AFR ratio questions
 

I have a uego wideband on my supercharged 5.0 87 mustang.
Does your air fuel ratio drop down slowly to 11 or 12:X or does it go there right away under WOT and stay there.

Mine climbs slowly and when at 5000rpms its a 12 or high 11 to 1.

Thanks

Well, at idle and normal driving conditions it should be close to Stoich (14.67). Optimal at these conditions would be on the lean side for best fuel economy. When you go WOT your AFR should be close to your commanded AFR. So if you are commanding 12.1 AFR, seeing high 11's to low 12's I think you are golden. At first your AFR at WOT will be in the low 11.s and climb as you excelerate and increase your RPM up the graph to your commanded AFR. At WOT a car should always command less than stoich. I take it you are fuel injected and MAF controled. One way to dial that in is to tune the MAF table if you are fuel injected and make corrections by half percent error in small increments untill you get the AFR as close to Stoich as possible. One thing this also does is adjust your LTFT and STFT (Long and Short Term Fuel Trims). This will bring those within +3 to -3 of zero which also means better fuel economy and better command AFR.

Here is an explanation of how things work.

Air-fuel ratio meter - Wikipedia, the free encyclopedia

Hope this helps.

thanks
 

mine starts at 14 and as rpm climbs its goes to 11ish to 1. around 4800 to 5000rpms
correct maf converted.

Sorry, is this at WOT? 14 is good. 11 at 4800 to 500 is not bad either. The command AFR starts within the powerband at WOT. What RPM does it start to command ARF and at what RPM do you see low 12's?

I used to tune with HPtunes software so I am just trying to get a better understanding.

Cheers

thanks
 

hey i appreciate the help,

Always at WOT and approx 10lb of boost i see my AFR go from 14 to 11:8 ish.

14 at 2000 to then 13ish at 4000 then 11 ish at 5200.

Now if i want a bit more safety net i would just add fuel pressure correct maybe 1psi or so with 36lbs injectors. The numbers you see are at 40psi tap off.

low 12s are at 4500 and up