GM Stand Alone ECM Swap

[sil80drifter]

As much as I love being quoted (twice! my ego's about to explode), I will tell you this:

I've talked to a few friends of mine, and they are pretty knowledgeable about these things. The many many idle controls the KA engine has are very very redundant for our purposes. It will be much simpler if we get rid of the AAC and FICD, and just leave the 3rd, the Air Regulator, which is responsible for cold starts. The idle itself can be controlled with the initial throttle plate opening, just as it is in many other cars. This should not affect driveability and increase simplicity.

Stop worrying about steppers and non steppers, especially when going standalone and obviously foregoing any emissions related controls. And I don't mean forget emissions, as we all need to pass them, but the factory equipment used for those purposes, and for things like A/C idle increase.... well, doesn't really apply here.

btw, the pic used for my explanations is as follows:



I am personally going with Megasquirt, as the harnesses and etc are all available and easy for me to use, plus I've already bought it and would lose money and extensive research efforts I've put into implementing that standalone. Btw, MS does have an option for controlling stepper type IACV stuff, but I just choose not to use it. Of course I sort of lose the ability to control idle from my driver's seat, as it will be controlled by the throttle plate and the screw adjuster... but oh well.

I commend your efforts with the GM ECUs, and believe they could be a very viable option as their user friendliness expands with time.

sil80
Modified by sil80drifter at 5:03 PM 4/6/2007

[Chezedik]

Still IACs add a nice touch in that they improve mileage and driveability, while helping emissions. I would rather work that out, than to make adjustments via throttle opening and worry about low vacuum at idle.

[Edub1]

I still have my AC so I want to keep that valve.

Simple solution - remove the solinoid and plunger. Replace it with a plate with a barbed fitting. Run hose to the GM valve which is remote mounted. Now we have the stepper motor IACV, the idle adjustment screw and the thing for the AC.

Where am I going wrong?

[Edub1]

More good links.

http://www.syty.org/old/promguide.html

http://www.syty.net/forums/forumdisplay.php?f=22

[turbodig]

I still have my AC so I want to keep that valve.

Simple solution - remove the solinoid and plunger. Replace it with a plate with a barbed fitting. Run hose to the GM valve which is remote mounted. Now we have the stepper motor IACV, the idle adjustment screw and the thing for the AC.

Where am I going wrong?

This would probably be the easiest approach.. remove your stock idle control system, make a plate that allows you to mount the LT1-style IAC boss to a hose. Or just mount the LT1 boss there - We've had guys with sheet-metal intakes do this.

The GM IAC is basically a controlled vacuum leak. As was mentioned above, it's a 4-wire stepper motor.

later,

Dig

[turbodig]

Damn near everything on that list is a check. I don't know much about distributors or how speed sensors work - perhaps someone who understands them a little better will chime in. The FSM is here http://www.nicoclub.com/FSM/240sx/1989-90/ and it has info on the dizzy - E theory IIRC.

Anyway, TPS should mate up and the idle air control can simply be fabed up. Also, I'd think the Turbo Sunbird would be the closest memcal. Are these in the ECU?

Modified by Edub1 at 6:59 PM 4/5/2007

Modified by Edub1 at 7:00 PM 4/5/2007

Yep, memcal gets plugged in.inside the ECM There are *tons* of different applications, any thing that used a '730 or '749 ECM (as well as a few lotus ECMs) used a MEMCAL that would be compatible.

3 parts to a MEMCAL-

PROM - The physical memory chip that contains ECU code/data. Usually a 27c128 or 27c256

ESC substrate/wafer -White laser-etched circuit that takes the analog signal from the Knock sensor and converts/integrates it to a digital time-based signal.

CALPACk - a set of resistor neworks and hard-wiring that tells the ECM hardware how to operate in "limp home" mode, a dead or dying ECM.

As far as a dissy signal, all you need is a simple toothed-wheel reluctor, one pulse per cyl. You can run DIS with a custom crank wheel, needs a double-tooth on the number 1 cyl, though.

[Edub1]

I think I'm about ready. I might have found an ECU with the 2.0L turbo mamcal and I'm thinking I can make a conversion harness that will plug between the new ECU and the factory harness. Then it's the stepper motor mod and I guess it will be on to tuning.

I wonder how long it will take to get it right seeing we have so little data on our motors. Luckely, I ran across a post with the VE at various RPM. This should be a decent starting point but I'm thinking for bets results, I ought to give the car to a pro and let them work their magic.

[Edub1]

Tons of info

http://www.thirdgen.org/techboard/diy-prom/

[Chezedik]

Yeah, I was looking at 3rd Gen already. Do you have Willems or Moates?

[Edub1]

Moates.

And man is that stuff complicated. Still trying to figure out just WTF a memcal does. I did find that that is where the zif socket goes.

Anyway, that's why I'm suggesting that we get a few guys on board with this and I will have this guy show me what to do and have him do the tune on his dyno and then it would be easy to reproduce. Otherwise we'll be farting around forever like we are doing with the ECCS stuff.

First, I'm going to set my entire fuel map to all 1s and try to tweek the K and VQ untill I get 14.7 accross the board. If that fails, I give up.