D3 4.2 (BFM) ECU Vs D2 S8 (AVP) ECU.

[Nollywood]

Hello guys!

I'm currently getting ready to install the 4.2 V8 40V (BFM) motor into a 2000 B5 2.8 Quattro Sport.

Now my query is based upon me running the V8 motor through an 01E 6-speed. As the D3 never had a manual option, it will require a bit of work to get it to idle smoothly, and at the right rpm when the ECU looks for, and doesn't find the TCU it's usually paired to.

I have therefore opted to run the BFM engine with a 2001 D2 S8 (AVP) ECU. Both ECU's are Motronic ME7.1.1. The S8 ECU can obviously be coded for manual via VCDS. It will (may?) also allow the BFM motor to rev a bit higher, and overall remove the "softness" associated with the D3 4.2 V8 (non-FSI).

The BFM engine is very closely related to the AVP, down to the dual-stage intake plenum, same short vacuum actuator links too.

My query is this - will the D2 AVP ECU run the D3 BFM engine? Do both ECU's have the same pin-outs? I have the D3 wiring diagram, but not that of the facelift D2. If anyone has the ECU pin-outs for both ECU's, I would really appreciate it, and I'm quite happy to PayPal £10 for them.

Thank you all in advance.

[Architex_mA8tey]

Have you looked in the D2 tech dump folder? Pretty well all of the D2 info you're ever likely to need is there
Link for it is at http://forum.a8parts.co.uk/showthread.php?t=9345

[Nollywood]

Thanks Neil!

[Goran]

Why not try the trick TozoM8 did on his conversions, leave the TCU connected and leave the auto lever switch wiring hardwired to Neutral. That way theoretically the TCU wont interfere with engine power output.

That way you don't have to mess around with coding a different ECU from an older engine.

Although you would still probably have to resolve the ABS controller coding which would expect some kind of load signal from the TCU.

Alternatively, just get the BFM ECU mapped to ignore the TCU, it may end up cheaper than you think. I had some custom mapping out work done for only £150.

[Nollywood]

I understand where you're coming from, Goran.

Unfortunately, Tozo's method is not the right way to go about things. The ECU will only be fooled for so long, certain driving patterns will certainly make the ECU question the integrity of the set-up. The fixed values vs changing rpm and load will cause issues. It will work up to a point, but it won't be perfect.

Using the AVP ECU will be easier, both in terms of manual coding, and tuning for better drivability. Newer naturally aspirated ECU's are biased to smoothness and favourable gas mileage, and are less aggressive. I can safely say the D2 S8 motor has more urgency than the very similar engine in the D3 A8 4.2 QS, having owned both.

I just need to determine pin-outs of both ECU's, then the rest is easy.

Oh, I forgot to add, I'm retaining the D3 engine harness.

[Goran]

No worries, you know this stuff better than me. Good luck with the project, I hope you bring it along to one of the meets when finished it would be impressive to see it.