baffle-muffler

Background

After the initial excitement of actually getting the car on the road I soon realized that the exhaust sound was just WAY to loud! In fact it was absolutely deafening above 5,000 RPM! Something had to be done.

Plan A

I tried a racket buster on the stubby exhaust stack that was a few inches long right at the muffler. It helped a little but not enough to matter.

Plan B

I really wanted the exhaust from the muffler to go out the back of the car and it seemed logical that it should reduce the noise somewhat.. I used some stainless steel pool ladder tubing to fabricate the exhaust pipe from the muffler to the rear of the car. It really didn't change the exhaust noise level at all.

What should the next plan be?

At this point I started investigating why this muffler was so loud. Since it is the stock muffler that came with the GSXR-1000 I realized that something really screwing was going on. When I had removed the end cap from the back of the muffler to install the longer tail pipe, I noticed that the short outlet pipe in the muffler was a 9" piece of pipe that extended into the muffler to an open chamber. Most bikes that I've played with had some sort of baffle or screen with a porous material wrapped around it. This muffler had just an open pipe. I looked on Internet and found all sorts of motorcycle muffler baffles but none for the stock GSXR-1000 muffler.

I went to the local Suzuki dealer and got conflicting answers to my question if the stock muffler in 2002 had a baffle of some sort. Basically none of the service people had ever taken one apart and the parts book didn't show one. My personal service manual doesn't show a baffle either. But I'm pretty sure that there is supposed be one in there since I've never heard a Suzuki motorcycle this loud with the stock muffler.

I usually hang out on the LocostUSA.forums. I posted a question about the stock muffler baffle and got various responses including the suggestion that perhaps my muffler was originally designed to be used with a catalytic converter. I can't imagine how a cat converter could be mounted on my stock looking muffler, but maybe?

The part number on my muffler is ""40F0A" and as far as I've been able to determine is that it was used on the 2001 and 2002 GSXR-1000s. If anyone has any information about a baffle for this muffler I'd appreciate hearing from you.

The almost final solution

After building several space frame cars, go karts and Locouki I decided the heck with it, I'll just build a muffler baffle and see if it works. The main problem I was concerned with was that I didn't restrict the exhaust flow and cause excessive back pressure. I decided to build a tapered screen of some sort and keep the outlet end diameter of the baffle big enough to handle the rather large exhaust volume at 12,000 RPM. The pictures below show how I made the baffle.

The real final solution

10 May 2007
After driving the car around a bit with the tapered screen baffle, I realized that it was still too loud. I could hear the intake noise once in awhile but the exhaust was still way too loud. I removed the tapered baffle and hacksawed off about 1" of the small end of the screen (including the small washer). I then slit the screen into four 1/2" long pedals and folded them over on top of each other to form the new end. I also wrapped the baffle with some stainless steel (s.s.) wool and inserted it into the outlet pipe as before..

By shortening the screen, the whole baffle is completely contained within the 9" long outlet pipe. These changes resulted in the exhaust noise finally being lower than the intake noise. A lot of the noise I am/was hearing is caused by the intake but it is not an annoying sound. But it certainly gets your attention as it screams and yowls when you accelerate hard through the gears! With my air scoop open at both ends I think a good bit of the intake noise is directed fore and aft for my listening pleasure.

18 May 2007
I finally have my exhaust noise under control. The last version of my baffle with the s.s. wool packing was actually too quiet. So I modified the small end of the tapered baffle by opening the 1/2" screen pedals slightly to control how much of the exhaust/noise is bypassed directly to the outlet pipe. The packing seems to be holding up OK in the exhaust heat.

I want the exhaust sound to be slightly quieter than the intake unless I really give it the gas. That way my ears will be spared but it won't be so quiet that no one knows I'm there. Of course when you really give it the gas EVERYONE knows you are around! The intake system howls like four screaming organ pipes. Then add in the enraged exhaust roar to that .......................!

The following is a series of pictures that show how I made the baffle which tamed the beast.

This is the steel screen that I used to make the baffle. At this point I had just started forming it around a 1"diameter piece of pipe.	This is an end view of the same screen. The screen was originally an internal cover for a radio transmitter.
This is the baffle after I formed the material into a tapered tube. The washer on the left is a 1" diameter washer and has a 3/8" diameter hole. The larger washer on the right was machined to 1.7" outer diameter to fit snugly into the muffler outlet pipe. The hole was enlarged to 1-1/8" diameter. (This picture was made before I shortened the tube 1-1/2".)	This picture shows the baffle after the washers were brazed on the ends. Actually this picture was made after I had driven the car to test the baffle. Note that the cadmium plating has been discolored from the heat after a 10,000 RPM blast!
This is the outlet end of the baffle. I used some stainless steel screws to hold the screen together.	This is the "inlet" end of the baffle. This is the 1st version of the baffle. Since this picture was taken, I have shortened the screen length by 1-1/2" as described above. The screen pedals overlap each other slightly at this end of the baffle tube.
Here are all the pieces that go into and on the end of the muffler. The baffle is inserted into the exhaust pipe in the direction that it is shown. The small end doesn't extend past the forward end of the muffler outlet pipe. I wrapped the baffle with stainless steel wool before inserting it into the outlet pipe.	Notice the small hole at the top of the muffler output pipe where a stainless screw is used to hold the baffle and the tailpipe onto the muffler. You can see the sun shining through the hole onto the inside of the pipe. The tailpipe slips over the outlet pipe. The screw extends through the tailpipe, through the outlet pipe and finally through one of the holes in the baffle screen. This holds everything in place.
The baffle is partly inserted in this picture. The large washer will just slide into the muffler tailpipe. Since this picture was taken I've wrapped the baffle tube with stainless steel. wool. The set screw doesn't allow the baffle to rattle in the muffler.	This view shows the baffle fully inserted into the muffler. The baffle can be removed by using a large hex head bolt to grab the large washer from inside the baffle. The baffle is then just pulled out of the muffler.
This view shows the tailpipe slipped over the muffler outlet pipe, the set screw that holds everything in place and the original decorative cover that will hide the screw.	And here is the final product fully assembled. The pool ladder really makes a nice tailpipe. The tailpipe angles down towards the ground and then runs parallel to the side of the body towards the rear of the car. See "miscellaneous hints" for a way to keep the exhaust pipes from turning blue.

For those that are interested here are the dimensions of my muffler (Suzuki p/n 40F0A)

Total length...........................17"
Muffler diameter....................4-1/2"
Inlet pipe dia..........................2"
Outlet pipe dia.......................1.7"
1st internal chamber length.....6-1/2"
2nd internal chamber length...11"
Connecting pipe length...........5"
Outlet pipe length...................9"

General description

The muffler has two chambers connected by a 5" length of 1.7" diameter pipe. The walls of the chambers are made up of a perforated screen with some sort of packing between the screen and the outside wall of the muffler. The outlet pipe is angled to the axis of the muffler so that when the muffler was mounted on the bike the outlet was horizontal. The internal end of the outlet pipe overlaps the internal connecting pipe. This causes the exhaust to to be directed towards the rear end of the muffler as it moves from the 1st chamber into the 2nd chamber. The exhaust then has to reverse direction to enter the outlet pipe on it's way to the atmosphere.

Even though my muffler is labeled that it meets the federal requirements for noise at 80dBA it is VERY noisy without the baffle I made for it. There is NO way it meets that specification without the baffle.

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