my compression is whack. help!

[Denji]

Cylinder 1= 200psi
Cylinder 2= 208psi
Cylinder 3= 165psi
Cylinder 4= 180psi

Whats going on? cylinder three is looking pretty nice

All the other ones are making me

im running higher compression than the non turbos in 2 of my cylinders..what do i do?

 

[Slipstream]

Don't confuse compression ratio with compression test results.

Compression test results simply measure at what point your cylinders start to leak presssure (be it faulty ring or valves or what have you). These numbers only relate to volume in the most indirect way. (does it matter how many breaths it takes to fill the balloon before it pops if all you want to know is what the pressure was before it pops?)

Compression ratios speak as to the volume of one cylinder compressed vs not. a 6:1 means the cylinder has 1/6 it's original volume when compressed. This is where a NT would typically want higher numbers than a FI vehicle.

While your results are a touch on the high side I'd be happy with them..it means your cylinders have some exceptional sealing potential and your blowby is likely to be much less. IE your engine (at least as far as compression goes) is quite healthy.

 

[Denji]

wow..thanks man, that makes me feel better.
i had the two confused. any other opinions?

 

[Slipstream]

Yeah...treat it like gold....
edit: As a side note my last numbers looked like this
cyl:dry:wet
1:180:240
2:160:210
3:185:240
4:190:240

Depending on who you trust some claim a service limit of 133psi on a 2g. Others will tell you that so long as the lowest reading cylinder is within 75% of the highest cylinder it's fine. 165 is 79% of 208 (your low and high) so by either method you're fine...but via the second method you may want/need to fix your low one in the future. Take it for what it's worth...imo 165 is fine.

 

[Denji]

oh wait, those numbers were from a wet test... just kidding haha thanks for the quick responses, i'll keep an eye on that cylinder in the future.

 

[Denji]

also, how many miles are on that engine?

 

[Slipstream]

that's with about 135k on the clock, I can't say how the first 2 owners treated it (but it was under warranty and they hit every factory service on time..so that is a good sign) however the last owner and myself have babied the damn thing.

 

[liquordrunk]

slipstream what are you meanin by WET since my compressio nwas 207 207 211 and 212 im guessin this is a wet test accourding to u since it is so high but what is
WET

 

[Coup D E'Tat]

"Wet" is when you pour a little bit of oil into the cylinder to seal off the piston ring a little better, thus the higher numbers that go along with it.

 

[ITSME4G63]

he ok, so if your engine has low compression, meaning bad rings, you would fidn that out by puttin pol pm top the th episton right? if compression goes up, that means the rings are fine? if it stays te same the rings are bad?

 

[Coup D E'Tat]

No, if the numbers rise drastically with oil in there, new rings are probably in order.

 

[Slipstream]

using my numbers as an example #2 came back a bit on the low side of what i was hoping for when i ran the initial dry test and none of the numbers were exceptionally high (but all well withing service limits) so I decided to run a wet test. The oil helps seal the rings better temporarily. Indeed #2 showed significant improvement during the wet test, telling me it is likely a worn ring. The other numbers also jumped significantly...telling me that yes indeed all my rings are worn (what do you expect after 130k?) but #2 is showing the most wear. Wet testing is the cheap and dirty way to determine if it is a ring or a valve problem. (if rings the #'s go up, if valves they don't).