Ceramic turbos.

I've heard lots of stories about the ceramic turbos which came in several nissan cars.
But does anyone here have first hand information about exactly what they are and what they can take?

Here's what the internet has spouted so far:
Probably a T28
Ceramic exhaust wheel which loses all the fins after about 14psi boost.

they're very lightweight, so they spool up fast. which is Nissan's reason for using them in the GT-Rs. the problem is that in the event of being over-loaded, having too much backpressure or a backfire (i think) can cause them to shatter. not a problem if the broken parts go down the downpipe, but it's not unknown for the pieces to go back into the cylinders and cause a lot of damage.

they can support mild mild boost (ie just turning up the stock boost a few psi with a flashed chip) otherwise, they're not rated for much. you're far better off with a ball-bearing turbo like a Garrett GT-Series.

yes, they are T28s and they were made by Garrett.

not sure if this helps but if my memory serves me correctly, the turbos in the Skyline GT-Rs R32-34 are ceramic garretts and the T28 are used in various nissan cars.

Make of this what you will but another random bit of informantion that I have in my head;
most toyotas that have aturbo in them as standard tend to have ceramic turbines in them for the home market and steel ones for the UK market.

The other good thing about them is that they can deal with a hell of a lot of heat and they also radiate very very well. Means you don't have to give your engine that cooling down period.

The other good thing about them is that they can deal with a hell of a lot of heat and they also radiate very very well. Means you don't have to give your engine that cooling down period.

the cooling-down period isn't for the benefit of letting the turbine wheel cool, it's to keep oil flowing through the turbo as the bearing unit cools. this prevent oil from coking and damaging the turbo. keeping oil flowing as the turbo cools prevents any damage.

ahhh....
i always figured it was the turbine cooling too slowly and seizing up that way.
it never occured to me that the bearings also get hot.....

on a side note, don't they also use ceramic bearings?

nope, they're either wet plain bearings or wet roller (ball) bearings.

at least, i've never heard of ceramic bearings in turbos.

the cooling-down period isn't for the benefit of letting the turbine wheel cool, it's to keep oil flowing through the turbo as the bearing unit cools. this prevent oil from coking and damaging the turbo. keeping oil flowing as the turbo cools prevents any damage.

The ceramic wheel will have a benefit there.

The problems can occur shutting down a hot turbo where the steel turbine wheel (big heat sink) has a lot of stored heat but the bearings are still cool.

The heat soaks out of the steel wheel, conducting back along the shaft and cooking the oil in the bearings.
If a ceramic wheel holds less heat, then it can't heat the shaft up as much so the danger of cooking oil is less.

Turns out my new turbo has a steel wheel.
Shame to miss out on the hi-tech ceramic, but I gain reliability, resale value and ease of rebuilding.

steelies are better for power and reliability. ceramics can't hold the same boost levels and have fairly low limits. for example, GT-R owners can only turn the boost up a few psi on the stock turbos, because the ceramic wheels shatter under higher boost levels.

to be fair, if a skyline owner wanted more boost, they usually get a bigger turbo (if garret, it would probably just be a bigger ceramic turbine).

to be fair, if a skyline owner wanted more boost, they usually get a bigger turbo (if garret, it would probably just be a bigger ceramic turbine).

A bigger turbo is just a bigger turbo, boost is set by the wastegate.

but the physical size limits the amount of pressure the whole thing can sustain, no?
doesn't a bigger turbo mean you have more pressure in the system?

well, yes. there comes a point where the exhaust flow can't make the boost any higher, but that's usually past the point of engine damage (except in diesels, usually) if a turbo is slightly oversized for the engine, the back pressure will be limited because of the good flow ability.

most turbos can reach a point, where if the exhaust gasses aren't vented they'll make a lot of pressure. but wastegate springs are usually soft enough on stock cars that they open at ~8psi in the intake.

if you're talking performance diesel, intake pressures can be pretty high. my friend's drag diesel runs at a max boost of ~61psi with a twin-stage setup. some very high-performance petrol engines can run upto ~35psi with water/alcohol injection and a lot of fail-safe gear.

generally speaking, the wastegate controls the boost, unless it's fixed shut or it fails.

sorry, left out a word (can)

it should've been
"doesn't a bigger turbo mean you can have more pressure in the system?"

yes and no. it's dependant on a few factors.

think of it like this, take an engine that flows X amount of xhaust gas over a constant period of time.

a big turbo can flow this gas in that time, with the turbine wheel moving slowly (because it has larger capacity) and therefore the intake side moves slowly and there's low pressure.

this is reversed for a smaller turbo.

of course, there's far more to this than boost pressures, they're just used for rough workings. what's really important is volume flow (cfm and the like) because it tells you how much air the turbo can flow. this is shown in compressor maps.

sorry, left out a word (can)

it should've been
"doesn't a bigger turbo mean you can have more pressure in the system?"

Pressure is pressure, if your engine is being fed air at 15psi then it doesn't know or care what size turbo it's coming from.

But bigger turbos often produce less backpressure in the exhaust at higher flow. This can give you more power for the same boost setting.
The downside is you lose boost (and power) down low and in the midrange.

Basically turbo sizing is all about finding the set of compromises you're willing to live with.

what i meant was, in relation to the point that skyline turbos can crank if you up the pressure in the stock turbo; that a bigger (ceramic) version of the same can handle more pressure with less stress and still might be lighter and have less inertia than the steel one.

what i meant was, in relation to the point that skyline turbos can crank if you up the pressure in the stock turbo; that a bigger (ceramic) version of the same can handle more pressure with less stress and still might be lighter and have less inertia than the steel one.

i don't understand what you mean.

again, I left out a word:
"that you can have a bigger (ceramic) version of the same can handle more pressure with less stress and still might be lighter and have less inertia than the steel one."

essentially it was a badly worded question/supposition:
whether you can have a ceramic turbo that can perform like for like as a steel one and still weigh less.

with ball-bearing turbos, there's a small benefit to be had by using ceramic wheels, but not much. they offer benefits in response and the time it takes to spool up. with the new advances coming into road cars like variable-vane there's little benefit to be had. and steel wheels are much stronger than ceramic ones. so ceramic ones are better for high-response low-power requirements.

so has variable vane and funky sequential set ups rendered the benefits of using ceramic redundent?

to some extent, yes.

ceramics will probably stick around the japanese market for a while. they're good for stock "performance" cars, because they offer good response. but for high power and better reliability steel is the wheel of choice. so when you're looking to make about 320bhp from the factory, they're good because they can handle that and they're a bit more responsive than turbos with steel wheels.

variable-vane is expensive, so that limits its usage in the street market at the moment. although soon production costs will drop and they'll become more common, they offer everything. good low-end response and good high-end power. so there's very little compromise with a variable-vane.

what's the difference in mass between the ceramic rotating assembly and the steel one?

what's the difference in mass between the ceramic rotating assembly and the steel one?

You find and measure the ceramic one, I've got a few steel wheels I could measure the inertia of with a little tinkering.

so has variable vane and funky sequential set ups rendered the benefits of using ceramic redundent?

Completely different markets.

The ceramics are all about fast spool. The type of thing you'd want on a turbo street car running reasonably low boost (under 10psi).

Variable vane turbos are almost exclusively diesel and are running high boost, sometimes up to 42psi on a single turbo. This seems to be beyond the ceramics lifespan at present.
AFAIK the only production petrol engines running varible vane turbos were a few us casrs in the mid 80's and a few porsche's which have just been released.

Sequential setups are finding favour again in diesels running high boost. But the complexity and expense means if an automaker can use a single turbo they probably will.

Nissan introduced its ceramic turbo in 1987, and in 1989 they added ball bearings to it. The bearings and races are made of tool steel, which retains a high hardness at elevated temperatures. Tis turbo was Nissans own design.

The specs I've seen for Si3N4 (the ceramic used in the turbine) shows a tensile strength that is very high at elevated temperatures. So, if the turbine is well made it shouldn't shatter at high boost (high boost = high turbine speed = high centrifugal forces = high strength/density ratio required).

The variable vane turbo market is very underdeveloped for gasoline engines. It is much more established in the diesel market, as the VV technology tends to be very temperature sensative, in that the higher exhaust gas temps from gas engines tend to cause problems with vvt.

The only other ceramic turbos that come to mind are the non export (jspec) ct12b's from the jza80. I believe they were originaly hitachi products (the export spec steelies were), and suffer the same negative effects as the nissan units. Stock boost for a pair of ceramic ct12b's is about 11psi for the supra, which develops around 300-315hp at the flywheel in ceramic form. These turbos are only reliable to 14-16psi of boost, which yields around 350flywheel hp on the 2jz. After that you may see a puff of ceramic comming out the muffler. For comparrison, the ceramic ct12b's actually have a slightly larger compressor wheel (not much), a slightly thicker shaft, and in stock form develop less power than the steel units, which produce about 300whp in the 6-speed at the stock boost levels. Obviously the steel units are more durable, one or two people have pushed them over 500hp.

The variable vane turbo market is very underdeveloped for gasoline engines. It is much more established in the diesel market, as the VV technology tends to be very temperature sensative, in that the higher exhaust gas temps from gas engines tend to cause problems with vvt.

it's not the temperature that causes the problems. its lubrication on of the VVT system. on diesel engines the carbon/soot lubricated the parts, but petrol engines don't make as much carbon and so the VVT parts can fail because there isn't enough lubrication. so the VVT control parts need to be located outside the turbine. it that that's partly undeveloped.

it's not the temperature that causes the problems. its lubrication on of the VVT system. on diesel engines the carbon/soot lubricated the parts, but petrol engines don't make as much carbon and so the VVT parts can fail because there isn't enough lubrication. so the VVT control parts need to be located outside the turbine. it that that's partly undeveloped.

Exhaust soot doesn't lubricate and modern diesel engines run very clean. A Toyota Dyna van I saw the other day was running so clean the inside of the exhaust pipe was rusting.

Petrol engines don't have as much to gain from a variable vane turbo as the typical setup of boost only at high revs suits them well. On a diesel the short rpm range means you need to maximise torque throughout which places emphasis on the low end.
Also on a diesel variable geomtry turbos increase both power and economy, on a petrol it's always a case of pick one.
Porsche didn't care much about economy.

Exhaust soot doesn't lubricate and modern diesel engines run very clean. A Toyota Dyna van I saw the other day was running so clean the inside of the exhaust pipe was rusting.

Petrol engines don't have as much to gain from a variable vane turbo as the typical setup of boost only at high revs suits them well. On a diesel the short rpm range means you need to maximise torque throughout which places emphasis on the low end.
Also on a diesel variable geomtry turbos increase both power and economy, on a petrol it's always a case of pick one.
Porsche didn't care much about economy.

Petrol engine may not has AS much to gain, but there are huge benifits for roadracing application, especialy for smaller displacement engines that have to make a larger sacrifice to achieve higher top end power. Anything that lowers boost threshold and retains top end output is pretty high up on my list of worthwhile modifications.

But, on a need basis, yea; deisel engines technically benifit more.
I was unaware of any negatative impact to economy due to VV in petrol engines, will you please explain?

On a side note, is porsche making their own vv turbos or are they still getting all their stuff from Borg Warner?

I was unaware of any negatative impact to economy due to VV in petrol engines, will you please explain?

On a side note, is porsche making their own vv turbos or are they still getting all their stuff from Borg Warner?

Quite simply you get the best efficiency from a petrol engine with close to wide-open throttle.
Being able to run a turbo engine at cruise in a region where it's near full throttle without boosting gives you the best economy.

With a variable vane turbo, you're going to be boosting before full throttle. Which means you're throttling boosted air. A very bad thing for efficiency and economy.

Car makers don't make their own turbos. Even house brands like toyota are made by turbo companies under special agreements.

i believe Mitsubishi manufactures turbos. although, i think they ones they make are used for diesels, and their petrol engines use turbos from other companies.

i believe Mitsubishi manufactures turbos. although, i think they ones they make are used for diesels, and their petrol engines use turbos from other companies.

Mitsubishi Heavy Industries and Mitsubishi Motor Company are not the same outfit.
Same with Mitsubishi TV's and pencils.

Quite simply you get the best efficiency from a petrol engine with close to wide-open throttle.
Being able to run a turbo engine at cruise in a region where it's near full throttle without boosting gives you the best economy.

With a variable vane turbo, you're going to be boosting before full throttle. Which means you're throttling boosted air. A very bad thing for efficiency and economy.

Car makers don't make their own turbos. Even house brands like toyota are made by turbo companies under special agreements.

This is true, but it depends on engine load. You will never have positive boost while simply maintaining speed on a highway unless you are traversing a hill. Sure, under partial throttle acceleration you are 100% correct, as the engine is under enough load to produce boost. This is why the MKIV supra gets aweful economy in the city vs decent economy on the highway. the sequenial system can produce ositive boost by 2,000rpm given the required load, which isnt that much.

I didn not know about all the mitsu corporations being seperate. Ill rephrase the question, was porsche or borg warner the one to really develop the vv technology for their turbos?

This is true, but it depends on engine load. You will never have positive boost while simply maintaining speed on a highway unless you are traversing a hill.

With a variable vane turbo you can easily boost at cruise. But as you're implying, such a setup is pointless on a petrol engine.



I didn not know about all the mitsu corporations being seperate. Ill rephrase the question, was porsche or borg warner the one to really develop the vv technology for their turbos?

Why do you need to ask such a question? It's like asking if Donald trump drives his own limo.
Car companies develop cars, turbo companies develop turbos.

With a variable vane turbo you can easily boost at cruise. But as you're implying, such a setup is pointless on a petrol engine.




Why do you need to ask such a question? It's like asking if Donald trump drives his own limo.
Car companies develop cars, turbo companies develop turbos.

Didnt know the adjustability was extreme enough to allow boost during low load cuise, so I glad I asked.

Was simply curious about the porsche turbo's. The used to all be KKK units but Borg Warner bought up most of the small european companies; nothing more than simple curiosity

many newer cars have pretty smart BOV/bypass valves that stay open at lower throttle openings. This will not remove the restriction of the VV in the exhaust housing, of course.

Really, if your car is producing 15hp to cruise at speed, the difference between 2psi and 0psi isn't going to have much impact on economy. One of my turbo bikes, for example, makes 10psi while cruising on the freeway (measured before the TB) and it gets very close to the same mpg it did before I turbo'd it.....thats a much more extreme pressure difference compared to a car at speed, because this bike in particular is using a large percentage of its availible power to cruise on the freeway, comparatively