Experimenting with a different muffler

[rtking]

I wanted to look at free-flow muffler options that might work for the RX3. I looked for mufflers for a mainstream model and decided that the CBR250R would be our best bet. it's dimensionally closest to our engine... a single piston, 249.xx cc engine. The bore and stroke are slightly different, but not too different to make a huge difference. I knew none of the mounting solutions would work, so I didn't worry about that, so I focused on sound. I decided I liked the Akrapovic the best and I got lucky on a great deal on one on EvilBay.

Dimensions of the stock vs Akrapovic are very, very similar. Overall length roughly 17.5 each for both, length of can (weld to weld on the muffler can) of 14.5". The Akrapovic is a bit wider... about 4.5" wide vs. the 3.5" width of the stock can. The stock exhaust uses a 1.5" diameter exhaust pipe. The Akrapovic uses a 1.75" pipe, but the kit includes a 1/8" thick ring to reduce down to 1.5" inside diameter. I was a little surprised to weigh the Akrapovic on a bath scale (marginal accuracy) and it came out to 3.5 pounds. The stock muffler is 10 pounds

I'll have to get some flat aluminum sheet and spacers to make a mounting bracket for the Akrapovic muffler. And I'll need an muffler shop to extend the mid-pipe so it can mate-up with the stock RX3 header pipe. Not sure I can get that all done this weekend, but will update as I am able.

[SpudRider]

Thanks for letting us know about the great project.

I see CSC has announced the development of a similar muffler.

http://www.chinariders.net/showthread.php?t=15501

[Jay In Milpitas]

Looking forward to the finished installation, R.T. Is it rated to be louder or more quiet than stock?

About the weight difference, I believe the stock has a catalytic perverter,,,, converter incorporated.

[SpudRider]

Indeed, the stock muffler does have a catalytic converter.

[rtking]

Hi Jay - Spud is spot on - the stock muffler has a catalytic perverter () at the bottom of the muffler. If you look into the muffler, you'll see the honeycomb at the bottom of the muffler closest to the inlet.

The Akrapovic muffler will give a deeper tone and may be slightly louder. But it incorporates a baffle that can be removed and, upon removal, it WILL be louder.

I am taking the stock muffler (as a template) and the Akrapovic muffler to a muffler shop in the AM to see if they can bend pipe to match the stocker. That way, if, for any reason I'm not keen on the Akrapovic sound, I can always re-install the stock pipe.

[Weldangrind]

I'm quite interested in the result. I hope it breathes freely for you, without the need to modify the PCM for more fuel. Hopefully, the O2 sensor can allow the PCM to trim fuel as necessary.

Here's hoping you see an increase in power and economy, along with a good sound.

[SpudRider]

X2. Thanks for undertaking this experiment, and letting us follow the project, RT.

[rtking]

Thanks guys!

I had a little time today, so I tried to make some progress on this project. Some things I learned today:

1. The Akrapovic exhaust uses 1.75" diameter tubing (vs 1.5" stock.) This routes the exhaust pipe pretty close to the rear brake line. Care must be taken to orient the muffler and tubing to clear the brake line with enough room. (Akrapovic gives you an insert to convert the stock 1.5" header pipe to the 1.75" mid-pipe.)

2. The Akrapovic muffler for the CBR250R will need a bracket/hanger fabricated to mount to the rear-most muffler bolt. This will give you the best orientation and position when using this particular muffler.

3. You'll need to cut and lengthen the mid-pipe as provided by Akrapovic by about 8". (I'll get a better measurement tomorrow.)

4. Mounting the muffler so that it will clear the rear tire is a concern as well. Something to keep an eye on.

5. You won't be using the spring clips to hold the muffler to the mid-pipe. The orientation is wrong for this install... so I had the muffler shop tack-weld the muffler to the mid-pipe.

OK, so after all that, I have a terrible quality video of the muffler in action. (Sorry, was tired and used my cell phone to record video.) I've not published this video on YouTube (not searchable) since it's so bad, but I'll post the link here so those who are interested can view it.

The video doesn't really do the sound justice. The Akrapovic muffler with the baffle is just slightly louder than stock, but is much lower in tone. More guttural... if that makes sense. Riding back from the muffler shop, I could ride with the baffle in place with no issues. But pulling the baffle out makes the exhaust MUCH louder. I'll try to ride without the baffle to see if I like the sound.

The Delphi ECU seems to be able to adjust for the reduced back pressure. I saw idle at 2,500 rpm, but then it would settle down to 1,600. Even with the engine running, if I pull the baffle out, I can see RPMs rise to 2,000, then adjust back down to 1,600.

OK, two photos (showing the awful, temporary bracket I made), and the video of the sound. Again, sorry for the quality of the vid.

[SpudRider]

The muffler looks good, and sounds good. Thanks for posting the update, and the video.

[rtking]

Here's a photo of the bike re-assembled with the side panel on. I trimmed the home-made bracket and polished it a bit. Will try to take some ride-by videos later on in the week or next weekend and will post impressions at that time.

[Weldangrind]

That's really sharp, and it sounds good.

1. Will the panniers still fit?
2. Does the muffler have USFS approval?
3. Keep an eye on the plug for a while.
4. You need one of these: http://www.eastwood.com/mig-welder-1...5a-output.html

[rtking]

Originally Posted by Weldangrind

That's really sharp, and it sounds good.

1. Will the panniers still fit?
2. Does the muffler have USFS approval?
3. Keep an eye on the plug for a while.
4. You need one of these: http://www.eastwood.com/mig-welder-1...5a-output.html

Thanks Weld!

I believe the panniers will still fit as I measured to ensure that the muffler didn't push to far out from stock. But I'll re-install the panniers sometime during the week and will confirm.

The muffler doesn't have USFS approval. (The stock muffler doesn't either... neither will pass the "poke" test.) FMF makes a screen/baffle that can be inserted and that should work as a spark arrestor, but not sure if it will pass the 96 db test. Revving the bike, the muffler peaks at 103 db. If the measurement is taken at idle, then the Akrapovic will not have an issue passing the sound check.

Keep an eye on the plug? Sparkplug? Will do. I have an Iridium plug installed, but I'll check the insulator for color to make sure it's not running lean.

Sigh... yes, a MIG welder would be great! My Fox body Mustang could benefit from having the torque boxes welded... something I'd love to do myself.

[Weldangrind]

The spark plug will be the best indicator of how the muffler has changed things. Perhaps you should do an idle, mid-range and WOT plug chop.

Seriously, you'd love that welder. The learning curve is not steep.

[SpudRider]

Originally Posted by Weldangrind

...Seriously, you'd love that welder. The learning curve is not steep.

You have me about 95% sold on that Eastwood welder. I'm just waiting for you to test it, and verify it uses standard consumables.

http://www.chinariders.net/showthrea...t=15263&page=4

[Weldangrind]

Originally Posted by SpudRider

You have me about 95% sold on that Eastwood welder. I'm just waiting for you to test it, and verify it uses standard consumables.

I haven't forgotten. I've run into some challenges because it was not properly set up. I'm working with Eastwood on obtaining some new parts, and then I'll report on it.