Just fitted some new vacuum piping to the turbo and boost controller, also the feed back from the BOV and the boost gauge sensor.

Since doing this the car has lost 0.2bar of boost!

The bore of the replacement pipework is a mm or two smaller than the older pipe that came off, as its the only thing I've changed its got to be that, right?
The car is a MY05 UK STi..

Reason for changing it that the old rubber piping had started to perish.

Any help welcomed!

 

why don't you try replacing the pipe as a like for like then maybe you won't have any problems? i , personally would take this as common sense when replacing such pipe work

 

Yeah I'm going to get bigger bored stuff tomorrow. Just wondering if anyone had an idea on a minimum bore for effective vacuum piping?

 

Did the old piping have a restrictor pill in it at all? This is to reduce the pressure the boost controller/actuator see's therefore allowing higher boost.

 

Define: restrictor pill? The pipework was in two bores with a downstep. I've just changed one bore. Just got some bigger piping that's more like the original. Will play with it now and let you know.

 

Not sure if your car should have a restrictor pill or not, mine did but its a MY99 car.

The restrictor pill is a small piece of metal shaped like a "pill" , it goes in the pipe from the t piece to the actuator, it has a hole in it, think its about 0.6 mm or there abouts.

 

Changed the bore of the pipe and I'm back up to 1.6 bar! Woohoo!

 

Had the same problem twice,one time the hose was the right diameter, but was to supple when hottish, so it ballooned like a bugger.
Lost 0.5 bar of boost.

I also replaced the stock plastic T-piece with a festo brass T, and the slightly smaller diameter of the Festo T led me to lose 0.2 bar.

 

Its surprising how much difference a few mm makes isn't it!