I just dynoed my car adn it went fromabout 12.5 @2500 RPM to 11.25 @ 5500. It is still the stock program. What do you think?

 

it should be bettween 12.8 to 13.2 on a NA engine. you are way to rich. youve got some HP loss do to runnig rich.

 

Is this abnormal on a stock program?

 

its aliitle more rich than normal. the stock tune is 11.7 to 1.

 

You are way too rich for an NA setup. 13:1 sounds good to me.

Rich Krause

 

I hope this helps answer your question:

AIR/FUEL RATIO
.000 17.0:1
.100 17.0:1
.200 16.0:1
.300 15.5:1
.400 15.0:1
.500 14.7.0:1
.600 Dangerously Lean 14.6:1
.700 Getting lean 14.5:1
.800 Max power(Lean) normally aspirated 14.2:1
.875 Max Power normally aspirated 13.5:1
.900 Max Power (Rich) (NOS,blower,Turbo) 13.2:1
1.000 Very Rich 12.5:1

 

Using http://www.pcmforless.com

yeilded a 12.8 to 1 A/F this is on a 383 with LT4 hotcam, and bolt ons.

 

Appears you are trying to correlate stock, narrow-band O2 sensor output to a specific A/F ratio. That is not a good idea. The stock O2 sensors are only meant to be accurate in the very narrow range of about 14.6-14.8:1..... the stoichiometric A/F ratio, used in most EFI vehicles to produce the minimum combined level of the pollutants CO, HC and NOx.

Run any richer than that, and the sensors lose their accuracy. The curve of A/F ratio vs voltage becomes very flat.... a very small change in voltage reading represents a very large change in A/F ratio. Couple that with the fact that at those enriched A/F ratios the narrow-band sensors are extremely sensitive to operating temperature, and you lose all accuracy.

I would also challenge the values and interpretations shown. Peak power and torque NA are generally found in the range of 12.8-13.2:1. I've seen some LT1's though that got closer to 13.5:1.

But for a nitrous motor or an S/C or Turbo motor, 13.2:1 could be fatal. I think you will find that most well-tuned nitrous setups are pushing 11.0-11.5:1, at least as measured on a true, wide-band sensor. I would suspect that S/C setups are similar, and some turbo setups even more toward the rich side.

The stock LT1 tuning produces a calculated "target" a/F ratio that is typically in the area of 11.7:1.... not fixed at that value, but not unusual to see. Your stock tuning is producing exactly the results I would expect. Any mail-order tuner can pick up 15HP on a relatively stock setup by tweeking the PE tables to produce a target A/F ratio closer to 13.0:1.

 

That's what I was thinking. Thanks for clearing that up!