drilling pipes (again)

[xj11john]

I drilled 4 holes in my 4-1 muffler, it sounds better, but still screams with a sore throat

So I was wondering if I put two more 1/4" holes in it would I have to rejet? I have ind. filters and the 4-1, and have went from stock 117.5 mains up to 122.5's before I drilled, I'm hoping not to have to go up more but if i have to I will.

I'm hoping for a lower tone with going 70+ because at that speed the exhaust tone is too high pitched, I'm sure this will also make it louder so hopefully I won't need ear plugs, cause its pretty loud right now.

What would be really nice is if it gets lower and not so loud, but I guess I will see.

Thanks for any comments or suggestions.

[mason79]

i'm needing new pipes, what pipes are you talking about here?

[strom]

Take out the rear plate, tare the guts out, make a new back plate with one larger hole and let er rip! Shoulda get something from mad max.
If you want more chopper/v8 soud, you need 4in4... but only on idle... not that deep with just the pipes... you would need a bit wider mufflers for a nice deep sound.

LP

[mason79]

strom do you mean 4 into 2 i have not seen a 4 into4

[DiverRay]

John,
What BRAND 4 to 1 do you have? What size is the main hole in the baffles on the muffler?
If you can pull the muffler assembly, and put in a baffle with a larger center hole, you should get a lower tone. I have a Kerker on Daily ride, and the tone is nice. It's quiet until I hit about 5K, then it starts to scream. At 8K, everyone knows I'm around, and moving.
I do have a second 4 to 1 that is crome, and looks like a MAC. I chose NOT to use it, as the Kirker has a nicer look, and I believe they work well. I can try to take some pictures and email them to you, if you want to try and rework your muffler system.
Ray

[TopCatGr58]

Sonic Boom!

Hey DiverRay,

That's interesting info, it makes sense. A bugle sounds lower in tone than a clarinet or flute, and a tuba sounds lower than a bugle!! I've got an old 4-1 and I can remove the end cover/baffle assembly. I'll have to check into getting a larger diameter baffle and weld it in place of my original to see if I can get a lower tone!?
T.C.

[knewsom]

bass notes, sound frequency, etc; CAUTION: SCIENCE!

OK, so here's the deal with lower frequency sound - the waves themsleves are LONGER (hence a lower "frequency" - ie, less peaks and vallesy per second. One hertz would be a peak per second, and well below the hearing range of humans)

So, in order to allow lower frequencies to develop properly, one must allow not just a wider passage (more air moving at a given time, or in this case, exhaust), but a longer one as well.

Removing baffles doesnt' seem like it'd make the tone itself lower - perhaps LOUDER (unless the baffles constrict the actual passage of exhaust, and looked like little o's in big cicles filling the pipe).

Drilling doesnt' seem to be a viable option either - just more small holes - volume, but not deep.

The way good subwoofers work is to have non-parallel surfaces facing one another - what this does is cause the waves to bounce back and forth a number of times (but not infinitely), allowing them to develop a full, rich tone. Ideally, the inside of an exhaust would look like this, correct?:

-------------------------------------------------\
/ \
/ \
-------------------------------------------------/

Of course, a long, wide, twisting pipe ever growing in diameter would be even better - this is why tubas sound so great!

So, unless I'm completely mistaken (or the textbooks I had in college were lying to me), drilling or knocking out the baffles on the end won't do much for tone (though maybe a little bit by lessening overall velocity).

Perhaps the best thing to do would be to remove the baffles in the MIDDLE of the muffler, but leave the ones on each end, perhaps enlarging your final output pipe's diameter.

*scratches head* maybe? Or then again, maybe having NO baffles would be the deepest, since the exhaust flows one-way, unlike a speaker, which as an influx and an outflow.

[knewsom]

updated hypothesis

OK, so I started eating a burrito, and the nutrients brought some sense to my mind. Because the exhaust is only travelling ONE WAY, and will try to find the quickest easiest way out of the muffler, having multiple baffles for the waves to bounce off is ludacris - the velocity of the exhaust will simply push the waves along with it right out before it has a chance to bounce.

So let's figure out how long and wide the pipes will need to be in order to make the deepest possible rumble.

At idle, 1000 RPM, we're making a 67Hz throbing tone ( 1000/60 = 16.something, 16.something x 4 = about 67). A 67 hertz soundwave that travels 186,000 feet per second will have a peak every 2776.12 feet.

So, we'll need pipes that will be able to effectively match the mean of the angle of a 67Hz wave. a wide mouth like a trumpet will probably result in a wider frequency range of the sound coming out of the pipes, so in order to "tune" them, we shoul actually have opening be a more gradual angle, more like a clainet or flute, but much much larger in diameter, slowing the velocity of the exhaust, and allowing a broader wave to develop.

As the angle of the output port (mouth) of the exhaust widens, the angle of the sound wave will lessesn, resulting in a lower tone. Small output port? high pitch. wide output port? lower pitch. multiple small output ports? greater variety of sound coming from the exhaust.

My best guess is that a 4 into 1 exhaust is going to be the HARDEST to sound deep, due to the increased velocity of the exhaust travelling through the pipes, decreasing the amount of time the air in the pipes has to bounce around and develop a deep tone. 4 tailpipes would probably be deepest, but two tailpipes that are large enough and unconstricted should do the trick.

So, essentially, I'm agreeing - it just took me awhile to work out why removing the baffles will work better than drilling.

[mro]

Daddy played base, momma played ???

Remove baffles, install two bolts, one near front of muf and the other near rear, attach piano/guitar string(s).

Can't play but might hum along.



mro

btw
could ask Eliberty what pipes he's got on his bike.
Almost Hardley like

[xj11john]

Ok, so general concesus is remove baffles and/or enlarge middle hole for deeper sound.

Would I have to buy anther baffle with a larger hole? The end baffle has about a 1"-1&1/2" hole, and I dont have a drill bit that big

[TopCatGr58]

Baffled with BullSh*t!?

Knewsom, that's a joke! Great Sonic Info!

Hey XJ11John,

My 4-1 pipe has this flat round plate that the baffle is attached to, and I can unbolt the locking bolt, and slide the baffle and this end plate out! The baffle looks like those old LOUVER style cuts in it. I figure I can take a piece of Pipe, something a bit thinner than water pipe, more like conduit, that has a larger diameter than my 1.5" baffle, use my dremmel cutoff disc or so to cut out the baffle from that end plate, then enlarge the hole to fit the new pipe/baffle into it, cut slots and hammer/bend them into the pipe to make the louvers/baffle sections, and then weld the new baffle onto the end plate, and then stick it back into the muffler and see how it sounds?!?!
T.C.

[xj11john]

update

Hey guys,

Just scored a 2 into 2 system, think its a universal that fits several models.

I had to attach alittle addition on the exiting hangers, but fit and sounds good.

I may do what DiverRay, and T.C. reiterated with making the baffle hole larger on my 4 into 1 or I'll sell it dont know yet, have to wait and see how this new system works out.

thank again for all the replys.

Jon

[81xsproject]

Well, drilling made mine a little deeper.

[knewsom]

Originally posted by 81xsproject
Well, drilling made mine a little deeper.

I think that's due to lowering overall exhaust velocity by providing a secondary outlet - the lower the velocity, the more time lower frequencies will have to develop.

I do still maintain that removing baffles and increasing outlet size is the best solution. (at least, in my mind, scientifically).

I'd love to hear a side-by-side comparison of the same exhaust, drilled vs baffles/outlet.