Audi V8 Engine Comparison.

[Nollywood]

I'm looking at the different 4,2 V8 engines used by Audi. The V8 32V, V8 40V and the chain-driven V8 40V as fitted to the B6 S4.

In terms of reliability, and extracting as much hp as possible, which would you pick? Which has the best track record?

I haven't much experience with the B6 S4 chain-driven motor, but from various fora, the chain tensioner / guides and chain are a weak point, with quite a few documented failures (US-based fora have a lot of discussions with regards this). Quite a few bust B6 S4's floating around.

The 40V fitted to D2, C5 and early D3 (non-FSI) has the VVT, which whilst making the motor more flexible, is a weak point.

The 32V fitted to D11, D2 and C4 is more basic - no VVT and single-stage variable intake manifold. And it's proven in Motorsport (I remember the V8 DTM series).

What's your take guys?

[Singh]

The S8 AVP and AHC (?) motors are obviously the most powerful with 360 BHP, but the S4 engine looks like its half the size and a lot more compact, probably got something to do with the fact it doesn't have a timing belt. The S4 does have the chain tensioner issues as you know but the AVP And AHC units seem to be fairly bulletproof. Have you thought about a B5 S4 engine? You could easily get it upto S8 power and beyond, but it wouldn't sound as good. I dunno, how about an E39 M5 engine, 5.0 naturally aspirated V8, 400 BHP and no carbon build up issues that the B7 FSI V8 has. A8_Doc on here has sorted the Vanos issues on his fairly easily too.

(Didn't realise you were only looking at Audi V8s, hence mentioning the E39 M5 V8)

What are you planning to do with the engine anyway?

[Nollywood]

Thanks for your comments, Amar.

The B5 S4 motor's good, but as you said, it wouldn't sound as good as the V8. Couple maintenance issues with the turbos, requiring an engine pull each time, it becomes less attractive.

Gotta love the Beemers, they're my sort of car, and my original background is BMW. The E39 M5 will out-run and out-handle an S8, even a V10 one. Don't wanna praise BMW too much here, might upset folk.

[Singh]

Not only an S8, but an RS 6 too. When they both get upto about 100 MPH the E39 pulls away from the RS 6. Don't worry about upsetting anyone, I do all the time. I used to be anti BMW, drove one and realised that Audi could learn a lot from them.

[Nollywood]

Originally Posted by Singh

Not only an S8, but an RS 6 too. When they both get upto about 100 MPH the E39 pulls away from the RS 6. Don't worry about upsetting anyone, I do all the time. I used to be anti BMW, drove one and realised that Audi could learn a lot from them.

Hell yeah!

[Just_Ben]

The chain driven V8 is the B6 S4 is pretty good. 54mm (IIRC) shorter than the belt driven version but otherwise very similar. The chain is at the back of the engine, the reason for this is that due to being supported by the gearbox the crankshaft vibration is less pronounced than it is at the front of the crank where it has no support. This meant that the chain could be single width rather tha a twin duplex chain as the length was paramount to fir that, lovely, warbly V8 in the nose of the A4 chassis - that's why the A8 4.2 D3 of simalr vintage still had belt drive.

The issues arise if, as suggested, the chain or tensioners have problems. The chain tensioner on the right hand bank near the top tends to be a weak point in my experience but still Ive not seen many actual failures, usually just a brief rattle at start up as the oil feed non retrun valve fails in them. So long as the cam timing and variation is fully operational they are OK. If any cam is out of time it can mean the chain has stretch, but again, this seems rare.
If however, the chain syste, does need work it obviously requires engine removal to rectify as its at the back of the engine so not an easy job just with gearbox removed!

The AHC 340bhp 32v and AVP etc 360bhp 40v are all great engines. Only ever seen block wear if cambelt has failed casuing impact damage and ring damage. The cam link chain timing variators on the 40v do have issues, either with the oil strainers blocking causisng poor operation or the plastic guide guard can wear and come clean of inside the head. Either of these faults can be picked up upon inspection though and pretty easy to remedy. Besdies that, oil coolers are obviously an issue and Air Mass Meters are dear but great engines all in all.

The FSi V8's are wonderful but bring a whole load more issues! The increased fuel pressure (130BAR versus 3BAR!!) means they employ twin, cam driven mechanical fuel pumps. These can have internal seal issues, allowing petrol to enter the heads and contaminate the oil, and fuel pressure suffers causing high correction factors and missfires under load. They also require more interms of wiring and RS4 V8's use 2 engine ECU's but still, if you're happy to do the work, revving a V8 to 8500rpm is worth it!!!

[Just_Ben]

..... p.s, Amar's right, the E39's 5ltr V8 is STUNNING!

[Nollywood]

I'm aware of the chain-driven V8 requiring engine removal to service, another reason they're best avoided. Worse reliability history than the 2,7 Biturbo (as in replacing turbos).

On the other hand, the ABZ/AHC/AKH share the same fundermental design as the PT/ABH in the D11 cars, bar the addition of COP ignition. Same design utilized by the Euro S4/S6 Plus.

I owned a LHD '93 Audi V8 4,2 32V (ABH) for three years, which had 386,000 miles when I sold her, and she never missed a beat. All I replaced were timing belt, water pump, thermostat and one distributor.

[Adrian E]

Depends what you want to stick it in and which issues are easiest to live with, I guess?

If I was sticking in something for race/track day use and it had to be a V8 I'd go B6 V8 route because there's plenty about and they should be reasonable money. Chains seems to be more of an issue on cars that've been long life serviced rather than annual. Even if they rattle quite badly, going to a 5W40 apparently quietens them down a lot.

I don't see the VVC on my engine as an inherent fault waiting to happen and it's not too tricky to sort in any case. Some nice mapping and you're well away

The older the engine, the more you have to budget for stripping and repairing it too....I've known people spend a grand refreshing a 4 pot PSA 16V lump once you've delved into the bottom end and done some timely maintenance for long term longevity.

[Nollywood]

Originally Posted by Adrian E

If I was sticking in something for race/track day use and it had to be a V8 I'd go B6 V8 route because there's plenty about and they should be reasonable money. Chains seems to be more of an issue on cars that've been long life serviced rather than annual. Even if they rattle quite badly, going to a 5W40 apparently quietens them down a lot.

The B6 V8 are not as easy to find used, and they generally cost more than the older belt-driven motors. There were also more belt-driven V8's built.

The chain guides on the BBK motor are not easy to replace, given their location at the back of the block. I remember a couple of years ago, my local Audi dealership had a failed BBK motor in an S4 Cabrio, they replaced it with a new crate motor under warranty, because the owner kicked up a stink with Audi UK over its failure.

The car was 4 years old, and had covered 42,000 miles. It was also serviced by the supplying dealer, which is what made the failure all the more poignant. I was looking at a 2004 B6 S4 Avant before I settled for the older D2 S8. Possibly the bugs on newer cars have been ironed out.

But if you go by Shokan in the US, they currently have three B6 S4's parting out, and none were smashed. And the 'Zine has a fair amount of failures, the B6 S4 section makes for interesting reading. One of the guys there is actually installing a B5 S4 2,7 Biturbo into an S4 B6, which he bought cheap with a dead motor.

So far, the D2 V8 motors seem robust, I personally haven't seen belt failure, though I've heard of breakages, most due to exceeding the replacement intervals and running on borrowed time. Most non-smashed D2's are sent to an early grave by a bust transmission, so they do have their bugs.