Does the 4.2 in the RS6 have a flat plane or cross plane crank?

[Bigglezworth]

Just like the title states. I've searched the literature available to me and so far have been unable to confirm which style of crank our engines have. Judging from sound alone, I'm 95% certain it's a flat plane crank, but would like to get confirmation from any members out there that have performed detailed engine repairs or have a solid understanding of this specific 4.2L engine specifics.

Thanks
Tim

[ben916]

Just like the title states. I've searched the literature available to me and so far have been unable to confirm which style of crank our engines have. Judging from sound alone, I'm 95% certain it's a flat plane crank, but would like to get confirmation from any members out there that have performed detailed engine repairs or have a solid understanding of this specific 4.2L engine specifics.

Thanks
Tim

This is completely beyond my scope of engines BUT off the top of my head, I would think that Qisha might be the best source of this information you are looking for....

Thread jack - wtf?? "2003 Audi RS6 still stock after being scammed for a custom tune"

[650RS]

The RS6 use's the same crank as the standard A6/S6 crank.

[RS6-4dr911]

The above, while informative, is not helpful in answering the question.

Can neither agree nor disagree with that, but, page 10 of the training manual shows a clear depiction of the crank, definitely not a flat plane crank. It's my understanding those are quite rare, apparently not loved for their harmonics. The only one I know of is the Lotus Espirit V8.

[Bigglezworth]

The above, while informative, is not helpful in answering the question.

Can neither agree nor disagree with that, but, page 10 of the training manual shows a clear depiction of the crank, definitely not a flat plane crank. It's my understanding those are quite rare, apparently not loved for their harmonics. The only one I know of is the Lotus Espirit V8.
I figured the elite nature of the RS6 engine would see the use of the more exotic flat plane crank. Contrary to to what you cited, a flat plane crank has better harmonics than the cross plane. For cross-plane V8s, there is vibration from end to end of the engine, this is because the first piston is not in the same position as the last piston of bank, unlike an inline-4 engine. A 90° V8 solves this problem by introducing an extra-heavy counter weight to every cylinder. The counter weight is heavy enough to balance the weight of crank throw, con-rod and piston of that cylinder, thus resulting in lack of vibration. The disadvantage of cross-plane V8s is about the counter weights - not only do they increase the weight of engine, they also contribute to rotational inertia, thus making the engine less responsive and less revvy, dropping upper rev limit and top-end power. Moreover, the larger counter weights usually requires a larger crankcase to house them, thus raising the height (and more important, center of gravity) of the enigne. Therefore Ferrari all V8 models, TVR Cerbera AJP V8 and Lotus Esprit V8 employ flat-plane V8s instead.

[V8weight]

I figured the elite nature of the RS6 engine would see the use of the more exotic flat plane crank. Contrary to to what you cited, a flat plane crank has better harmonics than the cross plane. For cross-plane V8s, there is vibration from end to end of the engine, this is because the first piston is not in the same position as the last piston of bank, unlike an inline-4 engine. A 90° V8 solves this problem by introducing an extra-heavy counter weight to every cylinder. The counter weight is heavy enough to balance the weight of crank throw, con-rod and piston of that cylinder, thus resulting in lack of vibration. The disadvantage of cross-plane V8s is about the counter weights - not only do they increase the weight of engine, they also contribute to rotational inertia, thus making the engine less responsive and less revvy, dropping upper rev limit and top-end power. Moreover, the larger counter weights usually requires a larger crankcase to house them, thus raising the height (and more important, center of gravity) of the enigne. Therefore Ferrari all V8 models, TVR Cerbera AJP V8 and Lotus Esprit V8 employ flat-plane V8s instead.
You are correct, but the cars you listed (Ferrari, lotus) are naturally aspirated. Forced induction cars like the RS6 benefit from the rotational mass of a cross plane crank.

[Bigglezworth]

The above, while informative, is not helpful in answering the question.

Can neither agree nor disagree with that, but, page 10 of the training manual shows a clear depiction of the crank, definitely not a flat plane crank. It's my understanding those are quite rare, apparently not loved for their harmonics. The only one I know of is the Lotus Espirit V8.Man, was I not thinking. I dug up a hard copy of the manual and you are bang on. What a waste of time this thread was. Sorry guys. lol

[JRS-RS6]

Interesting read on Flat Crank setup for Chevy small block here: http://forums.hybridz.org/showthread.php?t=139545

It looks like this could be done but a lot of things would need to change -- Custom Crank, Firing Order, Valve Timing (i.e. camshafts), blah, blah, blah

[RS6-4dr911]

Well, either way, my understanding of the issue has been clearly exposed as being about as deep as a puddle.:doh:

[TozoM8]

The RS6 has a different crank end. It is bigger diameter and it has a 10 bolt flywheel patters instead of the 8 bolt like the 5V A/S6 A/S8.