Need help with A/F ratios

[raptorman02]

Guys I Dynoed my TA a few months ago and I started looking at the A/F readings and am a bit concerned. What do you guys think looking at this. It was around 18 all the way to 2243.17 then dropped to 16.75 @ 2855.58 then by 2990 it was back to 18 and stayed there all the way to redline. By the way that is the RPM's I am referring to. This seems wayway high compared to my Cobras steady high 11's to mid 12's. Any help would be greatly appreciated.

[Injuneer]

I think they put the wide-band sensor in the wrong place.... 18:1 (or even 16.75:1) makes no sense at all. The closed loop, part load tune is hard coded at 14.7:1, and the target A/F ratios in power enrichment mode are usually on the "rich" side... 11.7:1 in the LT1 stock PCM, don't know if the LS1 is that rich. Typical values generally run in the traditional range of 12.8-13.2:1 for peak power/torque. Some people have found values above 13.2 to be good for their particular setup, but 18:1 is what you would find in a "lean burn" 50MPG rice burner category......

[raptorman02]

Hmm

The odd thing is that I really expected a very rich condition not a lean one as my car runs very very fat when its first started and when it is floored. In my shop you can smell the unburned fuel when its cold and started, its not oil as it doesn't use a drop. I have the Computer burned by Ed Wright a few years ago when I built the car and it has had this problem since. I called them and they said that it was lean and I didn't belive them until I saw these reading because of the black exhaust and smell. Also my A/F guage is cranked all the way to the rich side when I start it but I figuer this was from the cold start loop. After it warms it fluctuates but does shoot to the lean side every once in awhile (I know these guages are for only general ideas about what you O2's are doing).

The DYNO was a Dynojet Mobile with the tailpipe sniffer and it seemed pretty accurate on the Cobra so I am thin kit was pretty good on the TA also. Damn I just want to make sure the car is okay for now. Is there any good tuning software our for these cars now that I could get (I hardly drive the car anymore but its still one of my favorites so I can't sell it and hate to see it sick).

Thanks again in advance

[Injuneer]

You can scan it and see where the factory O2 sensors are reading. These are NOT real accurate at 13:1... .but they will certainly tell you whether you are at 18:1, 15:1 or closer to 12-13:1. Look for readings in the range of 850-920mV at WOT.

[96TAragtop]

Re: Need help with A/F ratios

Originally posted by raptorman02
Guys I Dynoed my TA a few months ago and I started looking at the A/F readings and am a bit concerned. What do you guys think looking at this. It was around 18 all the way to 2243.17 then dropped to 16.75 @ 2855.58 then by 2990 it was back to 18 and stayed there all the way to redline. By the way that is the RPM's I am referring to. This seems wayway high compared to my Cobras steady high 11's to mid 12's. Any help would be greatly appreciated.

With my FBody club Dyno days, Ive seen hundreds of LS1's dyno, and Ive NEVER seen one higher than 15:1... and that thing had serious problems (not at all stock- tuning was a mess).

In my experience, most LS1's seem to run best at about 12.5:1-12.8:1 at WOT.

My measely stock/bolt-on LT1 dyno'd at 291 rwhp with 12.4:1 A/F.

-George

[Adam 2kSS]

yeah dude you want around 12.5 for best power. or 880 - 920 on the o2's. i too was expecting to be running rich with headers and hotcam, but am running a tad lean. my o2's read about 850 at wot.