I'm contemplating the same question, interested to see this. I have an '01 AR 6-speed and picked up a Passat for a BHW donor but driving the Passat it's obvious the BHW will represent a large step back for NVH in the Allroad against the V6 it has now. Still like the idea but makes it a little harder to get motivated for the swap when comparing the smooth and silent 2.7 in there now to the coarse 2.0.
Workable clutch options to mate the short crank BHW to the 01E are all expensive and have compromises as well. Adding up the cost of a clutch and related parts from overseas, suitable trans and diff, and everything else to make the BHW work as it should and looks like it could get close to parity with using the V6 instead. The tuned BHW is plenty strong enough to move the car well but the V6 could probably do better with less noise and thrash.
MPG and US parts availability/cost are the key advantages I see with using the 4cyl engine. The 2.5 has a reputation as a fuel hog compared to the 4 cylinders. Service access is much easier with the 4cyl, the V6 is packed in there tight, pull the timing belts off just to change the thermostat, pull the front end off to change a starter or alternator, etc. Any of those could go wrong on the 4cyl far from home and be a simple repair with off the shelf parts, where with the V6 it would be a show-stopper in both respects. Failing VP44 pumps and cams appear to be common. And I already have a good running BHW in the driveway, hard to justify shipping something else from the other side of the globe.
Even with the tradeoffs the power and smoothness are appealing though, not to mention hassle free clutch options, rad support and snub mount, etc.
What trans/clutch/starter did you choose for your BHW/01E combination? I'm leaning towards the US S4/A6 2.7 01E with a strengthened 228mm FW/clutch to avoid need for a spacer with the short BHW crank, add a 4.11 rear diff and eliminate the trans oil cooler. Should give reasonable cruising ratio with the .68 6th and larger AR tires. Euro TDI Allroad trans with the shorter R&P and taller 6th would be better and retain the cooler and stock diff but $ and I don't know that there's much advantage to pursuing minimum cruising RPM in this heavy and tall car.
Would you care to share your possible source for the V6 engine/AR trans package and cost by PM? Did it include ancillaries, harness, ecu, plumbing, etc? Know the engine code of the 2.5 you had lined up? I gather the later year Bxx engines with roller followers were improved.
