S2K

What should the compression be in our cylinders??? I recall someone saying it should be within 180-200psi and all 4 cylinders should be within 10% of each other...is this correct???

Sumtoc2

Honda manual says:
Nominal = 228 PSI
Minimum = 135 PSI (hope not....)
Max variation between cylinders = 28 PSI

Bieg

Just had mine checked when my mechanic did the plug recall. Wanted to see how it broke in and make sure the #4 cylinder was not wearing. Lowest 225 - Highest 230. Had the valves done at the same time.

Gernby

Does the manual say whether to check the compression when the engine is hot? I would expect that a hot engine would give more consistent readings.

S2K

Is a compression test the same thing as a leakdown test???

Bieg

No. In a leakdown test they pump the cylinder up with compressed air and measure if it leaks down past the rings or valves. A Compression test measures how many pounds of air the individual cylinder/piston is pumping when it is cranked over.

marcucci

Your cylinders should always measure within about 2-5% of each other, anything in excess of about 10% indicates a problem. Anything that is 10% lower than stock also indicates a problem. The results of a compression test generally go up with age (on a car in good health) as the carbon deposits on the piston usually increase compression slightly.

Compression on a brand new motor is usually lower, due to improper (incomplete) sealing of the rings. Anything below maybe 7,000 or 8,000 miles will be lower.

w1ngman

Thought I'd drum up an old thread...to speak to compression on an 'old' S2000 AP1 motor ... Today I competed a compression test on The Bruised Banana's motor (to-date: 193,300+....hard-to-average-driven miles).

The results:

Cylinder #1 = 261
Cylinder #2 = 255
Cylinder #3 = 255
Cylinder #4 = 255

All readings were performed twice on each cylinder, and compression test was performed in manner mentioned above: Pulled all plugs...pulled fuel pump fuse...and with clutch & gas pedals all the way to the floor, cranked the motor over numerous times [actually my mechanic cranked it 12 times per cylinder check as that is his SOP at the Honda shop] testing one cylinder at a time.

I plan to perform this test again with a different compression gauge (sort of an 'objective' testing if you will) to assure his gauge wasn't faulty, etc.). I'll try to report back here again once I do that.

Overall, I'm very pleased

- Dave