When is 2 wastegates required

[nanokpsi]

I do agree with the statement about bigger turbos needing smaller wastegates though.

The more boost you run, the smaller wastegate you need. Which needs a bigger wastegate to run 15psi, a 16g or a gt47r?

 

[SpoolN]

If you have a devided turbined inlet you SHOULD run a dual wastegate setup. How will you controll boost on the side that will allow exhaust gas to still pass over the turbine wheel and continue to spin it? Unless your wastegate is on the turbine housing itself or on the downpipe you might boostcreep. I do agree with the statement about bigger turbos needing smaller wastegates though.

We are going to have one with the turbo we are running. It will be divided that is why I was asking. So I take it we should run 2 if we are going to have the wastegate on the manifold.

 

[jo1]

The HKS cast T4 manifold is a divided outlet and has a single wastegate port, plenty of people have run just fine with it.

the wastegate single port is tap from both of the divided runner.

 

[Slow99x]

In theory this might work but there are makers of tubular exhaust manifolds that are already made for two wastegates like Shearer.

 

[Kevin Jewer]

just to note. big trucks like mack and motors in othere stuff with cat power, some of it dont even have wg's, the turbo slows down quickanuff they just dont need it. yet they are not pushing 25psi and are not reving 9000rpm, but they have piston big as coffie can's and push alot of air to the turbo at 4500rpm. its just when you let off the gas there less air to the turbo,
so the turbo slows down. thats why you dont need a big or dual wg'S.

Diesels are completely different and no comparison to them should be made in this thread, IMO. Diesels run massive turbine sides and use fuel flow to control boost. Many diesels do run WGs too, but they are often used more as an overboost safety device than anything else. They don't run BOVs that they can design to open early, etc (no throttle plates on diesels).

 

[94Jettameowpsst]

The more boost you run, the smaller wastegate you need. Which needs a bigger wastegate to run 15psi, a 16g or a gt47r?

Like i said earlier you really need one large or 2 normal sized wgs to run lower boost on a larger turbo. You need a large wg on the 47 because it will creep like hell if its not a sufficient size.

This was just taken from another post

I ran just such a setup, venting the collector of a SFP manifold. Venting only the number one runner or at the O2 housing, you may get more creep though. It's always important to state not only the size of the gate, but where you intend to mount it, since that makes a big difference in your minimum boost.

 

[Shearer]

Wastegate selection can depend on a variety of things; manifold design, turbo selection, precision of boost control needed, fitment, etc, etc, etc... To simply say that runing dual gates or a large single is stupid, not needed, or unneccesary is completely wrong. It may not be right for your set-up but there are plenty of other set-ups out there that can prove otherwise.

I prefer to twin gates on divided manifolds to keep the paired cylinders truely divided and to avoid any possible crosstalk that may happen between the cylinder pairs when running a single gate. We have seen some bad results from running a single gate with a divided turbine housing on a different motor. Sometimes theories and all the hard data in the world goes right out the window if you can't package everything within the envelope you have to work with, sometimes comprises do have to be made.

Two simple reasons why you don't need a big wastegate
1. You run a lot of boost all of the time.
2. Precise boost control isn't needed.
3. You aren't running a big enough turbo or aren't making enough power(see number 2).

The only negative(if you can even call it that) to running two gates, or a very large single, is the larger diaphragm area being used requires extra spring pressure to run high boost.

 

[punishment]

Well said, there are a bunch of contributing factors to wastegate size and placement. The amount of theory available on the subject is mind numbing.

If your really looking for more info on the subject it's out there, you just have to put in the time to find it

Tim

 

[4g63telantra]

Im running a divided inlet turbo with 2 wastegates on my setup.


http://dsmtuners.com/forums/showthread.php?t=248651