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low hp dyno reading tuners please chime in!!!

Discussion in 'Tech' started by throwdown, May 12, 2016.

  1. throwdown

    throwdown Well-Known Member

    I have a general question regarding hp on a dyno as compared to torque, I recently installed a engine I pushed with a superstock build(thin headgasket) because my engine went bang and was not worth fixing due to cost.
    My old engine that blew made 115hp and 50.99 tq on u4.4 with a thinner head gasket. I installed this fresh engine with the same thinner headgasket into my bike and nothing has changed, I.E. exhaust,fuel management, fuel used(u4.4). This engine on the same dyno makes only 106hp but the torque is nearly the same at 51.6, the ambient conditions between these two dyno runs are different however the original run was 37% humidity, the dyno run today was 80%humidity. So my question is does humidity only affect hp and not torque?
    Other data I am between 0 and 10 ft above sea level. The low hp reading seems wrong to my but the torque seems correct, should I even care? Just for shits I had them make a map for mr12 and it gained 2hp and 1 lb ft of torque. Less than I would've expected.
     
  2. nlzmo400r

    nlzmo400r Well-Known Member

    Need to see the graphs. You say it makes the same torque, but I promise the new engine makes less torque at higher rpm (which is why it makes less hp).

    Regarding dynos, short of the long - SAE correction factor should be used in the US which takes into account barometric pressure, altitude, humidity etc. So no, humidity will not effect the hp reading.
     
  3. throwdown

    throwdown Well-Known Member

    I'll post both graphs when I pick up the bike hopefully today
     
  4. throwdown

    throwdown Well-Known Member

    Damnit I can't get the pic to attach FML
     
  5. throwdown

    throwdown Well-Known Member

    It makes the torque earlier but starts to Peter out after 12k rpm, whereas the old one pulled all the way to 14k and started making torque later, so other than the hp difference, really all I should have to do is shift at 12k rpm and I should be fine
     
  6. stangmx13

    stangmx13 Well-Known Member

    You're joking about shift earlier, right?
     
  7. throwdown

    throwdown Well-Known Member

    No why? Should I have been? I meant shift at 12k instead of 13k where I used to
     
  8. stangmx13

    stangmx13 Well-Known Member

    the gear ratio change of shifting reduces the torque at the wheel and therefore reduces acceleration. if the torque at the wheel in 2nd gear is greater than in 3rd at any rpm, u should stay in 2nd until redline. u want to maximize the average torque output at the wheel. so if your torque curve drops off very sharply near redline, maybe u should shift a little before redline, maybe 500 rpm. but if its mostly flat to redline, def shift at redline. shifting at peak torque almost never maximizes torque output.
     
  9. throwdown

    throwdown Well-Known Member

    Yeah I understand, the torque isn't even close to flat at redline, it starts to drop sharply at 12k, that's why I said I'll start shifting then, really I'll have to ride it and see, I'm guessing whoever built this engine has the timing advanced that's why torque and hp start to drop off earlier than my old engine that I built. Once I get it back from the dyno I'm gonna look into the cam timing
     
  10. emry

    emry Can you count? 50 Fucking what?

    http://www.datamc.org/downloads/ Download the "Thrust Chart" and stick in your dyno numbers. Makes it pretty easy to figure out where you should be shifting.
     
    throwdown likes this.

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