Marc_986
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« on: March 04, 2026, 03:10:15 PM »
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Hi All,
Just written a good intro, but the session timed out and I lost it (should have copied before, but didn't). I am not rewriting the whole part, but do want to introduce my project.
I bought a Porsche Boxster 986 for cheap with the intention of turning it into a nice car again. I am nearly through the mechanical work of full suspension and steering refresh, transmission swap (with driveshafts etc), ABS upgrade and switch to electrical power steering pump. Next on the list is to give it some more power. For that purpose a Audi BBK engine is on its way. It is a bit (quite a bit I must say) more expensive than earlier S6 engines or in fact the VW Phaeton engine of similar power. But I hope it will fit the 986 engine bay better. To my knowledge this is not tried yet, so hoping for the best.
To prepare my engine arrival, I need to understand the ECU part a bit better. I need to get it to run without the other Audi parts. I will ask some questions on other parts of the forum for this.
For now, already many thanks for all the great info and knowledge here, fantastic!
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grayjay
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« Reply #1 on: March 05, 2026, 12:10:39 PM »
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Older ME7.1 ECU type should be fairly easy to work on. Challenge will likely be to get the Audi ECU paired and working together with the Porsche instrument cluster, ABS and TCU/TCM modules (if any), particularly if the ECU and cluster used different immobilizer types. You likely will need to make changes to the ECU EEPROM soft coding to get it matched to rest of the Porsche drivetrain configuration.
Replacing all the BBK's timing chains and guides before swapping engine in?
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Marc_986
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« Reply #2 on: March 05, 2026, 02:08:52 PM »
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Yes, I agree that there will likely be some work getting everything working together. I am assuming for now that at least my ABS (Bosch 5.7) will give the right speed signal to the ECU. The engine comes from an automatic gearbox car, so as far as I read it either need to swap this out for a manual one or reflash it with manual software. The cluster is none-CAN, so getting the tacho to work might be a challenge, otherwise I hope no big issues. Any pointers in the right direction might already help me prepare a lot.
It will be a two stage approach to get the engine in. I have an empty body shell (called 'the wreck') to make it fit mechanically and to get it started (fuel tank, pump, radiators all in there). Stage two will be to transfer to my real car. At that point I'll make sure there are no timing chain issues to expect (so either upgrade the parts or make sure it has already been done). Not that difficult with the engine out anyway.
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_nameless
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« Reply #3 on: March 05, 2026, 04:06:15 PM »
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You can flip a few bits in the ecu software to get speed from mechanical speed sensor or from canbus and same thing with rev counter should be easy. Immo off can be done by flipping 4 bites in eeprom or it can be done in flash too. Quite a few damos floating around for the 4.2 stuff so you should have enough material to get you started. Cool project, sounds like a lot of fun
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If you are broke or expecting free handouts DO NOT message me. I'll probably put you on blast if you do.
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grayjay
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« Reply #4 on: March 05, 2026, 04:19:02 PM »
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The Audi ECU can easily be modified to deactivate the ECU immobilizer function so that it will start and run without "authorization" from other immobilizer components. Audis of this IMMO III era typically had another immobilizer built into in the instrument cluster that sets off flashing alarm lights, triggers warning lights on dash, and stops radio and HVAC systems from working but the dash immobilizer does not actually prevent the engine from running.
It appears that your 986 uses a separate external immobilizer box, similar box also used in some (earlier) Audis and VW. You might just be able to leave the Porsche immobilizer box in-place to keep it from triggering any other alarms/lights, while running the audi ECU with a deactivated immobilizer. Just depends if the Porsche immobilizer box would freak out if ECU immobilizer is not present. More complicated but it might (doubtful) be possible to retain the ECU immobilizer and pair it with the Porsche immobilizer box??
Changing the soft coding in the ECU is all that is needed to make it run with an audi manual transmission. All the software for auto or manual is already there in the ECU, it just needs to be setup correctly via the soft code. Changing the soft coding and revising the ECU immobilizer can both be accomplished by revising and reflashing the EEPROM which requires triggering it into boot mode for the re-flashing, plenty of instructions for doing that can be found here.
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Marc_986
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« Reply #5 on: March 07, 2026, 12:45:48 AM »
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Thanks for the replies, makes me start to feel a bit more comfortable in this area. I'm quite sure that the Porsche immobilzer only interacts with the ECU, so the car won't mind not finding the original ECU. Will make sure though.
Does the Audi engine have a change of starting with the automatic software / coding, but without the TCU on the bus? Or will I need to first set it to manual? My idea is to first get it started with minimum changes, then update bits where needed. Immo off will be the first thing, so I'll dig a bit deeper in that, but from what I have seen so far, this is a well known area.
Also I'll see if I can find a proper wiring diagram of the Audi (I have the Porsche ones). It is a bit of a shame that the search engines get more useless each year. Many AI generated non-sense answers, blogs etc. Will need to find a few connectors on the car side so I can make a bench harness as well as one for the wreck, and one for my car ;-)
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BlackT
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« Reply #6 on: March 09, 2026, 05:35:17 AM »
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I will help you also
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Marc_986
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« Reply #7 on: March 15, 2026, 09:07:17 AM »
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Thanks all!
I have found some wiring diagrams of pretty similar engines / cars, so should give a pretty good base to start from. Will continue looking for the correct diagram, but need to have that final info from the engine first.
The engine itself will come in a few weeks. I'll first to a mechanical fitment to assess whether it even has a chance of fitting without structural work. If so, I'll continue on the electrical stuff.
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