[MikkiJayne]

Originally Posted by RICKY D

I’ll be honest I was thinking the C5 RS5 swap would be easiest (although the one I least want) due to the base engines being so similar. I’m sort of glad you’ve mentioned it’s not straight forward as I’m looking to whittle down the list to 2 if I go ahead with the plan.

Physically the engine is almost identical but with a larger bellhousing. D2 engine mounts would fit it, but you'd need an adapter to get a manual gearbox on it, or keep the RS6 5HP24. Its all the surrounding infrastructure that would be such a pain. People don't believe me when I say the D2 has a smaller engine bay than a C5, but it really does. The D2 is longer in front of the engine, but narrower at the suspension towers and the firewall is further forward. I've worked on V8s in both platforms and there is so much more room around it in the C5 its silly considering the size of the car.

The RS6 engine consumes every inch of space in the C5 and so the couple of D2s which have been done have had serious packaging and heat management issues.

Originally Posted by RICKY D

The 5 pot Rs3 engine is transverly mounted - not sure if it could be adapted? That lump with s DSG would be immense but I don’t know if I could mentally get over having “just a 5 cylinder” engine in such a big car?

Yes, it is transverse, but thats just an issue of plumbing and fabrication. The biggest issue would be the oil pan and oil pump pickup, which would have to be adjusted to clear the subframe. You'd have minor issues round things like coolant flanges and manifolds, but its all just fabrication. The Americans swap transverse VR6s in to longitudinal S4s and deal with all of that stuff. It would have to go on a manual gearbox since the RS3 DSG clearly wouldn't work.

There are a couple of D2s with the original 5-pot turbo. They have the classic Audi quattro sound instead of V8 sound, but they lay down some pretty impressive 11s

Originally Posted by RICKY D

The D4 S8 engine is the one that excites me the most. How do you know it mates up to a manual gearbox? Has someone transferred one in to a car already you’ve seen?

Likewise 800+HP in a D2 would be epic! There is someone in the US swapping one in to a B4 Coupe. He's posted some interesting pics of the back of the engine - the bellhousing is identical to the RS4 manual gearbox and even the RS4 flywheel bolts up! VAG hate changing things when they work
Electronics obviously a challenge, but these days there are people who can solve that. The biggest issue I can see with the D2 is getting the turbo outlets to clear the firewall, because the D4 ones will go straight through the D2 heater! I think its likely it'll need a chunk of the firewall cutting out and re-shaping and then a pair of custom downpipes making to tuck in by the back of the exhaust.

Its popular for the S4 guys to put a single turbo in the V on the 2.7TT, with the exhaust down the back of the engine, but the D2 bay is so tight even that isn't possible. The D4 engine would need some brave pills and a TIG welder but I reckon its do-able.

Originally Posted by RICKY D

The 2.7 TT engine from the B5 S4/RS4 C5 allroad is definately a close second just because of the bang per buck on them plus the switch to manual should be possible.

Strangely no one ever seems to have completed one of these and I can't figure out why. There have been a couple started then scrapped. Its the same basic block as the D2's V6 so it should just bolt in. Some plumbing, some fabrication, a bit of same-generation electronics. How hard can it be? I guess I'll find out Mine was supposed to be done by now, but other work has thwarted that. I'm hoping to start it in the summer.

Originally Posted by Adrian E

Would the supercharged V6 fit, I wonder? They’re capable of silly power with a stage 2 tune and not much else. Common enough I would’ve thought to not be silly money. Would need to be a manual conversion I suspect, but might be feasible to build the 7 speed s-tronic into it? I suspect all of this will depend on being able to control the engine management with a stand-alone ECU and still have the rest of the modules working without flagging. Errors constantly

I thought about that one, but figured if you're going to deal with all the issues of getting modern electronics running in a D2 then you might as well just go big and use the 4.0TT instead. Theoretically the 3.0TFSI should be much the same swap, and yeah the engines are definitely cheaper. You might be able to do one of those for <£10K.

Definitely manual though. The architecture of the newer drivetrains is completely different to the D2 - the new stuff has the front axle line right behind the engine bellhousing with the torque converter actually past the driveshafts. Its a weird setup but it gets the engine 6" further back in the body. The D2 just couldn't accommodate that - you'd end up with the engine in the same place, but the output flanges 6" further forward which wouldn't work at all!