Leak down testing (not strictly EFI related)

[James Boughton]

>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.

>Thanks.

>$$$ MAKE CAR FAST $$$
>bryantt at psc.fp.co.nz

Jim Boughton
boughton at bignet.net

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