Are Ceramic Turbine Wheels Really That Bad?

[ZILR-34]

well "VB-" wants to know why ceramic turbos are shit. im trying to say in other words if u boost them to beyond there limits they will fuc.k up.

[docang]

So lets get to the "right" ceramic compound. Inconel as used in axial flow turbines (jet engines) and R34 N1 turbos. Can handle the conditions, less likely to self destruct and lightweight. Everything the ceramic stockers need to be but at a cost.

Hi there,

Hks turbos use inconel material for their turbine blades and so is it the same with Garrett turbos, high-flows and other makers?

Tks.

[VB-]

well "VB-" wants to know why ceramic turbos are shit. im trying to say in other words if u boost them to beyond there limits they will fuc.k up.

yeah i know that, but what is exactly that f*cks up? GTRgeoff explained that they 'grow' and then the epoxy can no longer hold them in place. i thought it was the epoxy that was the only reason they let go, and thought if there was another way to hold the wheels in place, there could be some serious potential in them, but if indeed they do 'grow', then there may not be anything to keep them in place, and maybe thats why no-one has put any developement into them. still, it would be interesting to see, a bigger turbo capable of 30PSI+ with a ceramic turbine to help it spool up quicker, maybe even a ball bearing core...

[paulr33]

a ceramic exhaust wheel when given lots of heat presuably from increased shaft speed (running stacks more boost) and increase exhaust temps (tune or stacks of boost) it sweats and basically falls to pieces. parts of the blades will come off (literally snap) and then wheel will loose backpressure.

once you loose backpressure, it no longer functions as an exhaust wheel and is a dead paperweight. the compressor side wont spin fast enough and it wont make boost (ie: the exhaust wheel has failed)

[discopotato03]

Ceramic turbines were all about low innertia rotating groups . With the Hitachi's the sad fact is that they are too small and the blade sections too thick . This is why some modest sized GT28 turbos (with the right turbine ie NS111) kill the std Skyline Haitchi's performance wise . The std turbo was about having low engine speed boost but the cost is exhaust restriction particularly with a boost increase .

When you look at a turbo such as a GT2530 its not much if any larger than the std one but it performs MUCH better mainly because the hot side is higher flowing . No good stuffing more air in if you can't get the exhaust gasses out .

Metalic turbines have developed way past the point of being light and heat resistant enough to do the job on high performance engines . Super alloys like inconnel can use thin section blades which is far better from an aero point of view , high speed turbines need to be as light as possible out towards the tips to keep the polar moment of innertia down .

Cheers .

[jantolis]

I have been running my car without the restrictor, which means 1 bar, for about the last month. They are the stock GTR turbos. Nothing has stuffed up yet. I don't really thrash my car alot.

So are my turbos in alot of danger of going soon and all of a sudden??? or will i notice something first???

[GTRgeoff]

No, it will be sudden, and painful to the wallet.

[jantolis]

Not really the response i wanted. lol. Oh well i guess i won't be giving it a hard time that much until i atleast get my front suspension fixed properly. Dam these gtr's love taking money out of your wallet.

[psybic]

Upon reading a thread in supraforums about similar issues, I found it hard to find a boosted TT supra with turbo failure. Why are their turbos less prone to similar issues to the all so common R32 GTR problems. They are ceramic also and although supras are a few years younger, why are these guys claiming to be able to boost why higher than recommended GTR boost levels and seem to have hardly any failures?

[paulr33]

just because one engine running 12psi causes failure and another running 12psi doesn't, proves absolutely nothing.

each engine has its own various differences which affect output, heat, state of tune, effiency and so on. heat is the main killer when dealing with exhaust wheel failure. the rb26 may work harder or run hotter (compressor wheels past efffiency) at the same pressure as the 2jz, and this is the killer. could be many different reasons.

also comparing 1989 to 1994 probably doesn't help

[T04GTR]

they are poo. many times ive seen stock boosed one snap :

[MrStabby]

A failed GTR turbine often results in an engine rebuild due to ingestion of the particulates. Some suggest as often as 2/3 need rebuild.

Why is an engine rebuild required? The turbine is downstream of the motor, so the bits would just head down the exhaust and get caught on the cat. Does the disintegrating turbine often take the bearings and compressor wheel with it on the way out (so its bits of compressor wheel that kills the motor)?

tnx,

Kot

[3LGODZILA]

ancient topic i know, but id like to know the answer of this question. ^

and also another thing i dont understand is what the differnce is between a gtr turbo(s) letting go and a gts-t turbo letting go. ive read when gtr turbos let go they take the engine with them, but with gtst's the ceramic just goes through the exhaust. or have i read wrong and they can both take the engines with them or luckily go through the exhaust?

[Adriano]

NO you read right, gtr turbos kill motors, wheras gtst turbos dont. Could be due to the manifold design, cam timing, maybe because the gtr turbos are smaller, they spin harder and fly apart harder, who kmows.

[GT-RZ]

u have just Answered ur own question. ceramic is more lighter than steel and more Flexible. when turning up the boost there is more air pressure goin into the turbo which the ceramic as a matrial can only flex so much b4 it comes weak and breaks or bends. i myself never seen a turbo blade brake off unless ur running like 25psi of boost. but wat i have seen is when u turn up the boost to above 14psi the ceramic wheel will come weak and bend forward which will start hitting the front housing (shaft play) and start grinding its self away into ur engine intake system. as for steel under pressure it will resize only 1-2% as for ceramic its more like 4-5% which will cause shaft play and then the damage starts.

hope that Answers ur question

First up, i' using a very generalisation to steel and ceramic here. obvously different grades have different properties.

Ceramic is not more flexible than steel. Ceramic is however lighter than steel and can take greater compressive stress than steel and also has a harder more durable surface than steel. That's why these new 'ceramic silicone nitride' bearings work very well in a turbo. they are much harder which leads increased wear resistance followed by there lack of reaction to heat so smaller tolerances can be used.

The problem with ceramic is when it's faced with tensile stress (pulling apart). the elastic range of ceramic and the plastic range of ceramic is very close to the UTS (ultimate tensile stress) where right after it will fail. steel has much higher ranges across the chart in comparision to ceramic. What that means is basically it does not stretch if a force is trying to pull it apart (centrifugal force will increase with the RPM of the wheel) it will resist untill it reaches it's UTS and then tear apart. wheras steel will stretch and eventually plastically deform under much greater stress than a ceramic variant will. it has little to do with head as ceramic copes with heat much better than steel.

so obviously when a manufacturer designes a turbo they want it to be as responsive as possible for the cheapest possible price which means the lightest and most durable material for the cause given a budget.

All manufactures work in a large Factor of Safety for every part used, but. if you think about the boost people somtimes run these at (14lb)? that's almost double the standard and most definently well above there given FOS. add to that they recommond you change them every 60,000k's with nissan and you can understand why they fail.

Not sure if i explained it well. i gues you could crudely comapre ceramic to concrete. take massive compressive strees easily, takes massive heat but cannot take tensile stress easily and will not stretch but will simply crack.

import to note too like GTR geoff mentioned. ceramic wheels cannot be bonded as well as the steel variants can so maybe the bond lets go first followed by the ceramic hitting the housing. anyones guess, probably a blend of both. it's generally more likely for it to fail at the shaft even if only the ceramic was to blame as thats where the greatest force is placed on each propellor.

Edited June 15, 2009 by GT-RZ

[GT-RZ]

Upon reading a thread in supraforums about similar issues, I found it hard to find a boosted TT supra with turbo failure. Why are their turbos less prone to similar issues to the all so common R32 GTR problems. They are ceramic also and although supras are a few years younger, why are these guys claiming to be able to boost why higher than recommended GTR boost levels and seem to have hardly any failures?

If this is the case which as suggested is not. then the supra turbos may have being built with a higher Factor of safety (a larger safety margin) for example nissan may have used 30% and toyota may have used 40% who knows. going b the way toyota tends to build things it is probably true. thing to note though, generally the bigger the FOS, the more money is involved and the more weight. you could inturn reinforce a ceramic turbine with steel and get a lighter turbine with a much higher tensile stress but $$$ and not necessary in comparision to a steel wheels performance. (difference would not be much)

Why is an engine rebuild required? The turbine is downstream of the motor, so the bits would just head down the exhaust and get caught on the cat. Does the disintegrating turbine often take the bearings and compressor wheel with it on the way out (so its bits of compressor wheel that kills the motor)?

tnx,

Kot

.

if you think about the force that is ripping apart the ceramic wheel and then think about the kind of material that ceramic is. you realise that when it lets go and bashes in to the housing it too then will not just bend like steel would but it will break up and at the speed it was travelling the pieces are likely to be very small (dust) with easily enough force to travel back through the manifold

ancient topic i know, but id like to know the answer of this question. ^

and also another thing i dont understand is what the differnce is between a gtr turbo(s) letting go and a gts-t turbo letting go. ive read when gtr turbos let go they take the engine with them, but with gtst's the ceramic just goes through the exhaust. or have i read wrong and they can both take the engines with them or luckily go through the exhaust?

NO you read right, gtr turbos kill motors, wheras gtst turbos dont. Could be due to the manifold design, cam timing, maybe because the gtr turbos are smaller, they spin harder and fly apart harder, who kmows.

i think you will be right with the manifold design. GTR manifolds are very small with tiny bends in comparision to the GTST manifold. i still wouldn't bank on no ceramic dust getting in to the engine though.

Edited June 15, 2009 by GT-RZ

[MrStabby]

Some random points;

- Turbos have a service life, and while most are careful with replacing say timing belts at the specified interval, few seem to care about replacing turbos in the same way, which leads on to;

- A problem with ceramic is the way it fails, not just the fact that it fails. Since it's brittle it disintegrates unlike steel wheels, and this failure mode is much more likely to trash the engine.

[GTRgeoff]

The phenomena of ceramic dust ingestion is likely to both a mass inertia effect and the separate manifold design with one manifold suddenly experiencing a blockage as the turbine self destructs.

I don't do enough fluid dynamics modeling now to generate a theoretical result in reasonable time but the fact remains it has occurred many times, even though it is very counter intuitive. Severe scoring of bores and glass like shards embedded in the pistons and head can only come from one location.

These are a very robust design within the original operating design envelope. Plenty are still running faultlessly but increasing boost, cold startup and hammering off before allowing reasonable warmup and various other abuse can dramatically shorten the lifespan and result in a complete rebuild. It just isn't worth the risk if you plan to increase boost, unless you are strange and enjoy building engines like I do.........even though I've been too crippled to do any for a couple of years

[MrStabby]

The phenomena of ceramic dust ingestion is likely to both a mass inertia effect and the separate manifold design with one manifold suddenly experiencing a blockage as the turbine self destructs.

I don't do enough fluid dynamics modeling now to generate a theoretical result in reasonable time but the fact remains it has occurred many times, even though it is very counter intuitive.

Perhaps its counter intuitive from a fluid flow perspective, but if we consider the momentum of the pieces of turbine as the wheel lets go - those pieces are mostly flying off toward the manifold against the direction of fluid flow, due to the shape of the turbine lead in. So short manifold = not enough time for the exhaust to slow the shrapnel down and it makes it all the way pass the exhaust valve.

Just a theory.

[GT-RZ]

26 has three runners per turbo @ much shorter lengths and less bends.

20/25 has six runnders per turbo @ much longer lengths and harder bends.

I don't think it takes a genious to see why more ceramic can get in the 26 cylinders... either engine will get a taste of dust be it 25 or 26 TT or single