Leak Down Test Results. How to Decipher?
#16
Race Director
What are the compression test numbers? Compression test...
Originally Posted by Arrwin
Hey guys,
Just looking over some documents I received with the car. When the PO bought the car he had a PPI w/ a leak down test done.
The results were as follows:
#1 @ 6%
#2 @ 4%
#3 @ 4%
#4 @ 4%
#5 @ 4%
#6 @ 5%
How do you decipher these results? I'm assuming the lower % the better?
Thanks again.
Just looking over some documents I received with the car. When the PO bought the car he had a PPI w/ a leak down test done.
The results were as follows:
#1 @ 6%
#2 @ 4%
#3 @ 4%
#4 @ 4%
#5 @ 4%
#6 @ 5%
How do you decipher these results? I'm assuming the lower % the better?
Thanks again.
Easy way to get a good leak down test number is to squirt some oil into each spark plug hole, crank the engine a moment. The oil gets spread around not only on the rings/cylinders between the piston and cylinder wall but on the valve faces/seats.
An older engine with rings that have higher tension -- at rest press against the cylinder wall with more force -- and thus seal better (but with a cost in increased friction) can look better, get better leak down compression numbers than a newer engine fitted with lower tension rings which have lower friction but can still seal well under real world operation conditions because the increasing pressure in the compression/combustion stroke force the rings out and thus create a tight seal when it is needed.
Sincerely,
Macster.