just put my decat downpipe on,not too sure if its leaking or not,got a new gasket for the turbo/downpipe joint,have took it for a test drive sounds a bit iffy,the turbo sounds louder as it will do,sort of a quiet psss sound after the dumpvalve has let off and the engine revs drop, im in the dark on this area so any help will be usefull,how would i know if its leaking at the turbo/downpipe joint?will i be able to hear a leak when its idleing?or am i being paranoid?i know it will sound different,maybe putting my had over the back box and see if i can hear any leaks? cheers.

 

I run a decat'ed standard downpipe (cat scraped out!) so not completely the same as you, however the noise when driving lightly on boost is not very nice. I can only explain that it sounds like the joint is leaking - but it's not. Also you might hear a 'ticking' under light load, that's the wastegate. Although at WOT it's a different story ;-) Basically you are likely hearing all the mechanical noises now from the turbo, wastegate, etc.

To check for leaks get under the car and listen whilst someone else puts there foot over the back exhaust for a few seconds.

What MY impreza do you have? Not knowing the rest of your setup e.g. ECU mods, you will likely get a CEL with the new decat (unless you've sorted that already).

-Steve.

 

with a decat you can hear turbo more best test for exhaust leak is your hand so get it next to the area you think is leaking its best to do this when the car is cold as if you touch the exhaust when warm you might say a few words but you feel a leak straight away as it air blowing

 

if the downpipe isnt heat wrapped then it can sound like its blowing but its just the gasses making the noise inside the pipe. you will hear the turbo spooling up much more too.

 

crispyduck i have a my99 turbo 2000 as far as i know its standard apart from backbox and tsl panel filter,manifold spacers and header tank spacers,i can hear a little ticking and the turbo spooling up sounds almost like the sound of compressor stall at low thru to building up boost untill it peaks,boost is fine according to the gauge,im gunna jack the car up again and have a good inspection for leaks,found one at the end of the decat to the centre section,gasket pasted that up and no leaking from there now,so just the turbo joint now.no cel light has apeared also.

 

sob, most of my tuning experience is with newage Impreza's and getting a decat downpipe will usually bring on a CEL after anything up to 300 miles (on mine).

Someone on here will be able to confirm if this is the same with the Classic's.

 

ill wait and see about the cel,trying to get it sorted before wednesday as its going for a re-map at zen,just had a feel for leaks and cannot feel any at either end of the de cat if there is any there they are very slight.