Where to step down IC Piping

[jap55s]

Hey guys
So I'm going with custom stein less steel IC piping
I've noticed the sizes from turbo outlet and engine Inlet are different

Where should I step up/down the sizes.?
From IC or jut before Inlet.?
Cheers

 

[Rabbid-chop]

Theoretically, the cold pipes can be smaller than the hot pipes due to heat expansion of air - so might be an idea to put the reducer at the turbo?? *shrug* but don't quote me.

 

[jap55s]

The turbo is the smaller side
Or should I just make it all the bigger size straight from the turbo.?

 

[Rabbid-chop]

It makes more sense to put the step up on the turbo and make it all the same size.

 

[jap55s]

Cheers
What about that small black hose under my finger in the pic
Do I need to relocate it.?
What is its purpose.?

 

[Rabbid-chop]

That's the boost/vacuum reference hose that goes to the sensor to the left of your finger there. You need to have that.

 

[bods]

The forefront kit has a reducer that comes off the turbo outlet so the piping is the same size as the manifold inlet. They also have a little fitting on the cold side piping and a mount for the map sensor to bolt back on to...

 

[tweak'e]

you are better to have smaller pipe from the turbo to the IC, then big pipe from the IC to the engine. that may seam a little illogical but there is reasons for it.
the small pipe helps keep the volume down and as the gas is already high speed its better to keep it. the air then slows down through the ic (mostly due to volume). keeping a big pipe to the engine keeps the air speed low and less turbulent which makes it flow better. plus your not wasting power accelerating the air again.