Low air to fuel ratio

justabuickv6

Member
Joined
Nov 4, 2003
My A/F ratio at the end of the quarter is like 10 to 10.5. Is this low? What causes this? My 02's are 790's.
 
Are these values what your seeing in Directscan or do you have a wideband o2? The chip is controlling the fuel, maf value if you have an extender and are not hitting the 255 limit. RPM fuel addition as well as a time in PE fuel addition. Once on the big end you stay in certain RPM ranges(4000-5500) much longer than 1st-2nd gear also and you have more load so the fuel tables become more critical to keep the A/F in a good range.
 
Could also be a voltbooster thing

I am taking my booster out because it flat out makes the car dump fuel over 11psi. I have seen 10.0 a/f with the thing on. Seems way to hard to tune out of the chip. I am going to put a hotwire & 340 in: should take care of the fuel pump issues.
 
This is what my DS is showing. PTE93 chip, 20 degrees of timing. Stock MAF. MAF is around 235-240 at the quarter. The chip does not lock it at 255.
 
Originally posted by justabuickv6
My A/F ratio at the end of the quarter is like 10 to 10.5. Is this low? What causes this? My 02's are 790's.

The air fuel ratios as reported by DS are calculations, and have no real basis in reality as to what may really be happening.

Depending on the type fuel and boost/timing you're using on your runs, that 790 could be good (lower boost, etc) or it could be a little high (boost levels in excess of 22-23#).

At 25# of boost and 28° of timing, my O2's at the end of the run are closer to 750-760, just as an example.
 
Originally posted by justabuickv6
This is what my DS is showing. PTE93 chip, 20 degrees of timing. Stock MAF. MAF is around 235-240 at the quarter. The chip does not lock it at 255.

Look at the injector Duty Cycle.
It's probably pegged at 100% or possibly higher.
With the injectors being full on, the calculated AFR is bogus.

With the static injector strategy, and trying to get too much out of too small of injector, you can see all sorts of extreme AFRs and they're all meaningless. With the proper chip and proper injectors, you can then have the calculated AFRs line pretty close to actual.

And using the stock O2 sensor as any indicator of AFR is a quick way to disaster. If you want to go quick you need to learn to read plugs, get a WB and or EGT, perferably both.
 
Originally posted by bruce

And using the stock O2 sensor as any indicator of AFR is a quick way to disaster. If you want to go quick you need to learn to read plugs, get a WB and or EGT, perferably both. [/B]

AMEN TO THAT!!!!!:eek: :D :D
 
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