Well, I've pretty much got the VE table dialed in and the air/fuel ratio is spot on. If I wanted to run the car in purely speed density/open loop mode, I think it would run just fine. But while I am tinkering with this stuff, I want to look at the other options to see if maybe other modes would be better.
For instance, right now I have the MAF completely disabled as well as the fuel trims. My next step will be to re-enable the MAF and do some logging to calibrate the air flow through it. This is done by comparing the commanded fuel with the actual AFR detected by the wideband O2 sensor, and then apply the differences to the MAF table (B5001). This is basically just a single column curve table that provides a lookup of the frequency emitted by the MAF sensor and provides a value of the air movement past it that the PCM uses to determine how much air is going to be filling the cylinders so it can command a correct fuel charge via the fuel injector pulses. So this table has to be correct for the fuel charge to be correct, and consequently will show up in the AFR value detected by the wideband.
I'm thinking that if it runs well on the MAF, I could set it so that the MAF fails at the frequency where the table no longer provides any lookup data. Which is 12000Hz. I know I've seen values higher than that when logging data while in boost, so I'm thinking that if I fail the MAF at 12000Hz, then the fuel tables of the VE table will then take over exclusively, giving me (hopefully) the best combo of MAF tuning and speed density tuning. This is all theory, of course, so it will really depend on how the car FEELS when I drive it. That will ultimately make the decision for me, no matter what the data logging shows.
Then there is the matter of the fuel trims. While tuning the VE table, I had all fuel trims disabled, which is what you want when trying to determine the AFR of each cell in the VE table (B0101). This is a two dimensional table that provides cell intersections based on engine rpm and vacuum/boost as detected by the MAP sensor. But this is pretty much a static snapshot of HERE and NOW when tuning a car in speed density/open loop. And changes in atmospheric conditions will have an effect on this tuning, but how much is subject to debate. I doubt I will ever take that car out to the mountains, and if a huge low pressure cell moves in, I assume hurricane force winds and rain will also possibly be accompanying that cell, so not likely I would take the car our for a spin. But the positive side is that if I have to use ethanol laced gasoline instead of the stuff I'm able to get at the local Sunoco station, then the optimum AFR will change with the different fuel. Fuel trims will compensate for that to keep the engine from running too rich or too lean.
So once the decision is made whether to use the MAF or not, I will then re-enable first the short term fuel trims so see how it runs, then re-enable the long term fuel trims as well.
Of course, I'm now just twiddling my thumbs while thunderstorms whirl all around this area. Not really getting a lot of rain right HERE at the house, but all the roads around me appear to be getting rain if the weather radar is accurate.
So I'm close to wrapping up the major portions of the tuning. There are other things I'm sure I'll be pecking away at for a while longer, though. Things like the decelerator fuel cut off settings, sharpening up throttle response, and certainly trying to get rid of that initial startup stumble when I blip the accelerator. But I'm confident that everything can be fixed that I see on my plate IF I know which tables to adjust and figure out exactly HOW they need to be adjusted.
Yeah, I've learned a LOT about this tuning stuff. Still a lot more to go, but it doesn't feel as mind bending as it did when I first started looking into it. Of course, it pays to keep in mind that the tuning programs we use are not perfect neither. Bear in mind that those guys (EFILive, HPTuners, etc) are simply trying to reverse engineer the PCM in our cars by looking at the raw code and data trying to figure out what the heck it is doing. Some of the program code is really nothing more than guesswork. This is more voodoo than it is science.
So in effect, don't make your expectations unrealistic. As Mike Carnahan told me, my car is about the worst possible case I could have chosen to learn to tune with. Nothing can be taken for granted since everything has been changed mechanically. So nearly all of the tables in the PCM for a stock car no longer apply to MY engine and will have to possibly be tweaked. But as for being a perfect fast track course to learn a LOT about tuning, there probably couldn't have been a better test bed for me to play with. I HAVE to look at everything and try to understand what it all really means to me. Which, quite honestly, was extremely frustrating and overwhelming when I jumped into this.
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