SL/R230: New C&D SL 600:0-60 3.6sec 1/4 mile 11.9@120
02-04-2004, 08:43 AM
#26
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'03 BMW 330i ZHP / '06 Volvo V70R
As a mechanical engineer, it's nice to see people crunch numbers.
But numbers aside, C&D is always extremely hard on cars. That is why they usually have the best times.
In the end, no one (ok ALMOST no one) will buy an SL600 to drag race.
But numbers aside, C&D is always extremely hard on cars. That is why they usually have the best times.
In the end, no one (ok ALMOST no one) will buy an SL600 to drag race.
02-07-2004, 06:15 PM
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2004 SL55 AMG
120mph = 53.64 m/s; M = 1980 kg; Energy at 120mph = MV^2/2 = 2.85 MJ, average power over 11.9 seconds = 240 kW; engine is rated at 368 kW max power, so average power = 240/368 = 65%
Corresponding figures for the 0-60 time show the average power is less, which reflects the greater proportion of time spent at lower revs and the greater proportionate losses due to wheel spin.
60mph = 26.82 m/s; M = 1980 kg; Energy at 60mph = MV^2/2 = 712 kJ, average power over 3.6 seconds = 198 kW; engine is rated at 368 kW max power, so average power = 198/368 = 54%
Corresponding figures for the 0-60 time show the average power is less, which reflects the greater proportion of time spent at lower revs and the greater proportionate losses due to wheel spin.
60mph = 26.82 m/s; M = 1980 kg; Energy at 60mph = MV^2/2 = 712 kJ, average power over 3.6 seconds = 198 kW; engine is rated at 368 kW max power, so average power = 198/368 = 54%
02-07-2004, 11:07 PM
#28
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Other things being equal, you would expect a car to take 4 times as long to reach 120 as 60. In fact, and assuming the published times are correct, this is not the case here because the process of running to 120 is more efficient than running to 60:
- the engine is running at higher average revs and therefore producing more average power delivered to the driven wheels.
- losses due to loss of traction and ESP intervention occur mainly at launch and have a greater impact on the 0-60 time.
These two benefits are more than enough to counter the increased cumulative loss to drag to 120. The physics simply confirms what experience tells us: to improve performance of a given configuration, you need to:
- reduce weight
- minimise losses due to aerodynamic drag
- increase the engine output delivered to the wheels
- improve traction by increasing the weight over the driven wheels or by increasing the coefficient of friction between the driven wheels and the road - use bigger tyres or more of them, as in 4 wheel drive.
Any time a manufacturer is trying to improve performance, they are working on one of those objectives, more likely a combination. So, a typical performance car makeover will increase the engine power, reduce the weight, user better tyres and tweak the aerodynamics. In reality, the aerodynamics is a compromise because of the need to keep the car planted on the ground, not just for traction but also for steering. It may be necessary to incur an aerodynamic penalty to improve downforce. Feeling the steering of a car go light at high speeds is a heart-stopping moment...
Maximum speed of a car is reached when the drag and driveline losses match the engine output. Power is Torque * Angular Velocity (engine speed); torque also varies with engine speed and in the absence of any mechanical rev limit, maximum power will be reached when an incremental increase in engine speed causes a sufficiently large reduction in torque to reduce the value of Torque * Angular Velocity.
If torque is expressed as a function of velocity, f(v), that occurs when v.f'(v) = - f(v).
If a car does not achieve maximum speed at maximum power, the gearing is wrong. The SL600 reaches maximum power at lower revs than does the SL55, and has different gearing.
- the engine is running at higher average revs and therefore producing more average power delivered to the driven wheels.
- losses due to loss of traction and ESP intervention occur mainly at launch and have a greater impact on the 0-60 time.
These two benefits are more than enough to counter the increased cumulative loss to drag to 120. The physics simply confirms what experience tells us: to improve performance of a given configuration, you need to:
- reduce weight
- minimise losses due to aerodynamic drag
- increase the engine output delivered to the wheels
- improve traction by increasing the weight over the driven wheels or by increasing the coefficient of friction between the driven wheels and the road - use bigger tyres or more of them, as in 4 wheel drive.
Any time a manufacturer is trying to improve performance, they are working on one of those objectives, more likely a combination. So, a typical performance car makeover will increase the engine power, reduce the weight, user better tyres and tweak the aerodynamics. In reality, the aerodynamics is a compromise because of the need to keep the car planted on the ground, not just for traction but also for steering. It may be necessary to incur an aerodynamic penalty to improve downforce. Feeling the steering of a car go light at high speeds is a heart-stopping moment...
Maximum speed of a car is reached when the drag and driveline losses match the engine output. Power is Torque * Angular Velocity (engine speed); torque also varies with engine speed and in the absence of any mechanical rev limit, maximum power will be reached when an incremental increase in engine speed causes a sufficiently large reduction in torque to reduce the value of Torque * Angular Velocity.
If torque is expressed as a function of velocity, f(v), that occurs when v.f'(v) = - f(v).
If a car does not achieve maximum speed at maximum power, the gearing is wrong. The SL600 reaches maximum power at lower revs than does the SL55, and has different gearing.
02-07-2004, 11:29 PM
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CLS55 AMG
RU_MATRX, that calculator page you linked too is inaccurate.
For example, if you run the numbers for the CLK55 (13.4@106, weight =3450 + 180 pounds for driver), it tells you that the car is putting out 397 at the crank...which would be nice, but it isn't accurate. If you use the following equation, you'll get a more accurate number: spd = w*(spd/234)^3, which gives 3630*(106/234)^3 = 337.
This is, in fact, the number that the calculator you've linked to provides as rwhp; they then divide this by 0.82 (assuming an 18% driveline loss) to get the 397 figure...where they messed up is in not realizing the equation is actually for *crank* hp, not rwhp. Road & Track published this equation in their Tech Section, Sept. 2001 issue. Or, you can use this one, which doesn't mistakenly include driveline loss:
So, to hit a 120 mph trap speed at 4681 pounds with driver and test equip, the car would be producing 631 at the crank. Still waay above its rated, but remember: the E55's are running 116 trap speeds stock, which they'd need actual crank hp of 530+ to hit at their weight.
This is, in fact, the number that the calculator you've linked to provides as rwhp; they then divide this by 0.82 (assuming an 18% driveline loss) to get the 397 figure...where they messed up is in not realizing the equation is actually for *crank* hp, not rwhp. Road & Track published this equation in their Tech Section, Sept. 2001 issue. Or, you can use this one, which doesn't mistakenly include driveline loss:
So, to hit a 120 mph trap speed at 4681 pounds with driver and test equip, the car would be producing 631 at the crank. Still waay above its rated, but remember: the E55's are running 116 trap speeds stock, which they'd need actual crank hp of 530+ to hit at their weight.
Originally posted by RU_MATRX
Now this would be a pleasant surprise if the SL600 was the first application of the V12 TT, but how can one even account for this particular hotrod SL600 being so much quicker than MErcs own S600 and CL600 V12TT? 4501 lb vehicle needs around 728HP to attain a 120MPH trap speed period. The same vehicle needs no less than around 633HP to even get to that trap speed in 11.9 secs!!! This is simple physics. The 0-60mph is simply ridiculous cause my modified 996TT with consistent AWD, a 6 speed weighing 1100lbs less does 3.5-3.6 secs 0-60MPH and the 1/4 mile in around 11.6 secs which is spot-on for a 3388lb vehicle. It makes near 520HP, 510ftlbs TQ. Although we haven't even taken account of the driver weight so the ratings are still a bit optimistic.
Check here for the simple calculations.
http://www.speedworldmotorplex.com/calc.htm
Here's C&D's first review.,,,
"Mercedes claims the SL600 will waft to 62 mph in 4.7 seconds, which equals its claim for the snarling SL55 AMG that we prodded to 60 mph in 4.5 seconds. That car's supercharged V-8 is just 74 cubic centimeters smaller and is rated at an equivalent 493 horsepower, but its torque is, ahem, “just” 516 pound-feet. If the gearing were the same, the 12 would clearly be quicker, but a taller axle ratio (2.65 versus 2.82 in the SL55 and SL500) guarantees dignified throttle response in the SL600 and leaves some bragging rights to the AMG."
I'd love to believe these numbers BUT the physics don't make any sense at all given the proposed numbers. Torque and HP come up way short if we're talking about similar gearing to an SL55. Take a look at my post in regards to my experience with a modified 996TT vs my SL55 AMG under the SL55 threads. We need some true insight from someone here that owns an SL600
and can tell us if it's truly faster than say a 996TT stock 6sp that does ONLY 3.9 secs and 12.2 in the 1/4 mile. Can the SL600 really be 1 full sec (10+ car lengths) quicker than Mercs own S600 and CL600 that use the same V12TT application with the exact same ratings??? I think that this C&D SL600 isn't the same production vehicle you'll see at your local dealership.........
Now this would be a pleasant surprise if the SL600 was the first application of the V12 TT, but how can one even account for this particular hotrod SL600 being so much quicker than MErcs own S600 and CL600 V12TT? 4501 lb vehicle needs around 728HP to attain a 120MPH trap speed period. The same vehicle needs no less than around 633HP to even get to that trap speed in 11.9 secs!!! This is simple physics. The 0-60mph is simply ridiculous cause my modified 996TT with consistent AWD, a 6 speed weighing 1100lbs less does 3.5-3.6 secs 0-60MPH and the 1/4 mile in around 11.6 secs which is spot-on for a 3388lb vehicle. It makes near 520HP, 510ftlbs TQ. Although we haven't even taken account of the driver weight so the ratings are still a bit optimistic.
Check here for the simple calculations.
http://www.speedworldmotorplex.com/calc.htm
Here's C&D's first review.,,,
"Mercedes claims the SL600 will waft to 62 mph in 4.7 seconds, which equals its claim for the snarling SL55 AMG that we prodded to 60 mph in 4.5 seconds. That car's supercharged V-8 is just 74 cubic centimeters smaller and is rated at an equivalent 493 horsepower, but its torque is, ahem, “just” 516 pound-feet. If the gearing were the same, the 12 would clearly be quicker, but a taller axle ratio (2.65 versus 2.82 in the SL55 and SL500) guarantees dignified throttle response in the SL600 and leaves some bragging rights to the AMG."
I'd love to believe these numbers BUT the physics don't make any sense at all given the proposed numbers. Torque and HP come up way short if we're talking about similar gearing to an SL55. Take a look at my post in regards to my experience with a modified 996TT vs my SL55 AMG under the SL55 threads. We need some true insight from someone here that owns an SL600
and can tell us if it's truly faster than say a 996TT stock 6sp that does ONLY 3.9 secs and 12.2 in the 1/4 mile. Can the SL600 really be 1 full sec (10+ car lengths) quicker than Mercs own S600 and CL600 that use the same V12TT application with the exact same ratings??? I think that this C&D SL600 isn't the same production vehicle you'll see at your local dealership.........
02-08-2004, 02:26 AM
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2004 SL55 AMG
Thanks for the correction!
I was just doing a search for a simple HP calculator which is usually produces the crank (flywheel) HP figure, not figuring in driveline loss (~15% RWD). I understand now that the site's correction adjustment for driveline loss inflated the correct number.
I know that it's a relatively simple calculation. Thanks again for the clarification. The main point of my post was basically to support the fact that we're speaking of 630HP+ to hit a trap speed of 120MPH. The 11.9 sec quarter mile time calculator did give us around 633HP without adding a 180lb driver and test equipment. So for consistency, 630HP+ is where the SL600 needed to realistically produce at the flywheel in order to attain these numbers. Thanks again Improviz for the reference to Road & TRack's tech article. I've seen a few tech articles that explain how they calculate theoretical power output during their tests as well as how accurate it compares against the vehicle test results.
I know that it's a relatively simple calculation. Thanks again for the clarification. The main point of my post was basically to support the fact that we're speaking of 630HP+ to hit a trap speed of 120MPH. The 11.9 sec quarter mile time calculator did give us around 633HP without adding a 180lb driver and test equipment. So for consistency, 630HP+ is where the SL600 needed to realistically produce at the flywheel in order to attain these numbers. Thanks again Improviz for the reference to Road & TRack's tech article. I've seen a few tech articles that explain how they calculate theoretical power output during their tests as well as how accurate it compares against the vehicle test results.
Last edited by RU_MATRX; 02-08-2004 at 02:28 AM.
02-08-2004, 03:38 PM
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CLS55 AMG
Yeah, I agree...unless that was the mother of all typos, that motor was putting out
a heckuva lot more horsepower than advertised!! I think that there is a possible explanation for this, though: we've noticed (and verified through dyno tests, horsepower calculators, etc.) that two things stand out among the new 5.5L K motors:
1) they're underrated, putting out more like 530+ crank than their rated 493;
2) even though they rate the motor in the E55 at a lessor amount, it is clearly putting out the same as the the S55, CL55, and SL55.
Well, this might offer a hint as to what's actually happening here; the motor in the SL600 is the same as the motor in the Maybachs...in the Maybachs, it is rated at 543 hp/664 lb-ft of torque. Well, if MB did the same thing they did in the 5.5L cars, namely underrated the motor's power by a significant margin, and had it producing the same hp in all cars even while advertising it as lower in some than in others, it would account for some, but probably not all, of what we're seeing...
So, on a hunch, I checked out the numbers for the Maybach 57, which Road & Track tested in their September 2003 issue...with an as-tested weight of 6290 pounds, they ran a 13.4@106.4 1/4 mile, with 543 rated horsepower.
A quick check with the horsepower calculator shows that to hit a 106.4 mph trap speed with 6290 pounds requires 591 crank!
So, if in the case of the E55, MB told us a little white lie when they claimed they'd detuned this motor before putting it in the S600 and SL600, and if the exhausts were a bit less restrictive in the latter, it wouldn't be too much of a stretch for it to be pretty close to the 630 we're talking about...
But then, just to double-check myself, I decided to see if my theory held up with the road tests for the S600; answer: sorta, but not quite...the S600 weighs 4610 pounds, and Car & Driver tested it at a 12.5@115...so, adding 180 pounds for driver/equipment and using the calculator again gives its true crank hp as 568. Still waaay more than the rated 493, but not up there in the 600+ range...with the same motor, I'd expect the SL600 to be running more like a 12.4 or so, not an 11.9...so, something is still fishy here!!
1) they're underrated, putting out more like 530+ crank than their rated 493;
2) even though they rate the motor in the E55 at a lessor amount, it is clearly putting out the same as the the S55, CL55, and SL55.
Well, this might offer a hint as to what's actually happening here; the motor in the SL600 is the same as the motor in the Maybachs...in the Maybachs, it is rated at 543 hp/664 lb-ft of torque. Well, if MB did the same thing they did in the 5.5L cars, namely underrated the motor's power by a significant margin, and had it producing the same hp in all cars even while advertising it as lower in some than in others, it would account for some, but probably not all, of what we're seeing...
So, on a hunch, I checked out the numbers for the Maybach 57, which Road & Track tested in their September 2003 issue...with an as-tested weight of 6290 pounds, they ran a 13.4@106.4 1/4 mile, with 543 rated horsepower.
A quick check with the horsepower calculator shows that to hit a 106.4 mph trap speed with 6290 pounds requires 591 crank!
So, if in the case of the E55, MB told us a little white lie when they claimed they'd detuned this motor before putting it in the S600 and SL600, and if the exhausts were a bit less restrictive in the latter, it wouldn't be too much of a stretch for it to be pretty close to the 630 we're talking about...
But then, just to double-check myself, I decided to see if my theory held up with the road tests for the S600; answer: sorta, but not quite...the S600 weighs 4610 pounds, and Car & Driver tested it at a 12.5@115...so, adding 180 pounds for driver/equipment and using the calculator again gives its true crank hp as 568. Still waaay more than the rated 493, but not up there in the 600+ range...with the same motor, I'd expect the SL600 to be running more like a 12.4 or so, not an 11.9...so, something is still fishy here!!
Originally posted by RU_MATRX
I was just doing a search for a simple HP calculator which is usually produces the crank (flywheel) HP figure, not figuring in driveline loss (~15% RWD). I understand now that the site's correction adjustment for driveline loss inflated the correct number.
I know that it's a relatively simple calculation. Thanks again for the clarification. The main point of my post was basically to support the fact that we're speaking of 630HP+ to hit a trap speed of 120MPH. The 11.9 sec quarter mile time calculator did give us around 633HP without adding a 180lb driver and test equipment. So for consistency, 630HP+ is where the SL600 needed to realistically produce at the flywheel in order to attain these numbers. Thanks again Improviz for the reference to Road & TRack's tech article. I've seen a few tech articles that explain how they calculate theoretical power output during their tests as well as how accurate it compares against the vehicle test results.
I was just doing a search for a simple HP calculator which is usually produces the crank (flywheel) HP figure, not figuring in driveline loss (~15% RWD). I understand now that the site's correction adjustment for driveline loss inflated the correct number.
I know that it's a relatively simple calculation. Thanks again for the clarification. The main point of my post was basically to support the fact that we're speaking of 630HP+ to hit a trap speed of 120MPH. The 11.9 sec quarter mile time calculator did give us around 633HP without adding a 180lb driver and test equipment. So for consistency, 630HP+ is where the SL600 needed to realistically produce at the flywheel in order to attain these numbers. Thanks again Improviz for the reference to Road & TRack's tech article. I've seen a few tech articles that explain how they calculate theoretical power output during their tests as well as how accurate it compares against the vehicle test results.
Last edited by Improviz; 02-08-2004 at 08:37 PM.
02-10-2004, 10:12 AM
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'22 Alpina B7,'21 G63 Renntech obviously (wife), Wrangler(kids)
My E55 with Renntech pulley and ECU had 399 hp at the wheels.
As soon I get over 1k miles mark on my S600 ,I'll put it on the same Dyno to see what the true hp is.
As soon I get over 1k miles mark on my S600 ,I'll put it on the same Dyno to see what the true hp is.
03-05-2004, 09:41 AM
#34
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Ben, that's a killer garage 
I'm with you, I race everything at least once to get a number.
I agree that manufacturers will sometimes deliver ringers to magazines, but I say wait to pass judgement on the SL600 until after more people/mags do testing on production versions.
I'm with you, I race everything at least once to get a number. I agree that manufacturers will sometimes deliver ringers to magazines, but I say wait to pass judgement on the SL600 until after more people/mags do testing on production versions.
