barryl

<center><img src="https://www.audiworld.com/news/02/a8launch/a8020098.jpg"></center><p>Hey,

Take a look at the pic.

The timing belt is still there. Yes, there is also
a chain, but that is to drive the two cams per
engine bank. The timing belt drives the chain.
If the belt breaks, you are still in big trouble.

Regarding Audi's being more likely than other
manufacturers to break belts, I don't think so.
I have heard of problems with Porsche (944)
Japanese (Mitsubishi, Honda) and domestic (Saturn).

Best thing you can do is change the belt when
you are supposed to.

Barry

ryoung

.
The new A8 motor still has belt driven cams, now located in the rear?! .... It's only this new S4 V8 that gets chain driven cams?!?!

<img src="https://www.audiworld.com/news/02/new_s4/2003s4015.jpg">

PaulW

We talked about this thoughly and it was written up in the quattro quartly in the summer, the rear of the engine is where the chain driven cam is, plus there is another shaft that drives the auxiliary shafts on the bottom front in the picture (which is actually the bottom left of the engine).

That drives the alternator, compressor, etc and is accessible from the bottom left of the car, must be jacked up to get to those components.

They have significantly reduced the length of the engine by doing this. I have noticed that most of the engine pictures posted lately do not show this design shown in your post, but I believe that is the A8 4.2 engine that will come to the states.

pw

WClark

With the cam timing mechanisms hanging out over the rear of the engine (over the bell housing) the couple inches it saves in front is an actual reduction in the package outline between the front axles and front ofthe engine. This means the engine can fit into a shorter vehicle - or one with a shorter front overhang, like the B6 chassis.

barryl

Hi Randy,

Maybe there is a better explanation. What is a 2003 A8?
Is that the old 'current' version, or the totally new design?
Maybe the 2003 US A8 is the current, and the European
A8 is the new one?

Just guessing.

Barry

ryoung

.
even though AudiWorld called both pics 2003 motors.

ryoung

.
The old motor had to make room for two pulleys, the belt driving the exhaust cam and the chain driving the intake cam from the exhaust cam.

With the new motor, the same chain now drives both; and it's further inboard, inline with the exhaust cam chain on the old motor.

In both motors, the cams are driven off a crank pulley, so I don't think it can hang out over the bell housing.

Which means ... I have no idea why it's in the rear.

WClark

Well the picture from AW isnt that easy to imagine in a side view but it appears the "57mm" reduction comes from 2 things. The intake cam timing (which appears to be an electrically adjustable pully/sprocket) sticks out like the old timing belt did, but over the fly wheel instead of toward the radiator. Also the aux engine driven stuff looks to be chain/gear driven off the rear of the crank on the same plane as the cams and these bits are located to the sides of the engine which eliminates a front mounted serpentine belt.