If your MAF and/or VE tables did not change very much and now you're seeing lower line pressure, then there may be some other physical problem occurring (for example, line pressure valve/bore might be worn/leaking).

You can use a bidir scantool to command line pressure and compare against actual measurement at the line tap to see if they correlate sufficiently.

 

One beef I have with the method, is that it "corrects"
MAF (or VE) airflow for any fuel delivery error there may
be. Like, if fuel pressure is 63PSI and PCM believes it's
58, fueling will be fat, scheme will believe MAF reads high
and you'll reduce MAF table and indicated air mass. And
without fixing the actual error at all.

You have to be careful when training 'tards. Sometimes
they learn the wrong thing.

 

The pcm does not have a way to measure fuel pressure at all though correct? In the scenario you suggest, how would one correct it outside of an adjustable pressure regulator?

If the car is set up mechanically to run whatever pressure it is set to run would that remain fairly constant?

Again, no disrespect I am simply trying to understand and learn.

 

In the tutorial thread, one of the links points the reader to a page which has a list of mechanical/electrical checks to be made (pointing the reader to the service manual for repairs/diagnostics) and cautions that the whole vehicle/machinery must be working correctly before attempting any tuning.


( BTW: the procedure corrects the MAF, and calculates a new VE from the corrected MAF ).

 

You have to measure rail pressure with engine operating thru its range (this checks that the whole fuel delivery system is functioning correctly).

If FPR is un-referenced, then rail pressure should be constant with no more than +/-1 psi variation.

If FPR is manifold-referenced, then rail pressure varies with MAP... if you temporarily remove the reference, then rail pressure should hold constant (+/-1 psi) at base pressure + baro (i.e. same as WOT).

The IFR is calculated based on the measured rail pressure (before any IFR/VE/MAF scaling is applied).

 

And, I'm talking about knowing how to correct that.

 

Teach us oh great and powerful Oz

What's the point of posting just to say you know how to fix an issue, but not give any information to help?

 

You need to learn to read. Maybe when you get your GED?
If you aren't bright enough to correct your line pressure you shouldn't be trying to do this.

 

That wasn't the point of the thread. It was posted for the purpose of trying to learn the relationship between those tables and the transmissions behavior. I wanted to know how and why things happen not just "change this for this result". I am not a professionally trained tuner and I am not an electrical or mechanical engineer, but I am also not stupid. I will be the first to admit I am ignorant to a lot of this...hence the point of asking.

The transmission shifted fine before then with the new tune was having minor issues. I fixed the faulty data and everything with the trans also went back to working properly. Considering I only changed the MAF scale and the VE table it didn't take a rocket scientist to figure out one of them was behind it.

So I went back and rechecked my work rather than just up the line pressure to band aid it. After that was done I did rework the pressure tables based on the advice above.

 

For instantce, it you put an 85mm MAF on it, copy the MAF tables from something like a 2002 truck.

What I don't see many talk about is larger TBs, which make much more difference than scaling the MAF table.
I have seem many a 4L60E die from a large TB and not tuning for it. Any changes to line pressure due to a different MAD are very small. Not so with a larger TB.

 

I had my GED long after you walked out of Noah's Ark

 

Probably so!
LOL!