Do you guys think I should upgrade up to the newer ECM? Looks like kind of a difficult upgrade. I am planning to put a 406ci stroker in the very near future. And in the longer off future (7+ years) I might want to add Nitrous. This is going to be a CA street legal car.

Just hunting for opinions....

Richard

 

By all means do it now...for one simple reason. If you do it at the same time that you do the engine swap and the engine won't start or run right, you'll be troubleshooting 2 major systems as the possible problem. If you do it now, and get it all running correctly with your current engine, you'll have one less potential headache later.

As far as it being a "difficult" upgrade, hogwash, I did mine in 3 hours. Just some simple repinning of the ECM and some splicing of the wires at the ECM connectors. If you'd like I can give you a detailed run through of how I did it and the differences between what I did vs the directions on the (most used) web page.
The only problem I can see is that if a smog station ever has to hook a scanner to it, and that scanner uses the vin for its means of deciding which ecm file to use... it might have fits.

 

Maybe you should write it up and put it into the tech section. I would be interested in looking at it also.

 

I could only put up the differences between his method and mine as anyhting else would be plagiarism

 

This is the page I was refering to http://www.eecis.udel.edu/~davis/z28/ecm_swap/
The majority of the info is great and right on the money, however..some of his methods and reccommendations are...not so hot.

Firstly, he uses crimp on splices where he taps wires.
For this I used a new razor blade and carefullt rolled it around the insulation in one spot, then again 1/2" below/above that spot, then carefullt slit that piece of insulation and removed it. The wires can then be solidered and wrapped with a good grade of tape.
Next he uses a "donar harness" for the relays and runs them to the factory location.
There is no need to do that. Get the relay sockets either from the junkyard or auto parts store (they come with 10" pigtails) and wire them in, BUT, where he splices them into the harness used by the MAS module (which you are removing) What I did was to cut the wiring on the module (it is 6" long) and wired the relays to that so that I'd have a nice secure connection instead of crimped splices. then you can make a simple bracket to mount the relays on and stash them where the MAS module was. I figure this is better for the relays anyway, out of the elements and engine bay heat.

Also, I labeled the pins I was moving, first with the location they were coming from then to their new location (eg D2-C1) and left the tags on the wires in case I ever needed to switch back.

 

You can do it yourself above but check each wire to make sure it matches the wiring diagram, mine did not, so it can cause some confusion.

Or you can take your harness out when the engine is out, and send it to www.jimsperformance.com

He will check your entire harness and move the appropriate wires and add the new MAF connections all of @ $150.00,,, he found an intermittent grounding problem in my harness that had caused me tuning issues for several months.

 

So do I really need to do this modification? It doesn't sound like there will be a tremendous amount of gain to be had (only if I was continually tuning my car and needing the information from the computer).

Richard

 

Personally, I would do it if you are going to be putting in that 406, from the standpoint that the 165 ECM's are better supported and more widely avialable. Also, tuners usually have a lot more exp. working with the 165's than the 85' 870 ECM.

 

What good does an upgraded ECM do?

 

Do you have too,,, no, Corkvette runs his 1985 ECM and gets 10.XX quarter mile runs with it.

Would you be better off, I think I would say yes.

Why do I say yes,, more flexibility in the ECM/program and the AMF burnoff realys are off teh shel for 86-89 model years, the 85 MAF burnoff is discontinued or,, if not, I know it costs a bloody fortune!

 

How hard is it to remove the wiring harness from a car if the engine is out? I am thinking of upgrading to the '165 myself, but instead of repinning maybe just have my harness done professionally..

 

Gabe, send it to www.jimsperformance.com, it will only cost @ $150, he will replace any bad or broken connectors for you, and bad wires and do a full diagnostic on the harness. He found a funky ground in mine that caused many tuning issues. All for $ 150( I think this is what I paid).


I eliminated my 4+3 relay, and moved the MAF burnoff and MAF power so that it is now under my dash. He can lengthen any wires you want to whatever length you want too.

With the engine out, it is a piece of cake. There are two harness wrapped up in tape, unwrap the tape and seperate the two and send the part that goes into the dash/firewall.

 

I think it would be a HUGE waste of your time. There are several very STRONG running cars here on the site running the 85 ECM.

Ralph's - 10 sec street driven car 406CI
Beachbums - low 11s street driven 383CI
Corkvette - low 10 sec street driven 434CI
85vets - low 11s 383CI

The list goes on and on of VERY successful cars running the 85 ECM. Consequently I have tuned MANY of these 85 cars including some of the ones listed above. The 85 ECM is arguably the BEST out there for doing exactly what you want it to without all the "frills" of the ECM changing setting you want it to run, like the newer ECM do.

THe long and short of it is the 85 ECM is very much like aftermarket ECMs in that it does exactly what you want it to do, and doesn't change things due to other parameters. When you get into the guts of the ECM, it has the very basics: Fuel and ignition (granted there are some other things) but for the most part it has the essentials for effectively controlling a motor VERY well.

In addition, I would highly suggest NOT changing the ECM while the motor is out. This is a mistake MANY people make, and upon startup of the new motor; should a problem exist your left wondering if its motor related or something you might have done wrong to the ECM during the swap.

If you do decide to go with the swap, I would highly suggest getting the motor running and work out any bugs, then only make the swap - that way if somethig crops up, you know its most likely related to what you just changed.

 

Especially the part about sorting out the problems of a new motor and figureing out where the problem is.
Jerris

 

The only reason I am thinking of changing ECM's is that I can hook up my laptop and view live engine data without putting the car in diagnostic mode as with the '85 ecm.

Other than that, I am happy with the '870 ecm.

 

Hey Jesse,

How about we tap your knowledge here and get some useful info;

Can you list what you CAN DO with a 86-89/165 ECM and what you CAN NOT do with an 1985/870 ECM, or vise versa?

By doing this, the thread is less "subjective/opinion" and more fact.

 

LD,

That is a pretty large task to list all the differences. If we were to break it down into the simplist terms possible I would say to check out the PDFs on Tunercat. (keep in mind there are more thing that can be changed beyond tunercat) but this will get the point across:

http://www.tunercat.com/tnr_desc/do_tc.html

If you check out the info for the definitions for each platform, $1f for 85 ECMs and $8D for the 90-91SD cars. You can easily see the $1f has only 2 pages of parameters and I believe the $8D has around 4-5 pages.

This is not biggest part of the difference though. With many of the newer model ECMs there are many other algorithims to compensate for emmissions, which ultimately interfere with the "programmed/desired" settings.

For the average guy, it may not matter, but for those of us that want to be as consistent as possible - it matters a lot. When you look at the code of these ECMs, it gets more and more involved with each years progression. This just adds to the numbers of factors that could happen to cause you changes.

With the Aftermarket ECMs, your again back to "barebones" - program it, it runs it type scenerio. When I was running the 89 ECM I encounted some weird changes run to run, when I stepped up to the SD ECM, I experienced more, when I went to aftermarket, these events seized all together (except me breaking out on the brakes, Ralph will appreciate that comment and understand what I am talking about - air damn breaking the beams instead of the wheels).

Point being the more complicated you make a system, the more factors that can play into your end result that need to be considered. My thoughts are keep it simple, keep it easy. That is why you see so many guys still running locked distributers and carbs at the strip. Its simple and very effective. The 85ECM in my opinion is just a hair step up from that setup.

The one big downfall as mentioned in the post is the ECMs ability to log data effectively. That is about all I see it lacking from a performance standpoint. Keep the "Bling" is for girls.

 

Jesse, can you delete the 9th injector on an 85 ECM, and does the 870 have a cold start?

 

We have not had any ill effects from removing the 9th injector on the cars listed above, if that answers your question..

 

Excellent information. Confirming what I already thought. I am designing and building my own conrol system for various engineering enhancement opportunities on these engines so in the future I would like to put my own system on. Does anyone know if there is some emissions complication with this? IE do they scan the computer to see if it exists/has some identification #?

Richard