i hope sumone can help. ive got a w reg imprezza turbo and its makes a weird noise as the revs start to rise bout 2500. it sounds like theres hundreds of crickets under my bonnet its really load especially wen i drive past a wall or sumhing like that u can hear the sound bouncing of it if u know wat i mean. tha car is decatted. i never had this type of noise on my old imprezza which wsa decatted to. has anyone got any ideas? cheerz

 

wastegate chatter???
Boost solenoid doing its stuff maybe

 

i was going to say boost solenoid !! maybe exaust/header leake at wastgate end????

 

If your sure its to do with the engine, then its a possibility its piston slap ?
How many miles has your car done?
Is it the original engine?
I had a badly built engine that made a similar noise, and it turned out to be piston slap which normally starts to happen on older engines.

Kev.

 

noisy tappets (are they hydraulic or solid on a w reg?)
Its happening around the time when your turbo is on boost so I still reckon its related to that.

 

Could be a cracked heatshield. They vibrate and make a pretty awful noise. If it is a heatshield then it's likely to be the one on the drivers side exhaust manifold.

 

ahh good point, the heatshield. Is your decat newly put on? the heatshields do tend to need a bit of cutting to fit correctly

 

cheers for the replys guys. its definatly not piston slap because i get a bit of that from cold and at definatly dosnt sound like the valves or tappets. wen i brougth the car it was already decatted but they hadnt refited the heat sheald but i brought one and modified it to fit the down pipe and made sure there wernt no rattles any where so its not tht either. ive also checked all exhaust joints for leakage except for where the headers join the cylinder heads,could it be that do u think? has anyone got anymore ideas? the noise starts as the car starts to boost. the car drives and boosts perfect ecept for that noise.

 

. .

 

Check the heat shields on the headers (manifold) under engine. Mine were loose as a tarts knickers and vibrated for Britain. Luckily, I was able to engineer a fix with 60p................2 big jubilee clips. It was quiet as a mouse when I sold it!

 

ive checked all the heat shields on the exhaust and they dont rattle but ive had sumone rev the car a bit while ive listend underneath and it does sound like its blowing a bit underneath the engine. could this be the header gaskets blowing???