Just browsing the tial site... Do wastegates have a power limit? How do you decide what size gate to use? Does it go by how much boost you are building? or how much power? or what? Will a 35mm be to small for big boost/power?

 

no, you can not rate a wastegate by hp

 

Ok... so obviously your from tial... How do i properly choose a wastegate?

 

The theory is that a larger wastegate (44 mm) should be utilized on turbos using low boost vs. turbos that are running high boost which should run a smaller wastegate (38 mm). Where did this theory come from? Remember…a wastegate limits boost. If you want to run more boost, you don’t have to limit it as much. Running less boost means you have to limit it more. Think this premise through to get a good mental picture of it as this concept is terribly misunderstood.

If you are going to be in the low teens for boost than a 38mm should be fine. Any more than that than you should get a 44mm. If your WG is not big enough then boost creep and spiking can start. Thsi is because the smaller WG can't expel the excess manifold pressure created.

 

So say 700ish horse out of 2.0L with a gt42.... should be a 44mm?

 

i use twin 38mm wastegates on my gt4294 and holds low boost(20 psi) rock solid.

 

The larger the turbine, ex. housing, or exhaust, or freer-flowing the manifold, the larger the WG needed to run lower boost. More HP = faster turbo speed = less gas dumped through the WG.

Below 10psi many typical b-series will have slight boost creep (raises near redline) issues with a 35mm WG, some with a 38mm, and almost none with a 44mm.


btw 20psi isn't low boost, it's just YOUR low-boost setting.

 

700ish HP. I would go with dual 38s like another member has or a 60mm. I only mentioned 38 and 44 because they are the most common.

 

I guess thats a thought to since i do have one 38 already.... cool guys, thanks for explaining the theory to me.. i guess i shouldve known because now it just seems like common knowledge to me!

 

depending on the manifold design and turbo choice will also change the wg size your going to need. some people are having hard time controlling low boost when there running the gt35r turbo with up to 44mm wastegate on a ramhorn style manifold. now a very similar turbo is the sc6152s and its not as bad because of a different turbine wheel and not being ball bearing. I personally am running a 38mm wg and it controlls low boost 9 psi just as easy as 20 psi. on a cast spa top mount and a big turbine wheel with .82 hotside

 

mmmm. Close. If the turbo OVERALL is larger, (turbine, compressor, etc) greater than a midframe-sized turbocharger (for example.GT35R size + in size) and is using the lower boost settings more often than not, then the larger wastegate should be used to expell the large amount of turbine exhaust gasses since those gases are not being utilized as boost. This is where the 44mm and larger, or twin gates need to come into play; it needs more expulsion of gasses to control the amount of boost used. If it is a higher boost application where the larger turbocharger is within its efficiency range, you can use the smaller gate because you're not expelling much exhaust gas. If it is a mid-framed sized turbocharger running decent amount of boost over 14psi or higher, a 44mm or even a 38mm would work just fine. The creep issue really comes in more based upon the PLACEMENT of the wastegate flange relative to the manifold in addition to the size of that gate used.

the trick has always been for the street/strip guys. Those that want lower boost for "street use", then "occasionally take it to the drag strip" when they want to run higher boost levels. Depending upon the use of the car and the power level (from the turbo choice used) is where the correct gate can be used. Many people here go by the Larger gates because of this dual duty of the turbo.

 

high boost doesnt always mean the need for a big gate. you could run 40 lbs on a 42r and still have a 38mm gate regulate it well.