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Thread: Houston results changes for CMC

  1. #21
    Senior Member Carroll Shelby
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    The issue I would have running a carb is when the weather changes so does the mixture since there is nothing to compensate. If I dyno and get a 12:1 AFR, weather changes, and it pushed me to 13:1, I would be over power.

    Michael, how do you feel about out of region (CO) guys running with us, considering they are hitting the dyno at 5000ft. When BCurtis was at MSRC last year, his car was very strong, I'd say he was 10hp over based on how he pulled, I think he even switched to a smaller restrictor too.
    Tyler Gardner
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  2. #22
    Senior Member Carroll Shelby RichardP's Avatar
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    Quote Originally Posted by michaelmosty View Post
    Anyone is welcome to have multiple dyno's for various setups. Ex, you can have a 260 hp dyno for certain tracks and a 265 hp dyno for different tracks.

    Any change to carb jets will require a new dyno. The dyno form has a spot for jet sizes so if tech is performed, the jets in the carb must match the jet size on the submitted dyno.
    I have had many recommendations for more tech items confirming ignition timing, fuel pressure, etc. This would be something that falls into a similar category.

    I agree that's what the rules say but that's not what's happening. It's a break in the rules and also technically wrong, in my opinion. You can dyno your car at sea level in Houston with the range of jet sizes that you are planning on running for all of the different tracks you are planning on running for the season. When the car is running at sea level using the higher altitude jet sizes, it's not going to be representative of what the car will do at altitude. It's actually more honest to change your jets at the track to get your car running the same at altitude as it did at sea level even though that is technically illegal.

    The computer cars are certainly altering their parameters to match current running conditions. The carbed cars need to do that too.


    Richard P.

  3. #23
    Senior Member Carroll Shelby
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    In other news, they recently closed the observation deck on the 60th floor of the Chase tower downtown.

    What they didn't tell you is they opened a dyno shop in place of it.

    I have begun brokering secret NASA dyno certs for all Texas and Louisiana racers at this elevated altitude.

    Bring cash, leave with the most competitive dyno this side of the Rockies...

  4. #24
    At the west coast nationals Laguna Seca last year we dynod the Pumpkin to ensure we fit the thresholds of PTB (there isn't CMC out west). As you know they are very close to sea level. We were within 1hp and 1-2tq of our dyno sheet from the beginning of the same season at MAC Autosports (only place we've ever dynod at for CMC) which as you mention is at least a mile high elevation. We were quite impressed how close we were given the degree of elevation change.

    I read a little bit regarding the dyno woes at Watkins Glen this year. Anyone have similar stories of dynos out there following previous years trends of being way over on hp and tq compared to the ones we use regionally?

  5. #25
    Senior Member Carroll Shelby Fbody383's Avatar
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    Quote Originally Posted by Trublu View Post
    "racing snake physique"
    Yella Terra has hereby been replaced... can't wait to see the new logo.
    #39 CMC Camaro
    Orange is Fast!
    CMC-NT01 FTW!

  6. #26
    Senior Member Carroll Shelby
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    Quote Originally Posted by Fbody383 View Post
    Yella Terra has hereby been replaced... can't wait to see the new logo.
    Too many Shrimp on the Barbie and Miller Lites!
    Bryan Leinart
    CMC #24

  7. #27
    Quote Originally Posted by RichardP View Post
    I agree that's what the rules say but that's not what's happening. It's a break in the rules and also technically wrong, in my opinion. You can dyno your car at sea level in Houston with the range of jet sizes that you are planning on running for all of the different tracks you are planning on running for the season. When the car is running at sea level using the higher altitude jet sizes, it's not going to be representative of what the car will do at altitude. It's actually more honest to change your jets at the track to get your car running the same at altitude as it did at sea level even though that is technically illegal.

    The computer cars are certainly altering their parameters to match current running conditions. The carbed cars need to do that too.


    Richard P.
    Get a grip guys. Changing jets to maintain AF as conditions change is exactly the same as what your EFI computer is doing in real time. I think worth educating before introducing something that would require dozens of Dyno hours to produce.

  8. #28
    Senior Member Grass-Passer
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    I agree. A fuel injector is an adjustable Jet that your computer controls.

  9. #29
    Dynojet modifies the measured output to reference conditions which include atmospheric pressure (that's the SAE J349 setting on the machine) but the accuracy of this correction decreases as elevation increases.

    It's entirely possible we need to change what the book says re jets and rods, kinda how we ended up changing the requirements for carb cars around fuel pressure.
    Al Fernandez

  10. #30
    Senior Member Carroll Shelby Supercharged111's Avatar
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    Quote Originally Posted by mach1 View Post
    The issue I would have running a carb is when the weather changes so does the mixture since there is nothing to compensate. If I dyno and get a 12:1 AFR, weather changes, and it pushed me to 13:1, I would be over power.

    Michael, how do you feel about out of region (CO) guys running with us, considering they are hitting the dyno at 5000ft. When BCurtis was at MSRC last year, his car was very strong, I'd say he was 10hp over based on how he pulled, I think he even switched to a smaller restrictor too.
    I hit the dyno at 6200', but that dyno puts out the same numbers as Mac's (5XXX'). I'm the 2nd one to confirm that, so I feel good about using it. Come to think of it, Randy's car made the same numbers with the same plate as it did back in TX. When John and Sean came to Pueblo last year, John was able to shut down a run I got on him on the front straight, so I figured they weren't being cheated. This year with the Ken incident I know Craig and Mike were feeling cheated, but what I don't know is if they felt everyone was pulling on them or just Ken.
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