When does the wastgate open?

[MitsGSX]

Now I know the theory behind waste-gates, why and how they work, but I was wondering, in practice how often are they open? The reason I'm asking Is because I'm thinking about running a dump tube but I don't want the extra noise in daily driving every time I get into a little boost, but i do want it when I open her up :]

Thanks

 

[93laserAWD]

the wastegate opens to divert exhaust gas away from the turbine wheel. Say the wastegate is set at 11 psi, when turbo spool hits 11 psi, the wastegate opens, diverting exhaust gas from the turbine wheel. it opens whenever you decide you wanna go fast.. ha

-ted

 

[kenamond]

Usually, the WG starts to open before you hit peak boost. When you're at full boost, the WGA is open, and the gas is split "just right" between the WG exit passage and the turbine such that the compressor delivers the desired boost.

When the WGA starts to move will depend on your boost controller (type and setting).

If I understand your concern, you shouldn't move the actuator arm at a boost pressure lower than the actuation pressure of the WGA. You can find this out by putting a pressure/vaccuum tester on the WGA and pump it up until it starts to move. Any boost level lower than that will not (can not) open the WGA. So for a stock T25 WGA on a 2g, the lowest boost you can run is around 9psi (no MBC, straight connection to the WGA nipple from the IM). If you don't boost beyond 9psi, you shouldn't hear any dumping (unless the flapper is leaking).

On the other hand, the backpressure just upwind of the turbine which is "knocking at the door" of the flapper may open the WGA a bit, but I have no idea how loud that'd be.

If anyone knows something I don't in this matter, chime in.

Hope this helps (and hope I'm right ).

 

[oldman]

What is the purpose for the O2 dump?

 

[FlatBlackAndy]

It helps prevent boost creep.

 

[oldSchool90]

how do you have a dump tube? i mean how do you set up one? do you have to have a certain wastegate or could it be stock? i have a stock turbo and wastegate, would i be able to have a dump tube? im sure i dont need one but i was just wondering when do you think you should get one?

 

[oldman]

It helps prevent boost creep.

Nothing but a myth. The biggest contributor to boost creep is the poorly designed mitsu turbine housing, not the flow capacity of the O2 housing therefore O2 dump is pointless when dealing with boost creep in most cases. There are generally two types of people who uses an internal O2 dump.

1. People who enjoys the annoying noise. (AKA rice boys )

2. People who were mis-lead into thinking it will cure boost creep which I suspect is the case here.

 

[oldman]

im sure i dont need one but i was just wondering when do you think you should get one?

What makes you think you'll ever need one?

 

[MitsGSX]

call me a ricer but I think it would just sound cool. Also wouldn't it help reduce back pressure at WOT? or would the improvement be negligible? As SBR puts it "its scares the girls away"

 

[MitsGSX]

Nope.
wouldn't a little backpressure help to hold the flapper shut? or it just getting too far past my bedtime...

 

[oldSchool90]

well if it doesnt eliminate boost creep then what does it do and why do so many people have dump tubes?

 

[MitsGSX]

whoops I'm embarrassed, that last one I was thinking backwards. Now im a Nobie, but my best guess would be:
1- It sounds cool
2- In a custom turbo set-up, people might not be able to reroute the exhaust off the wastegate back to the DP
3- People with internally gated turbos want to look (and sound) as cool as the lazy people from #2

 

[oldman]

Also wouldn't it help reduce back pressure at WOT?

If you have 3" exhaust, no. If you don't have 3" exhaust, then boost creep shouldn't be an issue. The power gain associated with an o2 dump comes from the tubular part of the turbine path, not the dump part, which can be achieved with an tubular O2 that re-routes. Trust me on this, the "cool sound" gets old really fast when you realized the only people you will impress are little high school kids and the cops, that includes yourself.

 

[MitsGSX]

If you have 3" exhaust, no. If you don't have 3" exhaust, then boost creep shouldn't be an issue. The power gain associated with an o2 dump comes from the tubular part of the turbine path, not the dump part, which can be achieved with an tubular O2 that re-routes. Trust me on this, the "cool sound" gets old really fast when you realized the only people you will impress are little high school kids and the cops, that includes yourself.

Point well taken, I think I'm going to get a EVO III o2 housing, and I'm going to get some sleep also. Thanks a million for the advice, this forum is awesome!

One last question, Is the EVO III pipe worth it or should I just port my stock 2G piece?

 

[MitsGSX]

Sorry I'm planning on running a big 16G and 3 inch DP

 

[garrett21]

I agree with oldman, but if you want to buy my hks standard wastegate that is mounted on top of a evo 3 manifold, let me know.

Oh I did scare a guy in a 5.0 when it opened and i pulled him. Great attention getter, oh and get a HKS SSQ bov!!!

 

[oldman]

1. A well ported 2G O2 housing will flow enough for near stock applications, using an EVOIII O2 housing will require fabrication of the DP since the housing exits at a slightly different angle.

2. To eliminate the possibility of boost creep, port your turbo like this before you install it.

 

[oldman]

I agree with oldman, but if you want to buy my hks standard wastegate that is mounted on top of a evo 3 manifold, let me know.

Oh I did scare a guy in a 5.0 when it opened and i pulled him. Great attention getter, oh and get a HKS SSQ bov!!!

garrett21, please keep private dealing/offerings in the PM. Back on topic, internal O2 dump doesn't sound the same as an external wastegate dump. While an internal dump is pretty much functionless, external wastegate does become a necessity at some point, right around when your internal flapper starts to blow open under higher boost applications. With that said, I would still prefer a re-routed external wategate so I can hear my turbo instead.