External Waste Gate

[millsy13]

Hi,

Can anyone explain the benifits of this? I was looking at the Andy F webiste and saw this under one of the tuning packages and just wondered about it. I have zero technical knowledge so please try to keep it simple so I understand it.

[colin_ross]

An wastegate is what vents off excess pressure on the hot side of the turbo stopping it spinning it too hard. It has a spring that holds it shut but when a certain pressure is reached (depending on how strong the spring is) the wastegate opens and releases the pressure. Boost controllers can bleed away some or all of this pressure to make your car run the desired amount of boost.

An external wastegate is one that it not part of the turbo whereas the normal ones are built into the turbo.

The reason's for going external is that you get to a point when you're running a bigger turbo where a bigger w/g is required to vent enough gas. The built in ones are restricted in size but the external ones can be a big as you like.

There are other benefits regarding exhaust gas flow too as the exit from the turbo isn't disturbed when it is kept seperate.

[millsy13]

Cheers Playsatan2

[st3ph3n]

I'll have a go with some questions as well then:

I've seen a couple of project cars running 2 wastegates. Are there benefits of doing this?

[colin_ross]

twin turbo's?

[st3ph3n]

Nope. Single turbo. BIIIIG Turbo though.

[thewelsho]

  Playsatan2 said:

An wastegate is what vents off excess pressure on the hot side of the turbo stopping it spinning it too hard. It has a spring that holds it shut but when a certain pressure is reached (depending on how strong the spring is) the wastegate opens and releases the pressure. Boost controllers can bleed away some or all of this pressure to make your car run the desired amount of boost.

An external wastegate is one that it not part of the turbo whereas the normal ones are built into the turbo.

The reason's for going external is that you get to a point when you're running a bigger turbo where a bigger w/g is required to vent enough gas. The built in ones are restricted in size but the external ones can be a big as you like.

There are other benefits regarding exhaust gas flow too as the exit from the turbo isn't disturbed when it is kept seperate.

You know too much... do you ever get out!?

Don't suppose you could post an annotated pic of a turbo showing the wastegate?

Edited May 7, 2008 by TheWelsho

[AlanG]

  st3ph3n said:

I'll have a go with some questions as well then:

I've seen a couple of project cars running 2 wastegates. Are there benefits of doing this?

You mean twin wastegates or twin dumpvalves?

If twin wastegates, most likely the car is using a twin scroll turbo.

[steven_williams]

  TheWelsho said:

You know too much... do you ever get out!?

Don't suppose you could post an annotated pic of a turbo showing the wastegate?

If you look at my thread " A little bit of Scooby Porn" picture 4 shows the exhaust impeller and the wastegate. Hope this helps

[st3ph3n]

It's on the GT40R fog mount project on NASIOC - http://forums.nasioc.com/forums/showthread.php?t=1106146

So that is a twin scroll I think.

[AlanG]

  TheWelsho said:

You know too much... do you ever get out!?

Don't suppose you could post an annotated pic of a turbo showing the wastegate?

up-pipe and external wastegate pipe (non RCM)

Pipe in place (turbo sits on that 4 bolt flange

[AlanG]

  st3ph3n said:

It's on the GT40R fog mount project on NASIOC - http://forums.nasioc.com/forums/showthread.php?t=1106146

So that is a twin scroll I think.

Yes, it's a twin scroll. You don't need twin wastegates though.

[thewelsho]

  AlanG said:

Yes, it's a twin scroll. You don't need twin wastegates though.

What does twin scroll mean?

[colin_ross]

  TheWelsho said:

Don't suppose you could post an annotated pic of a turbo showing the wastegate?

The round silver part on the front of the turbo is the actuator, this is connected to the wategate on a standard turbo via a rod. When the actuator is pressurised it pushes the rod and open the w/g

The w/g is the hindged part inside the turbo to the right od the impeller.

The penny as it is called it opened to release the pressure down the downpipe.

[thewelsho]

  Playsatan2 said:

The round silver part on the front of the turbo is the actuator, this is connected to the wategate on a standard turbo via a rod. When the actuator is pressurised it pushes the rod and open the w/g

The w/g is the hindged part inside the turbo to the right od the impeller.

The penny as it is called it opened to release the pressure down the downpipe.

Top man

[marky.t.s]

so is it an external w/g that gives rally cars the "chirpy,chirpy,cheap,cheap" then or am i wrong??

[seafar99]

chirpy, chirpy blow off valve.

[st3ph3n]

I thought the chirpy chirpy was because they were not running blow off valves, and that said noise was actually the turbo cutting through the compressed air that had no where to go?

[Boydie.]

  seafar99 said:

chirpy, chirpy blow off valve.

Anything but!

  st3ph3n said:

I thought the chirpy chirpy was because they were not running blow off valves, and that said noise was actually the turbo cutting through the compressed air that had no where to go?

Pretty much. It's called Compressor surge, the chirpy/flutter noise is air travelling back through the the turbo after the throttle plate closes. When you're watching Rally, listen to the cars. They give off MEGA flutter due to Anti-Lag, awesome noise!

John, these pictures might help a bit.

External -

Internal -

On a side note, can anyone tell me if any of the WRX/STI turbos are VV?

Edited May 8, 2008 by Boydie.

[thewelsho]

  Playsatan2 said:

when a certain pressure is reached (depending on how strong the spring is) the wastegate opens and releases the pressure.

How does this work? Does the ECU detect the "certain pressure" thus opening the wastegate or is it purely mechanical, in that the "certain pressure" literally forces the w/g to open?

To run with an external w/g I take it that the turbo would not have an internal one based on it's larger size, thus the requirement for an external one. If that is correct, would it then be right to say that smaller turbos with internal w/g, cannot then make use of an external set up or conversion?

[fai17]

  TheWelsho said:

How does this work? Does the ECU detect the "certain pressure" thus opening the wastegate or is it purely mechanical, in that the "certain pressure" literally forces the w/g to open?

To run with an external w/g I take it that the turbo would not have an internal one based on it's larger size, thus the requirement for an external one. If that is correct, would it then be right to say that smaller turbos with internal w/g, cannot then make use of an external set up or conversion?

you can run an external wg on a standard internal set up by welding the wg penny shut and making new pipework for the external wg to fit.

[thewelsho]

  fai 17 said:

you can run an external wg on a standard internal set up by welding the wg penny shut and making new pipework for the external wg to fit.

I see - but the other parts of the question... do bigger turbos come without the internal gate meaning that only the external gate can be used?

AND...

How does the "certain pressure" open the gate, via the ECU or just physical force?

[AlanG]

  TheWelsho said:

How does this work? Does the ECU detect the "certain pressure" thus opening the wastegate or is it purely mechanical, in that the "certain pressure" literally forces the w/g to open?

To run with an external w/g I take it that the turbo would not have an internal one based on it's larger size, thus the requirement for an external one. If that is correct, would it then be right to say that smaller turbos with internal w/g, cannot then make use of an external set up or conversion?

The pressure is mechanical John. If you have, say a 1 bar spring in the actuator (to the wastegate) and you have a hose from the inlet manifold to the actuator, then as soon as the inlet manifold is pressurised to 1 bar, the actuator will open and hence open the wastegate to allow exhaust gasses which would normally have gone through the turbo to go down the wastegate path and hence keep the boost pressure at 1 bar. In other words, you're limiting the speed of the exhaust wheel in the turbo to limit the boost pressure created by the compressor wheel.

In terms of ECU control, if you can imagine putting a valve in the hose between the inlet manifold and the actuator (the 2 port or 3 port solenoid), then the ecu can open and shut this solenoid very quickly. If that solenoid was to stick in the closed position, then that would mean that the boost pressure from the inlet manifold wouldn't reach the actuator and so the wastegate wouldn't open, which means you'll have excessive boost pressure. With that in mind, then you can see that if you open and shut that solenoid many times a second, you can set your boost pressure to whatever you want i.e. if you have a 1 bar actuator and you want to run 1.4 bar boost pressure, your ecu can open and shut that solenoid many times a second to achieve the desired boost pressure.

In terms of wategate John, you would have either an internal one or an external one, not both, so you can't go out and buy one to add to your spec as is.

[thewelsho]

  AlanG said:

The pressure is mechanical John. If you have, say a 1 bar spring in the actuator (to the wastegate) and you have a hose from the inlet manifold to the actuator, then as soon as the inlet manifold is pressurised to 1 bar, the actuator will open and hence open the wastegate to allow exhaust gasses which would normally have gone through the turbo to go down the wastegate path and hence keep the boost pressure at 1 bar. In other words, you're limiting the speed of the exhaust wheel in the turbo to limit the boost pressure created by the compressor wheel.

In terms of ECU control, if you can imagine putting a valve in the hose between the inlet manifold and the actuator (the 2 port or 3 port solenoid), then the ecu can open and shut this solenoid very quickly. If that solenoid was to stick in the closed position, then that would mean that the boost pressure from the inlet manifold wouldn't reach the actuator and so the wastegate wouldn't open, which means you'll have excessive boost pressure. With that in mind, then you can see that if you open and shut that solenoid many times a second, you can set your boost pressure to whatever you want i.e. if you have a 1 bar actuator and you want to run 1.4 bar boost pressure, your ecu can open and shut that solenoid many times a second to achieve the desired boost pressure.

In terms of wategate John, you would have either an internal one or an external one, not both, so you can't go out and buy one to add to your spec as is.

Great answer!

I wasn't thinking about doing any of this Alan, just wanted to know

[fai17]

  AlanG said:

In terms of wategate John, you would have either an internal one or an external one, not both, so you can't go out and buy one to add to your spec as is.

i think its a waste of time and money but some boys from the US of A do it!