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external dump on manifold or o2 housing??

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1992awdlaser

15+ Year Contributor
3,051
26
Dec 5, 2004
Wallace, North_Carolina
In order to do an external dump off the manifold you need an external wastegate. Are you going to be using an external gate?
 

CTP

15+ Year Contributor
179
0
Feb 11, 2008
Southington, Connecticut
Both suck, but off the O2 housing sucks less. Anything is better than wastegating off one runner.
 

VETTE_50_TH

Banned Member
3,734
22
Jun 24, 2004
Columbus, Ohio
CTP is just a negative person, read any of his posts. I personally dump off the manifold and have no problems at all. The boost doesnt pull all the way to what its set to, its gradual about 2 psi before what its set, but that is what wastegates are suppose to do.

YouTube - Wastegate Spring Rate and Spring Pre-Load Explained

I have never leaked, creeped or anything, its set to 10 psi, with my evo III, car pulls hard and never goes over 10 or under.

James :laser::talon:
 

brute

15+ Year Contributor
1,551
41
Jun 29, 2005
Rio Rancho, New_Mexico
The key is to place it before the turbine wheel where the most volume is. That generally is the collector of the manifold or the turbine housing. So as long as the wastegate draws from one of these places, you should be golden. If you look at Forced Performance's custom turbine housings, they have an excellent wastegate location.

There are a few things to look out for, depending which route you take.

Manifold-mounted
Make sure the wastegate is placed on the collector at the end of the runners. You generally want it close enough to the flange for the largest exhaust volume, while still allowing a strong weld. Here's a DN Performance manifold that exhibits premium placement:

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^ This is actually for a split turbine housing, but the main idea is still clear: placement on the collector.
Here's another good example of excellent placement:

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O2 housing-mounted
Because this is where the stock internal is placed, the wastegate passage is your choke point. Essentially the hole needs to be large enough to evacuate the gasses efficiently but not detract from the structural integrity of the housing. So maybe think about having the hole ported before you put everything together. It's always better to do everything you can while it's apart (like a preemptive strike to avoid future headaches).

Here's what to avoid
Manifolds like the Turbonetics cast one that has the wastegate mounted on one runner. What happens (at least theoretically) when the wastegate opens is exhaust gasses in the collector will actually reverse flow and head "upstream" to exit the manifold. This is bad.

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Dumping to the atmosphere or recirculating is your choice, but if you dump, make sure you use an adequate dump tube. Get those exhaust gasses out of the engine bay and under the car. And make sure it's not pointing at anything. Good luck and let us know what you decide!
 

1992awdlaser

15+ Year Contributor
3,051
26
Dec 5, 2004
Wallace, North_Carolina
I have mine off the manifold with an sbr cast manifold. This is with a 50 trim. I don't have any problems at all with it. I personally will never use an external gate off the o2 housing.
 
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