I have a 05 WRX, with Perrin catless UP, Invidia catless DP and factory 06 STi catback. With just the UP and catback, the car sounded nice, just a little more rumble than stock.

After I installed the DP, however, there is a rattley-fluttery-metallic whistling sound coming from under the car. I went back under twice to check all the bolts, I don't think it's an exhaust leak. The sound is always there, kinda faint at idle, but if I get on the throttle when I'm next to something (like the median barrier on H-1) I can really hear it.

Is the sound normal because of the DP? Teriyaaaaki took a listen, said it sounds OK, but that was just at idle where it's not too loud. If the sound is normal, then that's fine, I don't mind. I just want to make sure that I didn't miss anything, or mess something up.

Oh yeah, I was trying to find the source of the noise yesterday, so I was blipping the throttle while leaning under the car and I could hear a slight backfire from the exhaust. Is that OK? Shouldn't the computer pick that up? I don't have any EM at the moment, maybe that's the problem.

TIA for the input and advice.

 

Due to no cats anymore..You will hear a bit of that whitsle sound which is your turbo,and the flutter is the wastegate flutter..Reason for the whistle sound now is that by removing all your cats you allow for your turbo to breath/spool better and therefore is gets louder and more audible.

As far as the backfire.If you have no exhaust leaks and are running the stock bypass valve it should be ok.If i'm not mistaken, then I believe that by installing a catless downpipe and running no cats,that allows for a richer condition and inproper air/fuel mixtures..Get engine management and that should correct the air/fuel mixtures and you should be fine.Cobb,ecu-tek,enginuity,ect,ect..

Please correct me if i'm wrong.

 

i got the same upgrades and i have the whistling sound too (it's sound good doesn't it). it's gonna happen just like teriyaaaaaaaaki said.

 

Cool. Thanks guys.

 

Might want to check your DP if its loose and if your running a bov guarantee its gonna run rich and cause that backfire. I had my DP loose and it caused a ton of problems for me. If its not then its the good old sound of turbo spool ^-^

 

it could be the catless downpipe. those catalytic converters also muffles sounds and certain frequencies which you are probably hearing now in the higher rpms....its more of a raspy raw exhaust note now right??

if its under the car i would check the up pipe, i believe its a common area that leaks, did you replace the gaskets?? did you torque the bolts down well?

 

I installed the UP and DP on two different days, I went back under and re-checked all the bolts twice each time. I'll probably check one more time, or just remove and retorque the DP just to make sure. I did use fresh gaskets every time something came off.

I don't have a BOV, I didn't see the point in hassling with one when I have the stock turbo and am running factory boost. Even when I crank the boost up to 16 - 17 psi with EM, I've been led to believe that the stock bypass valve should still be OK. Someone please correct me if I'm wrong.

 

The stock bypass valve should be fine up to 24psi..

 

mines sounds the same too-same set up- although i got rid of the rattling sti muffler and went back to stock wrx - back fires a little to btw.

 

that sound in my sti is there it may get a little bit quieter and your stock bypass is fine for function but a bov sure sounds neat i just put the one i got on and its pretty fun to get those funny looks from people