External wastegates

[TLicense]

How'd they work?

A decent cut-away sketch would be nice.

[Wez]

Hey Tony,

Here is a diagram of a typical external wastegate. Inside the wastegate is a diaphragm which creates a seal, and a spring which holds the wastegate closed. Spring rates vary depending on the amount of boost you want to run, typically they are given in a "bar" value for example 1 bar would be 14.7psi. This would mean that in order to open the wastegate you would need to excerpt a greater pressure than the 14.7psi spring holding the wastegate closed. In order for the wastegate to work you must have the compressor reference port hooked up to the compressor side of the turbo, if you don't have this vacuum line attached than the boost pressure will not be limited to the set spring pressure; it will build unlimited boost pressure until your engine is destroyed.

Normally pressure from a spooling turbo pushes against the diaphragm (though the vacuum line attached to the compressor reference port) which in turn pushes against the wastegate spring. When the pressure from the spooling turbo exceeds the spring pressure the wastegate's plunger opens releasing the excess pressure through the dump tube into the exhaust after the turbo or to open atmosphere. Typically, if you use the wastegate to control your boost levels you will experience a decrease in power and spool times. Why? Although the spring fully opens at its set spring pressure it tends to begin opening before reaching the set spring pressure. This "pre-opening" leaks boost pressure through the dump tube before max boost pressure is reached resulting in a decrease in power mostly toward the top end. This can be corrected by using a boost controller.

:thumbs:

[fisherjohn]

Hey Wez,

I am down in Angola as you know.
I have an HKS 60mm External wastegate fitted to my PHR
stage 2 turbo.
Are you controlling your boost with the AEM. If so does it work ok.

I have 2 connections from my wastegate, i assume as per your drawing the inner one ie closer to the coupling connects to the compressor side of the turbo and the other connection at the extreme end is used to feed into either an independant boost controller or for pressure read off to the AEM / Boost gauge.

My reason for asking is due to no fitting instructions with my kit at all, cannot download from PHR website and although i have an HKS EVC 5 controller fitted i would like to control mine with the AEM.
I intend leaving the boost controller fitted as it is a part of the glove compartment hks pod arrangement at the moment and do not want to rip it out and spoil the look of the interior

[Wez]

Hello John,

I am currently running wastegate spring pressure and do not have any electronic control, need to connect up the solenoid.

But I will be using the AEM for boost control and did use it to control the stock twins and it worked fine, i cannot see any issues using the aem for boost control, you have the option to wire up and boost target switch and you can also setup speed and gear dependant boost targets.

:thumbs:

[TLicense]

Cheers for that Wez. Very basic really. I'm just trying to work out which component contributes most to the $750 price tag. I thought for the kinda money they sell for there was something a little more trick to them than being a fancy dump valve for the exhaust. Obiosuly the diaphragm is made out of unobtanium or something.

Cheers

Tony

[Dragonball]

Originally posted by TLicense
I'm just trying to work out which component contributes most to the $750 price tag.

Tony

The name m8 - the name...

:p

[TLicense]

If that's the case paul, there's an opening in the market for you here mate! You could undercut them massively.

Doesn't bother me really. I've not got a single turbo, and if the missus has her way I never will. :mad:

[MONKEYmark]

this might be of use. found it on my travels

http://img.photobucket.com/albums/v163/MONKEYmark/external20waste20gate.jpg