Why No External Waste Gates?

[Begle1]

Why don't you see many? What are the disadvantages?

They're extra money, and they're extra fabrication, but what else?

There's plenty on eBay from $200 to under $100, why not use one in conjunction with a 12 cm w/g housing or even an HY-35?

[seeker1056]

I use one of each, external on the 35 and internal on the 55

[Begle1]

What kind of external wastegate are you running?

Are you using the 35's internal along with the external?

When you see all these externals for sale, they have from "6 pound springs" to "12 pound springs"; what does that mean?

Do you have pictures of your set-up?

[seeker1056]

my 35 does not have an internal wastegate anymore.

The external wastegate has a spring inside that works against the diaphram tha topens/closes the wastegate

You run a boost line to each side of the wastegate, witthe oen on the spring side being adjustable in some fashion.

By varying the boost the spring side sees, adjusts the wastegate

I have pix, but not that will let u see the actual wastegate, as it is down and behind the lower turbo.

[Begle1]

So when a wastegate has a 12 pound spring, it does open at 12 PSI... You need to put an adjustable regulator before the wastegate, and set the regulator where you want it.

You have the regulator open at, say, 30 PSI; the 12 PSI spring in the wastegate sees no pressure until the regulator opens, and then it sees 30 PSI instantly.

What sort of regulator does that?

[90firstgen]

Any kind of manual boost controller works in that way.

External gates make for a much better boost control. It's not as important for us because we don't have to worry about detonation/knocking from getting too much air. Pretty much all modified gassers use ext gates because of that. If they stayed with a factory internal w/g, boost pressures would still climb even when the w/g is open. The external gates have a much bigger surface area to bypass exhaust gas. Make sense? I'm not very good at explaining things through typing sometimes.

[Begle1]

So an HY-35/ external waste gate combo would be killer on spool up, and the double waste-gate action would be sufficient to vent 600 horsepower?

[KTA]

It should spool quick but no hy or hx35 is going to make 600hp #2 only.

[Begle1]

Not make it alone, but if I had a HY-35 on top with the internal wastegate going and one of these 1.5 inch externals, how much could that exhaust before excessive pressures?

[seeker1056]

An external does not work in that fashion at all.

the regulated boost on the spring side is added to the force of the spring, and the two together is workin against boost pressure on the other side of the diaphram.

So lets say you can make 50 psi, and want the waste gate to open so you only have 40 psi.

The regulator is adjusted so that boost through the regulator is at around 28 psi and combined with the spring pressure of 12 lbs then overrides the boost pressure on the other side and allows the gate to open no matter what the boost on the other side is doing.

The only reason to continue to use the internal wastegate would be if you put too small of an external wastegate on and needed the extra flow bypass.

Given you can get external wastegates up to 50 mm for like $50 on Ebay theres no reason to use both.