Hello,

Since I had a superchager on for awhile now, I was curious what kind of progress or what you can call it, "wear and tear" my engine has using a compression tester.

Everything was done when the engine is warmed up to 3 bars, and the gas fully depress at WOT.

Here are my results as follows:

cylnder 1 - 240 psi
cylnder 2 - 240 psi
cylnder 3 - 230 psi
cylnder 4 - 240 psi

- What is the ideal pressure for each cylnder?
- Are all these numbers normal?
- Healthy engine?
- What's w/ that 3rd cylnder being 10 psi's lower. I still have to do a valve adjustmet, if my ears aren't decieving me it's may be a lil bit noisy.. will that help?

 

A compression test result above 200psi is considered acceptable. All cylinders should be within 10% of each other.

A leak down test is more accurate and can pinpoint where a pressure loss is. You can determine if the headgasket is blown, poor ring seal, or a burned valve with a leakdown tester.

 

Thanks Slow2k for your feedback!!! What's a leak down test? I've only heard about it.

- Does anyone else have compression numbers to compare? Please feel free to post your results here too.

 

A leakdown test is done by pressurizing the cylinder's 1 at a time. Then rotating the engine untill the valves close on the cylinder you are testing. The Leakdown tester has 2 gauges, 1 is attached to shop air, and regulated. The second gauge is reading pressure in the cylinder.

For example, you pressurize #1, then rotate the engine untill #1 piston is at TDC on the compression stroke, with all valves closed. You set the regulator to 100psi. Then compare your measured pressure on the second gauge.If the second gauge reads 98psi, you have 2% leakage.

A 10% leakage rule is considered acceptable, but less than 5% is normal on a new engine.

Anything more than 10%, start looking for were the pressure is going. It's either making it past the rings, past the valve seats, or the head gasket. If the headgasket is blown, compressed air will enter the cooling system. It can be seen exiting an open radiator cap.

To tight of a valve adjustment will cause the valve to be held off the seat and air will leak past the valve.

To loose of an adjustment (which would be noisy) won't effect the leakdown, because the valve spring holds the valve closed. Unless a valve seat is burned/leaking.

 

Interesting. I learn something new everyday. Too bad it'll be a PITA to do a leak down test with the s/c'er sorta blocking the crank pully, and when doing a valve adjustment.

Thanks for the info!!!

PJ