Help,running rich with mail order tune.

[Earwax]

F Tune x 95 MAF VE.hpl

Yep, that's them! And that is right... some computers have two MAF tables so I wasn't sure if you'd have one or two

Give that a shot and see what happens. At worst your truck burns to the ground. Just kidding, 5% isn't too much of a change but it should help. The VE and MAF table both really need some time spent on them but this will at least get you closer.

And if you really want to know a little more about how it works.. if your fuel trims are positive prior to going into PE, then they ARE added to your PE fueling as a safety measure.. but if they are negative then it ignores them

I really wish GM would start using widebands like Ford has started doing

I have attached a log file I did yesterday. The changes you gave me seem to work great.The AFR is almost exactly what the commanded is.Its a lot leaner.I guess I`ll read up on setting the MAF and VE tables. It looks involved,but thats how you learn. Along with help from an expert tuner.I do have a question or two. Is changing the AFR in PE done with the Engine-Fuel-Power Enrich-Power Enrichment-EQ Ratio table? What does the VE table do? I assume that the MAF and VE tables got screwed up with all the airflow changes that I did to the engine (5.3-6.0,larger T/B,Square port heads with bigger valves,cam,CAI,Long tubes,4"exhaust,etc.)? Thanks again for the help and advise.I do appreciate it.Bill
Thanks again for the help,I appreciate it. F Tune x 95 MAF VE.hpl

[schpenxel]

F Tune x 95 MAF VE.hpl

I have attached a log file I did yesterday. The changes you gave me seem to work great.The AFR is almost exactly what the commanded is.Its a lot leaner.I guess I`ll read up on setting the MAF and VE tables. It looks involved,but thats how you learn. Along with help from an expert tuner.I do have a question or two. Is changing the AFR in PE done with the Engine-Fuel-Power Enrich-Power Enrichment-EQ Ratio table? What does the VE table do? I assume that the MAF and VE tables got screwed up with all the airflow changes that I did to the engine (5.3-6.0,larger T/B,Square port heads with bigger valves,cam,CAI,Long tubes,4"exhaust,etc.)? Thanks again for the help and advise.I do appreciate it.Bill
Thanks again for the help,I appreciate it. F Tune x 95 MAF VE.hpl

I'll look at the log in a bit, but good to hear it helped.

VE table = volumetric efficiency. It's basically a rating of how much air the engine SHOULD suck in at a particular RPM and manifold pressure (vacuum or boost). On a 6 liter, 8 cylinder engine, each cylinder has a volume of 0.75 liters. If at 1200 RPM's and 40kpa (I'm pulling numbers out of my ass so don't try to match these up with your tune or anything like) each cylinder actually draws in 0.375 liters of air on each intake stroke, then you would say its volumetric efficiency is 50%. Remember, with the throttle blade mostly shut it's acting as a restriction on how much air can get into the engine. If at a higher RPM/WOT it was pulling in 0.70 liters of air per stroke then it's VE at that point would be 93%. On a supercharged car you might have 0.9 liters of air per stroke, equaling 120% VE.

GM made the numbering system a little more complex on the gen 4 computers, so that's why you'll see the VE table isn't actually a scale of 0 to 100. They have built in some other calculations that escape me at the moment, but the idea remains the same.

The point of it is so the computer can very quickly calculate how much air is going into the engine. The MAF has a small delay and thus is not very accurate when there are fast airflow changes, i.e. you hit the gas real quick or something like that

The computer uses this airflow value to then figure out how much fuel to inject

So, if the amount of air that it THINKS is going into the engine doesn't match reality, then it will inject the wrong amount of fuel, and the actual AFR will not match what the computer is after. In PE mode there is no way for the computer to tell what the actual AFR is, so it's 100% reliant on the calculations when figuring out how much fuel to inject.

Yes, changes to COMMANDED afr in PE are done in the EQ ratio table. The formula is stoich AFR (14.7 for most) divided by EQ ratio = commanded AFR