1.2 bar on ceramics???
"Some Nissan turbochargers use ceramic turbine wheels - what are their advantages and limitations?
Ceramic turbines are wonderful. We've used them in Caterpillar engines and Detroit engines and they're very heat resistant materials, they're light and very responsive - but they don't like foreign objects. You've only got to have the engine tuned once on the dynamometer a little bit lean - it'll drop a bit of spark plug electrode and it's a bit like a puff of talcum powder out the exhaust. And then you don't have a turbine wheel any more. Even if you're pulling one of these turbos apart and you knock the head of the wheel, they will actually break.
The other thing that happens if they are drastically over-sped - and I mean fairly drastically - the head joint will let go at the back of the turbine wheel. It's not necessarily the turbine wheel that goes, but the assembly to the shaft. The OE has designed it to suit their application. They don't want you to go from 9 psi to 15 psi, because it's designed to be at maximum efficiency at 9 psi. Turn it up to 15 psi and the turbine speed has probably gone up 40 percent - the head of the wheel has never been designed to spin at those revolutions.
With some of them you can get away with lots of extra boost before you run into turbo problems - but it's model specific. We've not seen too many problems with basic modifications like an exhaust, air cleaner and a very mild boost increase. When you're chasing the horsepower that's available, though, that is when turbine wheel heads drop off - or if you're using the car for competition use. Over time - like in an endurance race - it'll get to the point where it fatigues.
Sometimes, with hand fabricated exhaust manifolds or even cast manifolds, if there's a little bit of welding dag or casting dag left in it - again - you might end up with no turbine wheel.
So they're generally very tough, very reliable items but they're not happy about impacts. I guess you could say they're an excellent fair weather sailer - when everything's perfect, they're wonderful. But they're not drastically good with foreign object damage."