What causes piston ring failure

[5teve L]

OK, looks like the rings have gone on my car, dumped all the oil through the breather last night & took out the bottom end in the process

Will high oil pressure cause them to go, the engine has always had high oil pressure, on the OE gauge (I know, I know) it has always been right up on 6 (I think thats the highest number) when driving & I don't think it's been lower than 2 or 3 on idle..
Just looking for the cause before I rebuild it & it happens again. I know James replaced the rings not long before he sold the engine for total seal rings & these are the ones that have blown.
Does the compression ratio have any effect also ?
Surely steel liners can't chew through rings that quickly, I hadn't done many miles & it had an oil change as well.
Ta

Steve

[5teve L]

Seen these , has anyone used them & I was a little concerned about this quote:

"If you wish to use steel liners they will need to be Nikasil coated to be compatible with the rings."

So what the hell is Nikasil coating? is it something that is in the metal or something you can have done ??

[Logg]

I think Robbie has. They're BB Tuning under there new name.

[5teve L]

I think Robbie has. They're BB Tuning under there new name.

Ah ok, well the chap was very helpful, he said if I had standard rings for cast liners they wouldn't last 1000 miles, I need special top rings for the steel liners or have the liners coated.. I may sell the steel ones & go cast again, never popped a liner yet... eve n at 2 bar on my old engine albeit a brief 2 bar, had 1.7 bar at pod a few times though..

[car.crash]

Oh dear bad luck steve. We was only talking about your rings and liners last night aswell.

[5teve L]

Oh dear bad luck steve. We was only talking about your rings and liners last night aswell.

TBH, I was allways worried about how heavy it seemed to breath from the off. I am going to try to find out about some rings, or I will have to get the liners coated as I don't want this hapenning every 1000 miles or so.. hate to think what I'll find when I get the sump off & whip off the ends/mains... I'm already thinking complete rebuild

[Shane P]

Seen these , has anyone used them & I was a little concerned about this quote:

"If you wish to use steel liners they will need to be Nikasil coated to be compatible with the rings."

So what the hell is Nikasil coating? is it something that is in the metal or something you can have done ??

http://www.bavarian-board.co.uk/nikasil.htm

[IANMM]

i got the same prob with my steel liners it passes oil on high boost...im going to change back to standard liners as really there is no point in steel ones unless your doing silly boost

[5teve L]

I have taken the head off, it gets worse... looks like a piston picked up
I was only running 18 psi, afr's were low to high 11's according to the LM-1 so I can't quite get my head round why it's been detting as it obviously has been pretty badly
https://www.rtoc.org/boards/album.php?albumid=1144

3 shortened steel liners anyone

[James5]

I have taken the head off, it gets worse... looks like a piston picked up
I was only running 18 psi, afr's were low to high 11's according to the LM-1 so I can't quite get my head round why it's been detting as it obviously has been pretty badly
https://www.rtoc.org/boards/album.php?albumid=1144

3 shortened steel liners anyone

Not another TDC sensor needing to be retarded is it

I done the same thing in July this year not as bad as you as i only knackered 1 piston and liner melting them together ran to lean on a long tight bend and fuel pump or the relay failed can't remember noe replaced both

[5teve L]

Mines the closest to the water pump, is that 1 or 4 ?
Anyway, it may be salvagable with some machine work as it looks like the piston is stuck to the liner..
I am dreading looking at the bottom end.. I'm feeling the cam may be the only thing worth saving at this point

I really don't understand it as I was watching the AFR's & it was ok, my old lump would run nearly to the 13's just as I crossed the line @ pod sometimes without issues...

[James5]

Mines the closest to the water pump, is that 1 or 4 ?
Anyway, it may be salvagable with some machine work as it looks like the piston is stuck to the liner..
I am dreading looking at the bottom end.. I'm feeling the cam may be the only thing worth saving at this point

I really don't understand it as I was watching the AFR's & it was ok, my old lump would run nearly to the 13's just as I crossed the line @ pod sometimes without issues...

That's number 4, I normally go by number 1 being flywheel end, mine was number 1 when I done that. I was wathcing your afr's aswell and all looked good temps looked ok also AFR's stayed around the 11.6's @ WOT ok not perfect but shouldn't have done that @ only 18psi.

[Markey Mark (BD)]

Thats bad luck mate, sorry to here that.

If i was to be rebuilding the lump mate i'd stick a set of new standard liners in there, for the spec you have your be fine with them. Maybe if you wanted to splash abit of money into it a set of forge pistons but thats about it.

As for the detting, is your timing sensor standard too? Also do you listen for det or measure inlet charge temps?

[5teve L]

Thats bad luck mate, sorry to here that.

If i was to be rebuilding the lump mate i'd stick a set of new standard liners in there, for the spec you have your be fine with them. Maybe if you wanted to splash abit of money into it a set of forge pistons but thats about it.

As for the detting, is your timing sensor standard too? Also do you listen for det or measure inlet charge temps?

I was thinking of putting standard liners in & forged pistons, poss rods as well, aren't the MSM spec blocks & liners decked though ?

Timing is standard yeah, never thought I'd get into det probs with 18 psi TBH mate so never bothered listening, I usually do when I go over 20psi...

Inlet charge temps should have been fine going on my old build with this intercooler as @ 24 manifold I used to see 30 deg with an Ian S gauge.

Open to ideas at this point as I'm slowly getting pi55ed off thinking about the useless lump sitting in the car...

[Jimmy_GTT]

Have you checked the vacuum membrane of your AEI? Only by sucking the pipe.
If it has a tiny hole than your ignition won't be advanced correctly.
And if you have some low octane fuel than it can det at this boost.
I do not know where is the limit of the oem ignition system.

My friend's GT had the same problem in January. Piston 1 was dead. I do not know the cause. And it was only running @10 psi.

[HAndy]

im gonna say bore wash

11.4 afr's and steel liners that don't hold any sort of lubrication (oil) like the cast o.e items,
and highish boost , theres your outcome,sorry

[Markey Mark (BD)]

What you got to remember now Steve is your engine is higher comp, your last was standard or slightly lower from what i remember. Higher comp engines are getting closer the that det threshhold so its vital you know its safe.

Just had alook at the pics of the head too, that don't look good thats been dettinating alot.
How thick is the head?

[rs250nut]

Jesus christ, those two motors are trashed, If oil is getting past the rings this will lower the octane rating of the fuel which could lead to det. I dont know why people piss around with steel liners, for all the agro associated with them. If you making enough power to crack a standard liner hats off to you but cracking one with less that 240hp has got to be down to a poor tune. If it were mine I would rebuild it with standard everthing other than a decent cam and forged pistons for safe prolonged use at 1.5 bar plus.

[rs250nut]

**** those valves and plugs are white

[5teve L]

So we are saying it's effectively scrap then apart from the cam.

[Markey Mark (BD)]

To save on machine work i'd poss go down the route of fitting standard height block and liners again, bringing it back to standard comp.

The crank may be ok to use again so not all scrap, i got a spare block here if you want to swap it.

[rs250nut]

Measure the head, if it has more than 73mm on it I would use it again.

[SCHWARTZ]

2 cars in one night thats just pure sods law hope both of ya get em sorted i know you will

[5teve L]

I'll have a look & see what can be done, I was thinking of maybe getting the liners machined out slightly oversize & then fitting some forged pistons, just not to happy to do it if the rings are going to go again because of the liners...

I would prefere going standard. liners & maybe slightly lower comp, maybe just the tops milled off or something

[car.crash]

if your going standard then you should just source another engine and start again.

[michael tierney]

too much oil(high level)breaks rings (can happen when cornering)
putting new rings into an old bore with a wear lip at the top will eventually break them
piston pick-up,getting too hot...fueling

[Rob@Backyardracing]

Nikasil will just help against wear plus holds oil better within its structure...

The bore has got hot by the looks, run a higher clearance maybe?

If your bored in life and want to read about bores, material, etc etc have a read of our guide on 996/boxster engines and what we do...

www.hartech.org/.../ buyers%20guide%20web%20format%20Jan%202008%20part% 204.pdf

[Tony Walker]

looks like its been burning oil on 2/3 for quite awhile

[THE MASTER]

lets clear a few things up first
pinking thats the rattle you hear when the timming is to far advanced . pinking dont normaly cause damage on it's own but can leed to destruction of the piston as pinking is a shock wave

deternation is different its caused by a cyl running to hot and causes an uncontrolable burn in the cyl . cause is normaly a to week mix as a week mix takes longer to burn thus heating up the top of the piston and causing it to come out of shape
distorting the top of the piston will leed to the ringlands going out of shape and not alowwing the piston rings to float and seal

so from wot ive said and looking at the pistons . i would say that det has caused the prob
https://www.rtoc.org/boards/attachmen...6&d=1288887457
this picky gives the biggest clue . look at the pitting on the face of the piston . it like it started to mealt
one thing you might wonna look at is even compretion . measure your head and see if its been skimmed . dont just measure at each end measure all the way along . if your head has had a previouse warp and skimmed to take the warp out the two outer cyl will have a higher comp ratio

[TNT ANDY]

And thus it has been said.

[5teve L]

I knew what the problem was as soon as I saw the pistons, I just can't work out why, AFR's were ok, a little rich but ok, then the intercooler was well up to the job on my old build at more boost so had no reason to believe that would cause an issue. It's prob because I forgot about the higher comp ratio the engine has.. Not sure what the cam is timed up to either, but I will be also checking my AEI unit vacuum module is ok.
I am thinking of going standard liners, machine them down to suit the block & then going for low comp forged pistons, I am assuming I will be ok to do this & the comp ratio will be between low comp & standard then
The only other thing that is worrying me is I haven't stripped the shells off yet to see the damage to the bottom end
There goes part of my Efi fund..

[ranj]

Well from my experience last year mate i would definately be looking at the renix module before i start putting more boost through another new engine...... Just to make sure its not gone faulty.

I did 2 engines in before i figured out my problem. I too had afrs that were fine and charge temps were great .... but engine was detting badly and i could never hear it from inside the car. I was Puzzled !!! . My afrs were fine , charge fine , head height not bad.

So when i put it back together again i retarded the tdc sensor by about 6 degrees to be safe and went to a rollers who could used det headphones to listen for det whilst i was increasing boost.

I had to have 10 degrees of retard to have no det...at 17psi on a gt28r. so with advice from rtoc members pointing to a faulty renix i bought a used one to try.

I changed the renix and now i run 21psi with no det but i do still have my renix retarded by 4degrees for extra safety at 73mm head height and 21psi. I could probably reduce the ignition retard a bit for slightly more power but i am happy as it is.

We always seem to look at afrs and charge temps when we look at det. We tend to forget about ignition timing because the renix takes "care" of it ... i dont know if my membrane went faulty or the unit itself went faulty but thats what was causing my det problem and melted 2 of my pistons

[5teve L]

If money allows I may even go ign only on an aftermarket ecu, then at least I have it there for when I manage to go full EFi at a later date.

[philr5t]

If money allows I may even go ign only on an aftermarket ecu, then at least I have it there for when I manage to go full EFi at a later date.

have you noticed mate that your block now has 2 hair line cracks between the liner and the oil ways mate

my guess is over reving or under fueling mate

[5teve L]

have you noticed mate that your block now has 2 hair line cracks between the liner and the oil ways mate

my guess is over reving or under fueling mate

Where, not seen that..
Just seen where you mean, I will ask the machine shop what they think when I drop the block off to machine the liners out to 76.5mm

[Jimmy_GTT]

If money allows I may even go ign only on an aftermarket ecu, then at least I have it there for when I manage to go full EFi at a later date.

That's what I did a year before. I'm running Megasquirt for ignition in wasted spark mode more than a year now. And if everything will be fine next week I'll start my car with EFI!
With the MS you have rev limit, you can set up boost limit and if you have an AFR gauge than you can connect it to MS and take logs.

[SCHWARTZ]

If youre thinking of lowering the comp of the high comp engine why dont ya just get a standard lump and start again? Im just wondering whats so good about this lump?

[5teve L]

Steel liners that will only go in a decked block, the cam & i'm assuming it was lightened & balanced.. Just seems a waste of £500 if i give up on it....

[SCHWARTZ]

Fingers crossed the bottom ends not to bad then matey. I know what ya mean would be a waste didn't realise it had been lightened and balanced just thought it was raised comp.

[d110rkjste]

I'll have a look & see what can be done, I was thinking of maybe getting the liners machined out slightly oversize & then fitting some forged pistons, just not to happy to do it if the rings are going to go again because of the liners...

I would prefere going standard. liners & maybe slightly lower comp, maybe just the tops milled off or something

ive got steel liners in my 5 with forged pistons so am i looking at the same prob?

[5teve L]

ive got steel liners in my 5 with forged pistons so am i looking at the same prob?

Well if they are untreated rather than nikisil coated & you haven't got special rings then yeah prob in the end as the steel liners are ring eaters apparently, so it will start to burn oil... Mine has been detting so you should be looking at new rings at worst, if it came to it....

[5teve L]

I have a standard liner & one of the steel items from this engine & I can see sod all difference in height at all

[IANMM]

[quote=5teve L;185879]ring eaters

[5teve L]

[quote=IANMM;186246]

ring eaters

You liked that one did you Ian

[IANMM]

reminded me of a girl i once knew

[James5]

reminded me of a girl i once knew

nasty

[James5]

I have a standard liner & one of the steel items from this engine & I can see sod all difference in height at all

I can see Feck all difference aswell in the height

[5teve L]

I can see Feck all difference aswell in the height

So I'm confused.... what makes it high comp

[Brigsy]

Pistons look to be standard, assuming rods are stock & the head is a decent height its got to be more or less standard comp ratio, tuner bs anybody?

[James5]

Pistons look to be standard, assuming rods are stock & the head is a decent height its got to be more or less standard comp ratio, tuner bs anybody?

Head is standard height well measures about 73mm

That's what me and Philr5t have just been talking about on the phone. Makes you that they do this all for a few extra ££'s. Phil told me another story about the same ex rtoc member come tuner