Hellcats at high altitude

Discussion in 'Dodge Challenger SRT Hellcat' started by Tea cups, Apr 14, 2016.

  1. Tea cups

    Tea cups Hellcat Member

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    Have one on order and I live at 7000 feet above sea level. Curious if any HC owners here live at high altitude and if you've also driven your car at lower altitudes to compare. I've owned a number of turbocharged cars and there's always a noticeable loss of power the higher you go up, just less of a power loss than a naturally aspirated car would have.
     
  2. usmc341

    usmc341 Gold Member

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    I live at 2200 ft and only get 9-10 psi depending in weather conditions.
     
    Last edited: Apr 14, 2016
  3. Mopar22

    Mopar22 Silver Member

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    I am at 5,000 ft and get 8-9 lbs. of boost. Depending of the outside temp my HP gauge reads 580 to 630; I have not yet taken her down to a lower altitude yet.
     
  4. ciphros

    ciphros Gold Member

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    You will be as much faster than other cars regardless of altitude, since they will all be suffering the loss. We used to love autocrossing at altitude with the Talon because the turbo really gave us an advantage over the rest of the class that had N/A.
     
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  5. Cruisin1966

    Cruisin1966 Silver Member

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    We're at about 3400 ft, although the DA is more often closer to 5000 ft. Next time I'm out in the car, I'll see if I can't notice the tiny amount of boost the car is actually making.
     
  6. stanssrt10x2

    stanssrt10x2 Hellcat Member

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    im in denver co. an took cat to kansas there is a lot more power in kansas than hrewr at a mile higher.totally different.
     
  7. Fionn MacCumhaill

    Fionn MacCumhaill Irish A'Hole - Wanna Fight About It!? Hellcat Car Club HCC Charter Member

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    ^This. I am in Denver as well and my max boost is 8lbs. (for now doing 9% OD lower pulley soon) I also drove down to closer to seal level and yes you can notice the difference, but keep in mind if you do any mods to your car that lives at high elevation, i.e. add boost through pulleys, get a tune, etc. and then drive down to a lower elevation you will need to adjust accordingly. After I add my lower pulley I should be getting 1.5-2lbs more boost, getting me closer to the 11lbs the car sees at sea level, but if I drive down to sea level my boost will be closer to 13lbs due to elevation drop. Without a retune this could cause major damage. So as someone who lives in a high altitude environment keep things like that in mind.
     
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  8. Ray Hunsaker

    Ray Hunsaker Silver Member Hellcat Car Club Gold Supporting Member HCC Charter Member

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    that's a advantage for using the metco pulley just change it out in 10 min:):):)
     
  9. Ray Hunsaker

    Ray Hunsaker Silver Member Hellcat Car Club Gold Supporting Member HCC Charter Member

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    so im at 4500 ft getting 8/9 lbs on stock pulley. metco 2.85 pulley will get 11.5 here. and you don't need a tune.
     
  10. jpex

    jpex Hellcat Member

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    i live at about 50' but did a trip into the mountains up to about 5000' and there was a significant drop in power but i was still putting out about 540hp as per the gauge
     
  11. Tea cups

    Tea cups Hellcat Member

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    It seems you would still want a tune if you are cranking up the boost via a different pulley at altitude - the supercharger is still doing the same work to produce 11 psi with the pulley change as it would producing 13 psi at sea level with the same pulley. Charge temps with the aftermarket pulley at high altitude are likely to be higher than a stock HC at sea level even though they are producing the same boost. This results in an increased chance of detonation on the high altitude car so it isn't an apples to apples comparison. Intercoolers are also less efficient the higher you go up.

    A lot is mentioned about turbocharged engines running the same peak boost at altitude but modern computer controlled cars have an electronic wastegate and the ECU will reduce peak boost targets at higher altitude to avoid going outside the turbocharger's efficiency range.

    Overall it just sucks for us at altitude but I guess it is all relative anyway. Certainly a reason I would not consider any naturally aspirated performance car - the difference there is huge.
     
  12. Ray Hunsaker

    Ray Hunsaker Silver Member Hellcat Car Club Gold Supporting Member HCC Charter Member

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    in my opinion at altitude we have less boost the engine can produce enough fuel to compensate for just getting back to normal boost numbers. I also hear of some guys running 2.85 at sea level with out a tune! but I think that's sketchy. IMO
     
  13. stoneipa

    stoneipa Rookie

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    supercharger.JPG
    I live high up and have obsessed about this. I would love a more accurate explanation, but this is how I look at it.

    A made a quick spreadsheet that calculates the approximate air mass and boost pressure at various altitudes making a lot of simplifications and ignoring any differences in intake air temperature. At 7000ft, you're only getting 79% of the air mass you would at sea level. So the same ratio as a naturally aspirated car.

    A turbocharger is a different in that the computer tells the wastegate to remain closed and keep spooling up the turbo until either the absolute pressure in the manifold is achieved, or the targeted boost pressure is achieved. I don't know which. In the case of the former, the turbo car at 7000ft would hit the same air mass/absolute pressure as sea level, assuming the turbo was big enough to provide the excess boost. In the case of the latter, the car would provide the same boost as the sea level boost, but the total pressure would be lower due to the starting lower ambient pressure.

    Either approach would provide more air mass than a supercharged car that provides the same boost as the turbo at sea level.
     
    Last edited: Apr 16, 2016
  14. jpex

    jpex Hellcat Member

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    Well said my other car is a 2008 SRT4 and when I did the same drive the computer let the turbo build to 22 psi vs the 19 I build at sea level, the turbo car defiantly did not suffer from altitude sickness nearly as much as the cat
     
  15. Mopar22

    Mopar22 Silver Member

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    Not on these blowers, its more like a good 8-10 hours to get the stock pulley off and blower back on the engine.
     

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