AKM Electronics

Tuning Document:


 The Basics

 Advanced Tuning

 Performance Measurement

 Reading the PCM

 Programming the PCM

 Using PCMcomm


TuneItUp's LT1_Edit - A firmware editor for your F-, B-, or Y-body GM Car


1.  Overview and Purpose

 The purpose of this document is to make you think before you do something. Whether that something be smart, or whether it be stupid, you need to think before playing with PCM parameters. Do NOT blame us if you do something stupid, though!

This document will discuss common configuration parameters required when tuning both stock and slightly to moderately modified motors. For heavily modified motors, professional tuning is recommended initially, but fine adjustments may be made using this software.

This software runs under Windows95 and Higher (98/NT4). For that, you'll need a decent computer (our recommended W95 minimum is a 486/100 with at least 16 MB of RAM - but use your best judgement here). Our software, including all the DLL's etc. takes up about 4 MB of disk space, so we're not going to hog your hard disk with stuff. A 200 MB HD should be able to run W95 and this software very easily, and allow you to store lots of copies of your PCM file. Note that these are minimums, and if you have a nice Pentium laptop, you'll be fine. :^)

A laptop is not 100% necessary. I'm running the programming software on an old desktop in my garage. 486/100 w/ 32 MB RAM. Probably worth about $150 these days. So, you don't have to have the latest stuff to do this.

We also require a good old RS232 serial port for communications - preferably with a DB9 connector. We do not do parallel ports, nor do we do USB.

PLEASE NOTE: Screen Shots in this document are subject to change without notice. Functionality will be similar, but the screens are subject to changing.

2. Warning

You knew it had to be here, right? We realize this may be excessive, but we are emphasizing the point - it's easy to screw things up, and we're not responsible if you do! This will give you an idea of what to try to prevent.

Warning, these tools are complex and powerful. You will have the ability to completely modify the computer that controls your engine and transmission. You will have the ability to cause great damage to your engine, transmission, car, and car's computer. It will be easy to either cause the computer to tell your engine and/or transmission to behave dangerously (can you say: shift into first at 80 MPH, or turn on the fuel injectors and not turn them off???) or to simply make the PCM non-functional. Do not take this lightly. You can destroy your PCM in any of the following ways. A destroyed PCM cannot be repaired. Even a GM dealer cannot repair it. It must be shipped back to the factory. If you destroy your PCM, all it will be good for is a doorstop. If you destroy your PCM, your car will not start. It will not run. You will be stuck. You will have to purchase a new PCM from a junkyard, dealer, or performance house. New PCM's are not cheap. Your car will not move.

You can destroy your PCM by:

  • Losing battery power in the car while programming  (do NOT leave a charger attached while programming, and do not attempt any other work around the battery)
  • Losing power to your computer or laptop while programming
  • Losing the cable connection while programming
  • Having a virus checker stop the programmer on your computer (please disable!)
  • Having a screen saver stop the programmer (please disable!)
  • Having a software defect stop the programmer
  • Having a hardware fault stop the programmer
  • Trying to start the car while programming
  • Having another application run on your computer that stops the programmer
However, if you are very careful and cautious, you can successfully reprogram your PCM over and over, and set it up exactly how you want. Please remember, the developers of these tools (hardware and software) make no claims nor warrantees. Users are solely responsible for use these tools, and all results from using these tools.

You cannot damage your PCM when you read it. We suggest the first thing you do is to make a backup of your PCM's original memory file, and put it away in a secure area (be that a directory that you'll never use, or a floppy disk in a safe, that choice is up to you). Back up your PCM file, please! Do several reads before you actually write to your PCM for the first time. That way you'll know you have a reliable connection. (More about programming / reading later in this document.)

3.  Introduction

 The authors of the LT1_Edit programming and editing software recognize the need for cost effective custom tuning. To ship your PCM to a professional tuner and have to wait for up to a month for it to be returned is unacceptable (not usually the case, but it happens). Donít get us wrong - there are tuners out there who are very good at what they do, and are highly recommended at providing you with a starting point when dealing with a heavily modified motor. The investment made with them could save you a lot of grief and time.

Once you get your PCM back, though, it may be "good enough". But then you decide to change gear ratios - up or downÖ Or you decide your idle isnít where you want it. Or you decide youíre hitting the knock sensor too much during a dragstrip run (or conversely, you donít have enough timing, and feel like your power isnít optimized). This is where our software comes in. Most mail order programmers charge $300 for the initial program, and then another $100 per program if you change something from the original configuration. So, having this software can pay for itself very quickly. You can have it at the track on your laptop and make adjustments in the pits before the next run (or during those 2 hours while sitting in line at the track if you run at Commerce GA on a Friday nightÖ).

So far, we have been talking about modified motors. For stock (no internal modifications) motors, we do not recommend any change to any of the engine tuning parameters. The factory settings are quite good, and by just "guessing" where to move timing or fuel, and if you donít have your own chassis dyno, you stand to lose as much power as you hope to gain. If you want to squeeze maybe 5 horses out of factory tuning, we recommend seeing a professional. Professional tuner, or Professional Psychiatrist, itís up to you. ;^)

So why should people with stock motors purchase this software? The answer is simple. It allows you to do everything the competitors do (Rev Limit Adjustment, Speed Limiter Adjustment, Rear Gear / Tire recalibration, Cooling Fan On/Off temperature adjustment, Automatic Transmission Shift Firmness Adjustment) at a significantly lower price. And if you do decide to go in to the engine later to add that HOT cam kit or the cc306 and Stage II heads, youíll already have the software you need to make adjustments. No need to purchase additional modules. (You'll spend $300+ on a competitive programmer, and then another $150 for a scan cartridge, plus another $150-$200 for a custom program later!) Plus, itís likely something your friends donít have. Laptop and software envy is a wonderful thing.

You can make a lot of parallels between using this software and porting your own heads. If you study and talk to others before grabbing your tools and grinding away, youíll probably do a good job, and get decent performance gains. If you just grab your tools and start grinding, youíre going to screw something up. No doubt about it. However, in either case, you probably wonít end up at the same level of power as if a professional had done the work (be that a professional head porter with a flow bench, or a professional tuner with a chassis dyno). Some sort of "performance measurement" benchmark is required when fine tuning a powertrain system like this. These will be discussed later, but include dynos, dragstrips, and accelerometers.

If you're just starting tuning (like many folks are), don't expect to go through the software, tweak every parameter, and get it right on the first try. Go slowly. Change only one thing at a time, and see how the car reacts. Something you do in one area can affect how the car behaves in another. Don't be in a hurry. Go slow, change only one piece at a time, and do lots of experimenting. I know someone who burned over 400 chips to get a car running perfect (a late '80s 'vette). Thank you, GM, for providing us with reprogrammable flash memory for our LT1! Take your time, go slow, and document everything. This is very much a scientific experiment - use the scientific process methodology! (Plan, experiment, document, review, repeat). Don't rely on your memory to remind you what you've done in a particular revision of your file. Write it down!

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