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    • Stock 2017 Challenger Hellcat struggles with a ZCP (Competition) F80 M3 DCT

      This one is a little tough to explain as the Hellcat should be faster than a stock ZCP F80 M3. The Competition tune for the F80 M3 from the factory is slightly stronger than a base F80 M3 but not enough to explain why the Hellcat gets dominated the way it does.


      All the M3 has is a full Remus exhaust. The Hellcat is an 8-speed automatic and stock.

      F80 M3's pulling like this on Hellcats is not anything new but those M3's had a tune.

      Is the F80 owner sandbagging?


      This article was originally published in forum thread: Stock 2017 Challenger Hellcat struggles with a ZCP (Competition) F80 M3 DCT started by Sticky View original post
      Comments 7 Comments
      1. Blown6's Avatar
        Blown6 -
        And a jb4 on the highest map....
      1. Eleventeen's Avatar
        Eleventeen -
        One factor is that a supercharged car does not have a specific boost target (but does have a boost limit and will bleed off extra boost when necessary). Since the supercharger spins at a fixed ratio in relation to engine RPM, boost cannot be automatically increased in higher elevations like a turbocharged car. Looks like this video was taken at ~4,500 feet.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        One factor is that a supercharged car does not have a specific boost target (but does have a boost limit and will bleed off extra boost when necessary). Since the supercharger spins at a fixed ratio in relation to engine RPM, boost cannot be automatically increased in higher elevations like a turbocharged car. Looks like this video was taken at ~4,500 feet.
        This is not true.

        The Hellcat uses a bypass valve design which is how boost is limited between the two keys to begin with.

        Just like the B8 Audi S4 boost can be increased through software and bypass valve control.
      1. Eleventeen's Avatar
        Eleventeen -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        This is not true.

        The Hellcat uses a bypass valve design which is how boost is limited between the two keys to begin with.

        Just like the B8 Audi S4 boost can be increased through software and bypass valve control.
        What happens when you are already on the red key and the bypass valve is closed? You would need to change pulley ratios to achieve more boost.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        What happens when you are already on the red key and the bypass valve is closed? You would need to change pulley ratios to achieve more boost.
        There is a point where you do need to change hardware for more boost but saying you can not compensate for atmosphere or increase boost without changing hardware on the Hellcat or supercharged applications is incorrect.

        The two keys achieve exactly this with software alone...
      1. Eleventeen's Avatar
        Eleventeen -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        There is a point where you do need to change hardware for more boost but saying you can not compensate for atmosphere or increase boost without changing hardware on the Hellcat or supercharged applications is incorrect.

        The two keys achieve exactly this with software alone...
        Okay, I was not aware of that.

        On the slow key it makes sense to do it that way. However, on the red key, spinning the supercharger faster than necessary and using the bypass valve to regulate peak boost long-term seems like a poor design. Overspinning the supercharger for a given pressure is wasted energy (and increases IATís). It would be like using the blowoff valve to regulate boost instead of the wastegate on a turbocharged car.

        Iím curious why the Hellcat didnít do better.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        On the slow key it makes sense to do it that way. However, on the red key, spinning the supercharger faster than necessary and using the bypass valve to regulate peak boost long-term seems like a poor design.
        It's not IMO. Because a positive displacement is always making boost a bypass to relieve pressure is a great idea and safe.

        As you can control the valve electronically then you can have it stay closed longer for say higher altitude applications. You aren't spinning the SC any harder you just are relieving pressure later so it builds more.