Whats this? And what does this pipe do!

[Guest]

Trying to get to know a bit more about this bike, and i came across this! Edit haha its the thing in the top right corner!

 

 

its some kind of air Vacuum thing i know that.. but whats its called? there are three pipes coming off it. The top pipe sucks in air from the atmosphere, the middle pipe goes to the inlet manifold and the inlet manifold sucks the air away, and the bottom pipe goes into the head.

Also, when i disconnect the middle pipe and block it, the bike loves to pop, bang and spit flames on overrun. Why? haha

if im vague then feel free to ask me the questions cheers!

[Tango]

I'm guessing that it's something like Secondary Air Injection (SAI)......basically an emission control. Allows air into the exhaust manifold to enable burning of unburnt fuel in the exhaust. It is controlled by the vacuum in the inlet manifold. Blocking the middle pipe probably opens the valve and allows a lot of air into the exhaust manifold causing the ignition of the unspent fuel in there. Well.....that's my guess anyway.....

[Stu]

Looks like a P.A.I.R valve it adds fresh air to the exhaust to lower the emissions at idle

[Guest]

How does it operate? i presume the top pipe sucks the air in, the middle pipe regulates the valve and the bottom pipe feed air into the exhaust. But how does the vacuum alter the valve? i.e when its blocked off is the valve constantly open? allowing more air into the exhaust.

[Tango]

Not sure exactly how it works on your bike....but here's a description of the principles.

http://en.wikipedia.org/wiki/Secondary_air_injection

On my bike the SAI is controlled by the ECU. Some ECU maps have the SAI disabled...but if the air ports to the exhaust manifold are not blocked off it can result in lots of popping and banging in the exhaust on the overrun.....