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      03-24-2007, 03:03 PM   #30
maq
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Quote:
Originally Posted by T Bone View Post
Horsepower is a measure of work. More work the drivetrain can do, the faster you accelerate.


Quote:
Revs are as important as torque in determining the amount of work a drivetrain can do.
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.


Quote:
So while you main get 85% of the engines torque low in the power band, you actually want to be pounding through the gears at the higher rpms (while trying to maintain torque).
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.

Quote:
The flat torque curve is really good for flexibility but when you are tracking / performance driving, revs are critical to extract max performance and a close ratio gear box gives you high revs with relatively constant torque.
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.
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