Waste Gate On Standard Manifold Vs Waste Gate On Turbo

[Ben C34]

Why not split the difference guys?

Stop all the arguing

But seriously, why isnt this best of both worlds?

I've seen one in real life, and it looked the goods. no welding of anything (except itself) and bam, theres your wastegate hole!

[Badgaz]

why not just buy one of these? $75 bucks

http://drivenperformance.co.nz/products-page/turbos/turbo-adaptor-t3-t3-with-38mm-wastegate-port/

[r34unit]

Why not just go N/A ?

No boost spike

No lag

No waste gate

[Ben C34]

Why not catch a bus?

They are turbo. ....

[ARTZ]

No wastegate and more boost FTW

[scotty nm35]

^ This.

Those adapters do not provide a good flowing wastegate path, but they should work fine at controlling manifold pressures.

A well designed wastegate path adds much more than good boost control, I know this from experience... Just sayn...

[Dose Pipe Sutututu]

^ This.

Those adapters do not provide a good flowing wastegate path, but they should work fine at controlling manifold pressures.

A well designed wastegate path adds much more than good boost control, I know this from experience... Just sayn...

totally agree, flow always takes the path of least resistance.. and fuark Scotty's gate job (that nearly sounds sexual) works a treat, I can set my boost to anything and I will only get a fluctuation of 0.02 bar at times from start to redline.

[Badgaz]

i thought that was true of water pressure but not air pressure.

[Dose Pipe Sutututu]

i thought that was true of water pressure but not air pressure.

ever seen a dim sim manifold with the wastegate flange on the opposite side of the collector? uncontrollable boost spikes

[scotty nm35]

i thought that was true of water pressure but not air pressure.

Exhaust flow at that speed seems to act very similar to water flow from my testing.

[Badgaz]

fair enough, i suppose if my tiny little brain is trying to understand it...the pressure builds from the closest point to where the flow stops? would that be a way to think about it?

[scotty nm35]

Ahh, the flow never stops, it just forces it through the turbo if the wastegate is closed, or the gate can't flow enough.

Imagine a spray gun, force air over a tube opening at 90 degrees and it will suck the paint up into the airflow, the opposite you would expect. Same thing would happen in a poorly designed manifold if there was no pressure helping, the gate would almost flow backwards.

[GTSBoy]

Water flow is always incompressible flow.

Gas flow can be either in the incompressible regime or it can be in the compressible regime depending on how fast it is going. If we use the example of air at room conditions, then the speed of sound is about 340 m/s. If you are at fairly low speeds (so, let's say about half that or ~170m/s or less) then you are in the incompressible flow regime and gas flow will generally behave EXACTLY like water. If you are at high speeds, like 60% of sonic velocity or more, then you are getting up into the compressible regime and gas flow will start to behave differently to water. It is actually a gradual change from one regime to the other.

Hot exhaust gas will have a completely different sonic velocity (no, I'm not going to calculate it for you) and therefore the velocity at which the regimes change will be different.

Regardless of the discussion of the difference in compressible and incompressible flow, when gas is flowing fast in a certain direction along a duct it has momentum in that direction. If you want it to make a 90° turn out through a hole in the side of that duct you have to give a convincing reason to do so. The only one available is a very large pressure drop (ie the pressure in the duct must be much higher than on the other side of the hole in the duct wall). The only way to do that is to have a very free flowing flow path out the hole. Almost no external wastegate meets that criteria even if it is a screamer, because the wastegate itself is a valve which is an obstruction in the flow. There will always be a certain amount of backpressure across the gate. And if the wastegate is plumbed back in, then there is even less pressure drop available because now the outlet end is at dump pipe pressure (which is a bit higher than atmospheric).

[jet_r31]

Why not split the difference guys?

Stop all the arguing

But seriously, why isnt this best of both worlds?

I've seen one in real life, and it looked the goods. no welding of anything (except itself) and bam, theres your wastegate hole!

They woudn't fit on some nissans though would they ben?, i looked at them for stageas, but with a .070 comp cover they would hit the

chassis rail with one of those fitted?

cheers

darren

[Ben C34]

The one I saw was in a 32 I think. It wasnt a parralel spacer, it rotated the exhaust housing a fair bit, so it didnt just space it also the way into the strut tower. I cant remember the turbo but it was decent, around 350rwkw

I think garage7 made or supplied it.

Memory is very dodgy lately though!

Edited February 26, 2014 by superben

[jet_r31]

yeh i remember that, think simon posted the picture

cheers

darren

[SkudR33]

why not just buy one of these? $75 bucks

http://drivenperformance.co.nz/products-page/turbos/turbo-adaptor-t3-t3-with-38mm-wastegate-port/

Has anybody ever tried this?

Seems like a good idea however you'd have to get new oil and coolant lines because they won't read the turbo...

[discopotato03]

I've changed my thoughts towards the housing rather than manifold because its easier to work with . Like GTScott I think it's about getting the gas to change direction once it's moving beyond a certain velocity .

It seems people hate theorising but anyway I believe it's a case of velocity pressure vs static pressure and velocity pressure wins .

As seen it's possible to fab a fair sized (diameter) tube/hole in the top of a turbine housing and having a large area means an easy vent path .

I think from an engineering point of view it may work better on the manifold because of the velocity trough the top of its twin ports at the collector but more difficult to do (mani off etc) and the manifold IMO is less of a consumable than a turbine housing .

I recently saw a pic of a compact (height/diameter) ext gate low down on on a turbine housing and it wasn't nearly as obvious as having it on top of the manifold or on an elbow off the same point . Just more stealth .

[Dose Pipe Sutututu]

Has anybody ever tried this?

Seems like a good idea however you'd have to get new oil and coolant lines because they won't read the turbo...

that's horrible for flow, why not just weld a gate flange off the rear housing?

[Ben C34]

Alright, I've figured it out. 3 gates -_-