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Author Topic: Muffler  (Read 3500 times)
Blacksheep
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« on: May 26, 2009, 06:28:35 AM »

Can a new muffler cause a bus to be sluggish on take off? I would think it would since an open exhaust creates more hp. Talking this over with a friend he came up with this thought and I am just curious as to why the sudden lack of power from a dead stop. First if you remember I thought it was the air filter. Now the muffler makes more sense!

Ace
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luvrbus
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« Reply #1 on: May 26, 2009, 06:59:18 AM »

Ace, is your boost pressure the same as before the new muffler, if it is I would check the bypass valve on the blower this will make the engine slow on take off till the turbo spins and makes more air      good luck
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« Reply #2 on: May 26, 2009, 07:31:01 AM »

Ace,don't forget to check the spark pugs and muffler bearing Cheesy

I'll go Quietly now Wink
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« Reply #3 on: May 26, 2009, 04:32:42 PM »

Could be the left over corn expanding.  Where did you leave it?
Jack
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« Reply #4 on: May 27, 2009, 07:22:52 AM »

A stuffed up muffler will most likely cause smoking at full throttle-not at take off.  If you are not getting smoking at full throttle, then it is not the muffler.  Simple-disconnect the pipe to the muffler and drive it-it will be a bit loud, but it will answer your question. Good Luck, TomC
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Blacksheep
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« Reply #5 on: May 27, 2009, 07:44:39 AM »

I doubt the muffler is plugged. The entire exhaust system is new from the turbo! I just noticed a difference in acceleration since it was replaced. Before with the old muffler that had a hole in it, it accelerated much quicker! Now it seems more sluggish!
Just an observation!

Ace
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« Reply #6 on: May 27, 2009, 07:50:51 AM »

I doubt the muffler is plugged. The entire exhaust system is new from the turbo! I just noticed a difference in acceleration since it was replaced. Before with the old muffler that had a hole in it, it accelerated much quicker! Now it seems more sluggish!
Just an observation!

Ace

Ace,

I bet thats exactly what you are felling.

When I redid mine with the dual outputs(easier breathing), I had a noticable pickup on takeoff, but that was it.

You are just feeling the "normal" without the the ventilated muffler casing(isn't that a nice way to say a muffler with a hole in it.. Grin)

Cliff
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« Reply #7 on: May 27, 2009, 08:04:16 AM »

Are you sure it is really slower?  I know in my younger days, putting loud pipes, or even just blowing a muffler, always made it seem faster, but it really wasn't (as proven by my competition).
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Blacksheep
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« Reply #8 on: May 27, 2009, 08:31:22 AM »

Its definitely slower! I NEVER had to floor the pedal. Now its floored until maybe 3rd gear. Before I could half throttle and jack rabbit off from a stop and shift on thru the gears! Now its seems to be a slug!
I have another new muffler compliments of Prevost. I might look at maybe doing some internal modifications to have quiet and performance!

Ace
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« Reply #9 on: May 27, 2009, 09:40:02 AM »

Just a dumb question on my part since I know you just had a bunch of work done on her, but didn't they damage the turbo? Or am I thinking of someone else? When you floor it, does it heave out black smoke?
I'm not the brightest when it comes to these beasts, but I think I'd do as Luvrbus suggested and check the boost pressure and the bypass valve before going any further. It sounds logical, Good luck, Will
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« Reply #10 on: May 27, 2009, 10:07:32 AM »

Ace,

Luvr usually goes straight to the meat of the matter.  Determining the boost pressure would eliminate that turbo they dropped and chipped as having anything to do with your problem.

TomC made good sense, as usual, about eliminating the muffler as a cause.  Disconnect it.  I think you said that you were pondering installing a Prevost muffler anyway so that move would put you half way there in that operation.

Isn't it logical that if you have taken a hit in the power department you are probably going to suffer in the MPG arena?  I think you have good reason to be trying to resolve this......it will probably pay dividends.

Don't forget Sean's dismal experience with "dirt" trashing his 8V92 after an overhaul.  Some real incentive there...you betcha.

The shop you were dealing with got high marks from you.  What do they say?

Thanks,

John
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Blacksheep
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« Reply #11 on: May 27, 2009, 11:04:00 AM »

Hmm, completely forgot about the Turbo incident. Might have to inquire about that!

As for the new muffler? It already has one. Its a long story of how I acquired 2 but I have another new muffler in the shop.

And for the shop that did the work? I actually went camping this past weekend with the owner and his wife. We talked briefly about the smoke and sluggishness on acceleration and I'm sure we can come up with a solution to the problem IF there is an actual problem. It may be me afterall!
It made sense about the NEW muffler having more back pressure than the old one with a huge hole in it.
As for boost pressure? My bus does not have a gauge so I would have to check with the shop to see if they could check it.

Ace
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« Reply #12 on: May 27, 2009, 02:06:49 PM »

Ace a turbo boost gauge will give you more info on what the engine is doing than anything else you could put on the bus.  They are cheap and only takes a small line going to the dash to install.  From what you have said it sounds like you have a leaking exhaust manifold.  If you have any leaks it kills your turbo boost.
Jack
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« Reply #13 on: May 27, 2009, 02:24:52 PM »

And starts a fire!

In the day it was believed that a leaking muffler or cracked pipe actually increased back pressure in some cases.  That was gas stuff for sure.  That was in the year of BD....Before Diesel.

Great you have such report with the shop.  You made that point many times throughout your adventure.  If it were me, I would be stuck to them as tight as you are.  Good relationships are hard to find....without reservation.

Good luck....and I doubt YOU are mistaken about the power drop....find the cause.

John
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« Reply #14 on: May 27, 2009, 05:00:00 PM »

I had a Donaldson muffler in my MCI 5A. I thought it had too much back pressure. I was chasing causes for running hot. The muffler had a "disc" in the middle, completely blocking "through flow". The exhaust had to go into the holes in the can and go around the blocking disc then exit back through the holes to exit to the tail pipe. So I punched the disc out. Damn it's loud, and I felt that the lack of back pressure resulted in a loss of power Huh May people I talked to said bigger pipe, even straight pipe without any muffler would give more power. I disagree. Like my old Harley, it has WAY more power with a 2 into 1 with a baffled muffler, than drag pipes give it. On that bike it is somewhere around a 10% increase in hp.
Also when I had to replace my heads, (6V92), I had the mechanic adjust the rack to hit a little faster. Properly adjusted it was very sluggish off the line. Now the throttle response is fantastic. This thing hauls a** off the line.

Don & Sheila
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Blacksheep
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« Reply #15 on: May 27, 2009, 07:20:16 PM »

Went out to dinner tonight with some bus nut friends and we were comparing notes on this problem. What we did was back stepped from when I bought the bus all the way to the present.

Thinking of all the things that I am used to such as knowing how much throttle I usually have to give it, rpm's, fuel mileage etc.. Susan reminded me that when I picked the bus up from the most recent service work that was done, I had commented on how much power it had. I DO remember saying that after I brought it home as she was following me. She also noted that it didn't smoke as much THAT day on the way home. Ok at that time, it had the same new muffler thatit has now so that kind of eliminates that as the culprit. ONLY item that was changed since the service work was the air filter in which I purchased and installed. It was only noted that after installing the new air filter that it became sluggish and began to smoke more and more on acceleration. Once it goes thru all the gears it's Katy bar the door! Ever since the original purchase I NEVER have had to floor the pedal to get it up to speed. NOW I do, and looking for more pedal to even go thru the gears. It moves, but ever so slowly up to speed!

Another thing I have noticed is more black smoke on take off. Could be lack of or not enough air? Again, pointing to the air filter! Also noting engine temps during day when ambient temps are the hottest, the bus seems to be running slightly hotter which is around 190 plus where as before it ALWAYS ran 180 and maybe 185 up hill all read from the dash gauge. Could lack of or not enough air cause for a slight over heating problem? Again, pointing towards the air filter!

I don't see any leaks from the exhaust pipe going TO and FROM the turbo nor do I see any leaks in or around the muffler, it's pipe, or ANY of the exhaust system. A leak WILL and should show pretty easy! All clamps are new as is the entire system.

This weekend I will be installing a filter gauge that I bought last year at the rally and compare the new filter to the old which I still have to see if there is any difference. Even though the new air filter I installed is for a Prevost, could it be the wrong one? It looked identical to the one I removed!

I might just have to take and replace the new filter for the old one and take it out for spin to see hear and feel if there is any difference!

This is just like a person swinging a 16 oz hammer day after day for years and then picking up a 20 oz hammer. You know right away something is different although the change is very little!

I will post results when I get more info...

Ace
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JohnEd
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« Reply #16 on: May 29, 2009, 08:49:12 PM »

Ace,

Your filter idea seems likely.  Did you install that boost gage yet? 

John
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« Reply #17 on: May 30, 2009, 04:53:17 PM »

The air filter wasn't wrapped in clear shrinkwrap, was it? Shocked
Just kidding. Hope you get to the bottom of the problem and it's nothing serious.
Good luck and please let us know what you determine, Thanks, Will
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Blacksheep
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« Reply #18 on: May 30, 2009, 06:37:18 PM »

Thanks for asking! I have not checked the turbo boost yet! I was down to the shop and spoke with the mechanic and he advised me to use my pro-link to check it. Duh! Forgot I could do that! I might try that tomorrow.
I DID install my air filter gauge that connects to the air tube pre turbo. I also put the old filter in and after starting the bus and running, it showed good air flow. I removed it and installed the new filter and it measured the same! I was hoping for a significant difference but looks like I will look further for what MAY be problem and what may not be!

Ace
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Sojourner
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« Reply #19 on: May 30, 2009, 10:26:21 PM »

I DID install my air filter gauge that connects to the air tube pre turbo. I also put the old filter in and after starting the bus and running, it showed good air flow. I removed it and installed the new filter and it measured the same! I was hoping for a significant difference but looks like I will look further for what MAY be problem and what may not be!

Ace

I am sure you meant the following but just to make sure that
Quote
after starting the bus and running, it showed good air flow
....was during acceleration and high speed driving (70s)

Make sure there is no leaks in the pre exhaust turbo pipe as well intake air after turbo to cylinder head.

Otherwise...sound like the turbo is not up to par.

Sojourn for Christ, Gerald
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« Reply #20 on: June 01, 2009, 07:27:23 PM »

   A good idea is to have a little test track so that if you do something different it helps or hinders you. I have streach of road about 1/2 mile slightley up hill that I try the bus on perodicaly, I try to have it warmed up the same ever time and let it shift by itself this will give some idea of performance.

                                         Roger 4106
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« Reply #21 on: June 02, 2009, 11:44:44 PM »

My "low Ace alarm" has gone off. Huh  How goes the quest for the lost HP?  These are like Nancy Drew novels.....just can't put them down. Grin

John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
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Blacksheep
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« Reply #22 on: June 03, 2009, 04:57:23 AM »

Haven't researched it any further. I am planning to take it back to my friends shop and let them do what they do best!

Ace
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