Can Anyone Explain This To Me? (External WG off O2)

[Shane2GSX]

I've been searching pretty much all day trying to understand how external wastegates work with the turbo/exhaust (whether on manifold or O2 housing). From what I understand of how an external wg works off of the manifold, is that in the wg there is a compressor reference port and boost controller port. Inside the wg there is a spring with a diaphram on the bottom, connected to a plunger on the bottom of the diaphram where the wg sits in the manifold. The compressor reference port is typically on the side and leads to underneath the diaphram. The boost controller port is on the top, above the spring and diaphram. Once pressure coming from the compressor port exceeds the spring strength and pressure from the boost controller port, the plunger lifts allowing exhaust to pass out of the wastegate dump tube (whether being vented or rerouted). This all makes sense to me on the manifold. But I don't see how this could possibly work on the O2 housing, since the exhaust has already gone through the turbocharger and removing exhaust trhough the wg at this poing should have no effect. If anyone can clear this up, I'd appreciate it.

Thanks in advance.

 

[fourreGsixty3]

Wow...now that you mention it, Im confussed on this...http://www.slowboyracing.com/more.php?id=1355&, like the WG is after the turbo...this confusses me, but the dnp 4G63 mani makes sence to me>>>http://www.slowboyracing.com/shop.php?sid=&cat=590, I believe its the 3rd one down...its the 2nd to last one. Like the WG should be before the turbo, with SBRs it looks as though the WG is after the tubo so wouldnt that defeat the purpose of having a MBC and WG? I would be interested for someone to shed some light upon this.
EDIT**Ok I think I figured it out, but not sure so if Im wrong dont kill me over it...just hoping to shed somelight on your/my problem, and to see if this makes any sence to others besides me. On the sbr link I posted easrlier, if the pressure gets to a certain point with in the turbo housing it opens the WG to let the excess pressure out through the dump tube, and keep the turbo from boosting overa certain point...just something I was thinking at the moment...could be right, but Im not sure, not a guru on WGs.

 

[evolveddsm]

I am not able to access the web pages to see exactly what you are talking about.
So I will try my best to explain what I think you are asking.
The external wastegate sits on the exhaust manifold (tubular or cast, doesnt matter)
Just like you said Shane, when the exhaust pressure exceeds the predetermined point (I.E. your target boost pressure) The pressure of the exhaust gasses exceeds the spring strength and boost pressure holding it closed. Wastegate then open's. The exhaust gasses are then routed to either the O2 houseing / DP. Or open air.
Since I cant see the web pages (work internet sucks) I will assume they are showing DP or O2 housing that is setup for the wastegate vent. side to bolt directly to them.

Hope this helps
B

 

[Shane2GSX]

EDIT**Ok I think I figured it out, but not sure so if Im wrong dont kill me over it...just hoping to shed somelight on your/my problem, and to see if this makes any sence to others besides me. On the sbr link I posted easrlier, if the pressure gets to a certain point with in the turbo housing it opens the WG to let the excess pressure out through the dump tube, and keep the turbo from boosting overa certain point...just something I was thinking at the moment...could be right, but Im not sure, not a guru on WGs.

That does make some sense to me after thinking about it. I could see it as very possible that relieving back pressure could stop the turbo from spooling any more.

However, in contrast, I've read many times that relieving backpressure is what makes a turbo spool faster. So this seems to contradict that fact.

But your theory does support the fact that SBR doesn't offer an WG O2 housing that recirculates back into the exhaust which would have no effect b/c you wouldn't be altering the pressure. But they do have a recirculated one that is internally gated, in which case would work b/c it's relieving pressure at the turbo and not after and thus bypassing it, and it doesn't matter if you rerout it or not.

If anyone can shed some light on this subject it would help both fourreGsixty3 and me. Thanks.

 

[Shane2GSX]

Come on, someone must know the answer to this...

 

[underradar92]

The way you are phrasing this question is a bit hard to understand but I'll try to help clear this up. The wg in the "02" is actually positioned just ahead of the exhaust turbine. When the actuator opens the "flapper" or trap door, it makes a short trip around the turbo & back into the exhaust and into the downpipe. Howz that? The SBR setup in question deletes the stock wg and dumps into the air, or a creative chap could recirculate it further down.

 

[GVR4592]

Take a look at your stock 02 housing. You can see there are two passages. One is the turbine outlet, the other is the wastegate outlet. Now imagine you remove the stock wastegate flapper on the wastegate passage and you have an unrestricted passageway from the turbine wheel to the exhaust that would not allow you to build any boost. Now put an external wastegate at the outlet of that passage and you have an O2 mounted external wastegate which allows you to build and control boost. Make sense?

 

[Shane2GSX]

Thank you guys very much!! I understand now. I didn't realize it was right at the turbine housing.

If anyone knows where I can get a diagram or pictures I'd appreciate that as well.

Thanks again.

 

[fourreGsixty3]

Oh ok, I didnt know it was ahead of the turbine housing either, that makes much more sence. Thanks everyone...even though it isnt my thread haha.