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[Orin Eman]

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> From: bob at bobthecomputerguy.com (Robert Harris)
> To: diy_efi at efi332.eng.ohio-state.edu
> Subject: The missing part - before Mr Helmholz
> Date: Mon, 17 May 1999 14:44:04 GMT
> Organization: Bob - the Computer Guy
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> In order to tune and use the acoustical pressure wave to our advantage, we
> must first be able to detect it.   Traditionally, dyno time has been used to
> tune such acoustics - the math involved and the radically changing physicals
> underneath it - are approaching unsolvable.   Not that there is not programs
> to do this ( and they are getting quite good - but consider selling your first
> born to afford one ) but they rely on excellent data collection and feed back
> to converge to an optimum solution - an extensive data collection effort that
> may not be available to DIY

> To measure the effect, we only need a camshaft angle sensors ( simpler to
> determine which TDC we are looking at ) and a sensitive pressure sender.  The
> angular sensor tells us phase and the pressure tells us sign and amplitude.  

> The pressure sensor tells us pressure at the port.  Flaw is that we need to
> sense the pressure at the port and few affordable sensitive sensors can
> withstand the temperature at the exhaust valve.  The first proposed solution
> is to us a small diameter tube from the collector to the sensor approximately
> the same length as the runner.  This delay line should place the acoustic wave
> approximately the same at the sensor as at the valve.

> We now can measure the desired effect - an acoustics pressure wave arriving at
> the exhaust port.  Now on to system concept to base our control mechanism on.