60-120 mph rolling times...comparo

Discussion in 'SRT Hellcat Performance' started by Driver72, Jan 4, 2016.

  1. Driver72

    Driver72 Gold Member

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    This post will highlight the differences and advantages of cooler weather/superior weather = lower DA and what it does for performance on a car.

    So a couple of months ago I went out onto my deserted testing road to do some rolling times.
    I did 60-120 mph tests starting in 3rd gear.
    60-120 highlights the acceleration at WOT.

    When I did the initial testing a couple months ago the weather was:
    85 degrees
    45% humidity
    29.92 inches pressure
    elevation of road is 10 feet above sea level
    Wind was calm
    This gave a DA of 1,910 feet above sea level

    60-120 mph ranged from 6.7 to 6.9 seconds with an average of 6.825 seconds.



    Tonight I went out again.
    Tonights conditions were as follows
    45 degrees
    65% humidity
    30.18 inches pressure
    Wind was calm
    This gave a DA of of -1138 feet (negative 1138 feet) below sea level
    So essentially like being 3048 feet lower in elevation.

    60-120 mph runs at this below sea level DA was DRAMATICALLY better.

    I did 8 runs this time and got 3 at 6.0 seconds and 5 at 6.1 seconds for an average of 6.063 seconds.

    An average improvement of .7625 seconds (and up to .9 seconds improvement). That's an 11.2% improvement average.

    That just goes to show you that when guys at tracks like ATCO and similar tracks that often have below sea level DA's (even in summer) their 1/4 mile times and traps are so much better than those at tracks with a bit of elevation or who don't get sea level DA's. That's why you absolutely CAN NOT compare one track to another or one car to another car on different tracks. And why it's silly for anybody to claim "world's fastest" on a stock car, or a lightly modified car (i.e.: DR's, driveshaft, lightweight wheels, race gas) when they have access to a "fast" track that's below sea level and other people do not. Those (truly) stock cars that did the 1/4 in 11.2 seconds at sea level or below may actually be no better or maybe even slower than someone who got a 11.6 at a track that doesn't have below sea level DA's

    The car felt like an even stronger beast tonight with that oxygen filled cool below sea level DA, almost like having an extra 20-30 hp. It was nice.
     
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  2. BULL

    BULL ________173.7mph_______ ___2016 Colorado Mile___ Gold Supporting Member

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    The altitude here is right at 5100ft, the DA is typically 6500 to 7200ft...

    :(



    EDIT: Tonight it's 31degF, that brought it down to ~4100'DA

    (Used my Kestrel 4500NV) :p
     
    Last edited: Jan 4, 2016
  3. BODUKE

    BODUKE Gold Member

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    Good point different tracks bring different results.
     
  4. Evil_GTR

    Evil_GTR Hellcat Member

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    Temp makes a big difference in these cars......

    My car ran well during the summer(100+*), but its a complete animal right now in winter(40-50*). Temps play a roll in any forced induction car, but this car is very sensitive to them.
     
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  5. MattG

    MattG Gold Member Hellcat Car Club

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    interesting read on the change in temps.

    My question is what is "DA"

    I have seen this before but never asked.
    Matt
     
  6. BULL

    BULL ________173.7mph_______ ___2016 Colorado Mile___ Gold Supporting Member

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    DA = Density Altitude

    It's a combination of factors: temp, pressure, etc, that combine to determine the actual density of the air and is related in a corrected altitude relative to a "standard day at sea-level".
     
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  7. BULL

    BULL ________173.7mph_______ ___2016 Colorado Mile___ Gold Supporting Member

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    So a lower number means "thicker" air which in our case translates into more power....
     
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  8. MattG

    MattG Gold Member Hellcat Car Club

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    thank you sir
    appreciate it.

    Matt
     
  9. NorCaletch19He77Kat

    NorCaletch19He77Kat Silver Member

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    of course your competition will be where ever you are--the HellCat should dominate especially on 60-120 type rolling scenarios..
     
  10. Tweaked

    Tweaked Hellcat Member

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    Altitude makes a big difference with these
    Cars. The altitude where I live is 3600 feet D.A. can be upwards of 6500. Had to take a trip to south Texas the altitude there is 171 feet, all I can say is there is a big difference. The cat was angry while there it even had a different sound.
     
  11. Driver72

    Driver72 Gold Member

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    DA is actually MORE affecting on a natural aspirated car than it is on a turbo or supercharged car.

    Years ago one of the car magazines demonstrated this by using a
    BMW 540i (a V8 powered naturally aspirated sedan) and a
    Volvo S40 (a 4 banger turbo sedan)

    At sea level the 540i which had over 100 hp more would easily walk away from the Volvo.
    When they went up to 10,000 feet in elevation where the air is much thinner, the Volvo would run equal to the BMW...or maybe it would inch away I can't fully remember).

    Either way, the Hellcat does feel nice and strong in the cool air compared to the summer heat.
    Just too bad the tarmac is cold too and makes for getting traction below 50 mph even tougher. LOL
     
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  12. Driver72

    Driver72 Gold Member

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    FYI also, forgot to post this but 60-130 mph times are 7.725 seconds with a DA of roughly 1000 feet below sea level (-1000).

    I did some 60-130 mph times several months ago when the DA was 425 feet above sea level and got an average of 8.0 seconds.

    So figure 7.9 seconds at sea level.

    93 Octane
    1/3 tank gas
    A8
     

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