VERY low compression 30psi

[Nik_GTI-R]

Ok since my mate has been having problems with his R i said i would help him diagnose the smokey problem he has.
Well in my other post,i was told he should check the compression b4 he goes any further.
Well he done it 2day and got circa 160 on 1,2 and 3 but only got 30psi on cyl 4.
Now does this mean its the rings??Or i have seen ppl mention "ringland".Whats this??
And is there any other way to tell which of the 2 it could be??Or does the compression say it all??
I know both are bad,but what is the best out the 2 to have??Fixing wise.

cheers,Nik

 

[pulsarboby]

lol neither! its an engine out job or head and sump removal with it in situ, but neither is good.
if you only have 30psi then i reckon 99% that you have detted on that piston and its melted leaving a big lump out of it.

all you can hope for is that it hasnt damaged the bore or its deffo an engine out job and rebuild time (which tbh would be the best bet anyway)
but then you need to take a look at whats caused the problem in the first place or it may happen again!
ie dodgy injector, mapping, too higher boost, insufficient or too much fuel, timing, overheating etc all can cause meltdown in one way or other!

 

[Nik_GTI-R]

He had the head off tho to check it and the pistons etc were fine.There wasnt even any play in them.
As far as hes aware it hasnt been modded to run higher boost(no 1 bar boost loop or fmic etc)
Hes gonna rebuild it anyway,just wanted to know if there was a more or less exact answer with it having such low comp.
Hes more P'd off that the engine was out aswell so he cud fit a new box and now its gonna have to come back out lol.

 

[pulsarboby]

right i see! with that lower compression there must be something seriously wrong nik!
he should have carried out a leakdown test to check head aswell before it was removed to determine if theres any valve damage or possibly cracked head in between valves etc.

but seeing as its off anyway then he now needs to remove piston and check ringlands between the rings themselves. if they all appear to be fine and theres no visible damage to cylinder or piston, then i would take head into a precision engineers and have it leak tested as it may be cracked internally if theres no visible damage to the valves or the head face.

ask if the exhaust port around number 4 was wet with oily substance! thats a good teller of piston damage. if its dry then problem could well be head related;-)

 

[Nik_GTI-R]

Thanks very much bud,thats a big help.I will let him know the bits to check and see what he says.