rssshen vette

I have a 85 that needs to be tuned. I don't have much knowledge on tunning a TPI or custom chip burning. I've done a few mods(see signature) since my first custom chip which was done by Alvin at PCMFORLESS. I'm considering buying a after market computer (Accel DFI) to replace my stock ECM. Would this be a good investment? Has anyone done this before?

89onlyZ51

Trouble is, you'll need the same knowledge to tune a DFI that you will to tune your factory ECM other than actually burning your program to a chip (which is real easy). The concepts you need to know are exactly the same. The Accel software and tune-on-the-fly makes things a little easier, but it's a lot to pay for that.

Oh yeah, if you go Accel, make sure you go Gen 7 and not Gen 6. I looked into Gen 6, and if you have trouble figuring out how to burn a chip, you will have an even harder time learning to use its DOS-based program. Also, I felt a lot of stuff was missing from the Gen 6 compared to a factory ECM (for example, a table that compensates for low battery voltage at idle and modifies injector firing accordingly so you don't stumble/stall).

rssshen vette

Well, one way or another I need to learn how to tune this car if I'm going to keep it. I everytime I add a mod that requires a change in tune, I have to do a mail order. I need to create a better choice for myself. Since I do drag race the car,(on the weekend) I think it is to my advantage to learn to tune it or at least to adjust the current tune. Thanks for your input!!

tjwong

What mods have been done to your car? The old 870 ECM is fairly easy to tune and will handle most mods easily. It may not be worth going to the expense of the Accel DFI system, the only drawback of the old ECM is that its scan data rate is very slow.

Bullshark

Only drawback????? What about real time tuning on the fly. By the time you upgrade to an emulator and go thru the all the scanning and prom reprogramming BS, it makes aftermarket ECU's look pretty attractive to me.
Not only that you get all the bells and whistles like dual spal fan control, easy selection of multiple fuel maps for perfomance or economy, NOS control, Boost, etc. etc. Worth every penny IMHO.

Bullshark

tjwong

Well, fortunately for me I own a emulator and a chassis dyno for tuning. Many people can't afford a $2000 DFI or XFI system not to mention if the ECU takes a dump one weekend where are you going to get one, plus its going to be $800 for a replacement where a GM ECM will be <$100 at the local AutoZone parts house. No the stocker can't do boost or NOS or blah blah blah, but if what the guy has is a streetable camshaft and the basic Super Ram, Mini Ram etc, the stock 870 or 165 ECM is more than adequate to handle the job, maintain OE quality and reliability as well. I sell both XFI and DFI systems, and I would be more than happy to sell one, but I always tell it like it is as well just to give the man/woman an second option.

mseven

it is a big advantage to learn how to tune it yourself. Buying something like an an APU-1 package from moates will have everything you need and is money well spent (this system allows for real time tuning "on the fly"). For learning this is a good place to begin reading/learning:
http://www.thirdgen.org/techboard/di...uide-book.html

Bullshark

Peace Tom I did not intend to question your knowledge, I know you are in the business.....we talked in the past wrt MEFI remember. I just wanted to point out that there are many advantages that these aftermarket ECU's offer over the older technology. IMHO it is well worth it. I am a EE design engineer and for money you can have that old technology. Sorta penny wise / pound foolish. BTW, as I am sure you already know, you can get the Accel Gen 7 DFI ECU under $1K and rewire your old harness. If you have the knowledge to deal with emulators and prom programmers etc. wiring should be a piece of cake. I also believe that by the time you purchase all the stuff needed to support older ECU's you could have gone ahead purchased the newer technology for close to the same price and saved alot of time. Just pointing out alternatives


Bullshark

tjwong

Not a problem, I was just pointing out that on a mildly modified engine that a OE ECM can be used with good results. That is provided that one tunes it properly. I still dable in the MEFI stuff as well, I am waiting for the new MEFI5 to come out which is much like the new LS2 PCMs. It has a on board TAC module for fly by wire throttle control. I finally figured out why that ETC controller on that 40 ford kept on tripping out. It appears that the little servo motor could not handle the additional torque requirements of having to move 8 throttle plates with engine vacuum applied to it and the additional friction of all the linkage. The little motor just overheated and current increased by 150%+ which trips out the ETC TAC module. Motor sizing 101, unfortunately there is no other ETC motor that I can use other than designing something from scratch which isn't going to happen.

rssshen vette

My latest mods are Ported SLP runners, a completely Ported Plenum (mini ram coming soon)and gutted main cat. Prior to those changes I had the car Dyno. My A/F ratio was pretty high 17.81. Switching to an after market ECM is expensive, but I'm looking for an alertnative route to adjust my computer programing without going thru a mail order tune.
If I could get my car tuned without going thru a mail order or driving over two hours just to get to a shop, I'm for it. For now it seems that my best option is to up grade the ECM and learn to tune it. I have a friend that's knowledgeable in tuning that will give me a hand, and I know I can count on the forum for help

tjwong

The AFR you reported seems very high for something with just very basic bolt on mods. Did you pull a spark plug after the dyno pass to verify the lean condition, seeing nearly 18:1 would be a very very white ceramic insulator. Plus if it was truely that high, I would bet the power curve would have dived over by the time it hit high 14s at WOT, and that the engine would run fairly bad. At that AFR I would expect it to have lean misfires consistently. I am willing to bet that you got an erroneous AFR reading, especially if the dyno shop read it from the tail pipe, or you experienced a misfire during the run. Typically on a stock calibration with such simple mods I still expect to see low 12s AFR with a stock prom.

larry00

Believe me at $400.00 bucks for a Dyno Tune anything you can learn will pay off.
I too am doing mods which nessitate getting a new tune on occasion.
I have the gen 7 DFI and a snoot full of mods.