if im not mistaken stock psi should be about 155 for a compression check.

 

Well my friends Elantra (06) has about 190psi on all 4 cyl, which his stock compression ratio is 10:1.

 

Wow... thats way higher than mine! Dave says that as long as all cylinders are about the same and are around 150psi you are in good shape.

tim

 

http://kb-silvolite.com/article.php?action=read&A_id=36

 

good answer

pretty much yes and no valve timing also greatly effects cylinder pressure

 

Correction, I said about 150-160 for a decompression engine is about normal.

180-200 is about normal for a 10.3:1 compression engine. A compression check is with the valves closed so having VVT doesn't matter. That's why its called a static compression test.

Think of it this way. The higher the compression ratio the higher the static compression will be provided the rings and valves seal correctly.

 

Wow dude... then there is something wrong with my car or the compression checker thing! Piston rings are bad? Valves don't seal right?

Wish I could travel back in time before I modded my car and slap myself in the face!

 

I doubt all of your rings/valves went out at the same time. What have you done to your car that would effect this?

The general rule is the higher your compression ratio and the bigger your block, the high pressure numbers you should have. Based on this I would say they should be ~200psi.

 

between 200 and 210 is ideal.
most I4 tibs and elantra's should be between 180 to 190. if your compression is lower than that or you have a problem cylinder put a cap full of oil in the cylinder and then repeat the compression check... the oil helps to seal the piston rings, if your compression returns to normal, your rings are worn / leaking.
If your compression does not return to normal there is a problem with the valves.
if there is a problem with the valves run a leakdown test.... now listen to the throttle body and exhaust.... you'll hear air leaking in one or the other.. that's where your problem valve is.

when you got 150 on your compression check were you holding the throttle body wide open and was your battery fully charged? A dying battery spins the motor slower and gives lower readings... it'd have to be pretty dead to read 150 tho.

 

took out all spark plugs. let try to turn over 3 times. check gauge. read about 155ish on all cylinders except #1 = 160ish

turbo, ported head... having issues with PCV/Breather at the moment but will fix that when parts arrive. Also have Vac leak. Will diagnose when parts arrive

so if compression goes to 180-210 range after put some oil in cylinder then rings are bad? What is the cost of some direct replacement rings? Will I need my block to be rehoned or can i just swap out the rings?

tim

 

My compression is abotu the same... im getting 150 across the board with my total seal rings. Im running a lower compression motor (wesico pistons) as well as crower forged rods

 

you dont have low compression pistons or a decompression plate do you?
The ported head will also effect your compression #'s.
210 or so is the theoretical max for stock everything... the more you change your motor, the more that number will change.
also, did you hold the throttle body open when you were doing the tests? if not the tests are useless.
if it is your rings, then the block needs to be honed.

 

nvm i failed at multi qoute and dont want to try again.

 

ive got stock (10.3:1) compression. and yeah... my exhaust ports are pretty big. TB was open durring check.

 

As long as the valves are still stock and the combustion chamber hasn't been messed with it shouldn't change the static compression too much. I would try the oil in the chamber trick and see if it raises the pressure at all. If it does then maybe you should do a thorough leak down test. This pressurises the cylinders via an air compressor and measures the pressure lost. It also helps you figure out where the air is escaping. If the rings are going bad then you will get air out the dipstick, if the valves, valve seals, or valve guides are going bad then you will get air out of your PCV/Breather ports.

 

<2006 XD 2L. 100,000kms. I did ours and it's 210lbs flat across all four. I used a new OTC compression tester kit. I was surprised by the reading, so to the service manager at the dealership.

 

To answer this correctly.
Compression Ratio (also known as CR) is the difference in volume inside the cylinder with the piston at bottom of the stroke to the top of the stroke. A 10:1 CR means the volume at piston BDC (bottom dead center) is 10 times as much as when at TDC (top dead center).
Compression pressure (typically when checking the condition of the cylinder, valves and rings while cranking the engine) is a function of condition of parts, altitude (high altitude is lower pressure due to less air) and crank speed. Typically you should se a value a bit more than.....Ambient air pressure (get from a weather site) times CR.
Example, with everything good at sealevel (14PSI), a 10:1 CR should be over 150PSI due to dynamic filling of cylinder while cranking. Basic goal is having all pressures within 10% from lowest to highest.