Jerseyzillest

I have a blacktop sr20 (I believe it's stock as that's what I was told) the car never gets driven as it's a project car.
Anyways i live in jersey and its been sub 30 degree weather lately. I decided to do a compression test to have an idea of how healthy the engine is. Well I'm a bit thrown off and confused.

Compression test cold

1 - 124 psi
2 - 119 psi
3 - 125 psi
4 - 125 psi

Now I also decided to do a warm test (this is where I'm confused) the compression numbers are very similar to the cold test. So I decided to put some oil in each cylinder to see if the numbers jump.

1 - 150 psi
2 - 145 psi
3 - 150 psi
4 - 150 psi

Now I know that when the compression numbers jump it usually means bad rings, however I'm confused as to why the compression remained the same between cold and warm. 🤔 Maybe I didn't wait long enough for the engine to warm up?

no prior symptoms no lack of power or anything to have me question the compression I did it just so I know where I'm at.

Any input is appreciated 😬

KAT-PWR

Rings are worn (it's a natural process that happens no matter what). Probably still fine. A leak down test will tell you more. If you aren't having blow by issues I wouldn't worry about it

Was the engine at full operating temp?

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Jerseyzillest

I waited until the temp gauge was at temp before I did the compression test but the engine didn't seem hot when I was doing taking everything off. Plus it's probably been a few weeks since I started the car.

Kingtal0n

the test may indicate high mileage, or an atmosperic blow-off was used, which continually washes the rings with gasoline and gradually lowers compression on a stock sr20 (maf). 15 years of ring washing and/or 150,000 miles will bring the compression down to 120~ cold. The oil test is clearly showing a lack of ring sealing because it obviously jumped back to OEM target range with the oil in the cylinder, which wouldn't happen if the compression was leaking via valves. If it does not smoke and seems to run normal, the plugs come out clean, I wouldn't mess with it just keep driving it gently. Use an oil pressure gauge to ensure the bottom end doesn't become garbage so it can be re-furbished (hone + new rings + valve job) in the near future, this way you avoid the machine shop and get back a nearly fresh engine. (change the engine bearings using the stamps on the block, install a new oil pump, new timing equipment, buy a honing tool and new rings, don't let a machine shop touch the shortblock). Do it in a 'clean' room.

Option B is buy a next longblock, which would cost less but obviously will give you the same 20 year old parts so selection is thin and difficult. But entirely possible.

Jerseyzillest

Looks like I might have done the compression test before the engine was fully warmed up, the psi jumped ups bit and is now sitting at around 145 psi per cylinder. I'm happy with that for now.

Jorgs_7

A weak battery can also skew the overall numbers.

If they're close to each other (which they are), run it.

Jerseyzillest

Thanks, yeah that might have been part of the issue, when I re did it I got better numbers.

Now I have an idle issue that I'll be posting to see if anyone can help me.

https://youtu.be/GXS753vpqPc

Nissan2nr22

My s13 sr had 178-183 compression all across cold and hot

id say your engine is pretty tired and getting there, seems fine but i wouldnt beat on it