Effects of low compression

[Vetal]

On my CA18DET compression is about 10 on all cylinders. According to manual, it is time for repairing motor.I'd like to know, what processes are happening in the motor when compression lowers from 12 to 10? Will I loose any power?

Now motor puts out ~230whp with T28 turbo, exhaust, chip, FMIC.

[nab911]

Low compression from bad rings, headgasket will take away your power, make u probly blow oil/coolant smoke, and just get worse in time.

[Notchbackca]

10psi? if you had 10psi on all cylinders I doubt the car would run

[USDM_OneVia]

He is from Latvia, it's the guy I sold my Spec Stage 1 to. It is 10 bar, not 10psi DOWN WITH THE METRIC SYSTEM! Joe

[Doogz]

10 bar isn't really all too bad. Probably needs some minor reworking but if you wanted to then you could definately drive it like that until you decide to rebuild.

[Jezz_s13]

10 bar isn't bad.

[float_6969]

10 bar is on the low end of ok. The VERY low end of OK. 10bar = 147psi (appox). Thats what I had on mine and I've got some horrific blow by. I can't even keep the dipstick in it if I boost. Smokes like a biatch too. It needs rebuilt.

[slw240sx]

is your pcv valve working?

[float_6969]

it's brand new. I have to drain my oil catch can every few weeks. I know the rings are shot.

[Vetal]

USDM: your clutch is being fitted right now

Guys, I have 10 BAR comp (of course on 10psi=0.7 bar it wouldn't run LOL), BUT:NO SMOKEburns oil about 1liter/2000-3000miles, which I think is OK

So what is happening when compression is lowered in such a way? Do gases in cylinder leak between piston and cylinder wall? If so, where do they get? If they're not leaking then I can't see a reason why the power would be lower and why Nissan recommends rebuild at 10 bar?So many questions

[float_6969]

It does exactly as you just stated. The gases in the combustion chamber leak past and go into the crank case. From there the PCV system reconsumes them back into the motor. Mine doesn't visually burn oil unless I'm on it really hard, and at first, it didn't burn it at all. IMO loosing a L/3KMiles is a pretty large amount, and I'm sure that you're burning that oil up. I didn't believe it at first either until I installed my oil catch can and saw how quickly it was filling up. Anyway, hope that helps.

[Vetal]

Assuming it is rings' fault, do I have to replace rings only or both pistons and rings?Also, from crank case, where do these gases go?

[float_6969]

Rings only, though you'll probabally want to put in new rod bearings and a new headgasket. From the crankcase the gasses are either sucked back into the turbo and then fed into your intake, or the PCV valve will open and suck them directly into your intake.

[Vetal]

So do I understand it right, that I get new (larger) rings, and then piston covers let's say 99.5% of cylinder's area, and rings will cover another 0.5%, and gases do not escape anymore and I have all the power available?

[float_6969]

You may not even need larger rings. It could just be that the stock units are worn and need replaced. Unfortuantly you won't know for sure until you get the motor apart, but with a cast iron block, I'd bed the rings wear a lot faster than the cylnder does.

[Vetal]

You gave me a hope

[CA18Fastback]

Ryan, u have any pics of your oil catch can installed? I got the same one with that Hybrid IC kit and was wondering how to mount it.

thanks,-Ian