Hey guys,


I'm lost. I have a 1985 corvette that I recently just Re-built. In the engine I installed new heads, Slightly larger Injectors and a mild camshaft that is comparable to stock cam specs. I also did a smog delete to have less restriction on my airflow through the engine. My understanding (and i may likely be wrong) is the stock ECM will try and make my engine run like a stock.

My questions are can I run my engine with a stock ECM. Will it hurt my engine?

If I have to re-configure my ECM can it just be re programmed? (I spoke to a tune shop and they said it has to be replaced because its so old and its about $2,500 to do so) I've gotten mixed responses about that.
Lastly If i have to replace it can somebody recommend a good ECM that I can install without killing my bank acct?

i'm basically just running my engine a notch above stock and I'd prefer to not mess with my ECM for the time being if possible. Just re-stored this car and would like to have it on the road for a month or so before continuing my upgrades.


Thanks in advanced,

 

1. 1985 ECM - You can use it - won't hurt engine if injectors not too large - can be re-programmed.
2. Next better option is to upgrade to the 1986-89 ECM. Many links on how to do.
3. Go aftermarket - many choices.

 

I have an 85 with stock ECM. Smog delete won't change anything that the computer is aware of, 85's only have one O2 sensor ahead of the Cat, so removing smog won't change that. I guarantee you that shop just doesn't want to deal with an 85 ECM, they are tune-able, they just require more work than plugging in a laptop. You'd have to call around you to find a shop that will deal with an older car, but they do exist. TPIS offers mail-order chips, which may cost alot, but they know a thing or two about these cars, so I'd suspect they'd take care of you. Back when my car got its chip, it was a mail order from TPIS. Runs strong, but it might need a re-tune since I put long tubes on it.
As for will it hurt your engine? Probably not, but it will run much better with a correct tune. The computer has some wiggle room that it can adjust in, but big changes will require the middle of that wiggle room to be reset, if that makes sense.

 

Hey guys,


Thanks for the advice. Basically i'm running aftermarket parts that are stock specs. 24 lb/hr injectors. Comparable cam specs and good aluminum heads (which wont do too much until there's a new cold air intake) So im hoping it runs alright with just a mechanical tune up. I do plan on going up a few notches with this car down the road but for right now, it's been off the street since summer of 2015 so i just wanna drive it for awhile before taking any further steps.

Blaster, your in Alton, IL? were basically neighbors then because i'm in STL. If you have any recommendations on places where you take your Vett, I'd be happy to hear your input.


Thanks,

 

With close to stock parts, it should be fine without a tune at this point. That's the wiggle room I mentioned. When my car was built, essentially everything was changed, top to bottom. Car would die if the gas was pressed at all, and it backfired like crazy. A chip from TPIS fixed that, and now it runs like crazy. So long as the car runs/drives well when you are driving (eg, not misfiring under load, not idling rough, not trying to die when put in gear/pressing gas), then you will be fine. If it makes bad sounds or exhaust smells rich, it will probably need a tune.

Yep, I'm right across the river. I do all the work on my car myself, so I've yet to take it anywhere for work. I got new tires at Roberts Ford here in Alton, since I worked there at the time, and knew/trusted the guys who would be working on my car. They also did my alignment, but it took them three tries since they didn't tighten the rear camber brace tight enough the first two times - so my camber fell out on the highway, which was a weird experience. My poor vette looked like a ricer Miata in the back. They fixed the alignment for free both times after it happened though. GM spec is 180 ft.lbs if I remember right, and they are on at 200 now. The first two times it was shy of 140.
When I did all four wheel bearings, I called Jim Butler Chevy to see how much they wanted to do it - they quoted 800 in labor, since I had the bearings already. It took me 6 hours one rainy weekend to do.

 

Yeah, I do all of my work myself also. However, this has been the biggest DIY job iv'e ever done lol. Just 6 months ago I had the entire top end broken down to the bare block to get the heads on.

With TPIS did you just tell them what you did to your engine and they configured a new ECM and sent it?

 

https://www.tpis.com/pages/efi

This webpage details all that they need to know to make a tune. I personally did not get the chip from them, but I have all the documentation/emails/receipts from the guy I got the car from. They are quite pricey, but seem to be well regarded. Mine has been my biggest DIY as well, these cars are fun to work on.

 

Are they doing datalogging and making adjustments or just guessing what your combination will do?

 

I don't think the cold air intake is going to do as much as you think it will. You may be ok with that depending on how large your new injectors are. You could also find a tuner in the meantime that will strap your car down and actually see what changes what and use a more aggressive cam instead of being limited to whatever is stock. Trick is, that means some delayed gratification which many seem to be unable and/or unwilling to do.

 

The info I have from them indicated that they will send you chips till you are happy based off of what you tell them. No datalogging, so perhaps not as good as a true dyno tune, but at least in my case they did amazing. I believe that if you take your car to them they will dyno tune it. Not sure of anywhere else that will dyno tune, so it'd come down to calling around.

 

Aklim, in 1985 they used 24 lb/hr injectors which is what I used. Later model C4s used 22 lb/hr injectors. So that being said i'm using the same injectors that where used from the factory
(Accel 24lb/hr) The cam is comparable to the stock cam, Basically just adds a meaner sound and the heads are high performance but they won't add much HP without other major add ons.
When talking mechanical engineering i'm pretty well rounded but when it comes to computer engineering i am a complete rookie.

Just wasn't sure if going a notch above stock would effect my ECM in a major way. I wish I had a carburetor for the simplicity of it all haha

 

www.dynamicefi.com
I did this in my Procharged l98 86 corvette. There is some re-pinning of wires in the computer harness (very minor) but you retain stock wires/sensors. New computer is exact casing of stock....Therefore, it fits in stock location. Mine started right up and accepted Procharger very well. The computer has self tuning abilities....VE learn (volumetric efficiency). Basically, you drive it and let computer tune itself. Your car will run smoother and faster than it ever has.

 

85 to an 86 computer is slightly more complicated than a few wires. Essentially the whole connector would need repinned.

Out of curiosity, what exactly did you buy from them? I'm slightly interested in moving to an 86 ECM.

 

If you don't datalog, how would you know what is happening other than "I feel" or the SOTP dyno? The ECM can compensate but you really don't want it to since it is masking what your butt dyno feels. Kinda like I break your leg and give you morphine. You don't feel the pain but your leg is still broke. Stand on it and ......

Actually, I took it to the guy who used to work for TPIS that partnered with someone to do run a speed shop. They might still work on it. HiTech Motorsport.

 

I assume they just get the tune to within the self learning wiggle room and that's that. My car dynoed 390 at the wheels before long tubes, so somethings is working right.

 

EBL Flash installed $430
EBL port mod $25
TT-1 $not sure - allows you to switch to a wideband O2 sensor

email them they are very helpful, knowledgeable and quick to respond.

 

I think they also dial back on the power for safety. When we did it, starting point was about 370, made some changes to the program and got more, made more changes and got more till it started going backwards At that point they went to "last known good" and worked on the non-WOT part of the program.

They used to only do dyno tunes but later would do mail order with the caveat that it might not be all that it could be. I have talked to other tuners who give the same disclaimer. Reason being that it's better to leave something on the table than to blow up engines. Can't say it blame them for not pushing it to the edge if they can't see it.

 

Thanks, I'm looking in to this now. You just plug it in and it goes? That sounds too good to be true! How heavily modified is your car? And it runs just like that?

It looks like a little repinning plus a MAP sensor is all it would take for an 85 Harness. This might be a sweet deal.

 

I repined per instructions, plugged in computer, uploaded base tune and told it I was using map 2 bar (changes fuel delivery). Then, I started right up a drove it. I have been driving for a year now and my corvette mechanic says it's one of the best running c4's he has seen. I just tuned through VE learn to refine. The computer comes with a base program. Yes, forgot about map sensor I bought a used grand national 2 bar map sensor off ebay.

I will admit that the tuning instructions extensive on the dynamic efi website but I didn't need to do most of that tuning. The computer learns a lot through the wide band 02 sensor -TT1.

mods: l98

* D1 Procharger
* 30 lb injectors
* Mini ram intake
* BBK throttle body 52mm
* egr delete
* smog delete

* 3" Mangaflow exhaust no cats

 

Cool, gotcha. So I'd need a wideband 02 sensor, I assume those won't use the same one wire connector that I have, so I'd need to run a new wire? And how's the MAP sensor install? Just a tap into the intake? I'd really appreciate info on both sensors, since those are the only parts that are hanging me up on getting this sysyem.