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I've done some quick google search on dynosheet, and what it does is that it measures the power output of the car with respect to its frequency.

My initial understanding of the dynosheet is that it reads the output in horsepower(power) and its frequency space is in the unit of rpm, which checks out because you want the unit to be proportional to [time]^-1. or radian/time.

I'm not sure if it's logical to think that since a car has 5-6 gears (unless if it's an electric motor car, but even if it's a DC motor of one gear, it'll still apply), it'll have different responses for each gear. Assuming each gear will produce a result similar to a low pass filter (which isn't impossible since low pass filter is just a concept that not only could be applied to frequency but also wavelength), is the purpose of having multiple gears merely a way to compromise for the lack of efficiency due it's dampening effect in the high frequency? At the higher frequencies of each gear, the dynosheet reading is negatively steep almost as if it's a cliff.

I guess if the above reasonably checks out, I'm just wondering if it's logical to say that I can do a fourier transform on the car's dynosheet, or if the dynosheet is already by itself a fourier transform, since the power is a function of its angular frequency P(Ω)/P(Ω=0). Normalized or not, I find the mathematics to be somewhat convincing for me to believe that that could be/ is the case, but verification is appreciated.

I've read some papers from searching on google that people actually use Fourier Transform spectroscopy to analyze the emission of certain gases, as well as using dynanometer to measure the tangential force of a wheel running at a certain angular frequency. I would guess that my initial idea is not too far off from real world applications...?

Like I said before, it's nice when someone can confirm!

Thanks!!

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  • $\begingroup$ A dynamometer is used to measure brake power compared to engine rpm in various gears so that rates of acceleration ie max power delivery can be obtained, then in race cars they will then select the matching gear ratios for each track for best performance. $\endgroup$
    – Solar Mike
    May 26 at 6:22
  • $\begingroup$ well then... is the reading of a dynosheet by any means similar to a fourier transform? Edit: As you mentioned in race cars it selects matching gear ratios... is it necessary or logical to think that it's similar to fourier transform? Should I ask another MechE Prof about this? $\endgroup$ May 26 at 6:35
  • $\begingroup$ What is the purpose of a Fourier Transform? What is the purpose of a dynamometer? $\endgroup$
    – Solar Mike
    May 26 at 8:27

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I'm not sure if it's logical to think that since a car has 5-6 gears (unless if it's an electric motor car, but even if it's a DC motor of one gear, it'll still apply), it'll have different responses for each gear.

It is not logical. Power is the same in any gear, which is why engine ratings in HP are much better than using torque. Gearing affects acceleration through machine advantage. A dynomometer uses the car's gear ratio to normalize the results - if you ran the car in 2nd gear the factor in the dyno would just be different and the result would be the same.

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