Wastegate mod - screamer pipe

[Toms Supra]

Has any done this and how do you do it, apparently is helps. Open WG also reduces exhaust back pressure which gives a hp increase. And makes is sounds like a jet? How do you do it and is it a big job?

[Branners]

Its normally only done with an external wastegate on a single/twin setup. I have one on my car and it does make a lovely sound.

 

JB

[Guest a71ak]

I think it's the opposite ... when you allow more air to go through the waste gate you're loosing boost so loosing power ....

[JohnA]

Alternatively there is a T-piece you can get from the States, which Tees off with an actuator at certain boost pressure, bypassing the whole exhaust.

Interesting theory, only in practice the flap tends to expand and deform under operating temps, and when it doesn't rattle on idle it leaks and sounds quite antisocial. Needs more development.

[Gamer]

I think it's the opposite ... when you allow more air to go through the waste gate you're loosing boost so loosing power ....

 

I belive you are mistaken. The wastegate will open at what it is set to and the hot gasses coming from it are then vented into the atmosphere and not re-introduced into the exhaust piping. Most race applications use a screamer pipe...

 

The only reason they are ususally plumbed back in is the noise.

[JohnA]

You two guys are talking about slightly different things.

 

a71ak is talking about gasflow through the wastegate as the car is building up boost

 

gamer is talking about gasflow through the wastegate once the preset point is reached and the wastegate has opened

 

Yes, plumbing the wastegate gases into the main exhaust path is indeed done mainly for noise purposes. And yes, there is additional backpressure introduced at full boost as the wastegate gases mix with the outflow from the turbine.

However, plumbing them together at the correct angle and 2-3 feet away from the turbo gets rid of most of this extra 'drag'

 

If you've ever been in a car with a 'screamer' pipe, sheeeesh it's antisocial

[Gamer]

They don't call it a 'screamer' for nothing

 

Antisocial ? me ? never !

 

[Guest a71ak]

I do understand this very will ... I just said that because he said Open WG reduces exhaust back pressure which gives a hp increase and we know Open WG do the opposite isn't it?

[Chris Wilson]

The wastegate only opens when max boost is reached, where it vents doesn't make a lot of difference. As a power enhancing tool it's not worth considering. If you want to make a lot of noise and be ineligible for 99% of track days, it may be

 

To convert the stock sequential set up to external gate would be a total nightmare, maybe impossible.

[JohnA]

..where it vents doesn't make a lot of difference. ....

It does make a difference Chris

 

I've driven the exact same car with stock internal wastegate, and with a downpipe where the wastegate pipe was separated for a couple of feet (then merged with the main pipe)

It was much better under full boost.

I expected the improvement to be rather minor, but it wasn't.

 

Looks like the turbulence introduced by the wastegate gases does interrupt the flow off the turbine to a noticeable degree.

[Gaz Walker]

To convert the stock sequential set up to external gate would be a total nightmare, maybe impossible.

 

Dale/Boneyard's car has it done. It was done by the previous owner though.

 

Gaz.