Forum » General Tuning Discussion » Commanded AFR doesn't match

Commanded AFR doesn't match

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
73 Views

I'm tuning my 2015 Mustang GT and I just did a log and was logging EQ Commanded Ratio (SAE). In my WOT table I have 0.88 Lambda as my target and my log was showing 0.90-0.91 Lambda. I've looked through most of my multipliers and can't really figure out what's going on. Any help? Thanks.

Things to check:

-- Dirty MAF?

-- Clogged fuel filter?

-- Clogged Injector(s)

If you've changed the MAF (or related air plumbing around the MAF), then you may need to rescale MAF transfer function. If you've changed the injectors perhaps the characterization info needs updating. Although you are within about 2%, so it's unlikely that it's one of these last two.

Sometimes you just need to command a slightly richer mixture to get what you want. So you could try commanding .86 LA to get .88

I haven’t changed injectors or intake plumbing so everything is stock mapping. I was really just wanting to dial it in. My Actual AFR is right on where I set my tables but for some reason my commanded doesn’t show what is in the tables.

It's almost certainly going to be a modifier that is affecting the commanded AFR and the interaction of the modifiers and the weighting of those modifiers can be quite complex. In general however if you make a 0.02 lambda target change in your main table, you should still see a corresponding change to the commanded lambda irrespective of the modifiers.

I think I found the modifier. I went to the fuel multiplier per individual cylinder and it does have a modifier of about 1.02 in the high rpm range. I made those all 1.00 for each cylinder in that range. Would it be wrong to just make the whole table 1.0 or is it mainly a failsafe? Thanks.

You can do this and of course then you can be pretty certain of what you're going to end up with. The factory modifiers however are there for a reason and I tend to leave them untouched unless I have a specific problem area where I'm not happy with the AFR.