What are the factory specs for a compression test?
on the B18B1, the cylinder pressure must not exceed 199psi or be any lower than 135psi.
on the B18C1/B18C5, the cylinder pressure must not exceed 270psi or be any lower than 135psi.
on all three engines, there must not be any variation greater than 28psi between any cylinders.

If it goes up when wet, that means your rings are sealing better eliminating blowby when the oil is added meaning your rings are on their way out. It really shouldnt changve much when you add oil. A bit is normal but more than that signals that your rings are starting to become toast

 

How does a better seal mean they are on their way out? Id think that once the oil is added if it bumps compression that means its being retained in the cylinder and thus a better seal. Not worn rings.

 

Imagine a car with bad rings and very little seal...as the cylinder oscillates, the air to be compressed escapes past the sides and rings of the piston. This is known as blowby, and is one reason compression in said cylinder would be low.

Now lets look at a wet compression test. Remember when you were a young kid playing with bubbles? You know how the soapy water filled in the gap on the bubble wand so you could blow a bubble? The oil that you add to the cylinder in a wet compression test acts in the same way. You know how if you just blew a little bit that the bubble would flex but not release?That is what the oil does which keeps the air etc. inside the cylinder creating less blowby and raising compression.

Now if we did this to a cylinder with good rings, there would be very little blowby for the oil to improve upon which is why the compression test would not increase much.

M

 

nevermind.

 

Imagine a car with bad rings and very little seal...as the cylinder oscillates, the air to be compressed escapes past the sides and rings of the piston. This is known as blowby, and is one reason compression in said cylinder would be low.

Now lets look at a wet compression test. Remember when you were a young kid playing with bubbles? You know how the soapy water filled in the gap on the bubble wand so you could blow a bubble? The oil that you add to the cylinder in a wet compression test acts in the same way. You know how if you just blew a little bit that the bubble would flex but not release?That is what the oil does which keeps the air etc. inside the cylinder creating less blowby and raising compression.

Now if we did this to a cylinder with good rings, there would be very little blowby for the oil to improve upon which is why the compression test would not increase much.

M

Damn....that brought back memories. Back then they also had this sticky stuff and you put a little bit on a tiny tiny straw and you blow in it to create a bubble/balloon type thingie. HEHEHE.

 

I see. Just trying to figure it out. Thanks for the explanation

 

Nothing here has been any help. The question is 5-10psi increase alot or somewhat normal. Malhoun sorry but your first post was no help as that is already known to me, and probably most mechanically inclined people, thanks though.

 

First of all, what ARE your compression numbers? That's way more important than the change from dry to wet. Any kind of increase with a wet compression test is caused by wear on the rings. How much is cause for concern? I wouldn't be worried about 5-10 psi if your compression numbers are good otherwise.

 

Compression test numbers were within spec, I'll post them when I find the paper I wrote them. My car has slightly over 180k, so I was just wondering is 5-10psi change normal.

 

yes that is normal... sounds like your engine is still healthy. you would get a slight increase like that on a car with only 50,000 miles on it if the engine is cold.

 

you said day 2 that the car was warmer; compression tests should only be done on a fully warmed up engine, and that is probably the biggest factor for the higher numbers. 5psi is about avg rise for a wet test, 10 sounds a bit high. Do a leakdown test on a warmed up engine and you'll know if you have an issue. compression tests are not a diagnostic tool.

 

Ya but if you do the comp test with the car fully warmed your risk getting the tool stuck in there. I think valve seals are my issue.

 

Ya but if you do the comp test with the car fully warmed your risk getting the tool stuck in there. I think valve seals are my issue.

That's why you use anti-seize on the threads. Without the car being fully warmed up, the compression results are not very useful or accurate.

 

Search for compression . I guarantee you...guaranteeeee you, you will find the acceptable range and nominal values for any integra engine...in less than 5 minutes.

 

Justin Speaks the Truth