Okay, to make fabrication as simple as possible, i wanted to go with a GT3076R with an internal wastegate. My builder told me it would be around a 20hp difference with the in/extrenal wastegate, and i would still be in my goal of around 400-450whp. What do you guys think? Is it really that big of a performance hit or is it worth it to spend the extra 150 to have a external wastegate fabricated (flanges/bends/pipe/welding is why it costs so much)

oh, and i heard that internal wastegates arent very effeicent for high boost too. is that true?


Modified by Mr.Hankey at 4:34 AM 9/17/2006


Modified by Mr.Hankey at 5:12 AM 9/17/2006

 

bump

 

yes internal wastegates don't care for high boost, go with a tial external

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tannerLSt &raquo;</TD></TR><TR><TD CLASS="quote">yes internal wastegates don't care for high boost, go with a tial external</TD></TR></TABLE>

um thats not totally true. my internal gated te32e was fine at 30 psi on my t type BUT, once the boost was up, and with an automatic tranny, you were always in the gas. so creep was never an issue either.

i can see the hp loss on the exhaust housing though. thats a valid point.

 

Ive seen first hand why external wastgates are better then internal. If an internal waste gate goes bad then it sticks closed and youll boost way more then you want to. But if a external wastegate goes out then youll have little to no boost at all.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MrPotatoeHead &raquo;</TD></TR><TR><TD CLASS="quote">Ive seen first hand why external wastgates are better then internal. If an internal waste gate goes bad then it sticks closed and youll boost way more then you want to. But if a external wastegate goes out then youll have little to no boost at all.</TD></TR></TABLE>

again not entirely true. you may have seen a failure there the spring had an issue.
if the diaphram rips on an external, there is nothing to push the valve open. the spring will hold the gate shut both ways.

it all comes down to application.
in a stick car I THINK and thats my oppinopn, an external gate will hold boost better on a bigger turbo at lower boost.

 

Are there any articles or anything i can read that has a direct comparison to internal/external wastegates? Im not saying anyones opinion is wrong, but i need some facts. I just dont want to get either or and end up with the wrong one.

 

the 3076 is a larger turbo, small engine. an external gate will help you alot more because an internal gate on a larger turbo will be a little prone to spike/creep because of the smaller port on the internal. if that makes sense. he hee.
go with a 38mm atleast and youll be fine. depending on what the manifold is flanged for.

 

For high boost (16+ psi), I'd go with external... Mos internal wastegate actuators are single chamber, so the boost acting on it only assists the opening of the flapper valve and not the closing it.

Once you reach high boost levels, exhaust pressure builds up and it tends to physically push the flapper open resulting in boost drop or boost falling off near redline. By placing a really stiff spring in the internal WG actuator, it could remain closed at redline, but boost would spike like a b*tch because the same pressure from the boost signal acting on the diaphragm (boost source from intake manifold, etc) doesn't open the flapper as quickly and briskly as before with the softer spring.

I wouldn't be too concern about actual power loss between internal and external wastegate. The engine picks up power from an external setup because 99% of the folks would run a dump tube. Without a dumptube (wastegate outlet plumbed back into downpipe), there is probably no difference between internal and external in terms of power.