Audi A6 Allroad engine swap with inline 5 cylinder 2.5tdi

[chirpy]

Hi,
Can any of you guys tell me whether I'd be able to put the inline 5 cylinder engine from a C4 A6 into the C5 A6 allroader which currently has the 2.5 v6 engine in. If so, what problems/issues am I going to have to overcome. Will it fit in the bay, ie is it the same subframe, will it be able to able to able to drive the 4 wheel drive, will I have a lot of electrical work?, any other issues?. Before I get any 'why bother?'s, I have been running peugeot 405's on veg oil for years, and they are getting rare now, so am looking to the future.

[zollaf]

welcome to the forum.
this is a good question. i doubt you will anyone thats done this conversion, so you may be the first. yes, it will probably fit, the 2 a6's are not that much different. yes, it will be an electronics nightmare, you will need the loom from the old car to fit into the new car. wil it fit to the gearbox, maybe, but yes, it will have the grunt to run it. i look after an lt46 5 pot running an elsbett kit and that was converted 8 years and 150,000 odd miles ago. great engines, not as sophisticated or powerful as the v6 but a lot more reliable ad easier to fix. i think it would make a good conversion myself, although a pd will also run straight veg so you could just get an a6 or a4 quattro with the 130 bhp pd tdi, but the allroad is a nice truck to own...

[chirpy]

Thanks zollaf. I have a degree in electronics which would help with the electrical stuff. I'd hope to get a whole donor car, and a recipient with a dead engine if possible. 150,000 miles on veg oil is impressive, thats why I want that engine . Ive read that the pd engines arent as good for veg oil.

[zollaf]

the pds are ace on veg, but a much more complicated engine altogether, and don't like just running veg without a conversion. i look after a few that are done with the elsbett kit and have not had a veg oil related probem, apart from clogged filters. one beetle has done about 150k as well since conversion and its still going strong.
the immobiser may be the biggest problem, as its part of the dash, but the ecu can have this written out of it anyway, so should be good to go. all the vws tend to use the same bellhousing so that should be straightforwards enough. a degree in electrics will certainly come in handy. blimey, you have got me thinking now, i like the allroad but am scared off by the engine. could go for the bi turbo but i already have one in my s4 that drinks enough fuel...

[ametlib]

Hi,
Great idea !! I can tell you for sure that if you replace the 2,5 v6 with an AAT or AEL you also replace Audi's worst engine with their best !! Have no idea if the R5 will fit in instead of the V6, but you might find the allroad to be a bit to short in the front as
the v6 is very short and the R5 very long ... I think the tranny will fit, the exhaust will ofcorse not fit and the electrics will be a bloody hell .
Away from guessing I also happen to have both the cars in question parked right outside, so when I find time I'll do some quick measuring and post back

BTW I had to start the R5 this spring to mowe the car. After 2 yrs. standstill it started when the 1st piston turned !! the engine has not one working glowplug and it was freezing cold ... wonder if anyone can
tell me one thing that became better with the c5 ? ( I know about the sunroof, but exept of that ?

[ametlib]

C4 from bellhouse to front of viscouse fan measures around 64 cm, while the allroad seems to measure around 58. The small difference looks to be a result of the fan wich is pulled forward on the allroad. The C4 engine mounts seems not to be attaced to the subframe but directly to the cars body, so I doubt if that can be done without velding.
Most of the electronic nightmare can be taken care of by using a pump from 2,4 AAB vich bolts right on, if you then add a manual tranny and some black tape for the dash .... Abrakadabra ...

[beelzibus]

I shall watch this thread with interest, it sounds like a great idea.
I believe I'm right in saying that basically all the five cylinder inlines, all the V6 engines and all the V8s share the same bellhousing, so if that's true there shouldn't be to much problem mating the 5 cyl TDI with whatever box the Allroad started with.

[ametlib]

Yes, think the bellhousing are the same. Another thing is the R5 diesel is quite easy to get more hp. from. There are a few videos on youtube showing that .
Away from that I think this will be a rather big job and if you buy an A6 Q from 96 or earlier you'll find it already have a 140 hp. R5 engine . And as that is'nt enough, the C4 is a far better and reliable car than the C5 and
when something breakes down it costs peanuts to fix compared to the C5 ......

[adamss24]

As i happened to own both cars i would say that the c4 is better built and much stronger engine, however the c5 is much more refined and can tune much, much easier than the c4. What you need to know is that the I5 engine uses an archaic 8 Bit ECU with no VNT provision so folks are converting them to run the later T4 multivan ECU which can be flashed trough OBD and is capable to run a VNT turbo. As above dash will have a few lights on but a bit of black tape over the LED's will sort it out !

I will say get the later BAU/BDG/BDH v6 tdi engine, strap a hybrid turbo on it, throw some race nozzles and a clutch and presto 300 Bhp and 800Nm is within reach ! You will have to strenghten the I5 engine to a great deal in order to deal with 300Bhp on a daily basis !

[zollaf]

i think he just wants an allroad he can bang veg oil in chris...