WTF is a Diffuser?

[Crazy Dazz]

The Mistubishi 4N14 is a TD, described as having a "variable diffuser".

Now I'm only guessing, but assume this is the view without any of the intake, which presumably would run through an intercooler to the other side.

So what is the "Diffuser"??
And what does it do??

That big thing on the exhaust output, is that a DPF, or just the cat?
I know some engines mount them very close to the output.

[Dr Smith]

IIRC the job of the diffuser is to slow the speed of the air flow while increasing pressure.

My uni studies are very old but I think Bernoulli's principle is releveant here.

[Franco Cozzo]

Originally Posted by Crazy Dazz

The Mistubishi 4N14 is a TD, described as having a "variable diffuser".
image
Now I'm only guessing, but assume this is the view without any of the intake, which presumably would run through an intercooler to the other side.

So what is the "Diffuser"??
And what does it do??

That big thing on the exhaust output, is that a DPF, or just the cat?
I know some engines mount them very close to the output.

I reckon the big *** canister near the turbo exhaust housing will be the DPF - close to the heat from the turbo.

[Crazy Dazz]

Originally Posted by Dr Smith

IIRC the job of the diffuser is to slow the speed of the air flow while increasing pressure.

Ah ok, so it's on the air side.
Might not even be in the picture, as the intercooler etc is missing.

[XR Martin]

Pretty sure it's a cat.

Dpfs are further down the exhaust.

[dunga]

my take on it is a variable vane in the outlet diffuser That is the (technical name of the compressor housing)just like they do in the exhaust housing but in reverse .

[XByoot]

Yep, as others have said. It’s a divergent duct, reduces velocity but increases static pressure. The Mitsi in the ad probably has variable vanes similar to a jet engine compressor I’m assuming. More crap to fail in the never ending quest to make the wheel rounder

https://www.mech4study.com/2017/11/c...ompressor.html

[ute83]

Originally Posted by XR Martin

Pretty sure it's a cat.

Dpfs are further down the exhaust.

Agree. I would think a dpf would be situated more horizontally to catch any matter.

[baboon]

Found a reference here of another type of variable diffuser but i'd say idea is the same with the mitsubishi one: http://www.glturbo.com.cn/english/vvd.asp

Variable Vane Diffuser (VVD) controls air flow by adjusting outlet vanes. An outlet vane has optimized asymmetrical sectional area that results in the adjustment of airflow area and minimization of outlet air obstruction.

[simon varley]

Originally Posted by XR Martin

Pretty sure it's a cat.

Dpfs are further down the exhaust.

Originally Posted by ute83

Agree. I would think a dpf would be situated more horizontally to catch any matter.

not necessarily. combined CAT and DPF bricks are common, and in fact this close coupled configuration is exactly what the 2.0 in the Ranger uses.

orientation of the DPF has no impact on how the soot is trapped.

look carefully at the outlet of the can. the tube is for pressure sensor and that is to determine how full the DPF is

[ute83]

Thanks simon. Appears to be a ceramic coated dpf. I have not seen this system before. I have only seen dpf's horizontal and further down the system.

[CyberWasp]

They put the diffuser in the air intake, so you can use different oils to make the exhaust smell nicer.