I CAN’T DRIVE 145mph

Mopar Performance Issues

  1. loganscuda

    loganscuda DON’T reMember

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    Stock 5.7 Hemi with 545rfe trans. 373 gears and can not go faster than 130mph now. What do I need to do to get up to 145mph.
    Plan on doing an open road race in West Texas at Big Bend National park.
    It is 118 miles round trip and want to run the limit for my cars specs. What to do?
    FYI I do have Alterkation front and Firm Feel Leafs w Bilsteins. Handles very good now. Will add spoiler to front.
    I did not check my rpms when I was at top speed. I did have overdrive on. Do not know if that makes a difference. Looking for the simplest way of doing it.
     
    Last edited: Jan 10, 2019
  2. roccodart440

    roccodart440 Well-Known Member

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    If you weren't at redline it's a power issue.

    I mean aerodynamics obviously hold you back but our cars are flying bricks so refer back to my first line.
     
  3. loganscuda

    loganscuda DON’T reMember

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    That’s what I figured I wasn’t sure if I changed from a 373 to a different gear it would help
     
  4. Treblig

    Treblig Well-Known Member

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    "What do I need to do to get up to 145mph."


    Really good tires????:steering:
     
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    • fishmens67

      fishmens67 Well-Known Member

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      are you driving the fastback in your avatar at speeds of a buck 45 on the highway ?
      If so, you are cheating death. imo in my experience driving my 67 fastback, at about 110 mph with a little wind she begins to float, a little spooky on the frontend.
       
    • loganscuda

      loganscuda DON’T reMember

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      Yes the fastback but not on Highway My brains are a little bigger than that. On a formula1 track. Circuit of the Americas
       
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      • autoxcuda

        autoxcuda Well-Known Member

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        Does the stock Hemi computer have some sort of speed limiter?

        Is there some real long special straight area at Circuit of America for speed trials?

        I’d think there might not be a section of track on the road course to get up to 145 until you’d have to brake.
         
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        • loganscuda

          loganscuda DON’T reMember

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          Yes there are 2 straights. Maybe there is a limiter on there I have not done a custom tune only have a Diablo tune on it. Did not think of that being the problem. Will have to find some place to go to test. The COTO track is too expensive for me I got lucky and got in after someone dropped out of a group rental.
           
        • loganscuda

          loganscuda DON’T reMember

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          Love your car by the way. You have helped me out tremendously over the years.
           
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          • mbaird

            mbaird mbaird

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            Are aerodynamics different on the track vs the highway?
             
          • loganscuda

            loganscuda DON’T reMember

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            Only if your smoking and the window is Down on the highway.
             
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            • Treblig

              Treblig Well-Known Member

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              Depends on whether you're going sideways or not!!!:lol:
               
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              • brian6pac

                brian6pac Well-Known Member

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                Put it up on some good jack stands and start running through the gears and see what speed & rpm you are running, no wind resistance!
                 
              • loganscuda

                loganscuda DON’T reMember

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                Aaah I remember now, About 6 years ago I put in on a Dyno at MATS Las Vegas and it topped out at 155 and it would not hold at 5500 rpms it would drop back down the speed would stay but the rpms would not go up past that.

                I had 323 gears and I had the overdrive on, I did not have the switch hooked up to turn it off.
                 
              • TrailBeast

                TrailBeast AKA Mopars4us on Youtube

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                Keep it out of OD and let the engine run to it's highest HP producing RPM's.
                AND make sure you have tires that are up to it, like mentioned.
                 
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                • loganscuda

                  loganscuda DON’T reMember

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                  Tires are good. Goodyear eagle F1. Thanks.
                   
                • Pascamp

                  Pascamp Well-Known Member

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                  Don't know your tire size, hp, or rpm, but might be aero/hp related. My 392 Challenger will comfortably cruise at 160. That's with the 6spd manual, 3.90 gears, and stock size tires. Truthfully it doesn't feel like it's trying very hard. The suspension and steering is a different story though.
                   
                • DFX 340 Duster

                  DFX 340 Duster FABO Gold Member FABO Gold Member

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                  As previously stated, the cars of the 60s and 70s ares blunt nosed boxes trying to move through the air. Cleaning up the aerodynamic inefficiencies as much as possible is recommended to increase the power band (mph) and gain better fuel economy. These were some of the tips that were published back in the 1970s when we had the gas crisis: front chin spoiler or splitter molded in, a direct connection style spoiler on the deck lid, have a bottom engine compartment cover made to smooth out the air flow under the car (eliminates or reduces turbulence in the engine compartment), and a solid sheet metal/plastic dam behind the grill with indirect air flow through the radiator.
                   
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                  • loganscuda

                    loganscuda DON’T reMember

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                    0B32F91E-88CA-43A9-9265-05318CA6A91A.jpeg Soooo I need to do this!
                     
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                    • DFX 340 Duster

                      DFX 340 Duster FABO Gold Member FABO Gold Member

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                      • 65 Dartman

                        65 Dartman FABO Gold Member FABO Gold Member

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                        • Fisher

                          Fisher Old Guy with a Cool car.

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                          How tall of a tire do you have? A 26" tire with 3.73 gears will go 145 mph at 7000 rpm. so if you have enough motor to make power to 7000 rpm you are good to go.
                           
                        • Fisher

                          Fisher Old Guy with a Cool car.

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                          A 27" tire will do it at 6750 rpm.
                           
                        • adriver

                          adriver Blazing Apostle

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                          Some of that wind noise you hear is your drip rails.
                          Notice the lack of expose drip rails new cars?
                          And you have all that stuff hanging under the car.

                          The Super Cuda looses some trim.
                           
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                          • 66fyssh

                            66fyssh Don't Stop Believin' FABO Gold Member

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                            I just looked through your photo garage. KILLER car!! :thumbsup:
                             
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