Compression test results on RB20... Help!

[Ed G]

Hi,

As some of you may know from my other thread, I am having some trouble with a R32 front cut ...

I did a compression test 2nite, and was a little suprised with the results... so repeated the test 3 times with exactly the same results.... The motor only has 119000k on it.....

Results are ...

1 - 150

2 - 145

3 - 145

4 - 130

5 - 135

6 - 150

The cut has a 3 month warrenty... i've only had it a week, and have not made much inroads into stripping it... what do you all think? Call them and take it back?

Please help!

[SteveL]

Was the test done with the engine at operating temp, or cold. If it was done cold these results are pretty meaningless.

[Ed G]

was cold..... hmmm maybe i should put it all back together and warm it up

is it really meangingless tho ? not even an indication of internal health ? :confused:

[Roy]

I dont worry too much about the pressures, is your gauge calibrated...been dropped lately, read accurately in the first place?

Just go on the variation between the cylinders. Cylinders 4 & 5 look a little low, but i doubt they are low enough to justify replacement?!?!!?!?! Still mine read a lot closer then that when i had done 155,000kms on my RB20

[Ed G]

It's the variation that has me concerned But the whole motor is under warrenty.. so should I go down the path of trying to get it replaced?

[wrxhoon]

The variation is a little on the high side but i doupt they will take it back .

Its a second hand engine they will say to you ,what do you expect .

If you check with the nissan workshop manual , difference between cil limit is 14 psi so its almost to specs limit . Well number 4 is out by a little more that that .

Anyway you can try and see what they will say .

[B0oStEr]

A cold test is unreliable.

The results you have aren't that bad and just passes the 10% variation guideline.

Do the test warm and the results should be a bit closer.

[xr8eater]

how many rev's have you tested it at its maby a good thing to count them as cheep comp testers keep presuring up and down as thier internals arnt so great in conclusion your test readings are not so bad if say in cylinder 1 you did 7revs and 4 did 5revs this could be your issue also warm your engine up before hand it will make a diffrents

[Ed G]

All I did was turn it over until the guage stopped moving... I did not do the same on all.. I was not counting.... just stopped when the guage stopped

I will do it at running temp.. see what I get then... I cant see how it will make a huge diff....

:coffee:

[superspit]

your figures are not so bad!!! Didn't find any oil on your plugs?

[Ed G]

plugs looked fine...

[superspit]

plugs looked fine...

well....................alrighty then!!!

it will do you no harm asking/telling your mechanic of your issue, (and I understand that it can be an emotional one!!), see what he says about it.

(the guy u bought the engine off, or whatever).

Do your 'warm test' though, as your fellow Skliner's suggest, first up.

I know how you feel, but your baby will be fine!!! (got heaps of life left in the thing!!)

Remember Ed G......the test between a truly warm/hot engine and a cold one can be quite dynamic!! That's just the way they work!!

ah.......anyways!!!

Mark

[Ed G]

Yeah...just stressin!!

I'mnot going to call the dude until after I have done the warm test.... doing it 2moro (just put it all back together)

The motor is smooth tho, no knocks/clicks/taps etc, so just hoping for the best 2moro... Will post up the results!

I hope its ok!

[wrxhoon]

the only issue here is the diff in compression between cils not the actual number .

warm the engine and make sure the throtle is fully open too.

[The Dan]

The difference between ring end gap from a warm to cold RB20 is around 10 thou, so YES...this will make a difference. Also, have you done a wet compression test. This will give you a true indication of whether the rings are bad. All you gotta do is a normal pressure test, then pour about 2 capfulls of oil down the sparkplug hole and do the cylinder again. Note the new readings and then post them hear. I will tell you if the rings appear stuffed.

NO QUESTIONS...JUST DO IT!

[The Dan]

couple of other things, what wrxhoon says is right...make sure you have the throttle wide open while testing and make sure all of the other plugs are out when you do it.

[The Dan]

third time lucky...also don't pour too muh oil down there...ONLY 2 CAPFULLS (OIL BOTTLE CAP) otherwise you will hydraulic lock the engine...this is not good.

[Cubes]

2 Cap Fulls?!?!?! Thats quite a lot...

My RB20t when I pulled it out had 140 all round with 5psi variation +-.

I would have loved to see how much more it had left in it. I pulled it out at 169,000km's.

Its only ever run the stocker turbo on 1-1.1bar though.

There was a tinny little bit of oil that had coated the inside of all the piping but it was really stuff all. Probably just a build up over time.

[superspit]

Yeah...just stressin!!

I'mnot going to call the dude until after I have done the warm test.... doing it 2moro (just put it all back together)  

The motor is smooth tho, no knocks/clicks/taps etc, so just hoping for the best 2moro... Will post up the results!

I hope its ok!

Motor is smooth, no knocking, idles ok? ROSES!

there you go!

Do not pour oil down your sparky holes!!! Not a drop!

Like mentioned, comp lock can and will (to some degree) occur.

Just wait and do what you said you were going to do for now. 'Wet test' (if you feel you really have to) later.???????

[Ed G]

idle is not ok see other thread .. uhh will find the link...

Will do warm test... post then wet test if needed .... what does the wet test prove that a 'dry' test wont?? :confused: