I've been doing a bit of tinkering with a cone air filter, I noticed there are 2 vacuum hoses (?) going onto the air box but from what I can tell they are just plugged at the ends.

If I am removing the air box should I plug these hoses, leave them or what? Also what is the purpose of them?

I'm not looking to get bhp gains or anything I just like tinkering and finding out how things work

Thanks!

They are the air feed for the vacuum system! Do not block them whatever you do!

Heres what i did

Used a boost guage take off adaptor to plumb the vacuum hose into the air intake

Ah excellent thanks for clearing that up! I assume something like this will do the job then and just add them in as you have

http://www.demon-tweeks.co.uk/motorsport/gauge-pipes-adaptors/lma-manifold-take-off-adaptor

As already said it needs to be connected. On my k&n because it's rubber I drilled a tiny hole and pushed it through like this:

Ah great thanks for the advice guys. Will give it a go next week fitting it then.

They are the air feed for the vacuum system! Do not block them whatever you do!

Heres what i did

Used a boost guage take off adaptor to plumb the vacuum hose into the air intake

Excuse me borrow the thread but it touches the subject;

"Do not block them whatever you do!"

 

What can happen if these hoses are blocked?

These hoses on my car has unfortunately been blocked for a short time because I was misinformed when I tried a K&N CDA filter box with a collapsible suction intake hose as a result ... so I reassembled the original filter box again.

Afterwards, it howling / screaming from the car when accelerating while driving, probably because of the vacuum leak somewhere and the engine light is lightning due to error code from the EGR. But the car seems otherwise go as it should in several mounths after this operation.

 

What could it be?

How to troubleshoot vacuum system more than visually?

if these hoses are blocked, then there is no clean air at atmospheric pressure to reduce the vacuum for vacuum operated valves (like turbo waste gate and EGR valve) to return to normal position when vacuum is removed,

 

as you can imagine, not good for turbo (ECU will not be able to control boost correctly and turbo could spin to fast) and will cause EGR to be constantly open etc