car is a 2006 evo ix RS
has 87xxx miles
has a no name 3" exhaust, mbc, typoon cai, and looks like an aftermarket downpipe (2.5")
I picked it up from a used car dealer about a month ago. when driving around without boost the car is fine. when in boost the car is fine. However when driving around and building boost from a high vacuum to about 0# there is a weird rattle. I have already removed the plastic undertry and all the wheel well plastics to eliminate them as a source. I've put a rubber piece around where my cai is beside the battery. I've also removed the wire mesh from in front of the intercooler which was rattling from before i pulled it. noise is still there. I've lifted the car up on an engine lift and ran the car. I can't find any exhaust leaks. It only does the noise under load. I've got 3 highway videos of the rattle. they're pretty much the same but i gave multiple to make it hopefully easier for someone more experienced to help out. Thank you in advance!

 

Bump. I really need help figuring out if this is something bad or a minor fix. Some folks on other car forums have had issues at similar boost levels and the cause Is wastegate rattle bit I havent heard any sound llike mine

 

No answer yet. After some more runsIive concluded it really does it in 3rd-5th gear. I've ordered a turbosmart wastegate actuator to see If that'll maybe help with wastegate rattle

 

The timing belt tensioner pulley can make some weird sounds. Has the timing belt service been done?

 

a shop called "Concept One Motorsports" rebuilt the motor at ~76k miles ( I have full reciepts for it and I'm gonna take it there this weekend if I can't diagnose/repair it by saturday morning. New short block and internals. What's the easiest way to tell if it's the tensioner pulley? I'm gonna dig around but that still feels like a weird problem to have only when starting to build boost. Thankyou, I'll update as I investigate it!

 

So I've pulled the bumper, the wheel well plastics, and tightened up every bolt/bracket i can get ahold of. I still get the rattle when motors vacuum starts to lower under acceleration in the 2300ish-3000rpm range. Weird thing is it did it while car was at a standstill. So to me it still doesn't completely remove idea of wastegate ratte. I haven't installed the turbosmart 18# wastegate actuator yet bc I don't want to effect any warranty on it but I'm running out of ideas. Anyone have any other suggestions? There is an intercooler bracket on the driver side at the top of the elbow from the intercooler that has some play in it and it has rubber bushings on it. I don't think it's those but I'm gonna get some sort of insertable spacer to try to tighten it up.

 

Have you checked the exhaust heat shielding in the tunnel area. I smoked some road debris a couple months ago and it is all starting to let loose on mine. It sound similar to yours but mine just ended up ripping itself out before I could do anything about it.

 

I had the car up in the air the day I made this thread and i tried shaking them/recreating the noise by tapping it with various tools and couldn't although it does move some. I will pull the heat shield off and driving around for a short bit to see if it's gone tomorrow morning and I'll post results.