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Thread: Tuning OBD1 GM EFI

  1. #1
    Super Moderator Six_Shooter's Avatar
    Join Date
    Feb 2011

    Tuning OBD1 GM EFI

    Tuning OBD1 GM Engine Management
    Whether you are tuning a vehicle that came from the factory already using the GM OBD1 (On Board Diagnostics 1) EFI system or you are using these systems in a conversion, you will need some tools to do so. This is designed to be a basic guide for those starting into tuning the GM OBD1 ECM/PCM, that have little to no prior knowledge of tuning.

    Where to start?

    To start with, you have to identify what it is you need or want to do. Do you need to make some small changes due to a change in gear ratio, or change rev limiter, or do you need to re-tune for increased injector size, larger cam, change in intake manifold, non-original use of ECM (conversion), etc. You will also need to identify what ECM and code you are using to ensure you have the proper hardware and software. On OBD1 GM ECM/PCM there are service numbers, such as 1227730, 1227747, 16197427, etc. This number identifies the hardware side of the ECM. There is also be a binary file BCC (Broadcast code), usually a four digit alpha combination, such as AUJP, ANLA, BJWN, etc. The BCC is a code that GM used to identify the binary file being used in the ECMs and helps track how current it is. This information about the ECM/PCM service numbers and BCC will be touched on in a later article, on how it is used to gather the proper software files and to tune properly.

    Log Ďní Burn

    If all you need to do is make some basic changes, then you don't really need to tune in real time, and can usually get away with tuning using a little as a programmer, an EPROM and a MEMCAL or EPROM adapter along with tuning software.

    Real Time Tuning

    If you need to make more drastic changes then you should consider tuning in real time, by using an EPROM emulator to make changes on the fly and see the results right away. Using an EPROM Emulator will also help the tuning process go quicker than using the data log, tune and then burn technique.

    Now that you've identified your needs, you can start to select the hardware and software.

    Getting Data, or What Is My Engine Really Doing?

    For any real tuning to be done you should first consider an ALDL (Assembly Line Diagnostic Link) cable. This cable will connect to the ALDL connector that is usually found under the driver side of the dash, in most vehicles. This cable will allow you to connect the ECM (Engine Control Module) or PCM (Powertrain Control Module) to a laptop and retrieve data from it, while the car is running. This information can be as simple as checking for ECM or PCM entering closed loop mode, or as detailed as seeing what the Pulse Width (PW) of the injectors is at certain conditions, and many more variables in between. The ALDL cable is basically your way of seeing what the ECM does, and what it does with the information it sees, so that you can make the proper adjustments. The ALDL cable can be used as the only hardware connected to the vehicle or with other hardware as well.

    Now that you can see what the ECM is doing, you may also want to monitor other items a little more closely. This is where a Wide Band O2 sensor (WBO2) will come into play. The WBO2 will allow you to watch the Air Fuel Ratio (AFR) much more accurately than what a Narrow Band O2 sensor (NBO2) sensor will. Most WBO2 systems have their own data logging software that can be used, or in some cases the WBO2 information can be streamed into the ALDL data stream as well, more on that in another article.

    Letís change stuff...

    Log Ďní Burn

    Now that you can access data via the hardware, letís change the bin file. To do this, you will need more hardware, don't worry it's not a lot of hardware in the end, you'll see. Most people will at least want an EPROM Programmer. An EPROM Programmer allows you to read bins that are on existing EPROMS and program them with the new altered bin files. For some people this is the entire way that they tune their vehicle. They will data log to see what needs to be changed, then modify the bin utilizing a tuning program, then program an EPROM, install it, data log again, rinse, repeat. This is an effective way to tune, it just takes a while, especially when you're working on a new engine combination or made some fairly large changes to the engine, like a cam swap, or change in intake manifold, ported heads, EFI conversion, etc.

    Real Time Tuning

    How do you tune quicker? Well, that would be through the use of an EPROM Emulator. This is a device that plugs into the ECM in place of the EPROM, and allows you to change parameters as the engine is running, even while driving down the road, it is recommended to have someone else drive the car for the latter. With the use of an EPROM Emulator you can make several changes every few seconds and see the results immediately, verifying it was a change in the right or wrong directions very quickly.

    Once you have the refined bin file that you were able to develop with the use of the EPROM Emulator, you can then use the EPROM Programmer to program an EPROM, to have that bin in the car and not need to leave the Emulator in place. However, some people leave their Emulators in place all the time.

    Software, software...

    So now that we have selected some hardware, letís look at some software. There are a few different options here for software and if you ask 10 different people, you will get 10 different opinions on what software is best. They all have their advantages and drawbacks.

    Depending on the ECM you are using and what it is you want to do, from just basic data logging, to full out real time tuning will dictate what software or types of software you can use.

    Some basic data loggers are:
    WinALDL - Used for the 160 baud ECMs, such as the 1227747, and similar" onclick=";return false;" onclick=";return false;
    Datamaster Ė Designed for data logging OBD1 GM gas and diesel vehicles, as well as Ford vehicles." onclick=";return false;" onclick=";return false;

    Editing Software:
    Tuner Pro - The non real time version allows for bin editing.

    Combination logging and editing software:
    Tuner Pro RT - Allows for data logging all OBD1 GM ECMs and editing the bin file, can be used in real time tuning with the use of an EPROM Emulator.
    Tuner Cats Ė Allows for data logging and bin editing of Most OBD1 and some OBD2 GM ECMs and PCMs.

    Chris Rook
    April 2011
    The man who says something is impossible, is usually interrupted by the man doing it.

  2. #2
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    North Idaho

    Re: Tuning OBD1 GM EFI

    I had time to read that six shooter. I think it's a excellent writup! You can always add to it as time comes. I think it should be considered our Tuning OBDI article.

    I have read Dave w TunerPro writeup and it's totally differant which I think is good! Once he get's done with his bathroom and duplicates that writeup here you will have a spot to link to for "Tuning with TunerPro".

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  3. #3
    Super Moderator Six_Shooter's Avatar
    Join Date
    Feb 2011

    Re: Tuning OBD1 GM EFI

    I figured Dave's write up would be different by your description of it previously, so it sounds like there is no overlap thus far. :D
    The man who says something is impossible, is usually interrupted by the man doing it.

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