Best Audi 4.2 and ECU to work with Porsche Tiptronic?

[914turboford]

I've got a 2001 996/911 Tiptronic transmission. I'm planning to mate it to an Audi V8 for a rear engine project.

What year of 4.2 and ECU should I look for that would have the greatest chance of controlling the engine and transmission?

A company called Renn27 is making kits for installing 2.7 V6tt's in 996s. They claim that there is 100% compatibility between the electronics of the engine and chassis without reprogramming. However, they haven't yet done anything with an auto. I sent them an email and am waiting to hear back.

I suppose I should look for an engine and ECU from approximately the same era as the transmission, so approximately 1997-2003? My transmission is the 996.1 ZF unit, not the 996.2 MB unit.

Also, if any ideas on what torque converter/flexplate combo would be best I need to figure that out also.

[Rob Combs]

I've noticed no one is exactly jumping over one another to weigh in on this. There's good reasoning for that. I don't want to take the piss out of your planned project, but what you're getting ready to embark on is way more complicated than most people think it is and way more complicated to handle than a manual transmission.

German automatics can be EXTREMELY finicky even when moving from one vehicle of the same make to another. I used to work in an MB dealer. We once had an early build W211 that had the wrong line of code programmed into the instrument cluster - you read that right, the speedometer cluster was programmed incorrectly - and the transmission did not shift correctly; it would absolutely SLAM into one gear from another. Completely undriveable. I won't say how many parts were tried in an attempt to fix it, nor how long it took to get to the bottom of it and how many people were involved in getting to the solution. Because of the speedometer programming. It was difficult to say the least.

If your tiptronic's ECU has a CAN bus to communicate to a vehicle that is no longer there, you might want to do some serious research to find out if someone makes an aftermarket ECU to control it (and possibly the engine too) without the need for CAN connection (meaning standalone) and a damn good start on initial programming, or you might be in for a world of frustration unlike anything you've ever encountered in the automotive space.

I bid you good luck.

[914turboford]

haha thanks for taking one for the team on this. I appreciate the discouragement lol. I do realize this type of response is typical and perhaps even appropriate. Why not try to save some poor soul from getting in over his head?

I've got a line on a 2001 4.2 from an A8. The plan is to get the ECU, tcu and bcm from the Audi. The Audi boxes will think they are controlling a 2001 4.2 bolted to a 5HP24 when in fact they will be controlling a 2001 4.2 bolted to a 2001 5HP19. What could possibly go wrong haha?

Both transmissions are awd. One issue I foresee is that the Porsche transmission has no differential for the front viscous drive and has no electronic control of the awd as I understand it. Will the Audi TCU be trying to control a differential/awd components that do not exist? If so, I suspect that TCU will become frustrated and object to it's intended task.

[Rob Combs]

I do admire an ambitious project. I say this with zero sarcasm - I truly do hope you prove me wrong. Let us all know how it goes!

[914turboford]

[67rustavenger]

I have nothing to add to your thread.

What is the intent of this build? Meaning, what is it powering?

All interesting stuff you're doing here.
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[jpaull]

Knowing Audi and their vast selection of horrible engines and electronics, and trying to blend it with a porsche trans with thier vast selection of premature failers and horrible electronics, it sounds like this is a desperate cry for help.

Posting on the aircooled samba where we enjoy simple engines with no electronics whatsoever, things that break that are totally predictable and easy to diagnose, it seems your making a last call to normal people that might be able to save you from ending it all.

Dont do it! Nothing is worth what your about to torture yourself with.

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Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[Rob Combs]

The response about the type of transmission the audi ECU is programmed to recognize and the porsche transmission that will be paired to it just fully sunk in.

Setting aside for a second JPaull's (in my opinion, correct) comment about audi's reputation for less-than reliable engines and both manufacturer's electronics, and the correctness of his post in general, if you cannot verify 100% that the gear ratios throughout the planetary set and final drive are not identical to what the audi ECU expects to see, you will be in for incurable "implausible gear ratio" trouble codes that will throw the transmission into fail safe (in other words, locked into whatever gear the fail-safe is set to lock into) after your hard work and dedication to your project is all but complete.

Your estimated 15% chance of success might be a little optimistic. Again, I hope I'm proven wrong on this.

Now on with the show. Best of luck!

[Bub]

[Stripped66]

Absolute best-case scenario is if you source an Audi V8 from the same era and the CanBus data feed between the ECM and TCM is in the same format.

Worst-case scenario, you use a stand-alone transmission controller, such as MegaShift...this will require you jump on the learning curve to figure out how to wire and program the transmission. Another possible option, PCS has a few vendors who offer that controller with custom tunes, so maybe there's one out there already for ZF 5hpxx variants (I have a PCS controller for the ZF 4hp22 from a 993). Better-case scenario: Standalone TCM + ECM that communicate via CanBus would still get the job done (you'd have to confirm the two respective controllers will talk to each other).
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[914turboford]

[914turboford]

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[Stripped66]

[Bub]

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[Stripped66]