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2004-2007 Cadillac CTS-V Performance Mods Discussion, Dyno tune results from 2.6" pulley and 50/50 meth in Cadillac CTS-V Series Forum - 2004 - 2007; So I took my car back to the original dyno where i put down 452/425 max (2.8 pulley and volant ...
  1. #16
    OneFast V is offline Cadillac Owners Enthusiast
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    So I took my car back to the original dyno where i put down 452/425 max (2.8 pulley and volant intake) and was only able to best 423/436 (2.6 pulley and 50/50 meth) despite the boost going up a little over 1 pound (A/F can be ignored as the o2 sensor was not hooked up to my car but i have a wideband and i know it runs around 12:1). So I am really at a loss.. it doesn't look like belt slip to me. The car feel like it pulls harder. The only one thing i can think is that I'm running 275/45/18 in the rear now and that's about 1" taller than stock, does the dyno need to be told this because it is essentially like changing my gearing? The guy at the shop insisted it did not.


  2. #17
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Tire size, tire weight, and even tire pressure can effect the dyno results.

  3. #18
    OneFast V is offline Cadillac Owners Enthusiast
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Quote Originally Posted by darkman View Post
    Tire size, tire weight, and even tire pressure can effect the dyno results.
    interesting, i dunno what the tire weight difference is. well it appears to only be a 4% difference in tire size regarding revs/mile. if that translated into 4% more rwhp then im still only at 439hp but 453rwtq.

  4. #19
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    I doubt that your tire change accounts for all of the difference you are seeing. Setting aside mechanical differences, I think the largest differences in dyno runs on different days is the effective weather in the shop (air temp, humidity, number and placement of fans, etc). I know there are correction factors to mitigate weather variance, but those correction factors are not perfect either.

  5. #20
    OneFast V is offline Cadillac Owners Enthusiast
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Quote Originally Posted by darkman View Post
    I doubt that your tire change accounts for all of the difference you are seeing. Setting aside mechanical differences, I think the largest differences in dyno runs on different days is the effective weather in the shop (air temp, humidity, number and placement of fans, etc). I know there are correction factors to mitigate weather variance, but those correction factors are not perfect either.
    I would expect about 475rwhp with my current setup (using my 452rwhp as a starting point and assuming you gain 20 hp per pound of boost plus I went from the magnuson tune to a custom tune). This would mean almost a 12% change overall which just seems huge, although maybe it is possible I dunno. The temperature today was 75-78F outside and about low 80s in the shop. When i did the run last april 2011, I recall the weather being similar if not hotter, although it was early in the day (9am ish vs. about 2pm).

    I guess I'm just wondering if there is something I'm missing. I'm also bummed when I invest money trying to improve my car and the dyno makes me feel like I didnt get anywhere in the end.

  6. #21
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Well it does not sound like weather difference is the answer. I know nothing about forced induction tuning but isn't a 12:1 AFR a little rich, or is that required to keep down detonation?

  7. #22
    OneFast V is offline Cadillac Owners Enthusiast
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Quote Originally Posted by darkman View Post
    Well it does not sound like weather difference is the answer. I know nothing about forced induction tuning but isn't a 12:1 AFR a little rich, or is that required to keep down detonation?
    Generally the afr is kept richer for protection.

  8. #23
    NC-V is offline Cadillac Owners Fanatic
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Do you have the ability to post up a copy of your tune file or a log file of a dyno run? Sounds like the weather was pretty good so I would take that out of the equation, the increased tire diameter and weight will make a difference, but not that much. Did you have the meth already or was that an addition with the 2.6 pulley? If you just added the meth also then you should be making a good bit more power with additional timing. Are you running Cats? Is there ANYthing else that has changed between now and then?
    If you made a solid, repeatable ~452 on the first dyno runs (obviously there will be heat soak). Then dropped .2 pulley size and added meth and a custom tune you should be up ~30hp over what you were at and that is conservative. Something is up.

  9. #24
    OneFast V is offline Cadillac Owners Enthusiast
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    Re: Dyno tune results from 2.6" pulley and 50/50 meth

    Unfortunately I don't have the tune file as it was done by the tuner but if there are specifics I could probably ask him and yes the meth was in addition to the smaller pulley.

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