Well I do have some new information. A little about the MAP scaler but first, I've found the question raised again about the handling of boost. There is an opinion that the fueling algorithm will not handle values in the MAP axis of the VE table above 105 kPa, and this is the reason for the creation of boost tables in the custom OS's used on non-OEM boosted applications. This may well be, I don't know. If true it means my tables are essentially useless, also meaning I need to start shopping for a custom OS. So I guess that would be the next step and I should probably start a new thread and can likely wrap this one up. So back to the MAP.

The MAP scaler is set so that the ECM reads the correct values for MAP depending on the MAP sensor used. Basically, the scalar (B3601) sets the range and the offset (B3602) sets the position. A barometric pressure of around 30.2 is pretty generic and converts to 102 kPa. So, key on engine off, the MAP will read static baro and it should output about 102 on your datalog whether it is a 1, 2 or 3 bar sensor. Because the higher boost sensors have to measure a wider range they have to use a condensed scale. The same 0-5v output in every case. The scaler sets the range. Typical values are around 90 for 1 bar, around 190 for 2 bar, and I think about 280 for 3 bar but I'm not sure since that wasn't my focus. The scalar is adjusted so that let's say you have the ability to pull down to 30 and pressurize to 180 just as an example then you have a range of 150 kPa (probably requires a decent vacuum pump, compressor, and pressure regulator to do accurately) and you can verify that with your boost gage. Or you can run your engine and record the high and low numbers and compare that to your datalog. (probably the easiest) If your spread by gage is 150 and your spread by datalog is also 150, even if the numbers don't match then your scaler is right. If not, adjust it so they are.

Next adjust the offset so the numbers line up as close as possible at the bottom, top, and most importantly static baro point in the range. It won't be absolutely exact but should be very close at those three points. You now have a properly calibrated MAP sensor. The offset should be somewhere in the vicinity of 10 but might be more with the 3 bar. You are matching two curved lines. The one parameter you can't change is the radius of the curve but since both the sensors and the ECM are GM they have already matched that for you and it should be very close indeed.

In my case, I had values of 188 and 20 entered which was very close on the range but probably off by 10 on the position (offset). That should be close enough to run reasonably well. My problems are elsewhere and it makes a lot of sense at this point to start over with a COS. I've pretty much exhausted all other options. Hope I haven't exhausted you guys in the process.

Jim