Any progress on V8 engine swap options? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

B6T · 11-30-2017, 02:24 PM

Glad to see some discussion and progress on this! I'm going to be getting starting on my project in a few weeks. I've got a 2003 Boxster S. I'm also a mechanical engineer and I've also swapped/wired up Audi engines before (2.7tt swap into a B6 chassis A4). I have a lot of shops in the area that I deal with through work who can support fabrication or machining for my project. I have lots of Solidworks experience and a little bit of FEA.

I've got a 4.2L sourced locally, along with wiring harness and ECU from a 2003 Audi A6. This particular engine is an 'AWN' code engine. As well, I have a 5-speed from a B5 chassis FWD Audi A4, which is the same transmission used in the non-S Boxster. So I'm still sourcing the 5-speed conversion components (through Woody actually

). I knew that the 6-speed from the Cayman was compatible with the 986, but as mentioned, it's also around $3,000 USD. So the 5-speed will have to do for now, until I come across that winning lottery ticket. Or until someone offers me $3,000 for my 986S transmission.

One of the significant requirements of this swap is that it passes an OBDII smog inspection. This is a requirement in the area where I live in order to be able to renew your vehicle registration.

I'm not really worried about mechanical issues because I can sort those out. What I am worried about is more related to the electrical side of things...

My concerns are:
- Tachometer compatibility (some Audi ECUs communicate tach via CAN and other through a signal wire)
- A/C idle up (usually through CAN)
- Rad fan switching (some Audis have relay modules (early 2.7tt) and some use a PWM signal from the ECU (3.0L V6)
- Engine compartment fan switching (not a big deal, but anyway)

There are a number of swap online which show a functioning tachometer, which leads me to believe this isn't really that big of an issue.

Does anyone have any insight on the wiring for these swaps? I've started laying out wire functions and colours for the Boxster in a spreadsheet but haven't done so for the engine side of things yet.