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      10-23-2008, 04:19 AM   #6
BMRLVR
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Drives: 2011 E90 M3,1994 Euro E36 M3/4
Join Date: Apr 2006
Location: Fort McMurray, Alberta, Canada

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Quote:
Originally Posted by drvai View Post
Is there any exhaust system for the M3 that can give a high pitched sound as seen on the F430? (I know it won't get as good... but maybe close)

For a short answer..... NO!!!

The reason a Ferarri sounds like it does has nothing to do with exhaust. The reason a Ferarri screams with such a high pitched tone is because all Ferarri V8 engines use a 180 degree or Flat-Plane crankshaft where the 4 rod journals (two rods are mounted to each journal in all V8's) are spaced at 180 degrees. the M3 V8 on the other hand uses a 90 degree or Cross-Plane crankshaft where the 4 rod journals are spaced at 90 degrees from one and other or at 0 degrees, 90 degrees, 180 degrees and 270degrees.

Mainly what affects the sound most about a Flat-Plane V8 is that each bank of cylinders are working like its own engine, or essentially like two four cylinder engines running simultaineously, hence the high pitched scream. This has to do with the fact that the firing order of the Flat-Plane V8 means that every 90 degrees a cylinder is fired in an alternate bank (although some Flat-Plane V8's have been designed to fire two cylinders at once, this is highly uncommon in production engines) so the typical firing order in a Flat-Plane V8 looks like this: 1-5-3-7-4-8-2-6 (assuming the cylinder numbering proceedure that BMW uses of 1234 in bank one and 5678 in bank two) In a Cross-Plane V8 the crankshaft design necessitates that the firing order is somewhat uneven between the banks and not completely alternate. The Firing order for a typical American V8 would be 1-3-7-2-6-5-4-8 while the firing order for the M3's S65 V8 is: 1-5-4-8-7-2-6-3. Although the S65 does not have a firing order that is conventional to older American V8's it is still not a totally even firing order between banks


The main difference between the Flat-Plane V8 and Cross-Plane V8 is that the Flat-Plane V8 does not require large counterweights (the reduction in mass of the crankshaft due to the lack of counterweights equates to quicker revving, a higher rev ceiling, lighter weight and slightly more horsepower) on the crankshaft like the Cross-Plane V8 and a Flat V8 is much easier to tune with regard to Exhaust and Intake. The major drawback to the Flat V8 is that it is not as smooth or refined as a Cross-Plane V8 with regards to second order vibration. This is is why the Cross-Plane V8 is pretty well the universal layout when it comes to V8 Engines in mass production. Because Ferarris are more about performance then refinement they use the flat crankshaft due to its benefit in horsepower, weight, revability and simplicity.

I hope this helps!!
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Last edited by BMRLVR; 10-24-2008 at 11:23 PM. Reason: Correction