I am currently in the process of upgrading several components on my vette, and looking at everything it takes to custom program a prom. At first glance it would apear to be very difficult. I then decided to ask advice from a felow Texan Vette owner with no reply. If anyone out there is in the begining stages of a DIY prom, feel free to ask questions. No question is dumb! I guess some of these folks are too smart for their own good. I've decided to actually take the time and learn how this works and post my progress along the way. I encourage others to do the same. Sorry if it sounds like I'm venting, I just want to learn from others and hope to share alike. I look forward to this project!

 

89Texas,

The reason you did not get an answer back most likely is there really is no *easy* answer. Each car is different with what needs changed, and much of what needs changed is not written anywere.

Tuning is not something that is hard to learn if you want to put the time in and read/experiement ALOT! About 10% of it is research and the other 90% is experience/taking taking notes of what worked and did not. Then you come to see that what did not work 1 week ago, now suddenly works, because you changed something else a day before. Finding those links is the key.

Ever play with a rubics cube back in the day. That is exactly what this is like. Its very easy to turn the sides, but not easy to get the individual blocks in the correct spot at the end.

I would suggest that you take things very slow and start with the switch type changes such as fan temp kickon/off. Once you get the nack of burning the chips and confirm that the fans are coming on correctly, then move on to the cruise and see where the blms are in each cell. Try to get them all to 128 or as close as possible, with just the inj. constants. Then fine tune the fuel in the 2d graphs to correct the cells that are still out. Then you can move onto the 3d graphs (this is were things start to get fun) for the spark etc. You will see that once you change these, everything you changed before will change as well. This is were notes and experience will play the largest part and also the rubics cube analogy will speak its part.

Just be careful. Changing to many parameters at once without the proper knowledge WILL ruin an engine VERY quick.

Also WOT throttle should be the VERY last thing you change, the closer cruise is to perfect will enable you to get WOT that much quicker.

These are the things that took me a few years to realize, and hopefully it will help you in your endevor.

Good luck! :cheers: :cheers:

 

I've just started to attempt to learn this stuff myself. I guess the most disparaging part is the steep learning curve. It isn't like learning your multiplication tables (constants to be memorized), it is more like what ski said. Things change because you just changed something else. You can adjust the spark timing under load, but that doesn't necessarily make the spark under load under temp do what you want. Open loop and closed loop are different in themselves.
I want to adjust my BLM's, but feel I have to know what the engine is seeing and why first. Else, my changes may just be hit or miss, more likely the miss part I'm sure.

 

:iagree:
If you have the basics down of how to tune a carb. car then it'll come to you pretty easily. If you're starting out from scratch....then it's gonna take a while.
I'd highly recomend reading "How to tune and Modify Chevrolet Fuel Injection" by Ben Watson first-that'll give you a good insight into how the blm, int, etc interact.
And no, there's no way to summarize it without writing a book; which no one has done. So I'm afraid you'll have to go the route the rest of us have-finding items to read here and there. The first post at the top of this section gives a lot of good info to get you started. Also check out http://www.thirdgen.org Look under tech articles-and read the one on diy-prom.
The above sources should get you started-then pick our brains! Good luck, and when you get the habit and can't leave it stock...it'll be well worth it.

 

I will say this too as a word of advice:

One of the first items you should buy when tuning is a WB02. I don't care who you are. If you are using the 02 readings to tune WOT you are playing a dangerous guessing game. Dyno machines are fine, but truthfully. I would have a hard time tuning a car in the dyno time rush they send you through, plus dyno driving and track driving are two different things.

For the time and money you spend on your car 500 bucks will be paid for VERY quickly. There just isn't any better tool out there to help you pinpoint your tune.

:steering: :cheers: