Audio Tachometer for 2 stroke engine

I have a crazy idea to use a microphone near the exhaust of a 2 stroke
engine to measure the instantaneous RPM of the engine.

The idea is non-contact RPM measurment in the presence is wind and road
noise. (lets say a motor bike running at high speed)

For this application I'm interested in 10,000 to 40,000 RPM which is 166 -
666 Hz. If I acquire this signal and BP filter it then run it through a
FFT, do you guys think I can distinguish the (pop pop pop) frequency of the
exhaust stroke from the noise?

The high level requirements are

a. non-contact RPM measurement
b. sensor must be waterproofable (is that a word? :))
c. must output a signal that can be acquired by a small microprocesor or DSP
with A2D or Digital.
b. must be small relative to a 1.5" X 2.5" x .5" overall package
e. must be vibration tolerant (survivability and measurment accuracy)
f. At least several hour run time on a 2.8V, 800maH battery
g. Supply voltage is flexable but desired to be below 12V dc.








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Relevant Pages

  • Re: Cooking in the Cab ?
    ... logically use more vapour than a four stroke engine which only fires ... As a two stroke doesn't have an exhaust ... exhaust port unused. ...
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  • Re: Audio Tachometer for 2 stroke engine
    ... engine to measure the instantaneous RPM of the engine. ... The idea is non-contact RPM measurment in the presence is wind and road noise. ... If I acquire this signal and BP filter it then run it through a FFT, do you guys think I can distinguish the (pop pop pop) frequency of the exhaust stroke from the noise? ...
    (sci.electronics.design)