Measuring dynamic cylinder pressure

[Clare Snyder]

>
>
>----------
>> 
>> 
>> Has anyone ever installed a pressure transducer in the spark plug hole
>and 
>> run the engine with that cylinder's spark and fuel injector disabled? 
>High 
>> speed data acquisition would be required, but it would allow one to
>measure 
>> the effects of various mods (cam, intake, exhaust, boost, etc).  Higher 
>> pressure would indicate better cylinder filling, although some
>temperature 
>> compensation would probably be required.  The max pressure for a
>non-firing 
>> cylinder is 120 to 200 psi, well within the range of reasonably priced 
>> transducers.
>> 
>> Bryan Zublin
>> bzublin at nlvl.com
>> 
>
>Since thermodynamics play such a large role in gas flow, would you be
>getting an accurate measurement?  How about temperature sensors mounted in
>the exhaust/headers at each cylinder?  They might indicate combustion
>efficiency.  Hotter gasses=more power.
>	I know that cranking compression readings are in no way indicative of
>performance level. The only general rule that seems to apply is the longer
>the stroke, the higher cranking compression. 
>
I think someone is missing the point. Running this critter with a means of
reading mean cyl pressure WILL give a good indication of power gain, against
base-line. At speed, the power output goes up directly in relation to, but
not linear with, mean cyl pressure. This is why higher compression gives
more power output. Add to this the fact that Volumetric efficiency will
definitely effect the cyl pressure, and this indication has some validity.
If the cam, intake, and headers, or Turbo are working together to get twice
as much air into the cyl as the baseline measurement, the pressure will be
significantlyu higher, and the power as well.

He is NOT talking of cranking compression, I don't think.