ceramic wheel letting go

[KILL HSV]

ok, i know that the stock gtr turbo's can let go from age, and or too much boost

i've heard that most of the time the thing ends up in the cat, but i've heard that it can also get sucked back and bash against the engine, and bits of metal end up rooting a couple of pistons.

some ppl believe this is impossible, but some ppl have actually had this happen, and i'm just wondering how often/ common this is

[predator]

If it was a GTS-T i would say impossible .. and i've never heard of it happening to anybody who has destroyed their turbo on an rb25 or rb20 engine .

GTR is different kettle of fish, but again I am a little unsure of exactly how its possible in practice..

[Cubes]

If you are leaning on the turbo's keep the fuel a little richer towards the top end and it will help keep the EGT under control.

Heat is THE biggest killer of ceramic exhaust wheels.

[wrxhoon]

ok, i know that the stock gtr turbo's can let go from age, and or too much boost

i've heard that most of the time the thing ends up in the cat, but i've  heard that it can also get sucked back and bash against the engine, and bits of metal end up rooting a couple of pistons.  

some ppl believe this is impossible, but some ppl have actually had this happen, and i'm just wondering how often/ common this is

if your turbo lets go on the rb26 ( ceramic only ) i can assure you that you will stuff up more than pistons .

as it breaks ( the ceramic exhaust wheel ) it smashes againest the housing and you right you will find it in the cat but also sand like dust ( remember its ceramic not metal ) gets sucked back in the engine and it goes everywhere .

scored bore, stuffed pistons , stuffed oil pump even marks on the crank and cilinder head .

[KILL HSV]

yeh thats what i'm worried about, i'm pretty paranoid about this, but is it likely to happen that way and are there any telltale signs of it going to happen, cos if there's a good chance then i might have to wack on some 2530's

[MANWHOR3]

i know that the gtst also has a ceramic exhaust wheel. Wrxhoon, are you aware whether the engine will also get destroyed by the wheel coming off?

I have heard mixed responses - due to different valve durations on the rb25 and rb 26. i'm tending to beleive that the dust will get sucked back in?

Cheers

[wrxhoon]

MANWHOR3 , i'm not aware if rb25's will suck the ceramic dust back in the engine or not .

but i9 know the rb 26 will for sure

[gtst25]

I thought it'd all just go down the exhaust. The exhaust wheel/s are the only ceramic parts aren't they?

[Cubes]

Depends on cam overlap etc.

[Sydneykid]

Hi guys, here are my posts on this subject......

I have seen 8 X RB's with ceramic turbine failure, 2 X GTR's, 3 X R33 GTST's, 2 X R32 GTST's and 1 X R34 GTT and none of them had any ceramic anywhere other than in the cat. There wasn't any in the turbine cover or in the dump or in the engine pipe, it was all in the front of the cat. Blown there by ~200 cubic metres per second of ~600 degrees celsius exhaust gas, that's better than my Stihl leaf blower.

Maybe if you were spinning at the time and the engine turned backwards, you might get some sucked up into the manifold. Of if you where starting the engine at exactly the time the ceramic failed and it coughed and ran backwards.

I don't think so, Tim

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I am truely intrigued. If the engine is a single turbo (GTST) and is doing say 5,000 rpm, has standard cams, is a 6 cylinder 4 stroke of course, the numbers mean the ceramic has ~0.4 milliseconds to travel from the turbo to the bore. That's out of the turbine cover, up the inlet manifold and get past the exhaust valve while it is open and sucking (not exhausting). Part of that journey is against the exhaust gas pressure from the other cylinders. I could work out how many kph that is, but suffice to say it is way past the speed of sound.

I could see a GTR maybe doing it with aftermarket cams (longer overlap) at lower rpm's. A straight/shorter exhaust manifold would help. And if you heard the ping and shut the engine down, maybe.

Possibly that's why I have never personally seen it, we just don't have GTR's (or GTST's for that matter) with upgraded cams/manifolds and standard turbos. Plus they always let go at big rpm on the circuit, at full throttle and the drivers don't back off either.

Very interesting...........

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The turbine blades should never exceed the speed of sound, the mini sonic boom would destroy them. So I don't think speed is the answer. Maybe they let go big time and then shed little bits of ceramic over the next few times the engine is started. When you fire it up to put it in the workshop, on the trailer, stuff like that maybe would be a problem on a GTR.

It certainly isn't a problem on a GTST, I have seen one driven 200 k's home after a turbine failure, it only had ceramic in the cat. I know because we took the head off while the turbo was being done and did some porting and polishing. It was clean as a whistle inside.

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Put money where mouth is, I currenty have a Stagea with a ceramic turbine and I am not in the slightest bit worried about ceramic going anywhere but in the cat.

Hope that helps

[GTRgeoff]

I have to agree with SK in doubting the turbine particles could go into the engine, but as the turbo unbalances I have heard that the compressor can shave the housing sending particles into the intake.

Anyway if I'm wrong I would be keen to see photos or hear from those who had the failure or worked on it so as to investigate it a little more thoroughly

[MANWHORE]

don't think that it is so impossible.

i've heard it happen to a few people. wrx hoon i believe is one of them. that's why he had to have his engine rebuilt. basically, if you drain the oil through filter paper, you find gritty ceramic. and i'm not familiar with engine internals, but basiclaly, it's ****ed.

[GTRgeoff]

But for the particles to get into the oil it has to get past the pistons and rings, so they have to be destroyed, not just scored. Certainly I would agree that the filings from the compressor housing could get into the cylinders and score the bores, but again getting into the oil is a different matter.

Another way for the particles to get into the oil is if the seal in the turbo was destroyed enough for them to enter that way.

While the Inconel of the turbine is considered a "ceramic" it's not like the vitreous porcelain you would find around the house that will shatter easily, but it is still brittle.

[wrxhoon]

don't think that it is so impossible.

i've heard it happen to a few people. wrx hoon i believe is one of them. that's why he had to have his engine rebuilt. basically, if you drain the oil through filter paper, you find gritty ceramic. and i'm not familiar with engine internals, but basiclaly, it's ****ed.

as i said before it did happen to me and i know of another gtr that had the thing .

the wheel of the rear turbo broke off .

as it smashed in the housing it became tiny pieces like sand some of which found their way in the cilinders , the 3 rear bores were stuffed the front 3 very timy marks on them , the tops of the pistons had imprints of the stuff on them . the oil pump was slightly scored and even the crank had tiny score marks .

my engine at the time was completely stock .

sk if you want to see pics of the pistons i still have them .

[GTRgeoff]

I'd like to see them too if you can post them up?

Any suggestions from the engine builder as to how the particles got into the oil system?

[wrxhoon]

i'll see if i can post some pics of the pistons tomorrow .

i rebuild the engine , the enginnering place that does my reboring and head work said he has seen it before .

the dust gets sucked back in the engine throught the exhaust ports .

i wasnt driving my car when it happened , this guy took it around the block to get a brake meter reading for a pink and when he came back it was blowing smoke everywhere .

the oil was going throught the turboi seal straight in the exhaust pipe .

it was dumping that much oil in there when i put the engine back in the car it was still blowing smoke for like 15 -20 minutes ( burning the oil in the exhaust pipes and i washed the ex pipes as well )

as you can see from the pics the rear 3 pistons are badly scored on the sides and the tops the front 3 are very lightly scored . the rear turbo let go .

do you need more evidence ?

[wrxhoon]

there is another one

[Sydneykid]

as you can see from the pics the rear 3 pistons are badly scored on the sides and the tops the front 3 are very lightly scored . the rear turbo let go.   do you need more evidence ?

No, I'd say that is pretty conclusive proof that is wasn't the ceramic tubine pieces that scored the bores and damaged the pistons. Because personally I believe it is IMPOSSIBLE for the rear turbine ceramic pieces to;

*travel down the rear dump

*into the engine pipe

*down to the Y joint

*then do a u'turn (against the exhaust flow from 1, 2 and 3 cylinders)

*go up the front turbine engine pipe (against the exhaust flow)

*up the front turbo dump (against the exhaust flow)

*past the intact front turbine (against the exhaust flow and rotation)

*up the front exhaust manifold (against the exhaust flow)

*past a partially open valve (against the exhaust flow)

*into the combustion chamber (against the exhaust flow)

*and find its way into all 3 cylinders

Ceramic has low mass for size, that's one reason why it is used in turbines, so it losses it velocity very quickly. Particularly when faced by air travelling in the opposite direction.

I have seen this sort of piston damage many, many times, generally from not running air filters. I would say this engine, sometime in its life, ran with no airfilters or had compressor damage that found its way into the engine via the inlet tract ie; with (not against) the airflow.

Conclusion, I am totally unconvinced.

[wrxhoon]

lets get a couple things right :

the ceramic stuff didnt travel all the way down the dumps. as the shaft broke off it became thousands of small pieces, before it went down the dump some ( heaps ) got sucked back through the exhaust manifpld ports and in to the combustion chamber . thats the reason the rear pistons and rear bore were damadged ( you cant see that well from the pics )the front 3 are very lightly scored because the dust went everywhere even in the oil pump .

have a look in the top of the pistons you will see some cereamic imprints in there .

there is no way that it went down the dumps to the y front pipe then back up again i can assure you of that .

as for not running air filters , i can assure you i would never do that not even in the workshop , it had the stock airbox with paper type air filter ( still has ).

i hope thats convinced you if it hasnt you can inspect the pistons .

No, I'd say that is pretty conclusive proof that is wasn't the ceramic tubine pieces that scored the bores and damaged the pistons.  Because personally I believe it is IMPOSSIBLE for the rear turbine ceramic pieces to;

*travel down the rear dump

*into the engine pipe

*down to the Y joint

*then do a u'turn (against the exhaust flow from 1, 2 and 3 cylinders)

*go up the front turbine engine pipe (against the exhaust flow)

*up the front turbo dump (against the exhaust flow)

*past the intact front turbine (against the exhaust flow and rotation)

*up the front exhaust manifold (against the exhaust flow)

*past a partially open valve (against the exhaust flow)

*into the combustion chamber (against the exhaust flow)

*and find its way into all 3 cylinders

Ceramic has low mass for size, that's one reason why it is used in turbines, so it losses it velocity very quickly.  Particularly when faced by air travelling in the opposite direction.  

I have seen this sort of piston damage many, many times, generally from not running air filters.  I would say this engine, sometime in its life, ran with no airfilters or had compressor damage that found its way into the engine via the inlet tract ie; with (not against) the airflow.

Conclusion, I am totally unconvinced.

[Sydneykid]

lets get a couple things right :

the ceramic stuff didnt travel all the way down the dumps. as the shaft broke off it became thousands of small pieces, before it went down the dump some ( heaps ) got sucked back through the exhaust manifpld ports and in to the combustion chamber . thats the reason the rear pistons and rear bore were damadged ( you cant see that well from the pics )the front 3 are very lightly scored because the dust went everywhere even in the oil pump .

have a look in the top of the pistons you will see some cereamic imprints in there .

there is no way that it went down the dumps to the y front pipe then back up again i can assure you of that .

as for not running air filters , i can assure you i would never do that not even in the workshop , it had the stock airbox with paper type air filter ( still has ).

i hope thats convinced you if it hasnt you can inspect the pistons .

Let me make sure I have this right...........

The front 3 pistons are damaged because there was ceramic dust in the oil. How did it get there? Past the rings in the rear 3 cylinders. Down into the oil, picked up by the oil pump. Then through the oil filter. Hang on, let's stop right there...

How does 100+ micron dust get though a 10 micron oil filter? (For those that don't know a human hair is ~140 microns). :freak:

Let's move on.....

Assume by some miracle it makes it through the oil filter, then gets sprayed via the oil squirters onto the bottoms of the pistons then onto the bores. Then gets past the rings and onto the top of the pistons. :freak:

Was there any ceramic dust in the bearings? Ceramic dust would rip a bearing to shreds in seconds. The oil flow at the main and big end bearings is far greater than the oil scrape of the bores. Was there any ceramic dust in the oil filter? Have you had the pieces on the pistons spectro analysed to ensure they are the same material as in the ceramic turbines? Have you had the oil analysed for ceramic contamination?

On the race GTR that put the ceramic in the cat, I had the oil analysed by Castrol to make sure that the bearings were in good condition. Absolutely nothing to do with the turbine failure, that's not why I had the oil tested. I was simply following our normal procedure for checking a recently rebuilt and run in engine. There was not a single trace of ceramic in that oil. And it finished the race on one turbo, drove onto the trailer and into the workshop.

Bottom line, I still remain extremely sceptical.