Max Boost The Standard R33 Turbo Can Deliver?

[Galois]

sorry for the painfully newbie question, but what does turbo efficiency refer to? is it something to do with air intake temp, or something to do with the turbine and compressor wheel design? or the a/r ratios? thanks

[The Mafia]

Dude, I have held a series 2 compressor wheel, in pieces, in my hand, and it is most definitely NOT metal.

For everyone else, here's the dyno sheet:

+1 for S2 turbo and R34 GTT turbos both have Nylon(or could be baker-lite) compressors

The two I have held were metal. Maybe they were S1 turbos.

I have never seen a SII turbo let the compressor go. Only the rear.

Edited July 8, 2010 by The Mafia

[Harey]

sorry for the painfully newbie question, but what does turbo efficiency refer to? is it something to do with air intake temp, or something to do with the turbine and compressor wheel design? or the a/r ratios? thanks

It has to do with all of those things. It gets pretty complex, basically a turbo will efficiently flow a particular range of airflow. Outside of this range the air temp rises and all sorts of bad things. Thats the technical explanation

[Torques]

sorry for the painfully newbie question, but what does turbo efficiency refer to? is it something to do with air intake temp, or something to do with the turbine and compressor wheel design? or the a/r ratios? thanks

Hi!

NP ... just have a bit of a read here:

http://www.turbobygarrett.com/turbobygarre...bo_tech101.html

[Torques]

It can deliver it, we've established that already. If you welded the wastegate shut, it would easily go past 15psi.

Hi!

I think we have not established that.

At least not with the RB25.

I am using an EBC, and the controller tries to keep the boost at 14PSI by keeping the wastegate shut.

But if the turbo can not deliver the required flow for the engine, the boost pressure will diminish gradually.

The engine outflows the turbo and so the turbo can not keep the boost up.

If we are talking boost we have to consider boost @ flow, right?

So I contradict

Cheers,

Andrew

[Trozzle]

just because a turbo can flow 15psi @ 3500rpm, does NOT mean it will continue to flow is at 6000rpm

consider this:

You are trying to blow up a balloon, but this balloon has a hole in it. YOU represent the turbo, and the hole represents the engine post-manifold. The size of the balloon represents manifold pressure.

With a small hole in the balloon (low RPM = low volume of air into cylinders) you don't have any troubles keeping the balloon inflated to the same size (boost level)

As you increase the size of that hole (increase rpm = increase air flow into cylinders), you find it harder to keep the balloon at a constant inflation. This is going out of YOUR EFFICIENCY RANGE.

A turbo is merely forcing more air into the manifold to increase the air pressure inside it. The engine itself is RELEASING this build up of pressure. As the RPM rises, the rate at which this air is "leaking" grows, therefore the turbo must push in MORE air to maintain the pressure. A smaller turbo will have trouble doing this at higher RPM.

Just because an RB25 turbo went spaz and hit 20psi @ 4000rpm or something, does not mean it would have kept it there until 7000rpm (on the assumption it didn't detonate immediately)

Edited July 9, 2010 by Trozzle

[R31Nismoid]

Hi!

I think we have not established that.

At least not with the RB25.

I am using an EBC, and the controller tries to keep the boost at 14PSI by keeping the wastegate shut.

But if the turbo can not deliver the required flow for the engine, the boost pressure will diminish gradually.

The engine outflows the turbo and so the turbo can not keep the boost up.

If we are talking boost we have to consider boost @ flow, right?

So I contradict

Cheers,

Andrew

Weld it shut then and see what happens.

You might be surprised

[mad082]

the stock turbo can deliver 15psi and higher at high rpm. there may be other factors causing the pressure to drop. it may be the boost controller, it may be the intercooler is restrictive, it may be the exhaust is restrictive, it may be the intake pipe sucking closed a bit. there are many variables. whatever the cause is, if you disconnect the vaccum line to the wastegate so it runs unlimited boost, you will find that the boost very quickly goes off the gauge and will stay there all the way through the rev range.

that is the point here. if allowed to run unlimited boost the turbo won't simply get to 15psi and max out and not go any higher. the boost pressure will easily get to 20 or 30 psi on the stock turbo, and while the pressure may drop as it moves higher into the rev range, it will still be stupidly high at redline.

[Rolls]

Hi!

I think we have not established that.

At least not with the RB25.

If you force the wastegate flap shut I can guarantee you you will see at least 30psi until redline, motor will probably explode somewhere along the line though.

[Torques]

If you force the wastegate flap shut I can guarantee you you will see at least 30psi until redline, motor will probably explode somewhere along the line though.

Hi!

Well I can not argue with that, since I will not weld it shut.

What I could do is disconnect the pressure hose from the actuator and see were the boost goes.

(But I suspect it will be as before)

[Rolls]

Think about how a turbo works, exhaust gas = more air, more air = more exhaust gas, more exhaust gas = more air.... see where I am going with this? If the wastegate never opens it is essentially an infinite loop creating more and more boost, obviously the temperature will skyrocket and something will break eventually.

At a certain psi the exhaust gas might be under enough pressure to force the wastegate flap open even with no pressure on the actuator, could be why it drops down from 15psi when you have been trying it.

[joel_bruce]

I Have three main settings on my r33, 8psi - 10psi - 12psi - 15.5psi, Dont use the 15 much but it is real easy to get it thanks to the high flow exhaust, high flow intercooler, Greddy intake manifold, power fc and Gizzmo boost controller

its heaps easy to get 15psi outta the stock turbo and the response is silly, almost no lag at all LOL

The reliability of the turbo at 15psi is about as much as the lag, Its yet to let go on me atm thou