Im slowly buying parts for my turbo/swap project, and im now looking into wastegate's. My question is how do you know what size wastegate you need?

 

The size of the wastegate depends on how much boost you plan on running. The lower the boost, the larger the wastegate needs to be.

 

That's not entirely true.

For example, on 12 psi the 38mm Tial on my Talon would hold it steady all the way through. At 20 psi it would creep up to 22 or 23 psi.

The more boost you're running, the more exhaust you're making, and the more area you need to get it all out. Sometimes that surpasses the need to vent the higher ratio of wasted exhaust gas to used exhaust gas when you're running lower boost.


The easy way to tell what you may need is to compare with people who have setups that work. It depends on quite a bit of factors like displacement, boost pressure, header/exhaust setup, and projected power output for the particular boost level.

 

That's a good point too. And like you said, different setups will require different sized wastegates. Basically, you can't go wrong with a large wastegate. It will control low boost settings and not allow boost creep when you're making a lot of exhaust. I have a 46mm w/g and it does a good job keeping the boost at 10psi.

 

ok thanks for all your replys

 

The more boost/power you’re making the bigger it needs to be. The larger the turbine section is the smaller you can get away with. That is why you get boost creep when you turn boost up (well, at least until you get to the point that you’re moving more air than the turbo can efficiently)

Nutshell, it depends on your combination. I know someone that is running a >80mm turbo with a T08 frame and has adequate control with a single deltagate (38mm), but that is because he has a huge turbine side on it, I’ve also seen much smaller setups need MUCH bigger wastegates to control boost without boost creep…

FWIW, the larger the turbine side and the smaller the wastegate the more efficient the setup will be/the more power it will make till you get to the point that it won’t spool adequately.

 

I was thinking about getting a turbonetics racegate(45mm), butnow I don't know. Would that be a good choice?

turbo:
GT45
a/r 1.05(exducer)
a/r 0.66(compressor)
outlet 4.25/109mm(hot) 3.38/86mm(cold)
inlet 2.71x3.24/70.1mmx82.55mm(hot) 4.25/109mm(cold)
compressor major diameter 98mm

motor: (what I plan to run)
LS1 8.5:1
stock crank
forged rods
forged pistons
02+ z06 cam
patriot stage III LQ9 heads
stock intake(may be replaced with a fast 90mm)