Originally Posted by

**TriPinTaZ**
Assuming you want the easiest path first, you would lean out the PE table to compensate for the added fuel via meth. But you might have to adjust your torque coefficient ratio table if you go too low of a value in the PE table because then your torque model will be off. If you look at the stock coefficient table you see the numbers are above 1.0 during PE commanded equivalence ratio. Typically they are just over 1 in the stock PE area, then fall below 1 if you go above or below this equivalence ratio, and are 1.0 during stoich. If you go too low with your equivalence ratio where the coefficient table references a number below 1 you could have unexpected changes to your torque model. So you will need to adjust this if necessary. If you change the MAF values up top it will also change the final torque calculations as airmass is a large part of the calculation the ECU uses to determine torque output.

Your other question for commanded lamda. There is a stoich table that is typically a sliding scale based on ethanol content in the tune. Before E10 and E85 all tunes said stoich was 14.7:1 for gasoline. With E10, stoich is actually 14.1:1. And then it changes to a lower value for E85 on a sliding scale based on total ethanol content. That said, we are going to assume for this example that we are running E10 and stoich is 14.1:1 as referenced by the ECU. The math is simple though and reverse-able. Let's say you want to command .85 Lamda at WOT.

stoich = 14.1

WOT desired AFR: 12:1 (approx .85 lambda for E10)

If you take 14.1 and multiply by your desired lamda of .85 you get the following AFR (14.1 x.85) = 11.985:1 AFR. This is the math so that you can work out an Air Fuel Ratio to Lambda if you're still not familiar with working with everything in Lamda values.

So lets to go the ECU and the PE table. Stoich for E10 is known to be 14.1:1 by the ECU. Then in your PE table you have 1.155 commanded at WOT. The math for that is backwards of the above. 14.1/1.155 = 12.2 AFR commanded. Now you just need to work that into Lamda. All you do is divide commanded AFR by stoich. 12.2/14.1 = .865 Lambda.

Essentially you will need to use the value the ECU is reading for Stoich to do this math for any other fuel blends other than E10. But if you were running E10 and Lambda was reading .80 then your AFR is 14.1 x .80 = 11.28:1. If you have true E85 in the tank then the stoich is 9.8:1 so your AFR is 9.8 x .80 = 7.84 AFR. This obviously is why we all should be tuning in Lambda now because .80 Lambda on E85 is still .80 Lambda on E10 even though the AFR's are way different.

Just a note, your tuner may have tuned it a bit rich to safeguard in the event you run out of meth during a WOT event. The ECU may pull out enough timing to save some engine parts if its running rich and the meth runs out. Otherwise if you go from a great AFR on meth, then run out of meth and go lean the ECU may not be able to pull out enough timing and boom. There really isn't a whole lot of power to be had between .80 lambda and .85 lambda so don't go chasing tiny amounts of power over this. The only time I would worry about running as lean as possible is when you're at the track and you know your meth tank is full. I would leave the tune richer on the street. But thats just my personal opinion.