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      06-04-2008, 08:44 PM   #79
Hans Delbruck
BMW & MB - friends in my garage
 
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Drives: C63, 135i, 1959 BUICK
Join Date: May 2005
Location: Huntington Beach, CA

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Quote:
Originally Posted by jm1234 View Post
From running engine torque through the power train and factoring wheel size at 60 mph the M3 in 5th gear has about 1007 rear wheel torque (rwt) @ around 2944 rpm and the C63 has about 1044 rwt @ around 2283 rpm. In 6th it's 878 and 812 rwt @ 2567 and 1872 rpm (yes, more for the M3). You have to go to 3rd gear at 1772 and 2282 rwt and 4658 and 4383 rpm respectively that you see a significant advantage for the C63. Why doesn't the C63 need to downshift and the M3 does? At what speed and gear do you see this advantage? I can run the numbers for any speed/gear you'd like.

The M3 is lighter too and thus any given amount of torque will introduce 10% (or so) greater acceleration on the M3. Humans are not torsion meters, we only feel acceleration.

I'm not saying you don't perceive this advantage, I'm just wondering if it's real and from what effect it comes. More torque at the flywheel is great but if it isn't translated into greater torque at the rear wheels (by selecting the proper gear) then what good is it? From each shift at redline the M3 will loose a lot of torque because it has relatively high engine torque right to redline. The C63 definitely doesn't gain as much proportional advantage from downshifting but at 60 the M3's the better car if you don't downshift.

At 40 it's all C63 but one gear down on the M3 (which doesn't put the M3 near redline) puts the M3 up again on rwt in comparison to the C63. For example, the C63 at 40 mph in 4th gear is at 1430 rwt @ 2085 rpm. The M3 in 3th gear is at 1705 rwt @ 3105 rpm. That is hardly near redline and the M3 is faster.

I've heard this theory enough times that I'm going to call BS on it and hope you'll explain to me how I'm wrong?
I don't really understand what you're saying... but that might be because I flunked math in college and never took physics.

I'm not good with numbers. The only ones I understand are

451 > 414
443 > 295

j/k

I don't like winding out the gears. I do like being thrown back in my seat no matter how fast I'm going. That makes the C63 the better car for me. I have driven both the M3 and C63, hard, to redline. The numbers may look similar on paper... but in feel, there is a HUGE difference. That's all I needed to know.
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