quick question about the CALC.VE tutorial

[BlackGMC]

I read threw the tutorial, and i was wondering if it is possible to substitute my wideband in place of the LTFT bens...

[WeathermanShawn]

I would have to think about that...

I suppose that you could develop a CALC. PID that would utilize a WO2AFRBEN instead of a LTFTBEN. Of course that value would have to be around the stoich AFR/EQ value.

Its an excellent question. I will have to double-check with Master Mathematician Joecar to see how to do that.

It is an excellent question. We will get back to you..

[BlackGMC]

cool, the reason i ask. Last time i tuned my truck, i dialed in the VE table, then the MAF with my wideband (serial). then when i turned the trims back on, they were not exactly lining up... So i created a map that resemebles the switch point table, then i logged the ltft average and slowly dialed in the switchpoints with the trims... AFter i was done the trims lined up +/- 2%, they never went more than that after about a month of driving. I am just wondering if that was the wrong or right thing to do...

Since that is the background behind my question, I am assuming the wideband is more accurate than the O2 sensors/Trims because my trims were off when i was done....

any thoughts?

[joecar]

You would have to disable CL/LTFT/STFT...

(otherwise closed loop trims would be closing the commanded/measured gap ahead of the wideband).

:)

[BlackGMC]

ya i figured that, but what do yall think would be more accurate for the part throttle stuff? The wideband or the trim average?

either way you would result in a different airmass....

[WeathermanShawn]

I think a lot has to do with how one originally tuned the vehicle. If you originally tuned the vehicle Open-Loop with MAF disabled, then separately calibrated the MAF open-loop..and then utilized Trims (closed-loop) to fine-tune VE/MAF..it never seems to line up that great.

One of the reasons is that unless you are running a COS... IAT, ECT, altitude changes all effect the mapping of a pure SD tune. When you switch separately to MAF you likewise face challenges.

But, if you tune your vehicle closed-loop and MAF enabled then you see the how the two Airflow Models really interact.

In a nutshell here is what I am saying. Functional narrowbands are quite accurate at stoich. So your Trims were not off because your Wideband is any more accurate at stoich than the narrowbands. It is more of the method of tuning that dictates Trims distribution.

I may not have explained it that great, but if you just tune closed-loop, CALC.VE Table is very accurate.

Hope that helps.

[BlackGMC]

cool, yep i have been doing some reading on the charge temp stuff, and it makes sense.... That is why i posed the question.

I am gonna try your method this weekend and i will see how it works out.

BTW, i read you idle tuning tips, and i really like the idea of use the MAF for desired airflow, that is pretty slick! everytime i try to use the RAF process my desired airflow is toooooo low...

[WeathermanShawn]

Thanks!

Let us know how each works out...:)