BMW unveils special edition E60 M5 CSL with 580hp!

[baloo]

Originally Posted by K-1

At that point, you're looking at tail-lights from launch-4000.

You wouldn't, because both cars are limited by traction, not engine output in first gear.

[K-1]

Originally Posted by baloo

You wouldn't, because both cars are limited by traction, not engine output in first gear.

Another irrelevent point...

We're talking about two engines here. Traction can be affected by a number of things: tires, suspension, axles, etc.

The CTS-V was the king of the 'Ring, leaving behind both "peaky" and flat-torque motors. Obviously the LSA is doing something right. Until this new M5 proves otherwise, flat-torque rules the day.

[ptviperz]

Originally Posted by K-1

The other guy having problems launching has more to do with driver skill than the engine, which makes the point irrelevent. You may be "driving right past" above 5500, but he'll be revving up hard in 2nd when you're ready to shift. Any gains had by shifting later are nullified by having torque available across the RPM band, rather than just up high.

Torque is what moves the car, of course it's the be all, end all.

I don't think you understand -


Torque = Horsepower * 5252/ RPM

A really good example would be a L98 Vette vs a LT1 Vette

L98 250 @ 4000 340 @ 3200

LT1 300 @ 5000 340 @ 3600

Since, in your opinion, torque is the only thing that matters - the L98 should beat the LT1 right? Identical gearing and weight.

If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point.

On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline.

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

Do you understand now?

[K-1]

You've got that backwards. Horsepower is a function of torque, not the other way around. The torque is measured, the horsepower is computed. Everything in your scenario depends on the torque curve. The "peak" is advertised, but irrelevent.

[baloo]

Originally Posted by K-1

Another irrelevent point...

We're talking about two engines here. Traction can be affected by a number of things: tires, suspension, axles, etc.

It's not irrelevant at all. Extra torque only helps your launch if you can use it.

The CTS-V was the king of the 'Ring, leaving behind both "peaky" and flat-torque motors. Obviously the LSA is doing something right. Until this new M5 proves otherwise, flat-torque rules the day.

That, however, is an irrelevant point because low rpm torque doesn't matter on a race track, BMW never ran a timed lap, and lap times depend on dozens of other factors, not just the torque curve of an engine.

Besides, you're wrongly equating high rpm capability with peakyness. A current M3 for example has a flatter torque curve than a CTS-V, even though the M3 revs to 8400 rpm.

[ptviperz]

Originally Posted by K-1

You've got that backwards. Horsepower is a function of torque, not the other way around. The torque is measured, the horsepower is computed. Everything in your scenario depends on the torque curve. The "peak" is advertised, but irrelevent.

NO NO NO.....

Staying in the lower gear longer (via RPM) gives you greater torque multiplication via the transmission. My first gear acceleration for longer is faster than your shifting into 2nd early because your motor can't breathe past 5000 rpm. First gear = better acceleration than second gear. I can stay in the good power for longer in every gear so it only gets worse for you.

[K-1]

Originally Posted by baloo

It's not irrelevant at all. Extra torque only helps your launch if you can use it.

And that depends on a variety of factors, as I provided.

Originally Posted by baloo

That, however, is an irrelevant point because low rpm torque doesn't matter on a race track, BMW never ran a timed lap, and lap times depend on dozens of other factors, not just the torque curve of an engine.

Torque matters all over the RPM band. Unless you're running on an oval with zero braking, torque down low comes into play.

Originally Posted by baloo

Besides, you're wrongly equating high rpm capability with peakyness. A current M3 for example has a flatter torque curve than a CTS-V, even though the M3 revs to 8400 rpm.

Proof? We have a published CTS-V torque curve, with 400 lb-ft available from 1200RPM all the way up. Where's yours?

[K-1]

Originally Posted by ptviperz

NO NO NO.....

Staying in the lower gear longer (via RPM) gives you greater torque multiplication via the transmission. My first gear acceleration for longer is faster than your shifting into 2nd early because your motor can't breathe past 5000 rpm. First gear = better acceleration than second gear. I can stay in the good power for longer in every gear so it only gets worse for you.

First gear also = lower top speed. And with a low-torque motor, that first gear is going to be rather short to maximize that multiplication. So, you won't really be in first gear for much longer, if at all. If my power (i.e. torque) is greater than your peak power (i.e. torque) at all points across the band, my acceleration > yours. That's what this CTS-V vs. special M5 is all about.

[baloo]

Originally Posted by K-1

Proof? We have a published CTS-V torque curve, with 400 lb-ft available from 1200RPM all the way up. Where's yours?

Doesn't get much flatter than that.

[ptviperz]

Originally Posted by K-1

First gear also = lower top speed.

Pick one argument and stick with it Simple answer, it's always about the gearing.

And with a low-torque motor, that first gear is going to be rather short to maximize that multiplication. So, you won't really be in first gear for much longer, if at all.

But I will be in second and third gears -much- longer than the 5000 RPM engine. The current M3 motor revs to 8400 RPM. That's a minimum of 2000 more RPM (probably more like 2700 RPM) to make much more power before I have to shift. I'm going to run and leave you in the dust.

If my power (i.e. torque) is greater than your peak power (i.e. torque) at all points across the band, my acceleration > yours. That's what this CTS-V vs. special M5 is all about.

Engine torque tells you how much work is performed over any specific interval of crankshaft rotation, but does not tell you how quickly the work is being performed. acceleration = engine_torque x 2 x pi x engine_speed / (velocity x mass)

Wheel torque depends just as much on engine speed as it does on engine torque.

[K-1]

Originally Posted by baloo

Doesn't get much flatter than that.

Good deal. Now picture a similar line about 200+ lb-ft above that one. That's the CTS-V.

Originally Posted by ptviperz

Pick one argument and stick with it Simple answer, it's always about the gearing.

Within reason, yes. But you can alter the gearing for both engines, and the gearing itself has little to do with the engine itself.

Originally Posted by ptviperz

But I will be in second and third gears -much- longer than the 5000 RPM engine. The current M3 motor revs to 8400 RPM. That's a minimum of 2000 more RPM (probably more like 2700 RPM) to make much more power before I have to shift. I'm going to run and leave you in the dust.

Why does "my" engine have to stop at 5000RPM? Also, think about how much longer you're really going to delay before shifting. That extra 2000RPM doesn't buy you much time.

Originally Posted by ptviperz

Engine torque isn't what's important, the wheel torque is what matters. Staying in a lower gear with higher RPM will deliver higher performance.

Torque originates at the engine - of course it's important! Engine torque * gear multiplication = wheel torque. The gears can change all they want, but more engine torque makes for a less extreme gear. The more extreme the gear, the lower the top speed, the sooner you have to shift. It's simple physics.

[baloo]

Originally Posted by K-1

If my power (i.e. torque)

No, not 'i.e. torque'. The two are different.

If you have a water carrier that can carry 4 gallons at once and make 20 trips per hour, he will get more work done than someone who can carry 40 gallons and can only make one trip per hour. RPM is just as important as torque.

[baloo]

Originally Posted by K-1

Good deal. Now picture a similar line about 200+ lb-ft above that one. That's the CTS-V.

It's not though. The CTS-V's torque curve climbs, peaks at 3800 rpm and starts dropping immediately. There is no plateau, especially not one spanning half of its rev range.

[K-1]

Originally Posted by baloo

No, not 'i.e. torque'. The two are different.

If you have a water carrier that can carry 4 gallons at once and make 20 trips per hour, he will get more work done than someone who can carry 40 gallons and can only make one trip per hour. RPM is just as important as torque.

To make a point, you'd have to scale that to real life. You also need to watch your multiplicand/multiplier. In this case, increasing the "gallons carried" (torque, I assume) has a greater effect on total through-put than increasing the "trips per hour" (RPM).

4 * 20 = 80
4 * 21 = 84
5 * 20 = 100

[K-1]

Originally Posted by baloo

It's not though. The CTS-V's torque curve climbs, peaks at 3800 rpm and starts dropping immediately. There is no plateau, especially not one spanning half of its rev range.

Okay, let's say 150-200 lb-ft then. I originally had 150, but changed it to include the peak. Should have stuck with my more conservative number.

1200-6200 is above 400 lb-ft. Extrapolating out past 7000 is also above 400 lb-ft. Given that, the CTS-V is overpowering the M5 SE over the vast majority of the rev range. All else being equal, CTS-V (i.e. torque) wins.