Mystery Bird

I'm fine tuning my WOT AFR when I go to the track. Question is do I target the AFR to be the same from say 1000 RPM's all the way up to shift point or are there spots where I want it to be richer or leaner? I tried a search but nothing came up. Right now I'm shooting for 12.5 area all the way through.

razor02097

As the RPM's go up you want it richer. Are you using Tunercats? Using the two tables

% change to fuel/Air ratio Vs RPM at WOT
% change to fuel/Air ratio Vs coolant temp at WOT

You should be able to set your base AFR on the Vs coolant temp table and then use the Vs RPM table to ramp the values up or down depending if you want it richer or leaner.

Mystery Bird

I am using Tuner cats and a wideband. I've been taking the data from Datamaster and plugging in the numbers into a spreadsheet that gives me new parameters to tune. So I should start down low a little lean then slowly work up to a richer mixture? Should I do this according to the spark advance curve?

razor02097

You want to set your target AFR in the coolant table and adjust for any variants Vs RPM on the RPM table. If you want to try 12.5 through the whole range then setting the coolant table at 17.6 and the RPM at 0 should get you to 12.5 AFR.

14.7/(1 + [17.6+0/100]) = 12.5

http://www.lt1pcmtuning.com/tips/

about halfway down the page should help explain better.

razor02097

I created a spreadsheet to see the AFR for RPM Vs coolant temp...

The following is from the stock tables out of my 1994 PCM...

At operating temp the value for % change to A/F Vs coolant is 15.6, the RPM varies from -.8 to 4.7...

RPM | AFR
400 | 12.219
800 | 12.219
1200 | 12.804
1600 | 12.628
2000 | 12.628
2400 | 12.384
2800 | 12.716
3200 | 12.542
3600 | 12.628
4000 | 12.468
4400 | 11.835
4800 | 11.722
5200 | 12.029
5600 | 12.426
6000 | 12.426
6400 | 12.426
6800 | 12.426