Down in Power This Summer?

Discussion in 'SRT Hellcat Performance' started by VanishingPoint, Jun 24, 2015.

  1. VanishingPoint

    VanishingPoint Silver Member

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    My Cat seems to be down in power according to the dashboard HP readout, and I wonder if it is due to 88-90 degree weather and humidity.

    In the past, it generally made 695+/- in maybe 80 degree weather, but now in 85-90 degrees seems to only be making 640-650 on the clock. This was after two days of observation and no heat soak other than outside temps.

    This of course, right after the fuel rail service and coolant recall.

    Anybody else experiencing this? 'Cuz if I am the only one, the dealer is going to find out about it. I didn't pay all of this money for a 650 HP car.
     
  2. DGatzby

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

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    It's normal VP. You could be seeing a substantial difference in power!

    Let me give you an example or two.
    Say, 1000' elevation, 70 degree day, 30 degree dew point, barometer at 30.00. Our power that day is 98.9% relative HP. Nice day, everyone is comfy including internal combustion engines.

    Now heat it up
    Say 1000' elevation, 87 degree day, barometer at 30.00, dew point at 70 degrees. Our power that day is 94.8 %. People say it is HOT and engines hate it. Also notice the differences in intake air temp and S/C coolant air temp on a wicked hot day, and a cool day.

    Give you a wild example of real cool, dry weather. Actually this was the weather conditions when I had mine dyno'ed three weeks ago in MN.
    47 degrees, 37 degree dew point, same other stuff...101.3% of HP!

    That morning two of us were driving Hellcats (Speedman), both reported that nailing it at 60-70 was producing wheel spin. It was fun, but you need to drive like there is a light ice coating on the road! Mine showed 666 ft-lb at the back wheels that morning! That and cool roads will seem spectacular. Not so at 85 degrees with humidity.

    Yes the other day when it was 85 with a 65 degree DP outside I also noticed a BIG difference in the seat of my pants. Also, we went out and ran a 1/4. While we pulled a reasonable 0-60 it showed a difference in the time on the quarter. We pulled a reasonable 0-60 because finally my tires began to stick on the hotter roads. Also the computer may be penalizing us even more and dialing back some advance.

    Use: wahiduddin.net for these fun calcs and comparisons.
     
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  3. B5 Blue

    B5 Blue Platinum Member

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    Dang I forgot to bring up gauges at the track, oh well next time.
     
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  4. rayzazoo

    rayzazoo DRIVESRT.COM Gold Supporting Member

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    Power should be down. The engine has a measured SAE rating of 714hp @ 6200 rpm (707hp @ 6000rpm) at standard pressure and 77 deg F intake temp.
     
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  5. X-Men Fiend

    X-Men Fiend Gold Member

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    My intake air temp is over 130 degrees lately, no wonder my car doesn't feel too punchy!
     
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  6. Paladin06

    Paladin06 Have Guns Will Travel Staff Member Hellcat Car Club Gold Supporting Member

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    Yea, those 110 to 116 degree days suck the life out of Lizzy.
     
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  7. X-Men Fiend

    X-Men Fiend Gold Member

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    Wow, I was just stuck in some traffic in Tempe, and my intake air temp got to a brutal 173 degrees! (Thankfully, the climate controls work great in these cars, so I was still comfy inside, and the coolant was only around 220, so they obviously have top notch cooling systems.) I could tell power was down, but that's to be expected in this brutal valley heat! My passenger still thought it was plenty punchy, but I could tell it was weaker, from the driver's seat...
     
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  8. purnrg

    purnrg BANNED

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    I think they have 219 degree thermostat
     
  9. VanishingPoint

    VanishingPoint Silver Member

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    Well will someone please go out and carefully look at their power-on the dashboard, not the uconnect screen-and clock the HP, temperatures outside, humidity, and elevation-thanks!
     
  10. TallCool1

    TallCool1 Gold Member Hellcat Car Club Gold Supporting Member Nat'l Hellcat Tech Advisor HCC Charter Member

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    Did you see tsb RS very recently posted re knock and potential loss of power at high rpm?
     
  11. VanishingPoint

    VanishingPoint Silver Member

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    Yes, but the last time I had a reflash I was putting out 690+ in 80+ weather; makes me wonder if I got some bad gas, etc.
    Still, disconcerting as I pay attention to my gauges quite a bit!!

    I guess it could have come on with the fresh heat?
     
  12. DGatzby

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

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    Get a hurricane to shift this wet weather pattern up here, we will send you down a couple of nice cold fronts and that Cat will rock the world again VP. How far down in Texas are you?

    The other day when it was hot, I sat back, turned down the air, turned up the stereo, and still was driving one of the quickest vehicles on the road even though I knew it was not at its peak, sucker still is bad azz guys.
     
  13. rayzazoo

    rayzazoo DRIVESRT.COM Gold Supporting Member

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    I've found this document very helpful as a "rule of thumb".
     

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  14. Tammie

    Tammie SRT Hellcat Moderator Staff Member Gold Supporting Member

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    Really? Mine starts at 130 degrees before I even back out of the garage and is around 210 to 215 most of the day.
     
  15. rayzazoo

    rayzazoo DRIVESRT.COM Gold Supporting Member

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    Just to be clear, intake temperature will be between above ambient + 100 deg F.

    The water temperature will be between 203 - 240 deg F during normal operating/racing. Oil temperature will be about 5-10 degrees above water temperature.
     

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