Bonneville America Forums Forums Technical Forums Exhaust Steel Wool?

As most everyone knows, I've got those fishtail pipes on my bike. I love the looks, but sometimes the sound (especially on long rides) can get a little bit annoying becuse there is an almost 30" long echo chamber before the baffle. There is one all steel baffle at the end (no packing and it is spot welded in). I did install another baffle in the front of the "echo chamber" but it stick most of the way into the header pipe.

Anyway, someone was telling me that I could try to stick some steel wool into my pipes and that would help. It would increase the back pressure some, but make the sound so it isn't as sharp (it really isnt the loudness, but the sharpness of the sound especially between 4000 and 4500 rpm).

Has anyone tried this? Would just shoving a few pads of steel wool really help the sound? Wouldn't eventually the steel wool blow out? Can't steel wool be flamable? Would there be any reprocussions on the motor because of back pressure? What grade of steel wool would work the best?

Soren

steel wool will burn. have you tried earplugs yet?

Soren,
Stick a pair of these in.........

http://www.jpcycles.com/productgroup.aspx?GID=5EBE099A-07C8-4632-BE73-8BAB60082F50

I don't know about steel wool, but why not use muffler packing? i did this and it reduced the volume a good bit. I used "silent sport" which i heard is the best because it lasts far longer. Anyway, my thunderbike pipes are the same from your description. A baffle about a foot long at the end and the inner pipe is the length of the muffler. there are some slits called "louvers" along about 1/3 to 1/2 of it, so i'm sure those help. but even if yours doesn't have those i think it will still help because it at least deadens the acoustic properties of a hollow tube inside a hollow muffler. so i packed the space between the tube and muffler by tying it onto the inner tube with masking tape which only is needed to hold it there till it's inserted. I'm told it eventually burns off but it doesn't matter if it does or not. Anyway, i packed about 2/3 of the length because thats all the packing i had, and it made a considerable difference. I can now ride w/o earplugs (not that i usually do tho) and it doesn't sound so freaking loud. If you can drill holes about every inch around the tube it would help quiet it more im sure. the guy at silent sport told me to do that. But since it already had maybe 30 louvers i passed because the metal was too hard to drill.

Anyway, it will work to some degree. I can't say for sure how much w/o any hole since mine has those louvers, but it's worth a try and i'm sure it'll at the very least mellow them out just due to the acoustic resonation of the pipes being dampened. I haven't gotten around to it, but one of these days i want to pack the remaining third. I didn't buy the pipes for volume......i wanted the power and the tone with just a little more volume. But nothing like the stock thunderbike pipes. i don't understand everyone's desire to be loud. when a bike is loud, to me it makes it feel slower because it seems to sound like it's working a lot harder than it's going if that makes any sense.

JP cycles also sells a "baffle repack kit" comes with fiberglass AND STAINLESS steel wool"

I think what I might do, is get a Dremil Drill and attempt to break the welds off the baffle, then pack it with some genuine packing, then bolt the baffles back in. Depending the type of baffles that are in them, I may replace them completely. Then see what happens.

Soren

I'm glad you made another topic about these pipes, I didnt want to hijack the thread in the lounge. Were these pipes baffled from the factory or did or make your own? And how was the length? This was great timing, I was going to order some from JC Whitney this weekend but the ones your using might be better.
thanks
Dill

Hey Dill,

Maybe this pic will help...

The red baffle is the baffle that came with the pipes. It is spot welded in. The yellow baffle is one that I added. However that leaves that 2 1/2" empty area between the two that creates an "echo chamber". Because the sound bounces around and resonates badly, it can produce some pretty sharp sounds between 4000 and 4500 rpm. Below 4000 rpm it (especially at idle) they sound great. Above 4500 rpm (especially above) 5000 rpm, the sound is much more tolerable, but there is not much of a grumble (almost a sport bike whine sound). I am sure that it all has to do with frequencies (generated by the various rpms) and available echo area, but I am not an audio engineer, so I can't really explain it. I bet there are some mathmatical formulas, that may also include that I am runnning the bike a little bit lean as well.

One other solution I am thinking of, and I have no idea if it would work, is to eliminate the chamber completely. I would remove the welded in baffle and insert a 1 3/4" piece of exhaust pipe (I could get that at any exhaust shop like Midas) then use that inner pipe for baffles.


Soren

How was just the stock baffle? Also how about using the fish tail extension pipe. such as http://www.jcwhitney.com/autoparts/ItemB...ID:100000149272
I cant figure out how to put pics up, but it a straight wall extension pipe. I wonder if its the curves in the body of the pipe causing the odd sound.

Dill,

I think what I am trying to accomplish is about the same as having the straight fishtails. I thought about getting some (except for 36" in length), biut I really like the looks of the ones I have better (with the 2 1/2" chamber) rather than the 1 3/4" skinny pipe.

The pipes with just the factory baffle sound good but are loud and very sharp sounding at all rpms, except for idle (where they are just loud)

Barry,

Uncharted territory? Sounds like fun. Nothing like trying to experiment and discovering. I think your "untrained conclusion" makes a lot of sense.

Soren

The 3 main questions I have are what is the outlet diameter we need? And how did you do the hangers? Also what are you using for jetting? Like I said this was great timing, and will help me avoid some probelms. I also agree that shrinking/removing the expansion chamber should help. We dont want the bike to sound like a civic with a fart-can.
Dill

What is the outlet diameter we need?
• 1 3/4"

How did you do the hangers?
• Drilled a hole, used a large sheet metal screw

What are you using for jetting?
• Stock jetting until I get settled with how I want them to always run. I want to do it (the re-jetting) once and leave it. Right now, it is running a bit lean.

Thanks couldnt ask for more than that.

That used to be the standard fix for noise tickets. You have to take care that the stuff stays put though. A friend of mine learned too late that you need to drill a small hole in the pipe and drop a nail in behind the steel wool. The inspector was just about to sign that his car had been fixed and, on a whim, asked that he step on the gas one more time. That was enough to blast a steel wool pad out into his shins. Between the bit patch of carbon on his pants and the damage to his leg, he was not happy at all.

Soren, I took a stock America muffler and gutted it out then i took 1.5 inch pipe made to ends to hold it center. I then cut semi circles and bent them up so i could create back pressure. It seems to me the more i cut the lower the tone. The packing deadens the sound. I agree you are treading on uncharted territory and it's going to be a process of trial and error. I'm running Epcos now I just never did like the tone. I used string wrapped around the packing while i put the assembly in the Pipe, it just burns off mostly.

It may seem like uncharted territory, but actually it isn't. The straight pipe withing the fishtail pipe, would be just like running a straight 36" exhaust pipe with an outer shell.

Soren

Not steel wool, stainless steel scrub buds. They're at walmart at 3 for $1. Get 2 packs and stuff a couple in each pipe and see what you get. I noticed after a few months that one pipe was louder than the other. Checked it out and one pie had blown out the SS buds.