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Audi V8 in a Boxster

24K views 64 replies 28 participants last post by  mrmiatanut  
#1 ·
Looking at Hilly's V8 Lotus has me thinking of a similar conversion for my 99 Porsche Boxster. I have a 5 speed tranny which I believe is also used on Audi's. Intial look from some of the Boxster tuners they think the Audi V8 will fit in the engine bay. I know there is a LS1 conversion in the works, but I really want a German V8 in my car if I do this.

Question has anyone tried to hook up an Audi V8 to either a 5 speed or 6 speed Boxster transmision for a mid engine kit car? In looking at pictures of the Audi V8 it appears that maybe starter is in wrong place?

What do you do for engine managment with the Audi V8? Is this a very difficult task for a competent mechanic?

I'm coming from 914 world where we do engine conversions all the time. Boxster and V8 sounds like a very fun conversion but I'm unsure if this is going to work with Boxster transmission. With 914 we have kits to hook up everything from Subaru motors , to SBC V8's to 6 cyclinder Porsche motors. It would be a blast to have a V8 Boxster! Appreciate any input.
 
#55 ·
scottmandu said:
Also the Chain drive V8's aren't the best to go with, I'd look into earlier (and cheaper) cam belt models.
Can I bring up an old thread? I'm looking to put the 4.2 V8 into my Boxster S.

Would you elaborate on why the belt models are better? From what I've read, the newer '05+ engines are a bit more compact (which contradicts the measurements of ABZ vs BFM here in this thread), and it looks like they rev a little bit higher (I like the sound) and make a little more power. They are also pretty cheap, although not quite as cheap as the 1997-2004 engines. Btw, I'm interested in NA only, so maybe that changes which type is better?

Someone mentioned the LS1, and I've seen Brad Roberts' posts in various places. I've decided against this because the LS1 is too long. A full 7" longer than an ABZ, even in the shortest configuration possible (vette pulleys, crank). For the Boxster, when keeping the stock 6-speed, moving the gearbox back 7" is not an easy thing to do. However, having a tall/wide DOHC seems like less of an issue because 1) the Porsche H6 is already 28+" wide and 2) even with the convertible top down, there is 6 or 7" of space to fit a tall engine. I measured the Porsche engine at around 19" tall, maybe a bit taller on some parts of the intake manifold. I also know that fitting the 996 engine requires dropping the engine mounts 1-2", so I know there is space below to make things fit.

I'm having a hard time finding someone at a salvage yard willing to measure the dimensions of a BFM/BGK or I might have already bought one. If anyone here has one of these engines sitting around and could take measurements, I'll mail some beer.

[EDIT] Actually, I wasn't clear. The overall measurements of BFM were posted by timmmy, but I need bottom of sump to center of crank and center of crank to top of manifold to see if I can get the crank lined up well with the gearbox input shaft without having to move things up or down too much.
 
#58 ·
So Brad, where'd you pick up the 5 inches?

I did a lot of measuring and head-scratching for the 4.2L V8, and I'm pretty certain about 2 major points:

1. It fits in all dimensions. It might be about 1" too tall at the back of the intake manifold, but that is not a big deal as there is plenty of room under the convertible top.

2. The transmission from the base Boxster should bolt right up to the V8 and it even has a place for the Audi starter snout. The gearbox on the S would have to be slightly modified, but it should also bolt right up.

However, the 3.2L M96 still has some nice features that make me not quite want to give it up, like 7500 rpm, forged one-piece rods, a huge sump, and a low center of gravity. Sucks that it's only 250 hp, maybe 280 with bolt-ons.

On the other hand, I like to track my car, and having 350ish hp in an NA engine would be nice. Currently, I'm looking at a low-mileage V8 from a 2001 A8 and a disassembled V8 from a 2004 S4. The S4 engine is nice, but rebuild parts put the total price a bit too high. So I was thinking it should not be too difficult to get 350 hp (crank) from the 2001 V8 with nothing more than a good tune and some headers. It also doesn't have that gear driven power steering and A/C, which would make for an easier swap than the S4 engine.

Btw, RS4 engines for $3500? SoCal is only a day's drive for me, so maybe I'll start looking.
 
#61 ·
Hey wulfgang, I read some scary postings of a lot of chain drive v8 failures and there is also the S4k failure. What was suprising was all the valve train and piston/ring failures. I'm very glad I decided to go with a belt drive AUX. I don't know if the belt drives have a lot of failures but from what I've seen they are very reliable and can easily go 100k without major surgery. Most of the chain drive failures were under 100k and some down in the 40k mile range iirc.
 
#64 ·
40v4kq said:
Hey wulfgang, I read some scary postings of a lot of chain drive v8 failures and there is also the S4k failure. What was suprising was all the valve train and piston/ring failures. I'm very glad I decided to go with a belt drive AUX. I don't know if the belt drives have a lot of failures but from what I've seen they are very reliable and can easily go 100k without major surgery. Most of the chain drive failures were under 100k and some down in the 40k mile range iirc.
I ended up with a belt-drive 40v. But I sold the Boxster and got a Cayman, so I'm not doing the swap unless someone donates a Boxster ;)

The engine is for sale; check my other threads.