Thought I would share some numbers 2.8" pulley

[KenBMD]

Did you change the "STOCK GT" AFR from 12:1 to 11.5:1??

AMB

Yes I did

 

[analogdesigner]

A/F plot

KenBMD,

Thanks for the updated image! I didn't realize that the wideband sensors were still so expensive.

 

[nota4re]

This is actually not 100% correct. Your statements about closed loop are correct, but not for open loop. What you are describing is a speed density type system that uses VE tables for fuel delivery during open loop. The Ford GT and all newer Fords are mass air cars. There is a mass air transfer function that if calibrated correctly (not always true from the factory) you can indeed increase boost and still get the commanded A/F ratio. Since the MAF is measuring the mass of the air entering the engine (if the transfer function is indeed correct) it can add the proper amount of fuel. That does not make running a pullied car ok without a tune, but the WOT A/F is not the main issue when tuning a car that is pullied for more boost. There are many other things that do need to get changed.

KenBMD, thanks for your posts and clarifications. No doubt, you are on top of your game, especially with your previous work with other high-performance Ford products. Your A/F numbers look excellent (safe), and I am glad you shared them as well as your tuning methods. As for the accuracy of my statements, I agree that in lieu of writing multiple pages, I was trying to provide a simplistic explanation of closed vs open loop. I certainly agree that even in open-loop many other factors ar "digested" by the ECU - ambient air temp, engine temp, boost, and not the least of which is the metered air. However, as we both agree - even with calibrated metered air, the ECU is "blind" to know if AF's are being achieved. Further, I think we agree that despite a being mass air type of system, a "tune" is necessary - and it looks like you've provided a good one!