HP loss thru drivetrain

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    Author Topic: HP loss thru drivetrain  (Read 1794 times)

    Offline challenger72rt

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    HP loss thru drivetrain
    « on: March 18, 2005 - 08:44:35 AM »
    ok, I wasn't sure where to put this in Tech, so I will  leave it to April to redirect it....

    Like others, I plan on having my Dodge dyno'd this summer.  I was curious as to how much HP loss I can expect between the flywheel and the rear wheels?

    it is a 440, and the mechanic who built it (a former Dodge race car driver) estimated 450HP on the motor

    The car has power brakes, but nothing else.  Manual steering, electric cooling fans, no stereo or other electonic components other than guages, no A/C, etc..

    So, approximately how much power is lost thru the drivetrain, and what is it that takes the power away from the wheels?

    I know stuff like power steering, and A/C do, but what else??

    thanks
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    Offline Chryco Psycho

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    Re: HP loss thru drivetrain
    « Reply #1 on: March 18, 2005 - 11:03:33 AM »
    depends on the type of dyno but on a mustang dyno it is the lowest reading & typically loses 35% , auto trannys are bad for eating power , we hit 310 HP with a built 440 @ 4000' altitude & the dyno opertaor said that would be approx 500 crank power so 40% loss 
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    Offline Killer_Mopar

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    Re: HP loss thru drivetrain
    « Reply #2 on: March 18, 2005 - 12:02:37 PM »
    A lot of it is where your at and what dyno your on, but a typical drivetrain loss for a new car is 15-20%, for most older cars you can raise that by at least 5-10% and like CP said altitude also effects the readings(except engines with forced induction). There are a lot more items that will affect the RWHP, the biggest being the transmission...but the convertor, driveshaft, and even the rearend can effect it..... Outdoor conditions such as humidity and temperature also effect the reading, so if its a hot humid day expect a low reading
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    Plum6Pak

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    Re: HP loss thru drivetrain
    « Reply #3 on: March 20, 2005 - 06:45:58 AM »
    With that said, what about the advertised hp on the old muscle cars and are the new ones advertised the same? An example would be the 390 hp 440 sixpack engine. Crank hp or at the rear wheels? These must have been at the crank due to the high hp's advertised but I'm not sure.  :dontknow:
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    Offline Chryco Psycho

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    Re: HP loss thru drivetrain
    « Reply #4 on: March 20, 2005 - 01:19:50 PM »
    The HP in 17 was rated as gross which is crank HP driving no accessories like water pump or alt etc
     in 72 the rating was changed to net Hp which was crank Hp as installed in a vehicle , rwhp is much lower yet as it is after the tranny & diff losses as well
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    kudakidd

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    Re: HP loss thru drivetrain
    « Reply #5 on: March 23, 2005 - 10:52:44 AM »
    15%. ie 300hp at the flywheel will show as 255hp at the rear wheels. If you get a timeslip at a track you can easily get rwhp by using your mph and car weight.
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