pros and cons of venting the wastegate to the atmosphere

[bahnstormer]

just wanted to get some feedback from you guys on
venting the wastegate straight out rahter than back
into the exhaust....

pros = loud, shoots fire?, theoretically better flow
cons = loud, shoots fire?, more piping, pollutes atmosphere?, illegal?

as u can see i don't know much on this topic,
sooo, what do u say?

[T_C_D]

Jeremy,

He is talking about the wastegate going to atmosphere not the BOV. The eastegate is much louder.

Todd

[chrism]

keep in mind the only thing the wastegate does is vent excess exhaust backpressure, to reduce/regulate boost. i would imagine the only practical reason you would ever want to do it (other than it making some sort of different sound under boost when the wastgate is open) is maybe if you were to have some sort of boost spike from a restriction in the wastegate downpipe. unlikely it would be worth the effort.

[RDAvena]

ferrari did it on the F40,


the center pipe vents the wastegate straight to atmosphere.


[Edit by RDAvena on [TIME]1131598683[/TIME]]

[Skeen]

Lots of drag cars do it that way.

[Monotalonawd]

Pros:
-It would be easier to fabricate the piping (if external wastegate). Just run a tube under the car.
-Better exhaust flow if one is limited with a small diameter exhaust system.
-Meaner sound! (depends on personal taste)

Cons:
-More pollution if you have a cat (but most ditch them when they can!)
-Louder! if you're concerned with noise.

Personally, I would keep it flowing through the exhaust system 'cause I want my 535i to stay a sleeper. Just get a 3" exhaust and be done with it. A 2.5" exhaust is enough to support 400whp so...

[bahnstormer]

i see i see good info everyone
on another forum a bloke posted that they gained 20hp
from venting it right to tthe atmosphere...but i think that
car is making silly power, more than i will be at least

[gol10dr1]

that 'bloke" made 543 rwhp on that tune after madifying the wastegate dump pie and is now making 635 rwhp and is also able to build about 1 psi boost when revving the car which is neat b/c you techincally should not be able to build boost while not under load. the higher the boost, the more power will be made from venting to atmosphere. it is just one less restriction in the exhaust flow. and are you australian now???? "bloke?"


[Edit by gol10dr1 on [TIME]1131649151[/TIME]]

[bahnstormer]

hey m8 =] thanks for that info =]

[Monotalonawd]

[QUOTE="gol10dr1"] is also able to build about 1 psi boost when revving the car which is neat b/c you techincally should not be able to build boost while not under load
[Edit by gol10dr1 on [TIME]1131649151[/TIME]][/QUOTE]

... unless you have a small enough turbine housing. With my old car (stock turbo) I could just floor it from idle in neutral and by 6000 rpm, got 17 psi of boost! That made for some interesting all-wheel-drive launches! Or if I "pumped" the gas pedal around the 5500 rpm area, I could sustain more than 10 psi for as long as I wanted.

I suspect the restrictive exhaust housing was artificially causing more load on the engine since it had to work against exhaust pressure building up in the manifold, thus creating boost in neutral.

Generally, with bigger turbos you size the turbine exhaust housing larger, for more flow, so that is less likely to happen.

Andrew, I assume you can't build boost just by revving. Iirc, you have a 60-1. What is the A/R of your turbine housing?

[gol10dr1]

i have a .81 a/r and i can not build any boost what so ever unless under load. my buddy in question has a gt35r with the .82 housing and never could build any boost at neutral. he has a 3" exhaust all the way back but then he modified the wastegate dump pipe so it vents to the atmosphere and now he says he can build .5 psi to 1 psi in neutral. btw, he also made 635 rwhp on a turbo rated for 600 crank hp so this thing is a freak of nature Anyway!