A warning to people who don't do research!

[JohnA]

I think that the R34 turbos are slightly more sensitive to high-boost failures than those of JSpec supras, but it's hard to put a figure onto these things.

 

Knowledgeable tuners tend avoid exceeding 1.05 - 1.1bar on them (on customers' cars)

[Tricky-Ricky]

Yeah anything over 1.1 bar on most ceramic turbos and its just a matter of time! R34s are prone to spitting turbines at anything over 1 bar.

[Terminator]

When we fitted the RB25 to my sons car. We did a lot of research into the limitations of the engine once levels of performance above stock were required. It certainly appeared that the Skylines were much more susceptible to waste gate issues than the MKIV. The ECU also fights boost increases. For Toms power runs at Bruntingthorpe we had to reset the ECU three times. According to Skyline owners the turbo's do seem a little more delicate than the Supra and don’t have the same degree of head room about known safe limits.

Beyond 1.2 is dangerous territory on MKIV JDM turbo's. Allowing for spikes 1.05, 1.1 is a sensible safe limit. Having said that some have run at 1.4 and not shown any signs of failure, others have let go at less than 1.2. It is a bit of a lottery. I saw 1.45 on cold night before I fitted a restrictor. That was three years ago and my turbo's are still strong and get a 1.1 / 1.2 thrashing as often as possible. They just will not break.

Good air filtration will go along way to helping ceramic turbos live long. The velocity of the leading edge of the blades is colossal. So small particles will have the same effect as a large hammer if they come into contact with the blades at full operating speed.

[Kev.O]

define "too much risk":badidea:

 

Let's put it this way: if I had a JSpec, I woudn't run it over 1.1 bar.

The place is littered with blown ceramic turbos. Why do you think there are all those supras running hybrids and singles?

Some survive for weeks, others for months. It's a matter of time (and abuse) when the turbine will at some point dislodge from the shaft.

I'd treat 1 bar as the max 'safe' limit. Over that it's pot luck.

John, what would you treat as the 'safe limit' on UK turbos??

[JohnA]

They can take more abuse than the JSpecs, that's what I think.

 

There is no ceramic turbine to dislodge itself from the shaft, that's one thing.

The wastegate is much better sized on the UKSpec, so it cannot overboost like mad as the JSpecs once they lose their backpressure.

Mine wouldn't budge even at a fraction of a psi when fully decatted. Try that with a JSpec, lol...

Another indication is that the A/R ratio is larger, the whole assembly is geared towards higher engine speeds. However that is not the whole story, and without measuring shaft rpm at high boost it's hard to tell for sure when the limits have been exceeded.

Even the compressor maps we have are not 100% accurate, they are from equivalent Garretts with similar characteristics.

 

If you think about it, "boost" is not an accurate indicator of shaft speed either as it depends on temperatures and air consumption by the engine.

Cool down the charge and 'boost' goes down for the same number of air molecules, increase the engine's breathing and 'boost' goes down yet the turbo struggles to catch up. Too many assumptions for my liking.

 

From what I know, a UKSpec running 1.2bar will run for longer before it starts smoking like a sailor (over 1 bar you are overspeeding the poor thing anyway, so you can't expect it to live forever)

[Soonto_HAS_soop]

My ceramics have been at 1.24 bar for at least two years now, and I get the occasional spike to 1.7 in extremly cold weather. They have had several runs at 1.4 in the early days, and they are still kicking out good power.

 

Sods law that now I've said that......

[JohnA]

So do mine, but that doesn't mean that the shafts are free from play and oil doesn't seep into the intake