Mufflers only look simple, but they're actually engineered airflow mechanisms which need to meet the needs of sound reduction, sound quality, performance goals, weight and aesthetics — all seemingly in opposition to one another. And what do we do? Pull them off and toss them on a shelf and eventually the trash bin.
Years ago I decided to dissect a second-gen muffler just to see what's going on inside and maybe modify a stock muffler for better sound. I discovered that Honda had accomplished their goals in a typically engineering-oriented approach, without the use of sound deadening material (which wears out) or acres of perforated baffling, which adds weight and rusts out. The image below is from a Canadian dealer informational brochure showing a diagram of the OEM muffler for the 3d-gen (the pink notations are mine).
There's four sealed chambers, the airflow progressing rearward through the blue-colored tubes all the way to chamber #4, then forced to make a 180° turn, forward to chamber #2 through holes in the chamber walls, then another 180° turn rearward through the exit tube and out the rear. The sound is mitigated by the forced turns and chambers #2 & 4 absorbing the sound waves — at least that's how my non-engineering mind sees it. Air doesn't like making turns, particularly 180° turns, so back pressure is created, which is engineered to work in conjunction with the cool tuned header pipes. Ever wonder why those front pipes cross over one another? That's part of the complicated tuning of pressure pulses.
All that internal steel piping adds weight and takes up real estate, which is why the aftermarket has a much easier job in creating lighter, louder, more compact mufflers. Do they work better? Typically not, but they often sound better, or at least louder, at the expense of hearing loss and irate public opinion. The only way to achieve actual performance benefit is to tune an entire system, including intake and carburetion, to work together, but that's a doctoral thesis in itself. The Hindle system is an example.
Years ago I decided to dissect a second-gen muffler just to see what's going on inside and maybe modify a stock muffler for better sound. I discovered that Honda had accomplished their goals in a typically engineering-oriented approach, without the use of sound deadening material (which wears out) or acres of perforated baffling, which adds weight and rusts out. The image below is from a Canadian dealer informational brochure showing a diagram of the OEM muffler for the 3d-gen (the pink notations are mine).
There's four sealed chambers, the airflow progressing rearward through the blue-colored tubes all the way to chamber #4, then forced to make a 180° turn, forward to chamber #2 through holes in the chamber walls, then another 180° turn rearward through the exit tube and out the rear. The sound is mitigated by the forced turns and chambers #2 & 4 absorbing the sound waves — at least that's how my non-engineering mind sees it. Air doesn't like making turns, particularly 180° turns, so back pressure is created, which is engineered to work in conjunction with the cool tuned header pipes. Ever wonder why those front pipes cross over one another? That's part of the complicated tuning of pressure pulses.
All that internal steel piping adds weight and takes up real estate, which is why the aftermarket has a much easier job in creating lighter, louder, more compact mufflers. Do they work better? Typically not, but they often sound better, or at least louder, at the expense of hearing loss and irate public opinion. The only way to achieve actual performance benefit is to tune an entire system, including intake and carburetion, to work together, but that's a doctoral thesis in itself. The Hindle system is an example.
Below is my crude diagram of a 2d-gen muffler. The concept is similar, with the airflow path reversing to chamber #3, then again reversing outward (top). I also show how I make the cuts to shorten the muffler by about 5 inches and eliminate both 180° turns (lower). The result is a deeper, mellow sound without being too loud. I've not found a need to adjust carburetor jetting. This is also an effective way to salvage a road-rashed muffler, as I fill the dents and scrapes, then repaint black or silver. The 3d-gen muffler could be similarly shortened. Looks like I'll need to add a tutorial to the "Maintenance" page.
A simple tin canister? No so much.
A simple tin canister? No so much.
RSS Feed