Just wondering how many bars/PSI a healthy 6N 8V (1.4) should be getting in a compression test.

I realis eit will probably change over time so a range would be good. Also the range in difference between figures would also be good, can't seem to find them in the Haynes..

Thanks

dont know if this is any help to you, but the comp ratio should be 10:1 and i know a good petrol engine should be around 140psi, but agian please anyone corect me if I'm wrong.

yeah I dont know the exact figures for that engine either but anything 140-170psi (10-12bar) would be healthy for an NA petrol engine generally. Just under 140psi not too bad but anything less than about 120psi would be a concern. These figures aren't going to be the same for a low-compression FI engine though, probably want to knock off 10-20psi off each one depending on the engine itself, but as a rule of thumb...

yeah I dont know the exact figures for that engine either but anything 140-170psi (10-12bar) would be healthy for an NA petrol engine generally. Just under 140psi not too bad but anything less than about 120psi would be a concern. These figures aren't going to be the same for a low-compression FI engine though, probably want to knock off 10-20psi off each one depending on the engine itself, but as a rule of thumb...

dido..

my 1.6 8v was 200 on 3 cylinders and 150 on the 4th if thats any help?

OK cool, Rono would you have considered that 50psi difference on number 4 a worry? On my AEX I've got..

1 - 17bar (246psi)

2 - 17 bar (246psi)

3 - 16.3 bar (236psi)

4 - 16.3 bar (236psi)

I'm generally happy with that and it runs great, but I'm just a bit worried as before I did the head gasket it used to be..

1 - 17.75 bar (257psi)

2 - 17.75 bar (257psi)

3 - 17.75 bar (257psi)

4 - 17.25 bar (250psi)

I realise now that doing the head gasket was kind of pointless lol. I'm just a bit worried now as to why it's gone lower as opposed to stayed the same or increased (I did have the head skimmed..), and wondering whether there is a slight leak due to not being put on properly or it is just other innocent reasons.. ?

when i done mine originally it wasnt starting, once i done the test i assumed that one of the valves had shit the bed, the car later started so i never gave it another thought. car runs sweet, dosnt get hot or make any noises so all is well. plus if i do end up stuck with the car its going to get a bigger lump in it so I'm not bothered about this engine.

have you not thought about doing your compression test again. i would be worried with that much difference between cylinders.

mind you, as the old saying goes, if it aint broke, dont fix it!

Hi,

The Autodata manual gives a figure of between 7 to 15 Bar so that gives a big margin for wear!!!

have you not thought about doing your compression test again. i would be worried with that much difference between cylinders.

mind you, as the old saying goes, if it aint broke, dont fix it!

i done the test twice and both times the results were very similar, i havnt really gave it any more thought as i was originally going to park it up and do the work to just sell on, its now turned into my daily driver so i dont get chance to mess with it much. tax is up the end of the month so I'm tempted to park it up and get everything sorted, if thats the case I've got a few jobs on the engine to do anyways so ill look into it then but for now it runs so itll do.

Cleaning the carbon from the piston crowns and the head would lower the C.R. very slightly, skimming the head would increase it, again very slightly (depending of course on how much was skimmed off) Your figures look OK to me, I am always more concerned about large differences (2bar or more) in cylinders than in overall figures, particularly if this is between two adjacent cylinders, as that normally points to gasket failure.

Glad that you have got it sorted.

Regards.

Hi,

The Autodata manual gives a figure of between 7 to 15 Bar so that gives a big margin for wear!!!

wow yeah pretty big margin lol.. that's for all 1.4 8 valve engines? what exactly does it mean if my compression readings are higher than they should be? :S i have a shit compression gauge? lol

Edited 24 September, 201015 yr by CWA

Glad that you have got it sorted.

That's the thing, the fucker is still burning water! I'm sure it is.. I've got water coming out the tailpipe which I know could just be left-overs in the silencers, but also every time I turn the engine off, the water level drops in the expansion tank and I have to refill it.

Also my oil level has shot up and the oil really does look clearer like it's diluted.. but for some reason I have good compression readings? This car makes no sense..

aye was talking about rono's mate, hope you eventually get to the bottom of it, but personally if its running well, and you just have to stick some water in every now and then, dont worry about it too much. obviously its pointing to something ominous but i think its time you actually got out and got to drive the lil barsteward and pick up another engine for cheap when ou see one so you have a back up if your goes pop

aye was talking about rono's mate, hope you eventually get to the bottom of it, but personally if its running well, and you just have to stick some water in every now and then, dont worry about it too much. obviously its pointing to something ominous but i think its time you actually got out and got to drive the lil barsteward and pick up another engine for cheap when ou see one so you have a back up if your goes pop

thanks man, yeah think you've summed the situation up to be honest. only reason i was trying to get it all right was cos it was failing on emissions and i wasn't actually able to get it back on the road. it's definately better than it was and i've got my old engine as a spare anyway. going to book it in with a mate for the test, hopefully he'll see it through

if the water in your exhaust is coming through your hg i'd expect to see some white smoke when it's running tbh, what colour is the smoke?

when i put the 16v in my polo it was doing the whole water level dropping when i started it coming back up when i turned it off, also if i went for a run with it the level wouldn't come back up to where is was before and i'd have to top it up...

if this is the same problem you are having try bleeding your water system for air locks and change the expansion tank cap and see if this solves any thing

did you regrind the valves when you rebuilt the head?

i have the same problem on my gt worked out that i had upset the valves (they turned didnt go in in the exact same place) once reground got nice even compression ratio

Hi,

Those figures were for the AEX 1.4 8v

The other engine 8v codes are:- APQ 7~15

ANX 7~15

AKV 7~15

AKK 10~15

AKP 10~15

ANW 10~15

AUD 10~15

All 1.4 16v are 10~15

OK cool, Rono would you have considered that 50psi difference on number 4 a worry? On my AEX I've got..

1 - 17bar (246psi)

2 - 17 bar (246psi)

3 - 16.3 bar (236psi)

4 - 16.3 bar (236psi)

I'm generally happy with that and it runs great, but I'm just a bit worried as before I did the head gasket it used to be..

1 - 17.75 bar (257psi)

2 - 17.75 bar (257psi)

3 - 17.75 bar (257psi)

4 - 17.25 bar (250psi)

I realise now that doing the head gasket was kind of pointless lol. I'm just a bit worried now as to why it's gone lower as opposed to stayed the same or increased (I did have the head skimmed..), and wondering whether there is a slight leak due to not being put on properly or it is just other innocent reasons.. ?

It could be gasket-related, but if you've got the cam timing set slightly differently then that could account for the difference too.

The only thing that can give you a higher reading than 'normal', is that there is less clearance volume, i.e., there is something taking up space inside the cylinder (water?oil? fuel? carbon?)

As for your oil level rising, does the oil look contaminated (beads of water on the dip-stick or even emulsified oil).

If you think that the oil may be floating on the water, there are a couple of ways that you can check for that:

1) Thread a length of semi-rigid plastic pipe down the dip-stick tube, right down to the bottom of the sump, put your finger over the open end and withdraw it, examine what comes out when you take your finger off.

2) From your local petrol station, obtain (beg) some 'water detection paste', this is a coloured paste which they smear on the end of the storage tank dip-stick, if the paste has changed colour when it is withdrawn, it indicates that there is water at the bottom of the tank. Use a little of that on anything that is flexible enough to go right to the bottom of the sump. (suggestion, curtain spring) and test for water.

As for the water level going up and down, then of course it will do, due to the heated water expanding, then contracting when it cools. If, for example the bottle is over filled, then it will expel some water when it gets hot, resulting in a lower level when it cools down.The important thing is that it always maintains the same height in the bottle at a given temperature OVER A PERIOD OF TIME.

Regards.