How to Tune AFR

[Lumpo]

I ordered my Wideband a few days ago and it should be here anyday now and im just wondering whats the best way to tune AFR? I been doing alot of research and i cant find anything. I did find a really good write up on how to do it but i forgot to favorite it and now i cant find it. Anyone wanna point me in the right direction?

[BlackGS]

The best way to tune AFR would be on a dyno to measure peak power, but I know most of us don't get the opportunity to gain access to significant dyno time.

I started out by creating a histogram to measure wideband AFR vs MAF Hz, and a few others like AFR vs. boost vs. RPM's, etc. AFR vs. MAF Hz is really the main one I look at though. Make sure you remove FTC 1 from the data. You don't want decel AFR values.

You should probably have a good part-throttle closed-loop tune to start. There are a couple of different options for using the wideband after that. You can just keep your closed-loop tune as is, and focus on PE AFR with the wideband, or you can tune open-loop and use the wideband across the chart. I have been using the second option lately. Since I tune my car all the time anyway, I really don't see the need for worrying about keeping trims in line and fighting the PE transition if they are off a little. I just set closed loop enable temp to 255* and keep it open loop. Then I can simply adjust the MAF table to run the desired AFR in every cell. Right now, I have been keeping cruise AFR around 15.5-16.0 averages (1.05-1.10 lambda - I'm on e85), and I transition nicely into the higher cells with AFR's smoothly dropping for light boost, and down to 11.5-11.8 (~.8 lambda) at full boost. I tweak the PE adder for 3rd gear just as I've always done.

[5_Liter_Eater]

Put the car in open loop and clear out any residual fuel trims. If you're running in SD then set up a histo that plots AFR Error (not AFR) against the VE table. If you're running MAF then set up a histo that plots AFR Error against the MAF table. Log some data and copy and paste special/multiply by % the AFR errors into the VE or MAF table. Flash and re-log until AFR Errors are +-~3%.

[Lumpo]

Put the car in open loop and clear out any residual fuel trims. If you're running in SD then set up a histo that plots AFR Error (not AFR) against the VE table. If you're running MAF then set up a histo that plots AFR Error against the MAF table. Log some data and copy and paste special/multiply by % the AFR errors into the VE or MAF table. Flash and re-log until AFR Errors are +-~3%.

I dont think i can put my car in Speed Density because when i click on it its just blank. So really by doing what you say my AFR and LTFT will be correct by doing this and im wasting my time doing a MAF tune without my wideband hooked up? So basically i put my coolant temp to 255* to keep my car in open loop and then do a MAF tune to get my AFR correct and thats it just use AFR Error vs MAF histogram? How is my AFR determined by doing this?

[BlackZJ]

I dont think i can put my car in Speed Density because when i click on it its just blank. So really by doing what you say my AFR and LTFT will be correct by doing this and im wasting my time doing a MAF tune without my wideband hooked up? So basically i put my coolant temp to 255* to keep my car in open loop and then do a MAF tune to get my AFR correct and thats it just use AFR Error vs MAF histogram? How is my AFR determined by doing this?

You need to log "Air Fuel Commanded". This determines the AFR and is needed by the "AFR Error vs. MAF" Histogram.

You can tune in SD when you disable the MAF by setting the "MAF Fail High" to 0. (sets a DTC)
As soon as you flashed this bin, you're in SD and you can tune your VE table.

- Mat

[Lumpo]

I dont think im going to worry about VE im just trying to get all my facts straight to tune with my wideband. I understand how to do this...

"Put the car in open loop and clear out any residual fuel trims. If you're running in SD then set up a histo that plots AFR Error (not AFR) against the VE table. If you're running MAF then set up a histo that plots AFR Error against the MAF table. Log some data and copy and paste special/multiply by % the AFR errors into the VE or MAF table. Flash and re-log until AFR Errors are +-~3%."

I just dont get how i will be able to have a 11.8 AFR by doing it? Do i have to command 11.8 and then do this?

[5_Liter_Eater]

Yes, you need to set your PE (and/or BE if you have it) to 1.245 across the board (assuming your stoich is 14.7 then 14.7/11.8=1.245). So then you're commanding 11.8:1 when you romp on it and the AFR error tells you how far off from that you really are and when you copy and paste that % error into the MAF table it corrects it accordingly.

[Russ K]

Read up this thread for more info, but I would set the PE to 11.00 on a non intercooled 3800. Also the latest beta has the open loop tables for some of the V6 cars now.

http://www.hptuners.com/forum/showth...oop+maf+tuning

Russ Kemp

[Lumpo]

Everything i read i want to be at 11.8 AFR and by the way i am intercooled. Thanks for the link.

[Lumpo]

How do i average the cells that it skipped over? What exacltly am i suppose to do i cant figure it out.