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Thread: Power Transfer

  1. #1
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    Default Power Transfer

    Greeting Gents,

    Please tolerate two related queries in one thread...

    1. How much power is lost between the flywheel and the rear wheels on an M400? Cognizant of the fact that we are most interested in rear-wheel horsepower, it's sometimes nice to quote your "bragging horsepower" at the crank. 15% driveline loss? More? Less? 400RWHP = ? at the crank?

    2. How much torque can a stock M400 tranny withstand before inconvenient and acoustically unpleasant metal fragmentation occurs (assuming no clutch side-stepping from a dead stop, and overall sensible transmission operation).

    Your thoughts are appreciated!
    Dave
    2007 M400 Chassis #210 (original owner) - Carbon Fiber White! - Livermore rehab complete and highly successful! - 535 whp.
    2010 BMW X5M. ECU tune. 600 HP.
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    2010 Toyota Tundra. Stock!
    2010 Yamaha Raptor - header-back exhaust, intake, and ECU. 55 HP. By FAR the most thrill for the dollar!
    2011 Polaris RZR XP Aerocharger Turbo with fully built engine - 120 whp.
    2011 Coachman E450, 27 foot RV - with aftermarket tune...no joke, I tuned my RV!

  2. #2
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    I see that you have chosen the fastest color for your M400. Congrats. What color silver did you get?

  3. #3
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    Quote Originally Posted by Dave View Post
    Greeting Gents,

    Please tolerate two related queries in one thread...

    1. How much power is lost between the flywheel and the rear wheels on an M400? Cognizant of the fact that we are most interested in rear-wheel horsepower, it's sometimes nice to quote your "bragging horsepower" at the crank. 15% driveline loss? More? Less? 400RWHP = ? at the crank?

    2. How much torque can a stock M400 tranny withstand before inconvenient and acoustically unpleasant metal fragmentation occurs (assuming no clutch side-stepping from a dead stop, and overall sensible transmission operation).

    Your thoughts are appreciated!
    #1 - Yes 15% loss is probably about right. The stock M400 is stated to have 425 HP and should be about 365 RWHP if running properly. The calculation I have used is to multiply the RWHP by 1.16. So my 552 RWHP is probably around 640 HP. Your equation above would be 400 RWHP = 464 HP at the crank. Of course there is definitely some inaccuracy to these numbers for various reasons but it is a fair guess.

    #2 - There is not a simple and exact answer to this and if anyone gave you an exact number it would be a mistake. There are all kinds of variables and we are not sure exactly why some gear boxes have failed and others are still running strong. My car is the first M400 in the states. I understand that there may have been gear box improvements since my car but my gear box is still okay. The car has been tracked extensively at stock horsepower and torque. I am now at 550 RWHP and 508 ft lbs torque. So far so good. There are cars with significantly increased HP and torque that have not had gear box issues and there are cars with lower levels of power that have. The bottom line is that this is a big crap shoot if you increase power and torque and even with standard power there is no gaurantee that you will not have trouble.
    Last edited by richsd; 05-03-2007 at 09:18 AM.
    Rich

    '05 Noble M400 #063 Indigo Blue
    '68 Dodge Charger R/T (owned since new)
    '65 Shelby Cobra Recreation (Kirkham)
    '74 Pantera

    http://richsd.smugmug.com/Cars

  4. Default

    Quote Originally Posted by richsd View Post
    I am now at 550 RWHP and 508 ft lbs torque.
    With a standard clutch?
    --
    Richard

  5. #5
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    We are targeting 450 RWHP with stock clutch. Should I upgrade the clutch?

    DAVE

  6. #6

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    Power losses are probably more than 15%. The real proof is to actually run the car and check its trap speed over a standing 1/4 mile. Generally, the results will show somewhat less HP than the Dynos exhibit.

    Of course, no one wants to do this because it throws ice water on the really huge numbers, and some shrinkage occurs... Is anyone getting over 120 mph in the quarter with an M400?

    Really, I can't believe that anybody thinks that a quick run down the strip, where there is plenty of ambient air to cool the aftercooler is harder on the car than running indoors, slamming the gears to get a good dyno pull. After all, quick, hard shifts are not necessary to get an accurate trap speed.

    The gearbox is good for about 450 HP and 450 Torque. Whether or not it breaks sooner or later really depends on how the driver treats it. Bang high power shifts all day long, and it wont go well.

    Take your time, "Click, Click", and it can last much longer. Be accurate and smooth.

  7. Default

    Quote Originally Posted by S.J.Morgan View Post
    The gearbox is good for about 450 HP and 450 Torque.
    Upon what information are your figures based?
    --
    Richard

  8. #8

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    Quote Originally Posted by chillidog View Post
    Upon what information are your figures based?
    --
    Richard
    Mostly from experience in testing road cars for magazines, and documenting race car performance. Also, different drive trains absorb different amounts of power, and then there are the correction factors used during dyno tests.

    Do you think that an AWD Audi or Subaru has the same losses through the drive train as a Noble, or a GT3 Cup with its sequential, hyper efficient straight cut gear box?

    Haven't you ever thought "It should be faster than that" after having a dyno confirm 500 HP? Yet, the car is not appreciably faster or quicker than it was at lower HP.

    In any case, trap speeds and Dyno RWHP readings suggest that there is more drive train loss than 15%. Maybe closer to 20%. Just my EWAG. Besides, it makes the BHP numbers bigger.

    When some of these hyper Nobles produce trap speeds, it will be easier to determine dyno accuracy and drive train losses.

    I will have more information when I dyno the car locally.

  9. #9
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    I think Richard's question about what you are basing your figures on was directed at your statement about what HP and torque the gear box is good for (450/450) not about the power loss through the drive train.

    Also, I will try to get a run to get trap speed on my car within the next couple weeks.
    Last edited by richsd; 05-03-2007 at 12:17 PM.
    Rich

    '05 Noble M400 #063 Indigo Blue
    '68 Dodge Charger R/T (owned since new)
    '65 Shelby Cobra Recreation (Kirkham)
    '74 Pantera

    http://richsd.smugmug.com/Cars

  10. #10

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    Quote Originally Posted by richsd View Post
    I think Richard's question about what you are basing your figures on was directed at your statement about what HP and torque the gear box is good for (450/450) not about the power loss through the drive train.

    Also, I will try to get a run to get trap speed on my car within the next couple weeks.
    Sorry.

    Word from Getrag is 450 HP. Since the current M400 engine produces close to 400 lb.ft, torque equal to HP is probably a good number. Figure around 450 lb ft, max. I am thinking that the number is a little optimistic, as there are no front drive cars (the initial application of that transmission) that produce that much power.

    It is not that bad. If you get a couple of seasons out of the transmission on a race car, you are ahead of the game.

    What really makes the difference is how hard it is used (abused). Hard, gear banging use will wear things out, especially when your HP is up by half.

    Consider that at more than 450 HP, all you get is a Noble with more wheel spin.

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