04-08-2009, 06:05 PM | #11 | |
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How big or small the difference is relative the addition or subtraction of 500 pounds of load or 500 RPM...
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OH NOES!!!!!1 MY CAR HAS T3H UND3R5T33R5555!!!!!!1oneone!!!!11 Team WTF?! What are you gonna do? |
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04-08-2009, 06:29 PM | #12 | |
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JV, are your calculations torque at the contact patch, or torque at the hub? In other words, do you include the effect of tire diameter in your overall gearing calculations? Also, WRT fuel economy, another huge variable (in fact, probably the biggest variable) is wind resistance. Since the Corvette has a smaller frontal area than the M3 and probably a better coefficient of drag besides, it simply takes less work to move the Corvette through the wind at a given speed. |
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04-08-2009, 06:39 PM | #13 |
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Torque at the hub. Once you take into account the diameter of the tire, you're talking thrust (i.e. force).
Fuel economy is tied to throttle position but not nearly so much as it is tied to RPM for gasoline engines. Anyone who has ever delved into the programming for a gas FI system knows this, because injector firing rate is ONLY determined RPM and duty cycle is tied to airflow. The trim functions here are throttle position, intake air temperature, coolant temperature, and some other minor contributors. The other factor here is pumping loss - which is lowest when the throttle is wide open. The most efficient way that we know of to operate a gas engine is to have no throttle and manage the speed with valve lift and duration (aka Valvetronic for BMW)... but it's not necessarily practical for all applications (read: it's expensive to implement and not easy to build). In diesel engines, fuel economy is tied very closely to "throttle" position because there is no throttle - you're directly controlling the pulsewidth of the injectors. The bottom line is the BMW is damned fast - especially for how heavy it is - but once first gear is done, the BMW is going to get smoked by the vette. |
04-08-2009, 07:26 PM | #14 | |
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that's always the appeal of the M series. that a gran turismo is THAT fast. one obviously pays the price monetarily, carbon emissions-wise, as well as gearing-wise, for that 1st gear performance. for most people of a certain means, it's certainly worth it. my own personal journey with a leaden sled that has a rocket booster attached to it is that the curb weight really wears on you after awhile. the whole back end of the thrust proposition is that whole braking thing. no matter how good the brakes work, weight is something that is so visceral and it does literally weigh on you over time to constantly fight that static weight from a standstill as well as coping with that sheer mass on decel. engine to engine, the BMW is almost peerless for a DOHCer in street guise.
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04-08-2009, 08:18 PM | #15 |
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The M3 is not THAT bad... 3600lbs is the new 3000. A 997TT is as much. But yes, it is a gt, it is never going to feel like an s2000 or a cayman.
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04-08-2009, 10:24 PM | #16 |
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True. And as I've mentioned too many times already, the E93 vs. E90 M3 test drives proved how much of a difference 3700 vs 4200lbs is dynamically.
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04-08-2009, 10:36 PM | #17 |
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I love this thread. I really have nothing to add. It's a rare occurrence that I'm unable to out-nerd somebody. The fact that there are several posters in this thread alone that out-nerd me is either awesome or totally sad.
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04-09-2009, 06:33 AM | #18 |
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The M3 has been a GT for 15 years-- like every other BMW with an M badge, other than the E30 M3.
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04-09-2009, 07:19 AM | #19 |
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I'm still thinking about an M3 or 997S. They are both GT's, and right now, after 2.5 years of the more hard core cayman (not that it is faster, but it is light, loud etc.) I'm kinda looking for a gt.
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04-09-2009, 11:31 AM | #20 | |
Western Anomaly
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Quote:
age sets in.
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