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18psi through standard 33 turbo

letemlaf

By letemlaf,
in Engines & Forced Induction

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2rismo Grand Master

2rismo

Posted
Posted

Not usually. Well, not if it is still attached to a Series I or II R33 Skyline. :P

It's not a case of the motor not taking the extra manifold pressure, more that the turbine wheel is prone to de-laminating at shaft speed past about 1.0bar.

Adrian

Al Grand Master

Al

Posted
Posted

At 18psi you will most probably distroy the turbo's ceramic exhaust wheel. I have heard of someone running 18psi through the stock turbo, but this was done when the owner had the money to buy a new one. To everyones astonishment this particular turbo did not fall apart for a while (12 months), but this was just one of those freaks.

13psi is the highest "safe" limit, but even at this level some turbines will seperate from the shaft.

Al Grand Master

Al

Posted
Posted
I guess it all comes down to how well you have it tuned and how long you want it to last, engine and turbo.

Tune has no effect on turbo life, unless something from a blown engine goes flying into the exhaust housing. Engine is another story.

Sydneykid Grand Master

Sydneykid

Posted
Posted

There are two problems with the standard turbo, both centred around the ceramic exhaust turbine.

Firstly, being ceramic the turbine is sweated/bonded onto the common shaft and therefore it does not like too much resistance ie; the exhaust is pushing the turbine while the compressor is trying to move air into the engine. Too much resistance (boost) and the turbine and the shaft part company.

The second problem is one of heat, the ceramic turbine will only handle a certain amount of heat coupled with this resistance. The heat builds up over several minutes of very hard driving (say on a circuit) and the turbine shatters or parts company with the shaft. Leaning out the engine to achieve more horsepower also increases the temperature of the exhaust.

So to answer your question, our experience has been that 0.7 bar (10 lbs) is OK for a road car as long as it is only in short bursts so that the heat does not build up. If you do any circuit work or long distance high speed stuff, then 0.6 bar (9 lbs) may well be the safe max.

The boost readings above are at the engine inlet. The boost at the turbo will of course be higher than that depending on the airflow of the intercooler and the pipework. By reducing this restriction (better intercooler) you can have more than 0.7 bar at the engine but still have the same resistance (boost) at the turbo.

With a really good intercooler and pipes we have achieved 0.8 bar (12 lbs) on a 200 RWKW road car reliably. But 5 hard laps on the circuit and the smoke escaped.

Sorry that this is a complex answer to your questions but it is a complex scenario.

Sydneykid Grand Master

Sydneykid

Posted
Posted
Sydneykid, you're not supposed to let the smoke out!!  Thought you'd know that!!  ;)

:P

Adrian

Yep that's right Adrian, the engine runs on smoke, and if it all escapes then there is nothing to make the car go.

Don't know about the others Duncan, but I'm on holidays, got a few days off to go to Sandown next weekend and Philip Island the weekend after. Just waiting on some exhaust bits and a modification to the sump. Both cars should be on the dyno tonight, so no sleep for me.

Al Grand Master

Al

Posted
Posted
How so? You tune a car to run 50psi and this has no effect on the turbo life?!?!?

Don't twist the topic.

You can tune the engine for 50psi, but as long as you limit the waste gate to only provide 12psi of boost the turbo will be safe.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
BTW, this thread makes me ask....is it school holidays at the moment?

Yes indeed... well... sopme go back today, and some tomorrow depending on the schools.

All the little sh(ts in my house were up nice and early today getting back into it all.

This is Vic though... otherstates seem not to match up half the time

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