Gutting The Exhaust

[BajaBob]

I know I just got off my soap box about never moding but I am truly interested to see the sound differences in what can be done with a stock exhaust. I am setting out in the name of science because someone in town is selling a stock can for $40. I am an experienced welder and have all the tools, but the best part for the community is that I have the audio recording setup to properly document the changes as well. I will start by recording the stock can. Then the drilled baffle. Then with the complete overhaul. Attached is a sketch of what I am going to acomplish. If it doesn't work out hopefully we all will be a little better informed.

Exhaust comes to me next week. But I am throwing a Halloween party so I probably won't be active on this for a while until I get my packing material and stainless tubing.

Sorry for the bad diagram. It is my first mockup that I did on my phone. I am going after a design that encompasses the design of aftermarket cans while keeping the stock look. I particularly love fabricating so this will be a fun project for me.

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[bike10]

I did this a couple years ago. sbn has the write up. if you google it, you can find it also. it sounds throttier at low RPM, but sounds quieter at higher RPMs.

 

[BajaBob]

I did this a couple years ago. sbn has the write up. if you google it, you can find it also. it sounds throttier at low RPM, but sounds quieter at higher RPMs.

I have found possibly every thread out there. I recall that one as well. Do you have a better sound file of the bike after the change?

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[AURMEND]

Only if I have the same audio equipment as you. I'm making and internal Y pipe using 1.5" Perforated piping, with fine brass wool. I'll take pictures right now of where I cut it so you can get an idea.
Here are the links since the pics are so big.
http://i.imgur.com/5TPH6Kc.jpg
http://i.imgur.com/rjdAHX8.jpg
http://i.imgur.com/MZW8GaY.jpg
Take note of the places where I cut the welds. That is where the baffles are welded on. Do what you have to do if you want to open it In half. Also I'm removing the Perforated steel sheet metal to remove weight. For your modification I would leave those on.

 

[BajaBob]

This has taken a backseat as my seller fell through. Going to see if I can't meet up with another seller. Don't want to spend more than I have too.

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[bike10]

This is what I did in 2008:

The mod includes:
Stock muffler opened up and de-baffled as well as the cat has been gutted. The sound is a lot louder than stock and quieter than after market pipes. Has a sound equivalent to a two stroke and Indy car combined. The mod took 3.5 hours.

 

[bike10]

More pics of the mod. i just left it a big open can. I didn't connect any internal tubing.

 

[FinalImpact]

This is what I did in 2008:

The mod includes:
Stock muffler opened up and de-baffled as well as the cat has been gutted. The sound is a lot louder than stock and quieter than after market pipes. Has a sound equivalent to a two stroke and Indy car combined. The mod took 3.5 hours.

DO THAT ^^ and remove the OEM tips (!7/8"), replace them w/ 1.25" SS X ~ 6.0" and you should be good to go. In short: insert 2 SS 1.25" OD pipes 6" long and drill about 12~18, 3/8" holes in the first 2" entering the chamber.

NOTE: 1.5" is TOO big and will only allow the sound waves to rattle making it sound like rice. The OEM can gives volume, it just needs the tips opened and the flow out the tips straightened by using longer tubes.

 

[vr46fan]

Sorry to resurrect this from the dead.

How much louder is it going with the bigger pipes? I want my bike to have a good sound, I just don't want it deafeningly loud.

 

[FinalImpact]

To date; I'm not certain ANYONE has replaced the outlet pipes. Many go to the effort of gutting the internals and then buy aftermarket cans because their efforts didn't make it any louder, it just changed the tone.

With the smaller outlets, the velocity is higher and the sound waves travel in a linear fashion to the exit. Think, no side to side movement because all the sound waves are pointed the same direction. Its what gives it that WOOSH sound.
By increasing the diameter of the outlet size, the sound waves have more freedom. The velocity drops as the volume (air volume) increases, and the sound volume goes up as the gases can rattle about upon exit as they are no longer following that linear straight flow.

If you don't exceed 1.5" ID (38mm), it should be louder but not obnoxious. 1.25" is very safe, but may be disappointing. However, it may be perfect. Its a good starting point. It depends what you do to the insides.

I bought a spare muffler, grabbed the parts and then a set of Two Bro cans came up 4sale. Plus they were all black and in my price range. So I didn't stub it to 1.45" ID which was my plan.

Hint: my plan was this. Saw off the fake cover thats tacked on. Saw off the OEM outlet. Tack in a piece of metal to fill the hole. Using a Drill and a Hole saw (these want a center to support to guide them), Cut the area around the OEM outlet to 1.5" leaving a nice round hole.
- The inside can have pin hole leaks (just make CERTAIN, nothing is free to move and rattle). The outlet cannot have leaks.

Good luck!

 

[vr46fan]

I am more wanting a better tone then just volume. My plan is to put 1.25 pipes in. Forgive me for my ignorance, but what does drill holes in the first couple inches of pipe do for sound?
There is a YouTube video of a guy who replaced the pipes on his. I don't know what size he used but it sounds very nice.

 

[Koozi]

To date; I'm not certain ANYONE has replaced the outlet pipes.

About a year ago I bought an exhaust from ebay for $75 and gutted it with a perforated Y-pipe and used stainless mesh as an internal baffle. I cut the outlets out and replaced it with the largest OD pipe that would fit through the stock exhaust cover outlets.

It sounds way deeper at idle and low rev. At the higher revs it quiets down. It does not rasp or drone while you ride it.

As a mod I like it. As far as price vs a replacement exhaust it cannot be beaten.

My avatar is a tiny pic of the results. I have a few more of the creation process if anybody is interested.

 

[FinalImpact]

VR,
Did you notice the OEM parts are flared like a trumpet outlet? Unless you have the means to do something like that, most of us could drill holes. I believe the theory is to simply get the gases moving into the pipe to improve the flow. It seems pretty comon even for db killers from the big names.

 

[vr46fan]

That makes sense. I haven't started tearing it apart yet. It looks like the factory tips are 1.25", so I think I might just cut the welds off and see if I can use the bracket as a guide for the hole saw.

 

[vr46fan]

About a year ago I bought an exhaust from ebay for $75 and gutted it with a perforated Y-pipe and used stainless mesh as an internal baffle. I cut the outlets out and replaced it with the largest OD pipe that would fit through the stock exhaust cover outlets.

It sounds way deeper at idle and low rev. At the higher revs it quiets down. It does not rasp or drone while you ride it.

As a mod I like it. As far as price vs a replacement exhaust it cannot be beaten.

My avatar is a tiny pic of the results. I have a few more of the creation process if anybody is interested.

What size pipes did you use? And I would be interested in seeing the pics. I plan on starting to cut mine up today if I have time.

 

[vr46fan]

For those that have done this, did you reinstall the mesh packing? I'm curious how much hotter this will get if this is left out.

 

[Koozi]

What size pipes did you use? And I would be interested in seeing the pics. I plan on starting to cut mine up today if I have time.

Sorry I did not come back sooner. Even sorrier that I cannot find all my pics from when I did this. Usually I keep everything, but many of this project are gone.

I do have a few:
Here it is right after it was opened up. I am pretty sure this was mine, although it was in a folder with a bunch of "research" pics I collected before I started.

Everything out of the innerds:

Cutting out the outlets:

The only pic I can find of the new outlet pipes:

They are 1 5/8 ID
1/8 or 3/16 thick walls

I used perforated metal to connect the single in pipe to the dual out pipes.
I stuffed all the empty space around the pipes with stainless steel wool from walmart to avoid any buzzing or tinny sounds.

Scotch-Brite Stainless Steel Scrubbing Pads, 3 Pack: Cleaning Supplies : Walmart.com

I think I used 9 or 12 of them. Just pulled them all apart and shoved it in the empty space before welding the panel back in.

Hope this helps. I will try to be more timely if you have any other questions.