wastegate??

What exactly does a wastegate do?? and is an aftermarket one really necessary?

A wastegate regulates boost pressure. It opens and closes to make sure you get the exact amount of boost you want into the manifold.

You need a new wastegate if your old one is bad.

Aftermarket wastegates are needed for externally gated turbos (which ours isn't.)

so do our cars come with them?

Our cars have internal wastgates that are built into the turbo. The wastegate pretty much opens up when it senses a certain level of boost. It opens up at that boost level so that exhast energy can bypass the turbo and limit booost. With out it you would overboost untill somthing broke.

Quan L

To add, usually internal wastegate (WG) are operated by an actuator and rod, and an external WG is operated by a spring.

Here's a decent read that shows pictures to help you understand:
http://en.wikipedia.org/wiki/Wastegate

Bryan

i dont see the difference between a wastegate and a bpv or bov.....

Exhaust gas that exits the exhuast manifold have two paths they can go. Usually they flow into the turbo fins and spool the turbo, once a certain psi of boost is achieved, the wastgate opens and the exhaust gas has another exit to flow thru. Since the exhaust gas bypass the turbo when it goes thru the wastgate, the turbo doesn't make as much boost. A wastgate function is to regulate boost by manaing the amount of exhuast gas flowing thru the turbo. A bov/bpv has nothing to do with exhaust gasses.

Add to above,
In order for the turbo to function properly, it needs a wastegate (regulate and limit boost).
If it does not function properly, you will overboost or not boosting at all.
BOV/BPV is just an add on component to prolong life of a turbo.

oooo ok now i get it (sorda). thanks for clearing it up

I might as well add in a little while im here
So like everyone else has said the wastegate is to regulate the boost that the turbo can produce through redirecting exhaust gases.
A bov on the other hand vents charged intake air. Once the turbo sucks in the air, it gets compressed and forced into the motor. When you back off from the throttle theres a "butterfly" in the throttle body that shuts restricting air to go in. Now you still have all this pressuried air trying to get into the motor but since the throttle is closed its got nowhere to go expect where it came from... the turbo. This cause that flutter noise that you hear when you back off from boost. This "flutter" can shorten the life of the turbo because of the volient change in air direction, and on a performance side of things can create unwanted lag, since the air almost stalls the turbine or slows it down alot and then you have to re-spool it in the next gear. With a bov in place it vents that air away from the turbo thus saving the air rushing back through the turbo. No more lag, no more turbo worries