Smaller air hose under cold air intake?

While having my battery replaced today, I noticed the smaller hose below the mass air flow sensor was disconnected. I reconnected it but haven't been able to figure out what it is for, despite my googling efforts.

First off, what is it for? I'm sure it's a simple question for anyone who knows what they're doing, but not me... And second, what are the consequences of having it disconnected? I have no idea how long it has been disconnected.

2010 JSW TDI, 185,000 mi.

Thanks y'all!

That is the HAI hose, goes from exhaust area to HAI valve in aircleaner.


Hot Air Intake.


Consequences of deleting it may include increased power, MPG and reduced EGT.

Thanks FJ40Jim! Good to know it's not a problem.

Interesting

I did a dsg service on my 2014 JSW and noticed this hose had some holes in it. I taped it up good for the time being but now I am thinking I should disable it?

What is entailed in disabling it do I just unhook it and let it go?

Would this effect the cabin heat? I think my heater core is clogged and was going to replace that soon too but was unsure if this swissed hose could have any effect.

FJ40Jim said:

That is the HAI hose, goes from exhaust area to HAI valve in aircleaner.


Hot Air Intake.


Consequences of deleting it may include increased power, MPG and reduced EGT.

Click to expand...

When you say delete do you mean just the hose or does the valve have to be removed?...thanks.

The hose can be deleted. For a more sanitary look, the valve can be removed from the air box. I think I deleted the stove off the exhaust manifold also.

Theoretically, having the engine breathing hot air would cause an increase in heater temp, but I doubt it's noticeable in the real world.

Reducing TIT from 130°F to 30°F does increase efficiency.

That should reduce warm up time. As long as the valve is functional it shouldn't affect anything once up to temp. I would think the overall effect is to increase efficiency. I'd keep it if you live someplace that gets cold enough for snow in the winter.