Air fuel ratio...
Air fuel ratio... Just got my car outa its winter home. I added a couple of gauges. One was a wide band O2 sensor. (yes, it is before the cats)
I read that a "safe" ratio is 13-1. Is this normally the ratio before or after the cats? A little "test run" up the interstate (at WOT of course) showed my AFR ratio started at 11.8-1 and was 11.3-1 after it started to wind up. Last year on a dynojet with the tailpipe sensor, it was about 13-1.
Is there that much difference before and after the cats?
Thanks in advance.
I read that a "safe" ratio is 13-1. Is this normally the ratio before or after the cats? A little "test run" up the interstate (at WOT of course) showed my AFR ratio started at 11.8-1 and was 11.3-1 after it started to wind up. Last year on a dynojet with the tailpipe sensor, it was about 13-1.
Is there that much difference before and after the cats?
Thanks in advance.
If you have left your tune alone, then your car is damn close to where the PCM is telling it to be. From the factory it is set to command an 11.7AFR. As you get into higher rpms and higher gears, cat. overtemp. protection (COT) kicks in and adds a little more fuel. I wouldn't go by the tailpipe measurements -- especially if you have cats. AFR needs to be a pre-cat measurement.
