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where can I learn how to tune the PCM?

This is a discussion on where can I learn how to tune the PCM? within the Computer & Tuning forums, part of the LSx Technical Help Section category; I have an 02 ss, and prior to that a '99 ss, have been reading chevyhiperf and gmhitech magazines for ...

  1. #1
    Junior Member
    Join Date
    Sep 2005

    2002 Camaro SS

    where can I learn how to tune the PCM?

    I have an 02 ss, and prior to that a '99 ss, have been reading chevyhiperf and gmhitech magazines for a few years as well as ls1 and ls2 and ls1tech dot com. So I like to think I am somewhat knowledgable about how most things work, but I still feel foggy about how the PCM works in regards to keeping the motor running at optimum performance such as LTRIM tables, Vtrim?, KR, and all the other numbers.

    Is there somewhere I can learn how the algorithms in the PCM are setup to run the motor, or is it proprietary GM stuff that is kept secret? And for the places and people that advertise a custom tune, where did they get their info and how did they learn?
    What are the various tables and matrices of data in the PCM, and how are they used (where it's not obvious) to run the motor. And when modifying these parameters how does that affect things?
    I would like to play with mine but given tuning software is upwards of $500 and I'm not exactly sure how to use it make's me a little hesitant. Or if I were to buy tuning software does it come with really good instructions?

  2. #2
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    You can do what I am doing. I bought the software,,I am going to plug it in and see what it looks like, save the original tune and start playing around,,,then come back on here with a ton of questions I am sure.

    It's the only way to get your feet wet. I started doing the same thing with an Iroc I had, burning chips. It was a learning experience,,and I made good progress with it. That was an older car with older software that was not very user friendly,,,and I beat the boards down with questions,,,but I finally prevailed.

    I suspect this LS1 tuning will be the same deal,,,although the software is a little newer and there are no chips to deal with,,,so things may go smoother this time around. I still have problems with abreviations, can't stand that crap and would rather have it spelled out in front of me. And there are plenty of tables that I don't understand, don't know what affects they have etc....but it's something that has to be done if you want to play with the car at all. I don't believe it comes with instructions but a few guys here have given me links to websites that help explain a few things,,,enough to make me dangerous,,,,lol.
    This is coming from a guy that hates computers, and I am lucky to find this website and post,,,but I made the plung. The only way to learn is to dive in and start playing with stuff. It helps if you first have an understanding of how/what engines like and don't like as far as tuning, timing, fuel before you change anything drastic. I have tuned older muscle cars for years using AFR meters, dynos etc...,,but using wrenches instead of computers,,,so the whole computer thing is new to me.
    If you are even more scared than me (which would be hard to comprehend) then I would suggest a good handheld tuner, some people on here have been happy with a few,,,just ask around. Larry.

  3. #3
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    orlando, fl

    dark bowling green
    2000 corvette

    efilive lets you download their program, so you can look and play with it.

  4. #4
    Join Date
    Aug 2005
    Newport, Mi.

    1999 Camaro SS

    Well, I have a few comments on tuning, but bare in mind, I have less experience than many on this board.
    I think of tuning in three parts, 1. idle tuning, 2. cruising around tuning, and 3. WOT tuning.
    For idle, I tune for cold starts & warm(hot) starts. There are tables for fueling depending on coolant temp. For a colder engine, you want to be richer, then taper off the AFR as the coolant temp rises. Plus there is a table for idle RPM vs coolant temp. These two types of tables are key to a good idle. Idle tuning is critical if you have a big cam.
    For cruising around, hitting 14.7 is ideal, but on the highway, better mileage is important to some, so maybe 15.?:1 is best.
    For WOT, you want the AFR that the engine wants for best RWHp, maybe 12.6 to 13.1 would work for you. Here, you can let the 1/4 mile trap speed guide your progress in acheiving the optimum AFR for your specific setup. And even better, use a wide band O2 sensor.
    But, most importantly, you need an engine scanner to tell you what needs to be tuned, and by how much. You can not tune effectively without a good scanner.
    Another tip: to more accurately tune WOT, I had to get the LTFTs to between -5% and 0%. With the LTFTs slightly negative, prevented the LTFT correction factor effect WOT AFR. If the LTFTs are positive, they are added to the fueling stuff at WOT. If they are negative, the PCM does not subtract fuel at WOT for fear of running too lean and blowing the engine up. So with this in mind, it was easier & faster to get 13.1:1 for my car, and keep it there with changing weather.
    And then, its actually comes down to the same stuff from the carb days: air, fuel and spark. I found my '87 OBDI ECM actually mimicking what to do if a carb is flooded with the clear flood mode. The OBDII PCM in my 1999 is much more sophisticated, but its still, air, fuel, spark!

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