too much timing can leave you with a false lean.

A WB is only sensing O2, and is not the perfect mixture indicator. Timing will effect indicated AFR.

Not to mention is seems that some of the fuels *out there* generate less ash, then the you might expect.