Evo 3 16G: External WG Vs. Internal W/ Open Dumps

[mb3000]

Just like the title states, curious as to what kind of typical hp difference there is between running with the flapper welded shut external wg vented to atmosphere vs. internally gated but with atmospheric dump as well.

 

[IrishBeatdown]

Just like the title states, curious as to what kind of typical hp difference there is between running with the flapper welded shut external wg vented to atmosphere vs. internally gated but with atmospheric dump as well.

None, and very big difference potentially at the same time. It's all about boost control and the amount of boost you run. External wastegate makes it easier to control. Internally gated without MBC tee is limited to the amount of boost the wastegate actuator is rated for. ex stock t25 is 11 psi actuated.

 

[WES_393]

Like Irish said, there are no direct horsepower gains. It's all about boost control. An internal gate will allow boost to fluctuate a little. An external gate off the manifold will maintain your set boost limit more steadily. However its more expensive and complicated, too much so for an Evo3 16g.

 

[gprix1]

The short answer... there is no HP difference really but spool can be affected slightly in some cases. External's generally control boost better but in most cases an internal can work very well with a little work.
The long answer...With the stock exhaust system there is enough of a restriction that an internally gated turbo has no problem controlling boost. However, once you install that 3" turbo back exhaust (removing the restriction), now the W/G is responsible for all the work of controlling boost and often times the internal W/G may not divert enough exhaust to keep boost under a certain amount. This can be a real problem if you are trying to keep boost at say 15psi but it is spiking (boost creep) to 18psi and you are running out of injector.
An external W/G eliminates boost creep by diverting more exhaust than a typical internal can. Another potential benefit is faster spool since a lightly sprung internal gate can sometimes start to crack open early. After hearing this you might think an external is a no-brainer but there are also good reasons to run internal and in most cases you can make an internal work very well greatly reducting or elimnating boost creep. Here's some things to consider:
* Keeping the internal gate functional generally makes a turbo easier to resell.
* Internal is more stealthy and takes up less room
* Internal is quiet and uses stock O2 housing so less cost
* External costs $$.. External W/G, Aftermarket O2 housing, welding internal shut.
* External is not stealthy and are loud (unless you use an external-type recirculating O2 housing)
There are a few ways you can improve an internal gate to work well.
Internally gated turbine housings usually have an abrupt transition to the W/G hole reducing it's effectiveness. You can improve this considerably by porting the turbo inlet and improving the curve of the inside radius to the W/G hole. Some people install a larger W/G flapper but this is not needed in most cases and can increase the potential of opening early due to the larger surface area. Also, if you are going to be consistantly running 17+ psi, than a stronger actuator is the way to go since it will hold the flapper down firmer preventing it from cracking open early. Something like the 18psi actuator FP sells: http://www.dsmtuners.com/forums/vendor-announcements/448851-stock-fitment-dsm-18psi-wga.html
or 22psi:http://shopping.kinugawaturbo.com/turboactuatordsm1gevo1-3vr-4td05h14b16g17psi-2.aspx
Here is a how-to for curing boost creep with porting: http://www.dsmtuners.com/forums/articles-turbo-system-intercooler/186525-how-cure-boost-creep-porting.html

 

[foxracing4500]

Like Irish said, there are no direct horsepower gains. It's all about boost control. An internal gate will allow boost to fluctuate a little. An external gate off the manifold will maintain your set boost limit more steadily. However its more expensive and complicated, too much so for an Evo3 16g.

not necessarily expensive and complicated. I bought the HAFE stock looking exhaust manifold for the same price of a Forced Performance manifold W/o the 38mm. But boost control with my tune had to be precise, so I guess if you use the stock wastegate try tuning with the spike?

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EDIT: just read the post above me, I still have my internal waste gate on my 16g, just no vacuum lines hooked up*

 

[gprix1]

EDIT: just read the post above me, I still have my internal waste gate on my 16g, just no vacuum lines hooked up*

I bet that gives you a good boost spike
What psi does it hold? I bet a heavier 18psi or 22psi actuator would work better for you since most likely your flapper is starting to crack open at ~8-10psi with the a stock one. FP has the 18psi actuators right now for just $50

 

[IrishBeatdown]

not necessarily expensive and complicated. I bought the HAFE stock looking exhaust manifold for the same price of a Forced Performance manifold W/o the 38mm. But boost control with my tune had to be precise, so I guess if you use the stock wastegate try tuning with the spike?

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EDIT: just read the post above me, I still have my internal waste gate on my 16g, just no vacuum lines hooked up*

Wait so you bought a hafe manifold with the provision for the 38, and then didn't use it/blocked it off? You are right, it sounds cheaper that way. Didn't even have to buy a tial for that one.

 

[foxracing4500]

Wait so you bought a hafe manifold with the provision for the 38, and then didn't use it/blocked it off? You are right, it sounds cheaper that way. Didn't even have to buy a tial for that one.

no I did use a Tial 38mm, but I got lazy and never disconnected my stock waste gate actuator. Only reason I responded to this thread is because I need a new diaphragm for my tial, last night my 16g spiked somewhere over 25psi, I wouldnt have known until I looked at my logs in evoscan. I just thought it felt faster last night because of the cold weather

 

[mb3000]

IIRC the decreased turbulence in the turbine housing from using an external WG vs. the internal has shown a couple additional hp. Just can't find the thread ATM.

 

[honda_burner]

I hogged out my wastegate flapper hole and filled the hole where the arm went through.

I got a punishment racing o2 housing (around 150 I think, for the mild steel one), and got a Tial 38mm used for 140. So about 300 total not including labor time to install.

Works great. Once the wastegate opens its all or nothing. Im breaking in my engine right now and havent tested boost over 10 psi but before the new turbo and rebuild, it ran like a champ and slammed the needle to full boost once it opened up.

 

[agentorange313]

Wait so you bought a hafe manifold with the provision for the 38, and then didn't use it/blocked it off? You are right, it sounds cheaper that way. Didn't even have to buy a tial for that one.

You should read the post you are quoting, he stated "w/o" which in common means "with out". He has the manifold without the provision, so he can run an internal wastegate. I have the same exactly setup, HAFE manfiold with internal MHI turbo. BTW HAFE manifold is a beast. SS cast and thick ass flanges, this manifold over an evo3 and arguably a FP manifold.

 

[IrishBeatdown]

You should read the post you are quoting, he stated "w/o" which in common means "with out". He has the manifold without the provision, so he can run an internal wastegate. I have the same exactly setup, HAFE manfiold with internal MHI turbo. BTW HAFE manifold is a beast. SS cast and thick ass flanges, this manifold over an evo3 and arguably a FP manifold.

Bleh, don't be ridiculous. Re-read the post again. He has an externally gated turbo off of his hafe manifold. Thanks for the advice though.

 

[agentorange313]

Bleh, don't be ridiculous. Re-read the post again. He has an externally gated turbo off of his hafe manifold. Thanks for the advice though.

I did, my mistake, "38mm" was ambiguous and thought he meant provision not wastgate.