Compression results

Does anyone know what a cylinder compression test should come out as on a 4G63?

The engine I was going to buy ran 125 across all four, is that good?

Nope, 1G turbo compression service limit is 121psi, and non turbo is 145psi.

the engine is a 2g not a 1g

That makes it worse :(
The 2g turbo service limit is 133.

I asked a few people they said that theres came up around 121 to 128.

i'm confused about this compression stuff. what is the difference in standard and service limit?

I think standard is what it should be with a perfect engine. And then service limit is what it should not go below, unless there is something wrong.

I could be totally wrong, I want to find out too. I am going to do a test on my car when I get it back.

I really need a engine for my car and I can get this one for a good deal but I dont want it to be bad when I got it, people have told me a compression test of 125 is good, but I jsut wanted to make sure...

http://www.dsmgrrrl.com/FAQs/compression.htm

There are good numbers there, and the limit.

If I ever saw 125 on my comression guage that motor would be out of the car and in the back yard before dinner. ;)

Stock 1g turbo motors are typically 150 across the board for a good high mileage motor. 2g will be 160-170. They can be a little lower, as long as they are all close. 125 sounds like it needs some work, though I find it odd they are all the same at that level. Could be a low reading guage. Did you hold the throttle wide open during the test? Was the battery fully charged? Were all 4 spark plugs removed?

Was the car warmed up?
Is the engine rebuilt?

I will ask the guy that is selling it these questions and get back to you guys

See if he will do a wet test in all 4 cylinders.

I have a question about the Compression numbers.

I was always told that the "1" in the compression ratio is standard day pressure of 14.7.

Well 14.7 x 8.5 does not get you close to what you should be at.

What am i not accounting for? The constant number i come up with is 20.9 x 8.5 or 7.8 will get you whats on that page

There is no formula for compression.

I'm not saying it is a fomula. I'm just saying that a number is used other than 14.7 to get the numbers for the compression check.
And i'm just asking why.

"Stock 1g turbo motors are typically 150 across the board for a good high mileage motor. "

7.8 X 14.7 is not close to 150psi

7.8 x 20.9 gives you the correct compression for the compression test.

20.9 will also give you the correct numbers for a 2g at 8.5 to 1 at 177psi

Whoa dude you are looking into this wayy to deeply, there is way too many varibales to take into consideration.

Numbers are numbers, just leave them be

Yeah, but i just want to know why

in my opinion if it is like he says (across the board) I wouldn't just go throwing out the motor. yes these numbers tell you alot, but not as much as a leakdown test would. this would give you an excellent idea on what could be cause for low compression. By the way how long did you pump up the cylinders (dry cranking) before geting the reading, did you warm the car up? if the pressure holds steady at that reading, I would'nt worry about it to much, gauge might be wrong. a lot of things come into play when you gather compression readings. maybe the motor was rebuilt before, when you do this it can change numbers. do yourself a favor and either do a leakdown test or have someone else do it, it will tell you tons about the condition of the motor.
:2cents:

Yeah, but i just want to know why

The results will differ beacuse of the condition of the engine. Every engine is different, the rings are wearing, the valves arent seating 100% etc.