On a generic completely open exhaust system: If one wanted to keep the loud clear overrun crackle from the exhaust but reduce the excessive booming low down bass sound around 500-2000 rpm, would it be adviseable to:

 

 

Place a small muffler on the central section of the exhaust, or place it at the end?

 

All other things being equal.

Most of the time a resonator is placed about midway on the exhaust pipe to help with what you have described.

A resonator will help, but that boom noise is normal for all 4 cylinder engines. You can modify the sound, but never get rid of it totally.

 

nipper

In all my cars ive built exhausts for (4...2 of which were subarus) i found a glasspack resonator placed about 1foot after the downpipe or Y section gets rid of the crackle. Using a smaller pipe size to build the system takes away the boom.

 

Im getting pissed off with mine at the moment as its lovely and quiet during normal driving but you get quite a drone in the cabin on hill climbs. Generally between 2,000 and 3,000rpm. Im pretty sure thats down to the large diameter pipe used.

 

Did you guys in the states get those mufflers with servo actuated valves in them to control the loudness?

Another thought with that "droning" noise in mind can be determined by the pipe wall thickness. Thinner pipe wall will resonate differently than that of a thicker wall stuff. Just something to think about.

Another thought with that "droning" noise in mind can be determined by the pipe wall thickness. Thinner pipe wall will resonate differently than that of a thicker wall stuff. Just something to think about.

 

and the distance of the muffler on the pipe from the cats or engine, the placement of the mounts, its really very complicated to figure out, and sometimes you can you only get it right by experimenting.

 

 

nipper

In all my cars ive built exhausts for (4...2 of which were subarus) i found a glasspack resonator placed about 1foot after the downpipe or Y section gets rid of the crackle. Using a smaller pipe size to build the system takes away the boom.

 

Im getting pissed off with mine at the moment as its lovely and quiet during normal driving but you get quite a drone in the cabin on hill climbs. Generally between 2,000 and 3,000rpm. Im pretty sure thats down to the large diameter pipe used.

 

Did you guys in the states get those mufflers with servo actuated valves in them to control the loudness?

 

 

My '03 H6 has a small bypass in the muffler, but its just actuated by the exhaust flow pressure overcoming a spring and pushing a flapper open.

 

Dave

In all my cars ive built exhausts for (4...2 of which were subarus) i found a glasspack resonator placed about 1foot after the downpipe or Y section gets rid of the crackle. Using a smaller pipe size to build the system takes away the boom.

 

Im getting pissed off with mine at the moment as its lovely and quiet during normal driving but you get quite a drone in the cabin on hill climbs. Generally between 2,000 and 3,000rpm. Im pretty sure thats down to the large diameter pipe used.

 

Did you guys in the states get those mufflers with servo actuated valves in them to control the loudness?

 

I'm unsure as to what you mean. I posted this very question on a dozen forums, there the consensus is that bass is long wavelength so a muffler close to the engine (centre car) would prevent the standing waves from forming.

 

Another consensus is that a long thin muffler eliminates low frequency sounds better than a short thick muffler. Also that 2 mufflers of volume X mute more sound than one muffler of volume 2x.

 

What I gather so far is that I have to place a long thin muffler center car.