Internal and external wastegates

[vti-2]

1. What is an internal wastegate and how does it work?

From my knowledge, an internal wastegate is built into a turbo that is used for low boost applications and helps vent exhaust gases directly into the exhaust system. Am i right?

2. What exactly is an external wastegate?
3. How does it work?
4. Are there different types (i.e. sizes)?

Here's my understanding.

An external wastegate allows a higher exhaust flow than an internal wastegate, and basically eliminates uncontrolled boost (boost creep). It sits on the exhaust side and can either vent exhaust gases into the atmosphere (which is illegal) or can be plumbed into a downpipe. External wastegates are used for high boost applications.

That brings me to the next question.

5. What is a downpipe?
6. Is it the same as a screamer pipe?


Educated replies are what i'm looking for. Thanks in advance.

[Coolies]

5. downpipes increase torque by increase the flow of compressed exhaust gas from the engine...it increases torque from low to high revs...to get the best outta ur turbo performance.

[poid]

The downpipe/dump pipe is the pipe from the turbo exhaust outlet to the exhaust front pipe (basically the pipe that vents gases from the turbo into the exhaust), a screamer pipe is a pipe from the wastegate outlet that vents into the atmosphere.

Yeh an internal wastegate is built into the turbo's exhaust housing and uses an actuator to open the gate at whatever the actuator's boost level is (a vacuum hose is connected to the throttle body). The gases from the internal wastegate vent out next to the turbo outlet, so goes into the downpipe.

You're right about the external gates. Internals are usually used on smaller turbos and for lower boost applications. Externals gates generally dont creep as much as an internal gate could, and are useful for higher boost applications.

The way it works is basically this. It is mounted on the exhaust manifold, preferably in a spot where it can get gases from all of the cylinders' exhaust ports. It uses an internal spring and is connected by vacuum line to the throttle body, so when the boost exceed the spring rating the gate opens and vents exhaust gases so the turbo cant spool up any higher.

There are various sizes. For example Tial make 38mm, 40mm and 44mm gates from memory. The bigger ones are required for either larger engines or higher boost applications. You can also specify what spring you want (ie what the maximum boost level is).

[poweredbyhonda]

You don't nessecarily need one for big boost. I got one and at the moment on under 5psi. Only reason why I got this is because the turbo I bought needed an external. I'll be running about 10 psi once I get it dynoed. Turbosmart make a 45mm one which is the one I am using.

[poid]

no didnt mean to suggest you needed big boost to run one, but to suggest that if you were going to run one as opposed to an internal that would be one reason :)

Most T3/T4's and larger turbos need external , thats true

[CHU85]

if u want a big turbo with an internal gate have a look at the t37's. Able to support 770hp and spools up real well.
Thats wat i'm getting next!!! with about 20psi!!!!

[A'PEXi]

the wastegate is used to release the extra exhaust gases which are not required in the turbo to maintain boost levels....the extra gasses which are not used are directed away from the turbo

internal wastegates are used for basic, low boost applications

external wastegates are used for the opposite, ie. aftermarket turbos, high boost.

[fueltank]

screamer pipe is when the wastegate opens and vents direct to atmosphere, bypassing the exhaust system.

they are illegal but sound really mean.