zze86

Was cruising the FRS/BRZ/GT86 forums and came across an interesting thread. When switching over to a JDM STi catback exhaust, Subaru recommended replacing the hanger bushings with a different part number. This was to eliminate the resonance drone on the new exhaust.

Has anybody ever tried using different bushings/ bushing materials with their exhaust to eliminate droning?

TsukubaCody

Weird and cool. I would love to know if it makes a real difference.

Manga_Spawn

I mean it could make a small difference I guess but I doubt hanger alone would make that big of a difference.

Car Analogy

Hmmmm. The only way I could see this having an impact is in how much sound energy gets transferred into chassis via the bushings, as opposed to just sound waves via the air.

Sound waves making their way around the car and back up to your ears, some of it bouncing off pavement, some just out to the sides, wouldn't change much at all.

The sound transfered to chassis will then resonate chassis, which will act like a crude speaker. So the chassis design itself, and its resonant frequencies, will play a big part in how effective changing pliable hanger material to something else will be.

The sound energy which travels through the air, then impacts chassis and resonates it, seems like it'd be the largest carrier of exhaust drone to human. Thats because hangers are already rubber, and absorb considerable sound energy. That won't lessen significantly with different hanger material.

Manga_Spawn

Right but the hangers are already rubber what other material would transmit less? Maybe if they were worn out and allowed for more vibration?

noodels

^^^ Springs like old fashion microphones.
Mine does not drone now as put oem back on

Car Analogy

How about springs with rubber mounts at the ends?

zze86

This is the thread I was referring to and it seems to work on removing most of the drone associated with aftermarket exhausts.

Looking at the two different bushings, it is a different shape, with more meat on it but also larger cutouts. Not sure if there's any difference in material.

Manga_Spawn

Huh. It’s interesting for sure. If you find different hangers to try let us know.

Kyle

Softer rubber as well as design can have an effect on the amount of NVH transmitted. If you look at one hanger vs the other in the pic you can see that the left bushing has 2 air gaps in the hanger vs one. OEMs spend a lot of money on NVH reduction, so that hanger wasn't just arbitrarily designed like that. Honda also makes hangers that look very similar if you'd like to give it a try, and even if the shape is a tiny bit different between the two, I'm almost certain that most of these OEM Japanese manufacturers source their hangers from the same manufacturers.