Thump sound from Borla Exhaust?
 

Hey, just recently installed the Borla 140496 Cat-Back Exhaust. I'm really impressed with the looks, sound, and performance from the exhaust. However, lately i've noticed a strange "thump" after quickly releasing the gas pedal while I'm driving. More specifically, it sounds similar to a lower pitched drum being hit. This thump happens on practically every gear if i take my foot off the gas quickly. I didn't notice this with the oem exhaust so it has to be the new exhaust. Im thinking that the one of the bolts to the catalytic converter is loose. Any ideas?

If I'm accurately thinking of the sound you are describing then I'm pretty sure it's normal. I noticed when I put on a reduced backpressure exhaust, I would get a sound like a sudden deep whooshing sound upon sudden throttle release.

I think it's just a side effect of the more freeflowing exhaust either sucking/releasing air in that moment. Sounds pretty cool in tunnels :)

That was also a thought I had! Happy that i'm not the only one who has experienced this! It is an interesting sound but had me worried a little bit. It doesn't sound as if its metal clashing against metal. Its more of a "smacking a bongo" type sound lol! This exhaust definitely has a night and day difference due to how free flowing it is. The reduced back pressure makes the car much more enjoyable in my opinion... Love it. Thanks for the response!

It's normal. Happened to my brother's Miata too.

Awesome, no reason to be frustrated anymore. Thanks!

blightmike: btw, do you happen to still have sound tube installed? I recall hearing something similar that got only easier to notice with installation of TRD sound changer that passes more sounds from intake. If sound tube is still around .. plug it with cig plug from glovebox and tell if that sound is still there ..

If I were you, I would still check all the flanges and hangars to make sure they are tight and not drawing any part of the exhaust up close to the frame......;)


humfrz

Already plugged it, thanks!

Just took a look under. Hangers, tips , and mid pipe won't budge. Might have it checked out by a shop