how to interpret compression test

Apr 26, 2005 4 Replies

well i borrowed a compression tester and gave my 87 polo a test



1 2 3 4 cyl
11.9 12 12.1 11.9 bars
170 174 178 170 psi

this looks ok. but i am not completely sure i did the test right. i turned the starter for 5seconds each for each with gas pressed down fully after a drive (pierburg carb should be warm so choke flap should also be fully open)



i rigged it up so i could see the dial from inside the car. the needle would jump in steps.at around the 8th 'jump' it would reach the maximum psi attained.



i read somewhere in a haynes manual that each cyl would need 2 revolutions for the test. is 2 rev = 8 compression strokes on a 4cyl engine?



thanks



the method and results are fine.

mrcheerful

Looks pretty good mate, look elsewhere for a problem then!

Andy

Actually, 2 revs = 1 compression stroke. A 4-stroke engine goes up and down twice per power stroke (or compression stroke, or induction stroke, or exhaust stroke). The number of cylinders makes no difference. The cycle happens with each cylinder.

Rob Graham

Basically just keep winding until the pressure reaches its highest reading, those results look fine, what problem are you having?

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required