Flat plane crank in RS4?
06-20-2007, 08:20 AM
#1
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Flat plane crank in RS4?
European Car rag last month or so had a blurb in its last few pages where it referenced the RS4. In it I swear they said that 4.2 had a flat plane crank.
I'd find it odd that they changed the motor from that of which in mine in that regard - unless mine's a flat planer too?
Someone more edumucated here care to shed da light?
Danka.
I'd find it odd that they changed the motor from that of which in mine in that regard - unless mine's a flat planer too?
Someone more edumucated here care to shed da light?
Danka.
06-20-2007, 08:53 AM
#2
Well...first...I don't know what flat plane crank is...unless it has something to do with
the shape of the crank where it hits the oil. I'm assuming some have the shaped crank that makes it a cleaner entry/exit from the oil?
06-20-2007, 10:36 AM
#3
Flat plane vs. cross plane
A flat plane crank has all the con rod journals off set by 180 degrees. Cross plane has the crank pins offset by 90 degrees. Ferrari V8's and the V8 in the Porsche 928 is a flat plane design. The advantage is lower reciprocating and lower rotating mass which offers higher performance levels. The disadvantage is additional vibration since a flat plane V8 is basically two straight 4 cylinder siamesed together. I can tell you from experience that I dont like the weird vibration from a flat plane V8. I had a few 928's and the vibration is more like a resonance that changes with RPM. I found it unsettling and it feels like a high RPM missfire. Cross plane V8's are smother because they have different firing order and and extra counter weight which makes the whole motor assembly rotate smoother. I would suspect the RS4 has a special motor mount design to minimize the vibrations.
I'd like to know if the new BMW M3 v8 is flat or cross. A recent article in an automotive mag didn't mention it. Anyone know?
I'd like to know if the new BMW M3 v8 is flat or cross. A recent article in an automotive mag didn't mention it. Anyone know?
06-20-2007, 11:14 AM
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//M3 Forum has a thread on the topic. Ugly url provided.
<ul><li><a href="http://www.m3forum.net/m3forum/showthread.php?s=e781eb8dd964d3bda2fea955a3e05564& amp;t=107321">http://www.m3forum.net/m3forum/showthread.php?s=e781eb8dd964d3bda2fea955a3e05564& amp;t=107321</a</li></ul>
06-20-2007, 12:17 PM
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Ah, thanks Angus (or aka *** Poster heh heh). That's what I thought, mine is cross and the RS4 is..
...flat, based on the EC rag article. But it seemed VERY odd to me that Audi would change its development of its existing 4.2L lump like that.
Guess so then. Weird.
Guess so then. Weird.
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06-21-2007, 01:05 AM
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Development costs are essentially zero.
The only differences are ...
1. The crankshaft layout described by icsamaerica
2. An ECU that runs the new firing order.
3. Camshafts ground to reflect the new firing order.
4. Delete the H-pipe crossover in the exahust system. It's no longer needed!
1. The crankshaft layout described by icsamaerica
2. An ECU that runs the new firing order.
3. Camshafts ground to reflect the new firing order.
4. Delete the H-pipe crossover in the exahust system. It's no longer needed!