Reprogramming modern ECUs

[Alfred1]

I've been searching for information about reprogramming the ECU from the VR6 motor that I want to install in my 914 (so that I don't get error codes for things like the ABS system, transmission etc.) and I've come across a couple of companies that can reprogram ECUs through the OBDII ports without touching the chips themselves. Revo Technik in England sells a product for VWs to reprogram the ECU through the diagnostic port and a company in Australia sells software that will allow tuners to reprogram the ECUs on Subarus the same way. Pretty cool.

[lapuwali]

Personally, I'd just dump the OEM ECU and use an aftermarket unit instead. Much simpler, and you'll have full control over the thing. Using something like Megasquirt will be relatively cheap (but a non-trivial amount of work), and using something like SDS will be relatively easy (but not nearly so cheap). Trying to get the full OBDII system working after the swap will be a nightmare.

[Alfred1]

Originally posted by lapuwali
Trying to get the full OBDII system working after the swap will be a nightmare.

Are you talking from experience here?

[lapuwali]

No, but think about it. OBDII has several redundant sensors that are not much use except for checking up on an emissions system you won't have intact. There are two O2 sensors to account for (one before and one after the cat, which won't work if you're not using one), there's usually a pressure sensor or two to ensure the fuel system isn't vented to the atmosphere (and the 914s system is not fully pressurized), etc.

Unless you're planning on completely reengineering the 914 to modern standards, or planning on doing a lot of electronic hackery to fake the OBDII system, I wouldn't expect it to work as is. If the ECU will still operate the car even if the OBDII system says everything is messed up, then perhaps it won't be a problem.

Mostly, it's a problem of dealing with what you don't know about the ECU and how fully integrated it is. Does it attempt to adjust ignition timing based on what gear is selected, for example? Will it drop into a limp mode if certain parameters aren't within spec? Can you divine what those parameters are? Can you fake them? Is the anti-theft system integrated? Can this be bypassed?

The newer OEM systems aren't really designed to be swappped from one car to another easily, at least not by someone who doesn't know all of the details of the system. The aftermarket ECUs are designed for just this purpose, and are much simpler, and much more fully documented.

[Alfred1]

I'm going to contact a few different companies that are in the business of reprogramming ECUs e.g., http://www.giacusa.com , http://www.upsolute.com/eng/index.html , http://www3.sympatico.ca/mdsylva/products.htm , http://www.revotechnik.com etc. and tell them that I have a VR6 motor with all the related engine sensors in my 914 and ask them if they can reprogram my ECU to work with my new setup. I'm no computer expert but maybe they can just set the non-engine related sensor values equal to constants that are always within specs for that sensor. I'll have to see.

[9fourteen]

I recently picked up the tool for interfacing to my VR6 in my GTI from obdtool.com. Using the interface with the VAG-COM software from www.ross-tech.com I believe you could actually reprogram the chip yourself. It's just a matter of sending the correct codes to it. I just got this setup a couple days ago and haven't done much with it yet but there is section in the manual for recoding the chip. For only $71 it's a useful tool to have even if you get the chip recoded somewhere else.

[lapuwali]

I strongly suspect these tools will allow you to only alter the tables that govern various relationships, like fuel to airflow, or fuel to coolant temp, or ignition advance to rpm. So-called "maps". These tools very probably do not allow you to actually change the program that interprets these maps. If (and this is far from given) there are map variables that allow you to affect things like "ignore the (missing) second O2 sensor" or "don't go into limp mode if these values get completely wacked", then you're alright. It entirely depends on the degrees of freedom the ECU program itself allows, and how well documented they are.

Altering the maps is really all most tuners would care about, since they're not trying to disable unwanted "features", just trying to do things like raise or remove rev limits, or alter fuel and/or ignition timing parameters. In short, a very limited subset of what modern ECUs do.

I wish both of you all the best luck, but I still say using an aftermarket ECU would be less work.

[Alfred1]

Well, I emailed the businesses I mentioned above over the weekend and told them that I wanted to install a VR6 in my 914 and asked them if the ECU could be reprogrammed so that non-engine sensor inputs are always within specs and Upsolute replied and said "... it is not possible for us to program the ECU in a way, that all sensor readings are within the tolerances."

What's the worst thing that could happen if I installed the VR6 with all of the engine related sensors connected but other sensors like the wheel speed sensors for the ABS system etc. disconnected? I have no experience with modern ECUs but I doubt that the engine will be disabled to any great extent.

[lapuwali]

There's really no knowing w/o trying it, unless you can find someone inside VW or Bosch (or whomever does their ECU programming for them).

It's possible, even likely, that the system would just activate a warning light (pull up a pin on the ECU that you'll presumably not connect to anything) and go on its merry way if the ABS sensor was disconnected.

My most recent VW (a '95 Golf) once failed in a rather bizarre fashion: driving along the freeway, the dash LCD went out, the rev counter and speedo went to 0 (I'm doing 60mph here), the engine lost power and seemed to be hunting (like I was running in limp home, probably with fixed ignition advance). I was trying to get to my destination a few miles away, but after a couple of miles of running like this, the engine stopped completely. I pulled off, and the car wouldn't restart, then the alarm started to go off. I got out, locked and unlocked the doors a couple of times, and the alarm stopped. A few minutes later, just as I was contemplating walking, the engine decided to start again and the car drove fine. The next day, the dealer mumbled something about a service bulletin about the alternator wiring being bad (no sign of a charging problem), and replaced the alt to battery wire. A short time later, VW/Audi recalled a number of cars for faulty alternators (not including my car).

The problem never reappeared, but certainly showed me the alarm system/immobilizer was way too tighly integrated with the rest of the system. I NEVER activated the alarm system, and if it had been possible to buy the car w/o the alarm, I would have done so. And this was an OBDI car, when the software in the ECU was much simpler...

So, again, best of luck in getting the OEM ECU to work, but budget time and money to swap to an complete aftermarket system in case it doesn't work. No matter what, be prepared to learn a LOT more about engine managment systems.

[Dave at Pelican Parts]

The worst possible thing that could happen is pretty much what happened to Lapuwali, there. The engine dies on you, probably somewhere you really need it working. (Train tracks? Ref. earlier thread about the GAF...) The next-worst thing is that the engine won't run at all. I'd guess that to be somewhat likely.

The most probable thing, IMHO, is that the engine management system would default to some sort of "limp-home" mode, where it only lets the engine make 10% or whatever of its power, has a very low rev limit, and so on.

I also think it somewhat likely that the engine will run just fine, with some "turn a light on" signal on one of the pins of the ECU. But I think it more likely that you'd get the "limp-home" behavior.

Then again, I'm taking an absolute WAG.

--DD

[Alfred1]

I'm going to buy the Bentley Manual for this motor and look at the troubleshooting guide to get an idea what the sensors that are not directly related to engine operation have on the motor. Based on zero information, I am cautiously optimistic that the motor will run fine with just the sensors that are directly related to engine operation - but, I'll just have to try it and see.

[Alfred1]

Here's the email response I got from Revo Technik

Hi Alfred,

Your project sounds very interesting. Unfortunatley, we don't do anything in regards to the old VR6 software... The majority of the non engine related sensors won't effect the running of the engine if disconnected. They would just leave faults in other sectors of the ECU. As long as you've bipassed the immobillisor you should be okay, having said that I would be inclined to speak to either Stealth Racing 01926 812 259 or Midland VW 01543 486 101 as they have much more experience with the VR6 engine than I do. Have you considered afermarket management?

[lapuwali]

Well, that's something, sounds like it MIGHT work. However, if even the OEM pros are recommending aftermarket kit...

[silver2.0]

My biggest concern is that the o2 sensor will be confused. It directly regulates how much fuel to kick in based on the oxygen content of the exhaust fumes. If you can get this to work, I think you will be golden.

[Alfred1]

The oxygen sensors will be connected - I just have to figure out how to "bypass the immobilzer".

[Alfred1]

I just read on the VWvortex forum that the '99 Golf III VR6 is not drive-by-wire. Woo hoo! Makes my engine transplant even more straight forward.

[lapuwali]

You'll have BOTH O2 sensors hooked up? With a cat between them?

[Alfred1]

Yes, everything engine related will be "by the book" as much as possible.