OT, but Pinging David Cofer

[Guido]

Dave: What the devil does the inside of a MC muffler look like? I'm betting they are of no kin to an auto muffler? Straight through for sure, but???

Question, anyone: We found a straight through, ie. one can see daylight by looking completely through the thing, ---muffler, a glasspack. It utilizes small punched louvers on the throughpipe, all facing one direction. Wanting the least amount of loud from this thing, does one mount it with the exhaust being 'scooped' by the louvers or by the exhaust flowing over/by the louvers.

In other words, louvers pointing upstream, or downstream?

G

[dp]

I had Vance and Hines exhaust on my Harley for a while. Sounded great, nice performance. They were made by passing a perforated pipe through the expanded shell. Around that was fiberglass wrapped in high-temp plastic. Over time that packing deteriorated until there was just the perf pipe and shell and the sound was no longer sweet and burbly.

Other pipes have a central perf pipe with a baffle in it. The gases pass out of that pipe into the shell area, around the baffle, then back into the end section and out.

Yet others have two inner pipes that are not connected to each other and the gasses and sound traverse the space between them.

And then there are the double-baffle types that require several passes between segments before the gasses leave the muffler. They are the least noisey pipes but have the worst performance.

And there are megaphone types that have a tuneable tail cone section that allows dialing in backpressure on a case by case bases. They're very loud and not in a pleasant way.

The mufflers I have now are baffled but because I have a 103" engine they're designed with low back pressure. Nice sound and performance. I've ridden across the US with HD riders that have straight-thru's or stock mufflers that have had the baffles knocked out and after a day or two of that it gets pretty tiring.

[Dawai]

You could have pm'ed me..

BUT.. sometimes they are just "holy" sheet with glass or steel wool around it.. straight through. the baffles.. and factory pipes.. they have a washer there in the end.. most harley riders knock that out to start with.. SAY HUH? WHADDA SAY??? turn it up I can't hear it.. Just wait a few years.. Riding without a helmet can deafen you also..
Police used to run a billy stick up your pipe.. if it went.. you got a ticket.. meaning the baffle was gone..

Some bikes have a flowmaster-chamber type of muffler.. it resonates and the vibrations cancel each other out in there.. Most the older junk I work on thou is like I laid out.. contained fibre..

PROBLEM riding behind me when I got new mufflers.. pieces of "HOT CRAP" hitting windshield and face. I used to see the pipes on the old panhead turn red about halfway down them at night..

I about got the Porker brand pipes on my evo bike blowed out, they are full length thou and it is LOUD behind it.. not so much riding it. A good running motorcycle can "melt down" the "others" riding with you. AS a mechanic, if yours breaks, OMG. WORD gets around. I have a neighbor that believes I have two bikes.. ONE that sounds like a 747 and one harley.. both painted alike.. He keeps on talking about that "one loud bike" scaring his kids... (loud pedal?) It aint' fast, it is loud when it is twisted.. THE panhead, it was fast.. On top anyways.

GOD lives in the Assembly details.. It also is balanced by how much money you throw at a problem too thou. Sometimes being anal retentive is a asset.. othertimes, not so much..

Gotta go, fixing to swap a Demon carb on the wrecker for a quadrajet.. if the intake is drilled.. I can't remember??? THE demon don't want to run while cold..???

[Dawai]

day or two of that it gets pretty tiring

Which explains the big motor.. you stay in front of them? Not eating the exhaust notes?? Ha.. You can "feel" the open exhaust throb hours after it stops in reality.. your head - heart seems to time with it??

My hot-rod is still collecting parts.. the fatso.. I got about enough left over junk to build a shovel thou.. My bud up there in Iowa, he has this Timken-generator bottom end.. I kinda got the urge to build a kicker bike.. as if I could stomp it???
Panhead parts have gotten crazy priced..