Audi 4.2 V8's, are they any good?

sowen · Post by **sowen** » Wed Feb 04, 2015 8:21 am

Being winter it's typically cold outside so my mind has been wandering, anyone got any thoughts and opinions on the Audi 4.2 V8 engine family? Whole cars are coming into the breaker/donor price, and they also come with a manual 'box.

I'm toying with the idea of getting one to drop into my SD1, been looking around at the Jaguar and Lexus V8's, but the Audi seems to offer more on paper, but not a common conversion I believe?

kiwicar · Post by **kiwicar** » Wed Feb 04, 2015 4:08 pm

Hi
I think they are a typical modern multicam engine, make excellent power, go on for about 400k miles if you change the cam chain and tensioner every 100k very clean efficient on emisions so give good fuel economy and run the throttle and gearbox off the engine ECU so are a total and expensive pig to get to run properly in anything but the original chassis.
best of luck
Mike

sowen · Post by **sowen** » Wed Feb 04, 2015 4:29 pm

kiwicar wrote:Hi
I think they are a typical modern multicam engine, make excellent power, go on for about 400k miles if you change the cam chain and tensioner every 100k very clean efficient on emisions so give good fuel economy and run the throttle and gearbox off the engine ECU so are a total and expensive pig to get to run properly in anything but the original chassis.
best of luck
Mike

That's kinda my thinking, I have a Megasquirt kit going onto the existing RV8 I have, so presumably that should be capable of running the Audi lump and most other modern powerplants?

I've found a few good photos of the engine on the floor from the perspective of fitting to a different bodyshell and it looks to be a reasonable size and shape to work with, and also fairly plentiful. 6 speed manuals with ratios bang on the mark for my driving style are fitted as standard equipment, apart from the initial purchase and fitting costs I'm struggling to find a reason not to pursue the idea further

chodjinn · Post by **chodjinn** » Wed Feb 04, 2015 4:38 pm

Great motor, respond well to forced induction, only problem is converting to RWD, you are limited on gearboxes unless you can fabricate an adapter. I was considering one, ended up going for the lexus v8 in the end.

DaveEFI · Post by **DaveEFI** » Wed Feb 04, 2015 4:38 pm

Can't see any reason my you can't use an MS for the engine. Although some types of variable valve timing may not be implemented - yet. Gearbox control may be more tricky - but again will come if not already covered.

But aren't all Audis either FWD or AWD? Wouldn't that be more of a problem 'box wise?

sowen · Post by **sowen** » Wed Feb 04, 2015 4:58 pm

In reality, if sticking a basic Megasquirt system on using the same sensors that would run a Rover, I'd hazard a guess and expect to see somewhere around 250bhp on a moderate homebrew tune. Hitting the magic 300+ would be great but I prefer driveability and the 'feel' over quoted top trumps figures.

I'm not scared of fabricating stuff if need be, in fact I enjoy the challenge, which is partly why this idea appeals so much

. I think the front sump would sit forward of the SD1 steering rack, whilst allowing for clearance behind where the throttle bodies sit.

On the transmission, I've spoken to some people who used the standard Audi Quattro gearbox and modified it to rwd only on some other project I had a look at, something I was going to research further. Again, making gearbox adapters isn't new to me, just another challenge to take on

DaveEFI · Post by **DaveEFI** » Wed Feb 04, 2015 5:46 pm

Did you miss the SD1 with Lexus Soarer quad cam V8 on Ebay last week?
Only made a fraction of what it must have cost to build. Doubt it even covered the cost of the re-spray.

sowen · Post by **sowen** » Wed Feb 04, 2015 6:29 pm

Yes I was following that one, nice install but the time/expense to get a 230 or 260bhp engine which is notoriously expensive to fit a manual 'box to was what prompted me to start looking around and thinking about other alternative modern powerplants which with a little ingenuity and basic fabrication could be adapted to fit? The Audi 4.2 in standard form comes from 300bhp, and some of the other late 90's OHC V8's of about 4ltr capacity also push out similar numbers higher than the Lexus lump. So far the Audi 4.2 looks to be a really good all-rounder, except the price of donor cars is still high compared to the others.

Sometimes it just isn't about the cost, but the fulfilment from actually building something unique that works

unstable load · Post by **unstable load** » Tue Feb 10, 2015 7:24 am

sowen, you know you want to, so why not find a Quattro and stick that in the SD, just for giggles. Having seen your work on the P6's and the SD you are more than capable, IMO.......

sowen · Post by **sowen** » Tue Feb 10, 2015 6:01 pm

unstable load wrote:sowen, you know you want to, so why not find a Quattro and stick that in the SD, just for giggles. Having seen your work on the P6's and the SD you are more than capable, IMO.......

I reckon the O1E 'box would drop straight in, but getting the driveshafts anywhere near the wheels and keep the V8 within the engine bay, just wouldn't happen. If I was to go 4wd (which I've done some research into, one of the many ideas I've explored on the P6), it would be a system similar to the old Sierra 4x4, transfer box behind the gearbox and a driveshaft to a differential beside the sump, with driveshafts attached to each front wheel. Sounds easy!

I have found some more detailed dimensions and read a couple of build threads, and the Audi lump does still look very promising to me. Hardest part would be sourcing a manual flywheel, but there is a company which is selling a conversion to bolt over the existing auto flexplate. The blocks are alusil which is prohibitively expensive for rebuilding, but hopefully should last a long time without major issues.

chodjinn · Post by **chodjinn** » Fri Feb 13, 2015 7:43 am

sowen wrote:Yes I was following that one, nice install but the time/expense to get a 230 or 260bhp engine which is notoriously expensive to fit a manual 'box to was what prompted me to start looking around and thinking about other alternative modern powerplants which with a little ingenuity and basic fabrication could be adapted to fit? The Audi 4.2 in standard form comes from 300bhp, and some of the other late 90's OHC V8's of about 4ltr capacity also push out similar numbers higher than the Lexus lump. So far the Audi 4.2 looks to be a really good all-rounder, except the price of donor cars is still high compared to the others.

Sometimes it just isn't about the cost, but the fulfilment from actually building something unique that works

The later Lexus V8s had 300bhp. They're not 'nortoriusly expensive' to fit manual conversions to, there is a place in the UK that do kits for BMW boxes for a grand, plus clutch and gearbox you're looking at about £1500. The kit I have is a custom adapter for the auto bellhousing to R154, it's just a plate. I do have a rather expensive hydraulic clutch though.

But if you're not a stranger to gearbox adapters, then it's irrelevant what engine you go with isn't it? All I know is that if you can fab an adapter, the BMW boxes are cheap as chips and almost bullet proof.

sowen · Post by **sowen** » Fri Feb 13, 2015 8:07 am

I've read about the BMW 535D 'boxes being near indestructable, the Mercedes OM606 superturbo fans love them, but they put a lot of effort into welding a Mercedes bellhousing flange onto the fronts of the BMW 'boxes. I have a TIG welder, just haven't bought a bottle for it yet!

I may have done a deal on a cheap engine, will have to wait and see what comes of it. The target is to have something fitted, running and driving for less than £500 using what I already have to hand.

sowen · Post by **sowen** » Mon Feb 16, 2015 6:56 pm

I've now got an engine, come across a cheap lump complete with all ancillaries still attached and even had the quattro autobox thrown in with it

It's a 3.7 40v, but for the price it was a good deal, complete with ecu's etc. The plan is to strip all the unnecessary stuff off and get it ready to run on Megasquirt once I've got my head round running my RV8 on that first.

ChrisJC · Post by **ChrisJC** » Mon Feb 16, 2015 8:59 pm

I just love the way that Audi think it's OK to have a car with all that weight so far in front of the front axle!

Chris.

sowen · Post by **sowen** » Mon Feb 16, 2015 10:13 pm

It is odd isn't it! On the plus side it's a very compact lump to play with