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      03-24-2007, 04:42 PM   #31
T Bone
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Drives: 2008 335xi Coupe
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Originally Posted by maq View Post

Revs determine WHEN an engine produces a certain amount of HP or torque, RPM doesn't determine the actual amount of HP or torque an engine can produce.

Also, the use of the term drivetrain here is not appropriate. Drivetrain as a whole is not just what produces HP and torque, it also transfers engergy. Transmission, driveshaft and diff all are parts of drivetrain.

Read my previous post. I, and BMW never said "85% of torque low in the powerband." It's "the engine delivers 85% of max torque in A RANGE of 6500rpm." With a powerband this wide, you are wasting useful revs and giving up shifting time by using a CR box, which cuts you off quicker than a normally geared box.

And no, I wouldn't want to be pounding through the gears at higher rpms to mantian torque with this engine. Look at the graph, you get less torque after 6500rpm, and in the last 1000rpm you actually get less than 380NM.

A flat torque curve is good for EVERYTHING. For this particular engine, revs are only critical to extract max horsepower. This engine acutally produces most torque between 3500-6500rpm, whereas max HP is produced near redline. Mid range is where you want to be for constant torque, not the top end.

Also, a CR box doesn't give you more revs or make you rev higher. It only limits the length of each gear and drops fewer revs when upshifting. For high-sprung engines like built S52, S50B32 and S54, which don't wake up until 2000rpm to redline, yes, a CR box can keep you in the sweet spot. But the S65 is a different story.

I would suggest looking at the definition of horsepower and work. RPM is integral in determining a horsepower rating, along with Torque. SAE HP (an arbitrary definition of work created by James Watt BTW), says that revs after 5252 rpm has a great impact on HP.

We don't share a common view of the world or physics so it is pointless to discuss. In my world the sky is blue.

BTW, here is a hint for you RPM = Distance, Torque = Force
"Aerodynamics are for people who cannot build engines"......Enzo Ferrari

Last edited by T Bone; 03-24-2007 at 05:04 PM.