combustion pressure sensor

[Brian Michalk]

There is a company, Gami that is developing an electronic ignition system
for aircraft engines using spark plugs modified to work with these pressure
sensors.

Their system uses fiber optic cables to couple to the pressure sensor.  I
met with them, and looked at some of their data.  They are able to measure
the horsepower of the engine within 3% of a calibrated dynamometer.

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of BamaInstrument
> Sent: Tuesday, May 08, 2001 1:43 PM
> To: diy_efi at diy-efi.org
> Subject: Re: combustion pressure sensor
>
>
> Don't know that I agree with all this.  It seems to me that the force read
> is the force pushing the spark plug out of the hole.  Therefore, If the
> spark plug is torqued correctly then the force gauge would indicate a
> decrease of the tightening force.  Since the tightening force
> would be much
> greater than the compression force the transducer would probably be very
> linear.
>
> As for calibration, when the engine is cranked and not firing
> with wide open
> throttle, there is a certain pressure developed depending on the
> compression
> ratio.  This could be calibration.  I would suppose that calibration would
> change with temperature, I don't know the characteristic of piezo
> transducers.  The signal would be the first derivative of cylinder
> pressure - no DC measurements here.
>
> Very interesting device.
>
> dh
>
>
>
> ----- Original Message -----
> From: "Larry Heath" <lgheath at earthlink.net>
> To: <diy_efi at diy-efi.org>
> Sent: Saturday, May 05, 2001 4:49 AM
> Subject: Re: combustion pressure sensor
>
>
> > I think that they are using this device to detect the high frequency
> > pressure/shock waves or characteristic "ring" that are generated by
> > detonation and transmitted throughout the engine. Question is if it
> > "directly measures" or only indirectly corresponds to actual in cylinder
> > pressure or it generates a voltage signal variation based upon
> a change in
> > the local stresses and strains associated with the base stress
> and strain
> > induced in the sensor by the torque applied to the sparkplug. Therefore
> > every time you change the sparkplug(s) you would achieve a
> different base
> > voltage/calibration. After all this is or appears to be a simple pizo
> strain
> > gauge. You may be looking for or at signals that are only minute high
> > frequency variations on an overall base voltage that is generate in the
> > sensor by the torque/pressure applied buy the sparkplug and does not
> > "directly" read cylinder pressure. True pressure transducers use a much
> > thinner "window" that is directly exposed to the pressure and
> to which the
> > strain gauge is mounted or attached.  Now it appears to me that the
> > variations from one cylinder to another and from engine to
> engine and from
> > model to model would generate and insurmountable calibration
> curve problem
> > if one was trying to use the sparkplug/cylinder head as this window.
> >
> > Now of course if each cylinder was equipped with one of these
> sensors then
> > one could detect which cylinder and at what point in engine
> relative time
> > detonation set in and a relative severity for the detonation.
> >
> > Until someone gets more info on this device and its required associated
> > electronics and or calibration curve this is all speculation.
> >
> > Later Larry
> >
> > ----- Original Message -----
> > From: "Rausch, Bernd" <br at rnt.de>
> > To: <diy_efi at diy-efi.org>
> > Sent: Friday, May 04, 2001 8:44 AM
> > Subject: AW: combustion pressure sensor
> >
> >
> > > They call it "a unique approach in measuring severity of knock in gas
> > > spark engines", and "it yields an output voltage that corresponds to
> > > cylinder combustion pressure".
> > >
> > > regards,
> > > Bernd
> > >
> > > -----Ursprüngliche Nachricht-----
> > > Von: Larry Heath [mailto:lgheath at earthlink.net]
> > > Gesendet: Freitag, 4. Mai 2001 14:16
> > > An: diy_efi at diy-efi.org
> > > Betreff: Re: combustion pressure sensor
> > >
> > >
> > > From your subject line I think that your barking up the wrong
> tree here.
> > > This is a "KNOCK" sensor or at least that is what their calling the
> > > thing.
> > >
> > > Not that this might not be a bad tool, its just not a combustion
> > > pressure
> > > sensor.
> > >
> > > Later Larry
> > >
> > > ----- Original Message -----
> > > From: "Rausch, Bernd" <br at rnt.de>
> > > To: <diy_efi at diy-efi.org>
> > > Sent: Friday, May 04, 2001 7:34 AM
> > > Subject: combustion pressure sensor
> > >
> > >
> > > > looks interesting, does anyone know this senasor ?
> > > > http://www.pcb.com/products/custom/cus140m05.html
> > > >
> > > > Bernd
> > > >
> > >
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