External wastegate - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Howsie · 18th April 2003, 10:26 AM

When does it become necessary to fit an external waste gate and are what would be the reason not to fit one?

hipogtr · 18th April 2003, 12:54 PM

Generally, you swap to external wastegates when you can no longer control boost well - this happens in high boost applications as the internal wategae springs get forced open by the exhaust backpressure in the turbine housing. If you run greater than 1.4 bar boost regularly you may want to consider the external setup (unless you have a cracker internal wategate spring pressure).

The reason not to fit one would be costs (i.e. they are more expensive) or simply your internal setup controls boost well. Ultimately, the turbo size tends to dictate the need for an external setup or not.

Cya O!

Howsie · 18th April 2003, 06:48 PM

Very helpful. Thanks!

somberg · 18th April 2003, 09:55 PM

There's another consideration: for a turbo with internal wastegate to lower boost, pressure needs to be applied to the actuator. What happens when a control hose has popped off ? Right, no pressure will be applied, wastegate won't open, boost will go up, damage will be done

With an external wastegate, you can define spring force defining the inlet mfd pressure (or boost pressure if you will) that opens the valve. Apart from that, they feature an input against spring force as well as an input going with the spring force. The pressure of the inlet after the throttle is to go with the spring force and the output of the BCV is to go against the spring force (higher pressure from BCV prevents valve from opening).
This provides for a fail safe system: if the BCV hose pops off, all that happens is that the valve will open at the boost level defined by the spring pressure.
Also, this provides for an advanced way of regulating boost pressure, both on- as well as off-throttle.

Howsie · 19th April 2003, 07:47 AM

Thanks Somberg!

So in conclusion, its nothing but good news for a external wastegate, apart from the price.

Now where do the exhaust gases go? I have been told that they vent to atmosphere but I can imagine that is slightly illegal but must look/sound good.

Matt_S · 19th April 2003, 01:24 PM

Of the appilcation of EW ive seen, a "screamer pipe" is fitted - this vents to atmosphere like you say, but it vents just behind the front passenger wheel. As you come on boost and the wastegate starts to bleed the unwanted exhaust gases off, the noise is incredible!

hipogtr · 20th April 2003, 02:18 AM

Quote:

Originally posted by Matt_S
...., the noise is incredible!

I can vouch for that in a big way - with two of those suckers in sync!

Cya O!

18th April 2003, 10:26 AM	#1 (permalink)
Howsie GTR Register Member Join Date: Feb 2002 Location: Surrey Posts: 6,987	External wastegate When does it become necessary to fit an external waste gate and are what would be the reason not to fit one?

18th April 2003, 09:55 PM	#4 (permalink)
somberg GTR Register Member Join Date: Jun 2001 Location: Close to Ringland. Posts: 2,044	There's another consideration: for a turbo with internal wastegate to lower boost, pressure needs to be applied to the actuator. What happens when a control hose has popped off ? Right, no pressure will be applied, wastegate won't open, boost will go up, damage will be done With an external wastegate, you can define spring force defining the inlet mfd pressure (or boost pressure if you will) that opens the valve. Apart from that, they feature an input against spring force as well as an input going with the spring force. The pressure of the inlet after the throttle is to go with the spring force and the output of the BCV is to go against the spring force (higher pressure from BCV prevents valve from opening). This provides for a fail safe system: if the BCV hose pops off, all that happens is that the valve will open at the boost level defined by the spring pressure. Also, this provides for an advanced way of regulating boost pressure, both on- as well as off-throttle. Last edited by somberg; 18th April 2003 at 09:57 PM.

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18th April 2003, 12:54 PM	#2 (permalink)
hipogtr GTROC Member Join Date: Feb 2002 Location: Land of the Rising Sun Posts: 1,982	Generally, you swap to external wastegates when you can no longer control boost well - this happens in high boost applications as the internal wategae springs get forced open by the exhaust backpressure in the turbine housing. If you run greater than 1.4 bar boost regularly you may want to consider the external setup (unless you have a cracker internal wategate spring pressure). The reason not to fit one would be costs (i.e. they are more expensive) or simply your internal setup controls boost well. Ultimately, the turbo size tends to dictate the need for an external setup or not. Cya O!

18th April 2003, 06:48 PM	#3 (permalink)
Howsie GTR Register Member Join Date: Feb 2002 Location: Surrey Posts: 6,987	Very helpful. Thanks!

19th April 2003, 07:47 AM	#5 (permalink)
Howsie GTR Register Member Join Date: Feb 2002 Location: Surrey Posts: 6,987	Thanks Somberg! So in conclusion, its nothing but good news for a external wastegate, apart from the price. Now where do the exhaust gases go? I have been told that they vent to atmosphere but I can imagine that is slightly illegal but must look/sound good.

19th April 2003, 01:24 PM	#6 (permalink)
Matt_S GTR Register Member Join Date: Apr 2002 Location: Essex of course Posts: 553	Of the appilcation of EW ive seen, a "screamer pipe" is fitted - this vents to atmosphere like you say, but it vents just behind the front passenger wheel. As you come on boost and the wastegate starts to bleed the unwanted exhaust gases off, the noise is incredible!