Does anyone know the correct Donaldson, or equivalent, muffler # for a MC8? Any success stories?
For what its worth, my mechanic has removed the stock MC7/8/9 mufflers on 2 buses recently and knocked the guts out of it and then welded them back up and owners have reported they run much cooler.
My Series 60 was overheating and the same mechanic removed it and replaced it with a Resonator and my bus runs much cooler too.
The stock muffler is quieter which is kind of important when you have 40 - 50 passengers on board and driving thru big cities and when the bus is relatively new, but once the radiators start getting restricted, things start heating up and a restrictive muffler works against you in a bus conversion.
Something to think about before you order a replacement.
Or if you really want a stock muffler, you can run with your back doors open when thru Arizona in the summer like I used to do. ;D
Gary
Gary I am so glad Joe cut my muffler off and we put on the resonator. Our MCI 7 with 8V92 runs so much belter. Less smoke under power, doesn't bog down on hills like it used to, runs cooler and just all around better. I wish I would have known and done that 17 years ago. Thanks for introducing me to Joe
Donaldson style 5 is inlet and outlet on the same end, MCI is an odd size outlet 4.25" I think, I used a M120131 which is 5" in and out, resonator, with a turbo engine, the same size but a muffler is M120176. It is significantly smaller and lighter than the stock MCI muffler but with a little fab work on the mount it works just fine, sits in the original spot.
Have found a local supplier for the M120131 Donaldson MUFFLER for our MC8 - does anyone know if this muffler will work/fit in our MC5A as well? Stock ID was 8b-20-1. Thanks. :)
Many people are tearing out their MCI mufflers and installing straight-thru Resonators instead. The stock mufflers hold back too much air causing overheating especially when engines get old.
Others are splitting them open and cutting out all of the baffles to it can breathe better and welding them back up.
They will be a bit louder without a standard muffler but the resonator is not that loud and lets the engine breath a lot better.
I took off the giant transit bus muffler (was very quiet) and replaced it with the Donaldson 120131 10x15 oval 5" same side in and out. It is a high flow turbo muffler. If you look inside, it is empty except for the baffle that separates the right from the left. It puts out a nice tone-lets everyone know you're there, but not too loud. No need for an additional resonator. Highly recommend this muffler. I'm using the same muffler on my truck conversion. Good Luck, TomC
Yeah...it is not very loud from 35 to 40 feet upfront.
Quote from: chessie4905 on August 27, 2019, 10:27:10 AM
Yeah...it is not very loud from 35 to 40 feet upfront.
;D
This sounds like a great idea to help with hills and overheating. What is a resonator? is that simply a tail piece add on?
It's a muffler with a straight-thru design, usually with a perforated center tube with fiberglass stuffed around it, like the old hot rod "glass packs". It reduces the back pressure while making the exhaust sound more robust (or noisy in some ears). ::)
Great...
More old buses driving around making a hell of a racket.
And that won't cause the hobby any trouble with the authorities or public opinion?
Do we really need more attention?
If your bus overheats, fix the cooling system.
Happy coaching!
Buswarrior
Some call it "noise". I am a Bus Nut, I call it "music". And to use Jakes on top of that? WOW! ;D
When idling thru a campground, a Resonator does not sound that much louder than a regular muffler if you keep off the throttle.
I would much rather listen to a bus than some of those "noisy" Honda cars out there with "stock" mufflers that drive me nuts. >:(
I used to have a Harley in a previous life. I guess people would hate me for driving that too. ::)
Some of us hate you for all the noise. 🤨
If we have resonators we would still be much quieter than a Harley with straight pipes with the radio turned up loud so that everyone can hear it over the pipes. :o
Resonators are designed to be used behind another muffling device, in my case a turbo. Mine isn't significantly louder than the stock muffler without a turbo, and the actual engine is a lot louder than the exhaust at idle. Donaldson makes the exact same device as a muffler, 10 - 15 dB quieter, and that would be perfect for a non-turbo engine.
Quote from: DoubleEagle on August 28, 2019, 07:32:44 PM
If we have resonators we would still be much quieter than a Harley with straight pipes with the radio turned up loud so that everyone can hear it over the pipes. :o
True, but a Harley doesn't stay within earshot nor on the throttle quite as long as a 35,000 lb bus going up a slight grade from a controlled intersection.
1974 MCI MC-8, 8V71 turbo. Ok, so I decided to do some experimenting. The thought of possibly increasing horse power, and decreasing overheating by gutting the muffler or installing a new one is very intriguing to me. So I looked under my bus and saw that I have a 5+" exhaust coming off the turbo and going into the stock muffler. The tail pipe is only 4+", so with the baffles, I'm certain there is a lot of back pressure.
So, instead of taking the muffler out, cutting the top off, knocking the baffles out and reassembling, I am using a different approach (worst case is I ruin the muffler, and install a new Donaldson muffler anyway). I drilled a 4" hole in the rear of the muffler (without having to remove it) in the end panel about 3" to the left of the tail pipe muffler termination. After drilling through the outer shell end panel, there was another wall about 1" in, so I drilled that one out too. Looking inside, there is another baffle about 5" in with about a 5" hole in it allowing gasses to transfer from this cavity to the next one. I can also see where the 5" inlet pipe terminates in this cavity after first going to the rear of the muffler, turning, and returning to back to this cavity (it has a bunch of tiny holes in it drilled in a spiral fashion).
The cavity I have accessed would pressurize, and the exhaust gasses would go back to the rear of the muffler again through the 5" hole in the baffle, and eventally into the tail pipe, and out of the rear of the muffler. Since I am in the process of changing the oil, I have yet to fire up the bus and see how much air comes out of this new hole, but if this works out, I plan to install a tail piece to the new hole and terminate it as the original tail piece does out the rear of the bus.
My theory is that this will cut the back pressure in half, with the exception of some balancing efficiencies not being taken into consideration (most likely the two tail pipes will not have an equal amount of gasses traveling through them but I'm almost certain about the reduction of back pressure).
As with most of my half finished projects, I will let everyone know how this goes. I should be firing up the bus this week sometime. Glennman