PM MUFFLEREXTRACTECTOMY!!!!

[GM0406]

Ok, Here is what happened.  I went out to remove the plywood  apron from the rear of the bus that covers the opening in front of the bumper.  You see the bumper has been extended back to accomdate the muffler that lives inside it.     So I removed this plywood brain child after having to get out the dremel cut off wheel and finally wound up just breaking it out of there.  Next it was time to consider the muffler arrangement, because it was basically emitting vibes that were telling me there is serious trouble here!     After thinking it over, seeing that the muffler had two big holes in it where it had been welded, and subsequently ripped out, at the top to a piece of sheet metal on the engine rack, I decided that this muffler had to go.  With basically no isolation, sometime after the installer stuck this thing in there, it let go.    Now the only things that kept this muffler in there were the connection clamps and the trailer hitch supports.  Just luck that this thing didn't wind up in some poor souls face after a bump and bounce that could well put it through someone's windshield.    So, I had at the thing and loosened or broke the bolts holding those straight clamps which were all super tight except the one that was getting a real pounding by the engine and it was loose!  Finally extracted the thing and a couple of pipes in between the last downpipe from the turbo and the muffler.   

So, now to Plan B.  And that will be a straight pipe from the downpipe to just behind the bumper.  That's the way it was on the original bus, and it will have to live like that for a while until I think something else up.   

In my mind I justify this by asking the question, how much noise can get past that turbo?  There was a friend in our bus group who had two straight pipes on his 8V71 without a turbo.  And I am here to tell you that when that coach came through town, people knew it!!   

Bill T. 

[TomC]

I think you'll be surprised at just how loud a turbo exhaust can be.  I have a 5" inlet and outlet on the same side that you could mount where the A/C compressor used to be.  The muffler is 26" long and is an oval-and rated for turbo use.  It has a nice tone to it and flows quite well.  If you need the Donaldson number, I can look it up for you.  In this day and age, I'd highly recommend you NOT run without a muffler-just too loud.  Good Luck, TomC

[JohnEd]

I wanna hear too.  Run without it for at least a while.  Can you post a video with sound?  A picture is worth a thousand db.

John

[GM0406]

Well,  I finished it last night.  The downpipe turns toward the rear and then I added a 90 that I removed from the old setup so that it exits left under the radiator.  Not good for clearance, but that's all I have for now.  I will have to be very careful going over approaches.  Will see today how loud it is.  I started it with just the downpipe yesterday, and couldn't tell much difference in sound.  That turbo must be quite a muffler.  I know that the 8V71 N is awful with duals and straight pipes.  This has no resemblance to that thunder rummble!  And if Tom C. is coming to the Rally Saturday, he can hear it and see what he thinks.  Bill T.

[gm4106]

HI Bill
Here is a before and after muffler change I did on my GM 4106 8V71TA.
And like Tom said before new muffler new sound,love it

[gm4106]

Oops foregot the before

[JohnEd]

GM41,

Nice job!  Hope you post vid with audio.  But, I haven't a clue and can't do that either.

John

GMO4,

If you can possibly run without a muffler.....do it.

[CraigC]

Bill
I ran my 8V71TA in my 4104 for about 2 years with a straight pipe plumbed like GM4106's. It was very loud. I have had a few friends tell me they could hear it pulling away from stop lights in the city 2 plus miles away. Coming down hills with the Jake on the sound was not reasonable. I would turn the Jake off if I saw a patrol man. Even at idle it was too loud. There was nothing reasonable about my straight pipe.

I currently have a muffler it has is a very pleasant sound. It is a Napa 22771 that was not designed for a turbo engine. I have cut 12 - 3" diameter holes in it to lessen the restriction. My fan drive gives me 7" less clearance between the engine and fan blades. Finding a place to mount a muffler was a challenge.

GM4106
Is the muffler you have installed designed for a turbo. If it is would you mind supplying the make and model number.

Craig Craddock
Lemoore, CA
GM4104-765

[GM0406]

So, As you can see, my setup is different from GM4106 and Craig's.  My unit has an Air Research Turbo.  I have only seen one other coach with this arrangement that Gary Nickerson brought to the Rally in Quartzite a few years back.  In fact I wondered if he had done my coach since it looks identical to his.  Today is the moment of truth since I will be running this '06 to Monterey for the Rally.  So listen up all who are going.  If you hear me coming two miles away, call me on the radar (CB) and you can tell me if the noise is getting louder or softer.  If it is getting softer, I will know I am going the wrong way!  By the way, do those trains have mufflers on them?  If this coach is too noisy, then I will go back to the muffler in the bumper.  I am in better shape now with an aluminum apron that I installed yesterday.  The muffler in the bumper is a real neat trick.  I composed an interesting few paragraphs on experience in our Air Conditioning Industry on vibration control and included pictures, but the whole thing got lost because the pictures took too much space and you better be careful to copy what you write here to your clipboard in case you get dinged the same way.  Instead of allowing you to resize your pictures, the program here is hostile and kills eveything for you and then you are back to trying to remember what you wrote.  So to make a long story short, any mass you hang out there which is not bolted closely to the engine,  starts a fight that has a loser.  And that is going to be the weakest part of the piping or in this case muffler or whatever else is between the engine and the remote mass.  Reducing the remote mass is good, but ultimately, something will give.  Now, there is a critcal mass which if large enough will absorb vibration at the source.  You would think these massive engines meet that criteria.  If so, then go ahead and hang remote masses and all should be well.  Unfortunately I have some stress cracked parts of the old exhaust system to put in evidence here to make a good case for a remote mass hanging sanity check!  Not done with this yet.  There is another real problem with diesels and exhaust extended masses.  On shut down, a diesel will have a backlash torque that can yank the ex pipe big time.  Peugeot tackled this whip and used a ball socket flange connection with two bolts with spings.  The trick was to get the spring tension correct.  Too much and you crack the down pipe from the turbo.  Not enough and you have a hell of a knock and/or rattle at various speeds and bang when you shut here down.  Good way to get a good Peugeot cheap if some unexperienced gnave either overtightened or under tightened this connection.  The owner will gladly sell it cheap thinking that the thing is junk, when all it needs is correct pressure on the joint.  This may be where the expression muffler bearings or muffler springs came into existence since this joint is very close to the muffler!!!     In our industry to get away from the vibration monster, we use big concrete pads.  Mound the refrigerant compressor (some 12 cylinder) solid to these pads and then spring isolate the pads.  If the mass of the pad is correct, then all the vibration is grounded and you don't need to worry about your extended masses.  But without this concrete mass, sooner or later, you will have something in the piping break, and this is not nice when it comes to refrigerant and oil escaping.  Here we are only talking exhaust leaks.  On buses, we can't do the concrete pad thing, so we have to get a lot more creative.  Bill T.

[gm4106]

Craigc
Yes it's for a turbo motor. The muffler is a Donaldson part#M090595. Gave $105.00 for it. I felt this was a Good price. Hope this helps

[Utahclaimjumper]

Last Jan. I was sitting at an intersection in Quartsite and heard a B29 go thru the intersection, it was Gary Nickersons 4106, I followed him to the GMC parking area.
I've known Gary for a number of years and his bus has allways been loud.>>>Dan

[GM0406]

Folks,  Reality set in as we actually got out on the freeway and drove south.  Low and behold the double el that I put on the turbo downpipe got loose and my sson told me he heard rattling and I told him to check all the blinds to see that they wrere up and not the cause.  He said it sounded like it was coming from outside under the coach.  So I pulled off 101 South and got on Montery Road where we came to a stop under an overpass.  And yes, the 5" double el had separated from the clamp and was still held by the cable that I installed to hold it!!  Some scuffs, but still fine.  So we stowed it and headed South.  We went to Leguna Seca where the Rally was held.  Needless to say they heard us loud and clear coming up the 16% grade where the 871TA V730 wanted to shift to second on the way up.  Plenty of power to hop up over that hill, but noise was awesome!  So the cure was to spend from 10:00 AM to 7:00PM with my friendly (slow) muffler man who mounted a striaght through muffler I found at the truck wrecker quite securely so that we don't think it will fall off again!  There seems to be no power loss, and noise is definitely gone.  We used the semi's chrome stack end to turn the outlet down to the road.  About $400 later with a new stainless 5" flex, we hope not to be visiting this muffler tooter again!  Bill T.

[GM0406]

This is a picture of the finished rear appearance after the exhaust redo and my installation of my own aluminum apron.  Bill T.