For those of you who read my "Dunno if you've read this post...

Discussion in 'Dodge Challenger SRT Hellcat Forum' started by Hajo, Jun 17, 2017.

  1. Hajo

    Hajo Now that was dumb! Site Supporter Level 4 Site Supporter Level 2

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    I am having a problem with the math end of the dyno results by Kenne Bell. 620HP to the rear wheels. I've always been lead to believe that one gets at least a 20% to 30%...sometimes a bit more drop in HP to the rear wheels. Here's my math problem. We have smart folks here help me with this. A 20% drop in HP to the rear end would be 707HP -141HP= Approx. 560HP. The dyno test showed that there was 620HP to the rear wheels. If you read, the dyno test was in a controlled atmosphere and done by an independent party. Hell, it got 579ft/lbs of torque at 4100 RPMs.

    My question. Did dodge low-ball the number like they did with the 426 street and races HEMIs in the 60s?
    Or did the drive components become so efficient that there is less inherent drag through the drive train?

    Splain dat Lucy!
     
    Last edited: Jun 17, 2017
  2. Dodgeguy

    Dodgeguy Highway Star Member Relations Photo Winner! MOTM Winner! Public Safety

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    I don't think the loss is that great anymore. I thought it was more like 15%. And I don't think every car is at 707, some might be a little more.
     
  3. jklotz10

    jklotz10 Well-Known Member Member Relations MOTM Winner!

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    ^^^^^^^ I agree ^^^^^^^^^^^^
     
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  4. James Brackett

    James Brackett Active Member MOTM Winner!

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    Dodge definitely underrated the horsepower as well.

    The power loss isn't 20-30% anymore. Like @Dodgeguy said it's more in the neighborhood of 15% or less.
     
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  5. Hajo

    Hajo Now that was dumb! Site Supporter Level 4 Site Supporter Level 2

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    That's why I posed the question gents. Thanks for your replies. I'm old school from when you at least lost 25%.

    Evidently the engineering on drive trains and auxiliaries has gotten more efficient.
     
  6. Dodgeguy

    Dodgeguy Highway Star Member Relations Photo Winner! MOTM Winner! Public Safety

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    I wonder how much was gained by changing to an electric steering pump.
     
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  7. Hajo

    Hajo Now that was dumb! Site Supporter Level 4 Site Supporter Level 2

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    Good point Corbin. Let's add this stuff up, work with me here. We are turning a water pump, a supercharger, and air conditioning. Think of anything else under the hood Corbin? Oh! The crank is turning the cam! The we transmit the power from the crank through a manual transmission that has less friction then a automatic trans (this includes clutch on the manual) the auto has more gears to turn. Then we go to the driveshaft, the gearing in the rear end and finally the axles. Miss anything? I'm sure an electric steering pump would lessen the amount of load on the engine for sure. How much I have no idea. Forgot the alternator....geez and I don't know if the crank to cam should be added (timing belt). DUh
     
    Last edited: Jun 17, 2017
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  8. Dodgeguy

    Dodgeguy Highway Star Member Relations Photo Winner! MOTM Winner! Public Safety

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    Yeah it would not be a whole lot but it would have to be some. Lots of drag racers use electric water pumps. Also spinning an alternator which depending on the load would be taking some power.If the A/C is not on the compressor should be freewheeling so not much there unless you have a Demon.
     
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  9. dodge boy

    dodge boy Senior Member Site Supporter Level 2 MOTM Winner!

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    I agree too, 15% is a much more realistic number.
     
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  10. wvhemis

    wvhemis Well-Known Member Site Supporter Level 5 MOTM Winner! Military

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    I agree with Dodge Boy the N-1 A 5 is 15% the 6 Speed is more like 12% and I would think the A-8 is 12 based on the track times the A-8 SP's are turning.
     
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  11. Hajo

    Hajo Now that was dumb! Site Supporter Level 4 Site Supporter Level 2

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    Well, the figure 25% to 30% of HP loss at the rear wheels ought tell you how old I am.
     
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  12. Dodgeguy

    Dodgeguy Highway Star Member Relations Photo Winner! MOTM Winner! Public Safety

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    That would probably be with an auto. Manuals should be close to what it is now.
     
  13. Db2016sp

    Db2016sp Member

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    I think 15-18% drivetrain loss is the new norm for an auto. Prob 12% for a manual.
    An interesting fact is the IHI supercharger on the 6.2 takes 80hp to drive! In fact they claim that gross hp is 800! SAE rating with all accessories is 707 hp. Therefore it has 93hp of parasitic loss! That's at the motor!
     
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