Dynos...Again.

Discussion in 'SRT Hellcat General Discussions' started by VanishingPoint, Apr 3, 2015.

  1. VanishingPoint

    VanishingPoint Silver Member

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    I would always be cautious when reading dyno sheets.

    They are usually pumped. I think "press cars" were making a wee bit more than the 707.

    I think all cats at 4600 lb+/- (with driver) make a minimum of 707 HP on 90-91 octane at sea level (10.8/124 mph trap speed), with most maybe making 715-730 depending on 92/93 gas and how many miles on the clock (125 mph traps).

    Some seem to be making a bit more, like Tesla Killer Tony's who appears to be making 750-760 (on 93 octane) and has cut some truly impressive 126-127 mph trap speeds.

    Assuming he is the high end of well made engine'd Cats, with a pretty reasonable 15% driveline loss after the flywheel slings power through the massive 8 spd transmission, huge, heavy, and useless driveshaft, independent rear gears/axles, and 2 x 64 lb 20 inch rims, even at "760" it will give Tony a realistic dyno RWHP of 646 to the rears.

    So, please don't believe this car has 670 RWHP stock on an accurate dyno. I know some "press" cars have shown big numbers (Motortrend) but even their own race runs only had 125 mph traps, more indicative of a 725-730 HP engine.

    Further I do not believe the legendary "Texas 133 mph trap speed" was made w/o a late NOS squirt. That trap speed in that car is indicative of an 866 hp car. And 109 Race gas does not give 100+ extra HP either. The Dodge HC is not a 850+ HP car, without a little help from the bottle.

    Check your ego, read, and dyno your cat at the guy with the lowest dyno numbers in town. Learn the difference between "corrected" and "uncorrected" and what factors they are using.

    When people talk and throw numbers, ask "why?"

    Are they selling me/others something?
    Are they trying to impress me/others?
    What sells news and blog hits?
    Lies, jabs, controversy, etc.

    Everyone wants the most RWHP, it is the closest thing you can get to a bigger D@WK.

    Dyno guys know this and they are selling dyno runs.
    Go dyno it. Then run it at the track several runs...look at your weight and your MPH.
    Match the math, and always go with the lower number if you really want to know.

    You will have your Hellcat's numbers and find I am probably right at around 600-630 RWHP.

    YMMV.

    Sources:
    ET-MPH-HP Calculator



    I am far from an expert, but I have dyno'd many cars and motorcycles, and have researched HP ratings for quite some time.
     
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  2. buddyg

    buddyg Gold Member

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    Dyno numbers mean nothing as you have stated they can be manipulated. The only thing that matters is results at the track. That will prove what your car is making as you mention above with simple drag calculators.

    The only thing a dyno is good for (using an independent dyno not the tuners dyno) is making baseline numbers and then adding mods and running again to see the results.

    I would agree with your assessment that most Cats are around 630 rwhp.
     
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  3. Hellcat Jack

    Hellcat Jack Silver Member

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    Mine dynoed at 638 RWHP. There's definitely more she climbs straight up to the limiter. A few more rpm's ??????
     
  4. buddyg

    buddyg Gold Member

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    Wallace racing has a good calculator

    Wallace Racing - ET/MPH/HP CalculatorWeight is as the car sits on the line: driver and gas in it.
    The answers below will be for at sea level and standard pressure/temperature.
    (no weather correction).
    Calculate ET and MPH from HP and Weight
    Weight HP

    Your ET / MPH computed from your vehicle weight of 4600 pounds and HP of 730 is 10.76 seconds and MPH of 125.61 MPH.
     
  5. Next Phase

    Next Phase Silver Member

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    I love that video.... Partially due to the color and the fact that the host is truly impressed with the car.

    I've probably seen that video 20+ times.

    I thought those figures were inflated, but am hoping we see some other cats in the 650+ rwhp range.

    Hellcat Jack,
    How many miles on your car?
    What brand dyno?
    Do you have a dyno sheet you can post?
     
  6. Hellcat Jack

    Hellcat Jack Silver Member

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    I dyno-ed at 1750 on a mustang dyno. I'll post the sheet when I get a chance.
     
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  7. Hellcat Jack

    Hellcat Jack Silver Member

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    First runs at the track on street tires had repeated 125 mph speeds...... obviously the 60's sucked (1.9 - 2.2 ) lol...... starting in 2nd gear and peddling best ET was 11.6
     
  8. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    So if I have myself and another guy in the car plus say 50 lbs in the trunk (4600+200+50)=4850 lbs with a trap at 122. That is 687 at the rears and in line with the "press" numbers. (93 octane).

    With that I am believing the numbers above 650 coming off the dynos. Dodge is selling us everything promised and more. I also can tell you the 91 octane gas does not allow it to do that.
     
  9. Next Phase

    Next Phase Silver Member

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    From my experience, you'll probably gain rwhp once you get some more miles on the car... Mustang dynos are more stingy as well compared to the Dynojets in the area.
     
  10. Hellcat Jack

    Hellcat Jack Silver Member

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    Holy crap......how did that happen ?????? I know I typed ......638 rwhp !!!!!!
     
  11. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    An April fool deal?
     
  12. budkole

    budkole Best Color and fastest is undoubtedly WHITE

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    Im no dyno guro, but what does the weight of the car have to do with determining the hp? You cant determine hp based on weight and speed. Those calculators are misleading as well. In order for them to be correct, you would have to factor weather conditions, ie temp, wind..surface conditions; flat, grade, temp,...car; rolling resistance, tire pressure, weight of fuel in tank, etc...i can go on and on. For example, a diesel pusher may have 550 hp to the rear but weigh 22k...of course it wont get to 100 in 5 sec, but that doesnt mean it doesnt have the hp. The dyno is stationary so weight at that point is useless.

    please correct if im wrong....
     
    Last edited: Apr 3, 2015
  13. budkole

    budkole Best Color and fastest is undoubtedly WHITE

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    I respectfully, disagree.
     
    Last edited: Apr 3, 2015
  14. Top Cat

    Top Cat Gold Member Hellcat Car Club Gold Supporting Member Fastest Cat/Record Holder HCC Charter Member

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    You can dyno the same car on five different dyno's and have five different numbers, it's a tool for base line tuning and thrill seekers, can't tell you how many guy's go in bragging on how much they have only to come off looking like someone kicked them in the nuts.........
     
  15. budkole

    budkole Best Color and fastest is undoubtedly WHITE

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    so true:rolleyes:
     

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