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E39 M5 (1998-2003)

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  #1  
Old 02-25-2014, 01:29 PM
z06x60z z06x60z is offline
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2002 Corvette Z06 vs E39 BMW M5

Hello I am seeking some answers on my car vs the M5. I have a 2002 Corvette Z06. It is one of the most fun cars I have ever driven. It handles really well and takes turns flawlessly. I am however concerned about one thing. On the highway it seems to be sluggish in 4th and 5th gear. I want my car to be faster from a roll than it already is. Another concern I have is that its top speed is only 171-178 mph. It has a 405HP LS6 motor with a M12 transmission. The only reason the Z06 is faster from a roll is because its about 800-900lbs lighter. If the M5 was the same weight it would beat the Z06 from a roll. Now the M5 has the same HP as the Z06 but it has a higher top speed. I just don't understand why the M5 has a higher top speed and why it would beat the Z06 given it was the same weight. Both motors make about 400 HP. Is the LS6 a weaker motor when it comes to top end? How does it this work? I would appreciate it if someone can explain this to me. This same argument can be made for the C6 Z06 vs the E60 BMW M5. If I were to change the diff ratio on the Z06 from 3.42 to 3.90 I would be faster from a roll but lose even more top speed. The top speed would probably drop to 160 mph. I am really at a dead end here and would like to know what the answer is.

Z06
1st Gear 2.97
2nd Gear 2.07
3rd Gear 1.43
4th Gear 1.00
5th Gear 0.84
6th Gear 0.56
Final drive 3.42

E39 BMW M5
1st 4.227
2nd 2.528
3rd 1.669
4th 1.226
5th 1.000
6th 0.827
Final 3.150
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  #2  
Old 02-27-2014, 06:17 PM
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timfitz63 timfitz63 is offline
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I'm not up on how all the numbers mesh when it comes to drive ratios, but one might make the following observation about the numbers you put in your post:

The M5 is running at the same gearing ratio in 5th gear as the Z06 is in 4th; basically the same thing when comparing an M5 in 6th gear with a Z06 in 5th. In other words, all other things being equal (including weight), a Z06 would need to remain in 4th gear to match the acceleration potential of an M5 in 5th gear; and same with 5th gear on the Z06 compared to 6th gear on the M5.

The C5's are geared for economy in the top two gears; that's why a 400-Hp car gets upper 20's gas mileage on the highway. Chevy did that to avoid the so-called 'gas guzzler' tax on the C5. Even in its top gear, the M5 won't get that kind of gas mileage, and BMW made no such gearing concessions for the sake of gas mileage or the consumer's purchase costs.
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Old 09-13-2015, 11:12 PM
AfricanLax! AfricanLax! is offline
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Sedans are known for better aerodynamics than coups. Which helps with longevity in speed.
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  #4  
Old 09-14-2015, 09:28 AM
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timfitz63 timfitz63 is offline
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Quote:
Originally Posted by AfricanLax! View Post
Sedans are known for better aerodynamics than coups. Which helps with longevity in speed.
One would have to examine the values of drag coefficient (CD) for the respective vehicles to support this generalized statement.

The best CD number I could produce from the interweb for a C5 Corvette was 0.29; an E39 BMW sedan is surprisingly close, but still a little higher at 0.30-0.31. Combined with the frontal area of the E39 sedan (which I'm making an educated guess is greater than the frontal area of the C5), that CD will produce more drag (pounds force) at the same speed.

Lift will also play into this equation as well; the car that generates more downforce will have better wheel grip. Just eyeballing this one, I'd say the more wedge-like profile of the C5 gives it an advantage over the E39 BMW. But I'll be the first to admit I don't have hard numbers there.
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  #5  
Old 09-16-2015, 05:45 PM
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mark_m5 mark_m5 is offline
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Looks like an old thread, but interesting comparison. One of the reasons I was attracted to the M5 to begin with was that performance was very similar to the Corvette without having to sacrifice room for passengers.

Not sure what the top speed comparison is worth unless you're on a test track. Stock M5s without mods are computer limited to 155.

99.999999999999% of your driving should be less than 100mph, since above that on a public road they take your car away.

Quote:
Originally Posted by timfitz63 View Post
Even in its top gear, the M5 won't get that kind of gas mileage, and BMW made no such gearing concessions for the sake of gas mileage or the consumer's purchase costs.
We're talking E39 here, not E60...

I get mid-20s gas mileage on the freeway, and can get 30+ if I'm light on the throttle and coast downhill. Advantages of a stick shift I made it from San Francisco to my home in southern California on one tank of gas.
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  #6  
Old 09-16-2015, 09:23 PM
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timfitz63 timfitz63 is offline
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Quote:
Originally Posted by mark_m5 View Post
... I get mid-20s gas mileage on the freeway, and can get 30+ if I'm light on the throttle and coast downhill. Advantages of a stick shift I made it from San Francisco to my home in southern California on one tank of gas.
That's not bad. But my original point was that one can easily get 28-30 mpg highway in a C5 equipped with the six-speed manual. That's moving at 70-75 mph and without resorting to any special driving techniques either. I did Waco to San Antonio and back (~400 miles) on 3/4 of a tank in my C5 once.
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