Detonation Monitor

[Greg Hermann]

At 6:18 PM 5/26/01, David Hunt wrote:
>I have been thinking about the detonation situation and you have ignited
>some further thoughts on that subject.  You have mentioned that the
>detonation frequency would be at about the combustion chamber Helmholtz
>frequency.  I think you're probably right but it just occurred to me that
>the speed of sound should be quite high due to the compression ratio.

Mach 1 (speed of sound) in any gas varies with molecular weight and square
root of absolute temperature. Nothing else. NOT related to pressure!
Obviously, Mach 1 will be increasing in the chamber during the combustion
process.

Greg
>
>So, if the volume is (for a 350 small block Chevy)
>
>350/8 * sine(degrees BTDC) + .125(350/8)
>
>where:
>    The .125 is clearance volume for an 8:1 engine.)
>    350/8 is the volume of one cylinder.
>    sine(degrees BTDC) is the ratio of volume of the cylinder at that position
>
>And the pressure is:
>
>14.7PSI * .8 * 8
>
>Where:
>    14.7 is the initial pressure
>    .8 is the volumetric efficiency
>    8 is the compression ratio
>
>Then we should have the 'ping' frequency.  That's as far as I can go right
>now, I'll work more on it later.  I don't know the Helmholtz theorem right
>now.  But it seems that the ping frequency will increase depending on
>where the ping is started in relationship to the cycle
>


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