Quote:
Aren't pressure and compression the same? A compression test measures how much psi (pressure) the piston / cylinder can achieve,right?
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Not exactly. and Yes.
A leak-down test measures how long it takes pressure to leak out past the rings (& valves for a 4 stroke). So if you get 130 lbs of compression in a cylinder, that may be good. But if you pump in 100 lbs of air pressure, how much pressure do you still have after 5 minutes of the piston sitting at TDC.
So instead of measuring pressure, a leak-down test measures pressure
loss. Another name for this test is a cylinder leakage test.
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(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury