A buddy did my compression at work today and he said it came out
147,148,150,149. I asked him doesnt it seem kinda low and he said yea probably bad rings. I do burn oil but no constantly, mostly when downshifting or reving up. He cranked it 4 times with open throttle and fuel pump off. My question is, is that pretty low? Spark plugs are dry no oil. Motor is a jdm b18c with about 75-80k miles.

 

Bad rings will show up on the very first crank, the first crank should be over 50 but this is not written in stone, if you dont trust the first crank on that peticular cylinder then come back to it at the end of the test and retest it, also, a wet compression test is designed to test rings too, put about half a cap of oil in the spark plug hole, cover the holes with a towel and crank over to blow exess oil out then run your compression test, some noticable increase will show signs of weak rings. A true leak down test with the leak down tester is the real deal though, may have to pay for that one though. I also like more that 4 cranks, maybe 6 or 7, but not until the gauge maxes out, say 200 PSI.

Although yours looks low, only 4 cranks though, there should be a larger difference between cylinders, YES if they are all weak then all will have low readings, more cranks first please and watch that first puff.

 

Well from what I have read, it usually doesn't matter what the numbers are it is the variation between them. Because different gagues will give different numbers, but thats just what I have been told. But the best way to tell is you should add some oil in the cylinders and if the numbers go up a lot then I would suspect the rings. If not then I would say everything is fine, but maybe someone else can give more advice.

 

I'm going to go and try a leak down test, which should give me the answer if it is the rings or not. So Duane your saying i should crank it 6 or 7 times instead of 4?

 

The leak down test will provide more answers. Youy can also peform a wet compression test where you add about 1 ml of oil to each cyliner and repeat the test. If the compression increases dramatically, the rings are most likely bad.

 

thats not to low anything above 120 is good as long as theres no more than a 10-15 psi diff., in the cylonders.

 

Yes, 4 is not enough and dont go too long to max out the gauge, like 10 puffs. Remember first puff is important and if low, come back and retry at end of other cylinders, you may have only gotten half a puff.