Doc99SS

iTrader: (2)

I drive my car until it was fully warmed up. Stop the car and got out and pulled the connector to the MAF sensor. Engine stalls out. I restart the engine and start up a data logging session. The engine needs some throotle, it will not idle with a closed throotle, I am in FTC 22. I procede to drive the car and data log as I go.

While cruising around trying to get the PCM into different FTCs, I notice that while in FTC 7, the LTFTs on both banks oscillate from 0.0% 0.0% and -8.6% -7.8% LTFTs When its in 0.0% trim the engine runs rough, while at about -8%, the engine runs very well. I will have multiple lines of data at one LTFT level, then suddenly several lines at the other. So I have no correction for about 10 to 15 seconds, then suddenly I have positive LTFTs. There is no learning in between.

What is the PCM doing? Is it switching from closed loop to open loop, back and forth seversl times? I am confused.

edcmat-l1

iTrader: (10)

Turn off the long terms in the tune, and then reset the fueltrims using the controls in the scanner, and tune you VE using either the STFT or wideband correction.
Leave the long terms off until the VE is dialed in, and the maf also, if you're gonna run a maf tune.

Doc99SS

iTrader: (2)

I am data logging with an early version of AUTOTAP.

I do not know how to turn off the LTFTs. Furthermore, I do not see why I would do this, please talk to me about the merit of doing this. As I understand it, it is the LTFTs that stay in memory, while the STFTs are erased at key-off, and when you start up the engine on the next go, the STFTs are 0.0% and the LTFTs are at the values at the last key-off. So it seems logical to me that I should be working with the LTFTs to guide me in my tuning efforts.

I am going to re-read the article called "How to Tune Your VE Table Using Fuel Trims".

edcmat-l1

iTrader: (10)

You need to use the short terms to get your fueling + or - 3 percent or so, which in turn will keep your long terms from having to adjust much at all.
The long terms are only there to keep your short terms from having to make large changes. They adjust for "trending". The whole purpose of tuning the VE, and MAF is so the computer has to make as small an adjustment as possible. This can be done with long terms, but it takes too damn long. Turn them off, reset the fuel trims, and use your short terms.
As for how to turn them off, just go into the OL/CL section of your tuner, and set the LTFT to disable. Then, turn your scanner on, crank the car up, and reset the fuel trims. You then have 0% LTFT, and your short terms will probably be way the f**k off. Fire up the histo, and start logging. Copy and paste special/multiply by 1/2 to the VE til the fuel trims come into line.

Doc

iTrader: (9)

You have two airflow measurement systems on the LS1 based pcms- MAF and MAP. Below 4k RPMs or whatever you define in the tune you will have a blended mix of the two. After 4K RPMs or, whatever you define in the tune, you will have solely MAF air measurement. Best bet either way, MAF or, SD operation, is to disable the MAF and work on the MAP. After the MAP is sorted, dial in the MAF.

You have a closed loop feedback fuel monitoring system that is only accurate at stoich. Once you depart normal closed loop fueling, via vehicle speed, RPM, you are in open loop and are completely at the mercy of the accuracy of your tune.

The Merit of putting your vehicle into Open Loop Speed Density or, OLSD prior to running fuel trims or the MAF is the ability to isolate the malestrom of activity going on in Closed Loop MAF operation, CLMAF is much like hurding cats as you have already experienced.

Being able to isolate and correct your airflow measurement systems with a WBO2 in accordance with your new and, from what I have read, massively different from stock setup will lead you to the promised LSX land of reliability and performance you have already paid for.

Your idle situation, is all about getting the relationship between the pitch (physical position via set screw(or if electronic via software)) of your throttlebody blade and the commanded position of your IAC valve via the software in harmony with ECT parameters.

Sounds like an interesting project.