This question isn't actually seeking a CFM number, it's just a good way to sum up what I need.
I'm bored and I'm rebuilding/resurrecting a really nice old pressure washer. It's a Honda (copy) 212cc engine with a really nice 3600psi/2.7 gpm triplex pump and it will rip the smile off the Mona Lisa if you're not careful.
Long story short, the muffler is pretty rusted. I can get another plain muffler, but I got the itch to build one that isn't louder than a small bomb. I know most of the noise comes from the engine itself, but I thought I'd try to shush it up a little. I watched some online videos of other DIY attempts that were mostly unsuccessful, but something hit me in all of their designs. They sucked. They were basically reproducing a straight-through glasspack, which is probably worse than the factory muffler. This guy made a chambered/turbo setup and stacked a glasspack on the end, but he never upped the tubing diameter, and I have to wonder how restrictive it might be.
I was going to do a "turbo" style muffler, and since I have plenty of space, I can make it overkill flow. I'm thinking that if the factory exhaust tubing is 1" diameter, if I make a turbo style muffler with 2" perforated tubing and some fiberglass, it likely won't even know it's being muffled at all. Instead of trying to make a 1" quiet muffler, it will be like dumping the exhaust into a padded room.
Am I nuts?
I think the idea is solid. It sounds like the perfect place for a sport bike takeoff muffler. They are usually chambered, smallish inlet pipe, made of high quality materials that wont rust in pressure washer environment, and best of all will not just be nuts-it will look nuts too!
I've long been a vociferous proponent of actual turbochargers as mufflers--given that they take the exhaust note of a 13B Mazda rotary and mellow it right out, making an additional muffler unnecessary. Why not put an actual turbo on this little engine and get the horsepower bump that forced induction will give you?
In reply to Curtis73 (Forum Supporter) :
Yes, you are nuts. But we love you anyways.
I have a couple of Coleman minibikes. I bought a Chinese 212cc off of the jungle website that I'm hopping up. Most people run the most obnoxious header they can find but I want to make an exhaust that won't piss the neighborhood off.
I've bought a few types of mufflers to test out. One is a snowblower muffler that is supposed to be quieter that the massive box shaped stock muffler. But unfortunately I couldn't get it to fit in the minibike frame.
Part number of that muffler is 532444277.
The problem I was having was finding a muffler sized for the size of engine I was working with. Most were 2" diameter and up. But I found this muffler that has a 1" core. Its a glass pack style muffler, which I know you said wasn't really what you were looking for but I think you could weld some pipe to it or even run two in series.
I plan on having an exhaust welded up using this muffler and making the exhaust longer than most people would do in an effort to make it quieter.
https://pertronixbrands.com/products/patriot-exhaust-h3133-muffler-mini-style-1-core-12-length-1-1-2-case
I'd use some rockwool and chamber it back on itself then out. Wish I knew how to draw on this as I could draw up how it's would look inside. They are very quiet at any size. Bigger pipe will just give it a deeper and louder sound.
My first design idea. I have some 4" steel tube. In this design, I'll cut four plates 4" in diameter to make 3 chambers. One tube goes through to the 3rd chamber, one tube travels back to the first chamber, then a third tube spans the second and third chamber to exit. All tubes will be perforated as they pass through the second chamber, and surrounded by rock wool.
Something like this, but I can't get Sketchup to only put perforations where I want them.
Second design thought is similar, but would just make an open chamber, then three muffled chambers, then a third open chamber.
brad131a4 (Forum Supporter) said:
I'd use some rockwool and chamber it back on itself then out. Wish I knew how to draw on this as I could draw up how it's would look inside. They are very quiet at any size. Bigger pipe will just give it a deeper and louder sound.
Agreed. My goal is to more or less give it the same exhaust length to the muffler so as to not change the torque curve, then give it a padded room that offers no notable restriction. The nice thing is that (unlike a car) I'm not limited on flow characteristics. I just want it to present no restriction, but be more of a sound-deadening room.
1988RedT2 said:
I've long been a vociferous proponent of actual turbochargers as mufflers--given that they take the exhaust note of a 13B Mazda rotary and mellow it right out, making an additional muffler unnecessary. Why not put an actual turbo on this little engine and get the horsepower bump that forced induction will give you?
Could you use the airflow the turbo creates for cooling? Turns a turbo in to a muffler and a cooling fan.
dean1484 said:
1988RedT2 said:
I've long been a vociferous proponent of actual turbochargers as mufflers--given that they take the exhaust note of a 13B Mazda rotary and mellow it right out, making an additional muffler unnecessary. Why not put an actual turbo on this little engine and get the horsepower bump that forced induction will give you?
Could you use the airflow the turbo creates for cooling? Turns a turbo in to a muffler and a cooling fan.
I would have the first adiabatically-cooled pressure washer.
Well, for better or worse, this is what I ended up with. It's a mixture of the two above.
I took 9" of my 4" tube and divided it into four chambers. The header will exit into a 1.5" tall open chamber. Below that chamber is some perforated steel with rock wool, then a solid plate, then rockwool, then perforated steel.
The bottom showing the divider plate and two perforated 3/4" EMT tubes sticking down 1.5"
View from the top showing 4.5" of perforated tube sticking up through the divider plate.
The bottom after adding 1.5" of rock wool and perforated steel
Same for the top cavity. 4.5" of rock wool and perforated steel
The red arrow shows the direction of the inlet. The thought is it can enter and bounce around the sound. Then it goes down through the perforated tubes through the divider and exits toward the bottom cover. I'm hoping that some of the remaining sound waves will bounce up into the 1.5" of rock wool in the bottom chamber. Then it will exit the side (blue arrow)
I think it should work pretty well. There is zero "straight through" but there should also be next to no restriction. The header pipe off the manifold is 3/4", and the most restrictive part of this muffler is twin 3/4" perforated pipes.
Only downside (as you can maybe tell) is that the materials I had on hand are pretty beefy. Probably good for sound attenuation, but the thing weighs about 10 lbs :D. I'll have to support it on the bottom.
The only thing I'm 10% concerned about is how sensitive the engine is to these changes. The original 3/4" pipe is about 2" long before the muffler. I'm adding a tiny bit of diameter and length to the header, but then I think the rest is no restriction. I guess we'll find out.
Lol-You will definitely not get any sound from the muffler case drumming.
dean1484 said:
1988RedT2 said:
I've long been a vociferous proponent of actual turbochargers as mufflers--given that they take the exhaust note of a 13B Mazda rotary and mellow it right out, making an additional muffler unnecessary. Why not put an actual turbo on this little engine and get the horsepower bump that forced induction will give you?
Could you use the airflow the turbo creates for cooling? Turns a turbo in to a muffler and a cooling fan.
I'm not sure how well that could work, turbos need the airflow from the compressed air going into the engine in order to spin them up in the first place. (Ah, lag...)
I'm now curious to see how fast a turbo would spin when unloaded, and how the airflow is at zero pressure ratio at that speed.
The other thing is, they only really muffle when they are making boost and thereby loading the turbine. It's so weird to have a turbo engine that gets quieter when you open the throttle and start building boost!
MrJoshua said:
Lol-You will definitely not get any sound from the muffler case drumming.
Right? Those exhaust pulses will have a serious headache.
For a 212cc engine governed at a steady-state 3600 RPM, big power gains through huge flow and/or tuned length probably aren't realistic options. What's on there now was chosen because it was cheap, compact, and cheap, in that order. So you won't likely make it worse.
Stock headline diameter is, what, [EDIT: I see now that it is 3/4"]. Stay with the same diameter until you get to the muffler. Given enough muffler volume to spread the pulses out, I bet you could even drop to a smaller diameter outlet, maybe down around 1/2", without losing power. Plenty of very rapid motorcycles came equipped with mufflers you could barely get your pinky into. And that would help bring the noise levels down. Turning the tip down so it points at the ground will help a little, too.
If I was in your shoes, I'd probably smash the easy button and grab something like this for cheap money:
It's fun to experiment and build stuff, though.
