On my new engine (5.7l TPI, Edelbrock 6085's, 10:1 CR, mild Speed Pro Cam) I am getting some detonation with my ADS chip. On my original engine (with the ADS chip), I could run 10* initial advance with no detonation problems at all. Now, I have to back it off below 4*, and am not sure I have totally gotten rid of the problem.

So, I swapped my factory chip back in, bumped the timing back up, and it runs great! No detonation at all, but the trans wants to lockup too soon now!

I would like a prom that lets me run greater initial timing (better idle) like my stock chip, but has the convertor control tweaks of the ADS chip. I'm clueless as to what effect their fuel curve changes contribute to my problem. Any recommendations?

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'87 IROC 5.7l TPI - original owner!

 

The Edelbrock heads are more efficient than the stock heads, so they won't need as much timing advance at WOT. More static compression increases your chances of detonation, although a bigger cam will bleed off more dynamic compression (aka: brake mean effective pressure (BMEP)) which lowers the chances. The ADS chip adds timing at WOT, so you were right in turning back your initial advance. Your timing at WOT is probably the same with the stock chip and bumped up initial advance.

If you burn your own chips, you can bump up the timing table everywhere so that it runs better at idle and everywhere and you can tailor your spark advance up to the point of detonation. I've heard/read that lowering the WOT timing 1-2 degrees from the point of detonation will not affect the engine's max power, and is actually better since the computer drastically reduces timing once you get detonation and adds it back in slowly.

As far as the converter control and fuel curves, you can change those too with either GMEPro or TunerCat. Use a good scan tool and log plenty of runs to get some good data as to what the engine and computer are doing. As Bruce Plecan (Grumpy) says quite often on the GM-ECM list: "give the engine what it wants, not what you think it wants" or something like that.

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Greg Westphal
'87 IROC 305TPI/A4

 

As far as the converter control and fuel curves, you can change those too with either GMEPro or TunerCat. Use a good scan tool and log plenty of runs to get some good data as to what the engine and computer are doing. As Bruce Plecan (Grumpy) says quite often on the GM-ECM list: "give the engine what it wants, not what you think it wants" or something like that.

**BINGO**, that's it

 

Thanks for the input, guys. Though I use computers daily at work and programming is part of my job (Fortran), y'all are talking over my head. I don't have a laptop, or any of the other tools you mention. I can't justify their expense, either. I am willing to buy a new chip, but need to know what it's doing (the ADS purchase was ignorant).

I guess for now I will measure the timing (with an old-fashioned light) at 500 rpm intervals with each chip installed and plot the results to see how the curves compare. They will be under "no load" conditions, but maybe that will give me some idea of how they compare.

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'87 IROC 5.7l TPI - original owner!

 

P J Morgan,

Buying a custom PROM will cost you anywhere from $300 to $500. The cost of the equipment to burn your own PROMs costs about $200.

A little money and a lot of time will make you smile from ear to ear.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's after installing Hooker LT Headers and reducing weight.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I wouldn't suggest sitting under the hood of a moving car to do that plotting, and building an ecm bench to run diacom on gets real time consuming.
You don't need a laptop to burn chips.
You can't afford not to learn how to edit and burn your own.
For the price of two wrong custom chips chips your at a break even, and for the third you can buy a POS laptop for running a scanner on.

 

Hehe.. he's right! My POS 484 laptop only cost me 50 bucks.. and my previous 286 laptop was only 20 at a local thrift store. LOL Burning chips is CHEAP

 

OK, I'll bite. If it's so easy, why haven't I seen anything explaining how to do it? GM tried hard to keep us from figuring this out, didn't they? Is there some comercially available software for reading and modifying our chips? I have access to "dumb" prom burning hardware and software (I could copy chips, if I wanted to), but how do you put together the data to put onto the chip? How do you interpret what's on the chip (or how the ECM uses it)? THAT'S where the mystery lies.

I am an engineer, and I understand things like fuel curves and advance curves. But I haven't the first clue as how to read them from the chip or how to change them. I'm up against a huge learning curve.

Right now, my car doesn't run the way I want it to, and don't want to spend a year (or whatever) figuring it out. I want to fix it NOW!



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'87 IROC 5.7l TPI - original owner!

 

Yes. www.tunercat.com is one example.

IMHO Burning eproms is .1 percent of the work. The hard part is the tuning (assuming you already have a bin editor). Figuring out what the engine wants and which tables and parameters to change to meet it's needs is where the work comes in.

IMHO There is a great learning curve. Knowing how and why the ECM does things is important.

Here is a good starting place: https://www.thirdgen.org/newdesign/tech/promintro.shtml

 

It's easier then changing distributor curves or recurving a dissy
try reading the tuning.doc at DIY_EFI incoming.
Tuning=notes+measuring performance+looking at trends, change as necessary= go fast +good mileage= good karma

 

I think you've grasped the main point to all of this, PJ.. From now all the way back to the early days, the basic formula to make your car go faster has remained the same:

There's no replacement for intimate knowledge of the inner workings of your engine, and many, many hours of trial and error, ISOLATING A SINGLE VARIABLE EACH TIME. Like they say here, "give your motor what it wants" (or something like that .

The only step that is different here is once you've collected your data and really understand what it means, your next step is to write it to a chip and test your hypothesis. Back in the day, your next step would have been to change the jets in your carb and put in different weights and springs in the distributor, but the goal is the same. You could cut corners then and you can cut corners now (i.e. making changes without data to justify it), but once again the result is the same: Your engine won't be living up to its full potential.

Heh.. that's all easy for me to say, I haven't burned a single chip yet for my Camaro! I don't have a lot of time to put into the data collection right now, so I'm not rushing it. I'm just trying to absorb as much as I can, here and on the GMECM list. Hopefully before TOO long I'll be pretty proficient with this stuff!

 

Then after you burn a couple hundred little lights go off about gee so it I did this and this, or reread the DIY archives again and see that new material they're are allows adding, and it's oooww so that's what they meant.
I was thinking that I done well over a thousand, and the more I think about it it's way over that. And I'm still learning,
Like today, was Ohhhhh, so that's how I can do that (reference anti-lag with a turbo). Like on the 89TAAs (I got the same ecm) I have yet to see any AL stuff and they have been hac'd for 3-5 years now...
Course, now it will be the rage...
Oh welllllll

Just givin the engine what it says it wants

 

phew. over my head
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'92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,Crane AFPR (42psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch, Macewen white face gauges...ZZ9 cam (i still have to install it )

[This message has been edited by theformula (edited November 14, 2000).]