McLaren-Mercedes SLR Horsepower - Underated?

Discussion in 'European Cars' started by Cosworth, Dec 22, 2004.


  1. The SLR seems to have a lower power to weight ratio than the Pagani Zonda and Porsche Carrera GT yet it matches if not beat these cars at all out acceleration. The SLR weighs kerb weight of 1695 kg (EU), with a claimed 617 HP.

    The power to weight ratios of the 3 cars are:

    McLaren Mercedes SLR - 364 HP per 1000 kg
    Pagani Zonda - 442 HP per 1000 kg
    Porsche Carerra GT - 432 per 1000 kg

    I'm pretty sure McLaren deliberately underated the power of the SLR for marketing interests, as the McLaren F1 makes *only* makes 627 HP in road trim, and for the SLR to perform as it does, I estimate it is pushing 660+ HP given that it weighs a few hundred KG more than the competition.

     
  2. Ever heard of something called torque?
     

  3. HP and gearing determines acceleration, not torque.

    To accelerate at high speeds, the RPM involved are pretty well within the peak crest of their power bands, not the peak torque.
     
  4. bullshit dude, i dont know where the hell people come up with this crap.

    Power to weight, torque to weight, gearing, drag, grip are all important factors in acceleration
     
  5. Also torque!!!!!!!!!!!!!!!!!!!
    if you have same weight, gears and power, but different torque, you don't have the same performances! torque is important because you can have diffrent power at medium RPM's..and after change of gears!!!
    what you say?
     

  6. Yes, but for the McLaren to match the acceleration of the other cars with the claimed horsepower with the extra weight, it would need a far lower .Cd and a significant smaller frontal area to make up for the extra weight - which it doesn't.

    Grip isn't much of a problem at higher speeds with these cars. All 3 cars produce at worst no aerodynamic lift.

    Where's the bullshit now???







     
  7. Look at the actual BHP and Torque figures:

    McLaren Merc SLR

    Kerb Weight: 1768kgs
    626 BHP @ 6500
    575 ft.lbs @ 3250-5000
    0-60mph: 3.7 secs

    Porsche CGT

    Kerb Weight: 1380kgs
    612 BHP @ 8000
    435 ft.lbs @ 5750
    0-60mph: 3.8 secs

    Zonda C-12S

    Kerb Weight: 1350kgs
    555 BHP @ 5900
    553 ft.lbs @ 4050
    0-60mph: 3.6 secs

    The SLR makes over 100 ft.lbs of torque (peak) over the CGT starting at 2500rpm lower !
    The Zonda is closer with 22 ft.lbs (peak) less and starting 1000 rpm higher

    I don't think the differences between the SLR and CGT are that suprising when you take the above into account, and it's difficuly to know gear ratios etc. for the Zonda - but it is marginally the fastest of the 3 ...

     
  8. Also torque!!!!!!!!!!!!!!!!!!!
    if you have same weight, gears and power, but different torque, you don't have the same performances! torque is important because you can have diffrent power at medium RPM's..and after change of gears!!!
    what you say?
     
  9. In Europe the fastest of the 3 is CGT!

    62 to 124 Mph:
    CGT app.7s
    SLR 7.5s
    Zonda 7.3s
     
  10. i don't really compare it to cars like the zonda and CGT. those are real supercars.
    the SLR isn't, it's a grand tourer. but a bloody fast one at that
     
  11. Auto Motor und Sport has tested also SLR than CGT!

    SLR
    0-100 3.8s
    0-200 11.3s
    standing Km (Nardò test) 20.5s

    CGT
    0-100 3.8s
    0-200 10.9s
    standing Kn (Nardò test)20.4s

    Zonda 7.3 by Sport Auto.
    0-100 3.8s
    0-200 11.2s
    standing Km n.a. (but is approx 21s)
    Zonda has a bad Cx and long gears!
    1a 96 kph (7000rpm)
    2a 154 kph
    3a 215 kph
    4a 273 kph
    5a 328 kph
    6a 353kph (declaration at 6430rpm) but is difficult over 335-340 kph!
     
  12. I was looking for those figures <A BORDER="0" HREF="http://www.supercars.net/emoticons.html"><IMG BORDER="0" SRC="http://speed.supercars.net/pitlane/emoticons/tongue.gif"></A>

    The CGT is also just under 2 sec faster from 0-100mph than the Zonda (Not sure about the SLR or how official that figure is ...).

    I'm not sure what the redlines are on the SLR and Zonda, but the CGT peaks at 8000rpm and I assume goes on a little bit after that. Depending on gearing, etc. if the CGT makes the majority of it power at the very top, can rev for 1500-2000rpm higher than the SLR or Zonda and the gearing is just right then at higher speeds it could well have better ingear acceleration and sit in that gear for longer, creating peak power.
     

  13. The high speed accleration between the GT and the SLR are too close. Say 100 - 130 MPH. 2-4 tenths in it depending on which road test you read. There is no "torque to weight" advantage at the RPMs during acceleration at these high speeds as they are well within their peak power curves, but there is a significant power to weight advantage in the GT's favour. I estimate they are using the very last 1500 - 2000 RPM in 4th gear.

    If it had been a simple midrange acceleration test, say 30-70 mph, then there is torque advantage as lower RPM's would be used.





     
  14. Peak horse power is not what causes you to accelerate. This is because unless your car has a cvt does the car hit peak horsepower for more than a fraction of a second. What determines acceleration is the area under the horsepower curve. The flatter the curve is from the low end to the high end (ie less peaky) the faster the car will be since it will have more power at lower rpms. This flatter horsepower curve comes from the higher amount of torque across the rev range. So an SLR with lots of torque across the rev range will also have more horsepower at lower revs than a CGT.


    Having said all that, the SLR is probably underated. Ever wonder why the SLR is rated at 626 hp, just one less than the F1 at 627? This is not a coincedence.
     

  15. "well within the peak CREST of their power BANDS, not the peak torque."

    Did not say peak power.

     
  16. " There is no "torque to weight" advantage at the RPMs during acceleration at these high speeds as they are well within their peak power curves"

    ermmmm... no

    more torque, bigger gear, more speed
     
  17. Gotta agree with burning on this one, AMG knows torque. Torque is the only reason the E55 can do 0-60 in LOW LOW 4 seconds.
     
  18. Does anyone have photos of the McLaren Mercedes? I would like some, and I can't find it in the photo gallery. If it's there...point it out. Thanx!
     
  19. #19 MastrVipr, Dec 22, 2004
    Last edited by a moderator: Apr 25, 2016

  20. You don't understand what torque and gearing does.

    Do you not understand the definition of horsepower?

    High speed acceleration is done at high RPMs, where the peak power curve usually resides of each car. Torque does nothing to increase speed as it is only a twisting force.

     

  21. No one was comparing 0-60.

    High speed accelration, no torque advantage. The Carerra GT is at an entirely different RPM than the McLaren, where it actually makes power.

     
  22. high speed accelerating is done at whatever RPM it takes to put out the fastest time...

    HP sells cars, Nm wins races

    also look up the max output in Kw's
     

  23. "Torque does nothing to increase speed as it is only a twisting force."

    What ? I know sort of what you are getting at, but thats not right.


    Torque is what pushes the car along.

    BHP is the rate at which torque is delivered/the engines capability to do work.
     
  24. Vantage, Rafale...

    I'm not going to turn this thread into another torque and HP tutorial.
    there are plenty of good online materials can teach you guys that.

    The gear ratio simply maps engine speed to the desired speed range of the car (MPH/KPH), maximum power would be available to accelerate within the speed range.

    Take a look at the acceleration times of the SLR vs the GT. 100 mph to 130 mph is a huge demand for aerodynamics, power to weight and outright power. The difference is 0.6 seconds between the 2 cars.



    The SLR is geared to go from 100 - 130 MPH with 3rd gear. The RPM's that are covered during this test is 5300 - 6900 RPM. Well within the peak power band.

    0-100 mph: 7.9
    0-110 mph: 9.3
    0-120 mph: 10.8
    0-130 mph: 12.5

    The GT is geared to go from 100 - 130 MPH in 3rd and 4th gear. RPM's covered are 7500 RPM - 8400 RPM ins 3rd. 100 - 112 MPH, then 6600 - RPM to 7700 RPM.

    0-100 mph: 6.8
    0-110 mph: 7.8
    0-120 mph: 9.4
    0-130 mph: 10.8


    Drag x frontal area for the cars are.

    Production GT: Cd 0.39 x 1.90 sq m = 0.741 CdA
    Production SLR: Cd 0.37 x 2.053 sq m = 0.759 CdA

    The SLR fairs worse in the drag department.

    So given the fact that the SLR has far more weight, similar claimed power during high speed accleration and suffers more drag, there must be more power in the SLR to be so close in acceleration to the GT.

    Yes, the GT needs a gear shift which cost it some time, but for a extra 70 HP per 1000 KG advantage and lower drag, it would be *whole seconds* in front of the SLR if that was the case.

     
  25. as far as I know:

    torque: acceleration
    horsepower: topspeed
     

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