Leak down testing (not strictly EFI related)

[Tom Cloud]

>
>>R.e. Leak down testing. 
>
>>What units is leakdown typically measured in?  
>
>In theory leakdown is in percentage leakage.  However,
>typical gauges vary a lot from gauge to gauge so you
>need to be familiar with the gauge you are using.  I have
>heard that there are some gauges used for leakdown
>testing of aircraft engines that are much better than the
>automotive ones, but I have no experience with them.
>
>>What are some example good and bad numbers?
>
>Race engines: >10%
>Street engines: >50%  (obviously it depends on how
>	much you care.)
>Most of the time what you are looking for is cylinder
>to cylinder discrepancies.  Whether the engine is cold
>or hot can also have big effects.  Some engines only
>seal well when fully warm.
>
>>And what pressure does the cylinder get pressured
>>to?
>
>The gauge manufacturer usually specifies a line pressure
>for the cylinder.  It is usually less than 100psi.

I'd think the "measurement" would be in percent of
charge lost per unit time, though the volume of the
chamber being pressurized would have to be taken
into account to be able to make comparison

Tom Cloud <cloud at peaches.ph.utexas.edu>