Think LOGICALLY about the M5 performance data - Page 10

AJ · 23rd August 2004, 22:42

ah, you think that 0-60 is strictly traction limited, so 350 pounds of tq are plenty? good point.

however, herein lies the rub- with the higher tq engine you are able to solidify the driveline (ie engage the clutch) much lower in the rpm range and then in controlled fashion (smooth) push the tires without spinning. as oposed to the lower-tq engine where you will slip the clutch and once the driveline is solid you will easily overpower the rear wheels since you will be higher in the rev range and thus making some serious power. so, more hp is good when you have traction, but when traction is limited- tq is your friend.

living example- sl55 and sl600. same hp, about the same weight. however, the sl55 is a 12.5 car and the sl600 is a 12.0 car. the higher-tq car is able to exploit the adhesion of the tires better during launch. i had the pleasure to go to ned with an sl55 and sl600 and see them in action. the sl55 simply cannot catch the sl600 off the line. however, once going, the distance between the two stays the same.

alex
few cars

Erik · 23rd August 2004, 22:45

Quote:

Originally Posted by Tom_K

Do you have any tests from magazines to prove what you are saying about the 0-100 km/h times? Sport Auto tested the M3 at 5.2 s, M3 CSL at 4.8 s and E39 M5 at 5.4 s. Those times are as close to the official numbers as you can get. The CSL was 0,1s better than the official time and the M5 was 0,1s slower but they are very close. I would really like to see proof of anyone achieving a sub 5s time for the 0-100 km/h sprint.

No probs I just have to find them. But the fact you are asking me for prove tells me you think I lie.

why the hell shold I do that....

I have seen 2 test where the M3 does 4.8 sec 0-100. I where the car has run 100 000 km and the other of a normal test car.

Enigma · 23rd August 2004, 23:00

Quote:

Originally Posted by AJ

living example- sl55 and sl600. same hp, about the same weight. however, the sl55 is a 12.5 car and the sl600 is a 12.0 car. the higher-tq car is able to exploit the adhesion of the tires better during launch.

Those numbers look suspect to me...

Actually both of those are automatics. Depending on the configuration of the auto they may be restricted from exploiting the full potential of the engine. That said, a well setup auto is preffered for the really fast drag cars.

Keep in mind AJ, the M5 will not have drag slicks on it from the factory so it prbably will be traction limited through 1st gear. In 2nd you will already be in your power band so the crankshaft TQ is moot.

bernhtp · 23rd August 2004, 23:03

Quote:

Originally Posted by AJ

ah, you think that 0-60 is strictly traction limited, so 350 pounds of tq are plenty? good point.

Not really, but I think that 0-25 mph is, and that is all that is required to get it into the meat of the powerband where its gearing converts the HP into rear wheel torque.

Quote:

however, herein lies the rub- with the higher tq engine you are able to solidify the driveline (ie engage the clutch) much lower in the rpm range and then in controlled fashion (smooth) push the tires without spinning. as oposed to the lower-tq engine where you will slip the clutch and once the driveline is solid you will easily overpower the rear wheels since you will be higher in the rev range and thus making some serious power. so, more hp is good when you have traction, but when traction is limited- tq is your friend.

If launch control can dynamically modulate the throttle and clutch to maximize power and minimize wheelspin (similar to micro-adjustments of DSC), it shouldn't make a difference.

Quote:

living example- sl55 and sl600. same hp, about the same weight. however, the sl55 is a 12.5 car and the sl600 is a 12.0 car. the higher-tq car is able to exploit the adhesion of the tires better during launch. i had the pleasure to go to ned with an sl55 and sl600 and see them in action. the sl55 simply cannot catch the sl600 off the line. however, once going, the distance between the two stays the same.

I would be surprised if the torque curve explained the full difference in times - .5 secs is a lot - between these cars. My bet is on transmission or transmission electronics differences, but I really don't know.

Tom

Tom_K · 23rd August 2004, 23:11

Quote:

Originally Posted by Erik

No probs I just have to find them. But the fact you are asking me for prove tells me you think I lie.

why the hell shold I do that....

I have seen 2 test where the M3 does 4.8 sec 0-100. I where the car has run 100 000 km and the other of a normal test car.

I'm not saying you lie but I have simply never seen an M3 do a 4.8 s sprint to 100 km/h. That would put it right up there with the E55 AMG which is rated at 4.7s.

Are both the M3 tests from 2003? It's strange they couldn't achieve those times in 2001. Did BMW upgrade the engine in any way inbetween? If the 4.8s times are true, then the normal M3 is as fast as the CSL since Sport Auto tested it at 4.8s too.

vndkshn · 24th August 2004, 00:11

Quote:

Originally Posted by Tom_K

If the 4.8s times are true, then the normal M3 is as fast as the CSL since Sport Auto tested it at 4.8s too.

Every test I have seen of the CSL had it between equal and .3 seconds SLOWER than a regular M3 in the 0 to 60mph or 0 to 100km sprints.

Enigma · 24th August 2004, 00:27

Quote:

Originally Posted by vndkshn

Every test I have seen of the CSL had it between equal and .3 seconds SLOWER than a regular M3 in the 0 to 60mph or 0 to 100km sprints.

That wouldn't surprise me at all. The CSL comes with PSC tires which have a very stiff sidewall. They are not good for off the line acceleration. By comparison the Conti's of the stock car can simply have some air bled and then produce good numbers.

BmwNut · 24th August 2004, 01:26

The aircraft taking off post is really flawed. It goes slow due to the FADEC (full authority digital engine controls) not allowing full power. Turbines need to be spooled up slowly (better now with FADEC, idle to full throttle is generally 5-8 seconds), otherwise they would compressor surge/stall and shoot flames out the front.

In the old days, the pilot (or even flight engineer) would move the power levers by hand slowly.
Now running at 100% N1 power and dropping the brakes makes a lot more sense, which is the case of what AJ was describing at the drags. (btw, do that in a lightly loaded B-777, and you'll run a 7 flat or so to 60mph) Just try to keep the idea of a jet on takeoff away from this convo, as I doubt many people have felt a full short field procedure takeoff. Relating a normal takeoff just exaggerates the whole turbine low torque point too far. Good discussion on this thread BTW.

digger · 24th August 2004, 07:14

Another reasion why a 1000hp and 1000lb-ft car might out accelerate a 1000hp 300lb-ft car is that it would have more meatier power curve and not be so peaky. We seem to comparing peak values rather than looking at the variation of the above mentioned with rpm, and can never get correct generalizations this way.

If you design a racing engine you go for power, F1 always aims for power because proper gearing accounts for the torque transfer to the wheels, you go for torque (low-mid range power) if you don't have good gearing or if you are going to be towing or carrying alot of weight.

KKelly · 24th August 2004, 07:49

BMW has almost always used higher revving, high hp, aggressively-geared cars. Why do people want a torque monster? Driving the M5 is simply going to be a much more sports-car like experience. Simply stated, you take the current M5 and give yourself 1500+ more rpm of powerband. Nobody has ever complained that the E39 is some torqueless piece of crap. The torque numbers of the E34 are merely 265 and dyno's are 245 to the wheels yet they run a 14 second quarter in a 3800lb car built in 1990. Gearing and revs, that simple. Have faith.