Motronic ECU??? Help.........

[CRNT918]

A friend of mine had recently purchased a so called "racecar", however, it's more of a "cut and paste job to me. We're slowly getting the car up to snuff, keeping in mind that it's always ready for DE events. It's an '86 Carrera, 3.4 litre, cams(?), High Compression pistons, Dual plugs, Electromotive Ignition, Mass air
Flow sensor, but with a stock(?) Motronic ECU. We had planned to install, this winter, a Clewitt Engineering TEC3 system on the car. After an unfortunate mishap flooded out the ECU, we dried it out and it seemed to work perfectly until our last track day. An unexplained loss of power. We sent the car to our mechanic who said that the ECU was bad. We were going to change it anyway, so no big deal. While it was there, we told them to change the oil. Didn't want that scum in there while it waited for us to find the time. The mechanic said they found metal in the oil and it the engine should come apart. OK,no problem again, it's had a few hard years at the track. The Big Problem is, we don't want the mechanic to be involved with the installation of the TEC3, but want the car back in running condition. No finger pointing that way. Should we find a used Motronic ECU, and try it that way,
or just take the car back and install the TEC3? Does anybody have any other suggestions?
Yhanx,
Pete

[beepbeep]

I say make sure that he's not pulling your leg about particles in oil. On the other hand, your wrench might be wrong blaming the ECU, loss in power might have mechanical cause so rebuild is needed.

I think you need to troubleshoot first and then do the work. It can be ECU (sounds unlikely, it's only electronics, no moving parts), it can be mechanical (likely, particles in oil, loss of power), or both.

Of course, if you have the money just go for shotgun approach and tell your wrench to tear it and rebuild everything mechanical and say: "don't install TEC3 yet, we need some tweaking to do" and borrow Motoronic box just so you can do engine break-in. There is a chance that it won't be needed as your ECU might be working allright... does he have Bosch diagnostic computer to check error-codes?

Cheers!

[Wayne 962]

Read this first:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm

Then go get the TEC-3 from Rick and run with it!

-Wayne

[ChrisBennet]

I don't understand how you can have both EFI's in the car.
A Motronic based twin plug motor needs a custom chip.
How much do you want for your bad DME? (I hack them.)
-Chris

[Wayne 962]

He's got Eletromotive HPX, not the TEC-3 in there right now - just ignition...

The DME is the same as the ones in the BMWs, right? I have a whole pile of them Chris...

-Wayne

[ChrisBennet]

Originally posted by Wayne at Pelican Parts
He's got Eletromotive HPX, not the TEC-3 in there right now - just ignition...

The DME is the same as the ones in the BMWs, right? I have a whole pile of them Chris...

-Wayne

The BMW ("059") DME's and the '84-89 911 DME's are very similar.
Surprisingly, the BMW DME will start and idle a 911.
The 28 pin BMW boxes just need a chip change. The 24 pin boxes need a little more work. I just tested a 24 pin BMW one that I converted to a 911 one last night. It doesn't seem to support the CASIS (fuel economy) light but other than that it works great.
Thomas Owen is the one who figured out the "extra" jumper that was the key to the conversion.
-Chris
EDIT: I may be wrong about the CASIS light. My friend with the test car called me today and told me his light doesn't work with his stock DME either.

[MoreGAS]

CRNT918,
If it is a stock ECU you need to take your ECU and plug it inoto another 3.2L car and see if it works properly. I imagine with a MAF sensor their has been a chip change so oyu may need to change that as well. An engine that is giving up the ghost will most often suffer a loss of power.
You are wise to have the engine rebuilt(if it is necessary) give it your approval upon completion, then begin the new conversion.

Why do you feel the need to install and aftermarket ECU? Have you dyno'd the car and found it wanting for tunability(even with qualified chip burning help) or are you going to install throttle bodies or radical cams? These are valid reasons.

Kevin Roush
GAS Motorsport
Performance Porsche
909 985 2909

[CRNT918]

Hey Kevin,
The car does have radical cams, however, I don't have a clue of the exact spec. The main reason for the switch to the TEC3 would be driveability. The O2 sensor has also been eliminated, so from what I understand, the ECU is running in a "default mode". Doesn't the fact that the motor having a HPX ignition give a communication problem to the ECU system. The car is a "*****" to start and won't idle worth a S@#&
until it warms up at least 15 minutes. We just want to ONE complete
sytstem telling the motor what to do. Howevern any other advice would be greatly appreciated!
Thanx,
Pete

[MoreGAS]

It would be wise to have the cam's spec recorded when they are out for the rebuild(assuming you need one). Most companies stamp an ID # in the back of them. This will help determine whether a decent idle is possible. You might chk with whomever built the eng and or tuned it to find out what mapping /chip/scheme it has. We have made engines with a fair bit of cam and a bit of overlap like 20 degrees idle good on bigger engines. The lobe centers cannot be real narrow though. Maybe an idle of 1200-1300 RPM or something up a little could steady it out. 1st make sure that what you have there is working -like the head temp plugged in, idle speed stabilizer functional(assuming you have one there from a 3.2 or 3.6) .
Running without the O2 sensor is not a problem for any track car as beyond about 75-80% throttle it is ignored. We campaign aand maintain many 3.2 and 3.6 eng's on the track and never hook it up.

By Hpx you mean HPV1 or electromotive twin plug stand alone ign correct? I do not see how using the Bosch motronic to control fuel only could be effected by not using the ign aspect- but I have never done it this way.
You may want to make sure what is there cannot be made to work properly 1st before tossing it all away and starting over. A healthy engine 1st, then a dyno session with a savvy tuner and accurate A/F sensing would be the best place to begin deciding the future path. Also it may help to determinne why the thing has debris in the oil-detonation spun a rod bearing?? Bumber, to put it right back together and have it happen straight away again.

By drivability issues we usually mean the thing stumbles upon rapid throttle application, or dies on decel, or hick-ups and misses slighty part throttle cruising. Basically, what one experiences through the varied transient or constant conditions driving, not start-up troubles and idle. You may be able to get that right.

Good luck,

Kevin Roush
GAS Motorsport
Performance Porsche