New Exhaust Advice

buddydawg · July 20, 2010, 08:00:00 AM

It is time to replace the exhaust on my bus. I am contemplating the "what ifs". I have 2 avenues to go down. The first is to take it to my local custom exhaust shop. This is the easiest but most expensive route but I may choose it. I am at least going to get an estimate so I can decide if it is worth the hassle of option 2. Option 2 is to do it myself, with the help of my two near and dear fabricators. We have access to an exhaust tubing bender and swager.
This is where I need your opinions, advice etc...

1.   I need to choose a muffler. The engine is a 6v71 and the OEM muffler has all connections made on one end. I will probably put the new muffler in the same place unless someone has a better idea.
2.   What material to use? Should I use stainless or just go with mild steel?
3.   Right now my exhaust goes straight out the back, should I keep this configuration (change of banging it in low clearance situations) or I could exhaust it out the side or possibly out of the top.
4.   Are there any other improvements I should consider while I am doing this project?

Len Silva · July 20, 2010, 08:14:22 AM

All things being equal, I like the exhaust coming out the left side so I can see it better.

TomC · July 20, 2010, 08:15:38 AM

1- I'm using a Donaldson 10"x15" oval muffler that is 20" long with both inlet and outlet on the same side-5" pipe. It is a bit big for a 6V-71, but will work. It puts out a nice exhaust tone (my engine is a 8V-71TATAIC).
2-Stainless is REALLY expensive in 4" or 5". Even big rig diesels do not use that. They make aluminized steel-that works well.
3-I would suggest doing what many GMC transits had-up exhaust out the left small panel of the rear window. I have an up exhaust on the left side through the roof (it was stock on the AMGeneral) and I like it that I can see the exhaust through my rear view mirror.
4- I would make the entire exhaust system 5", using the suggested above muffler. Then when you finally get fed up with the feeble power of the 6V-71, you can easily change it to the more robust 6V-92TA without having to again change the muffler system. Good Luck, TomC

bevans6 · July 20, 2010, 08:18:57 AM

I went for a stack up the back so that I didn't put early morning smoke all around the camp site. Probably just my over-polite Canadian nature... There are a lot of places that have truck type exhaust parts that you can buy and use to put something together. Here is where I bought the stuff for my stack, just for ideas.

http://www.texisexhaust.com/ and go to Parts Catalog. they have all sorts of fun stuff!

Brian

JackConrad · July 20, 2010, 12:44:55 PM

Our exhaust exits at a 45 degree angle right at the Driver's side rear corner. 50,000 miles and no problem so far. I like to be able to see my exhaust. We have an on board AC powered air compressor for campground start-ups. We air up the bus completely, start the engine and are pulling out of the campsite within less than 1 minute after starting. Jack

gus · July 20, 2010, 02:53:21 PM

Jack,

What kind of air compressor do you use?

Most I've seen make more noise than the bus!!

I have a medium size 12v compressor which is still pretty noisy and it takes a very long time to do the job. If I had fewer air leaks it would probably take much less time!

Chopper Scott · July 20, 2010, 06:07:38 PM

Generally where I have been camping the least of things that irritate one is the sound of my bus airing up!!

Rick 74 MC-8 · July 20, 2010, 06:50:38 PM

Any truck parts will have all the 90% or 45% you need I just replaced the 5" 90% into the muffler welded a small piece of 5" over the oddball 4.5" outlet put a 45% out the left rear I all so cut in another 4" in the open space next to the original with another 45% it sounds real good not to loud and if I get on it hard it will only blow the smoke about 1/2 way across the next lane insted of 2 lanes over (LOL) It runs better too but I don't know is it was the tune up or the exhaust

Rick
74 MC-8 8v71na

OneLapper · July 20, 2010, 09:30:22 PM

Quote from: TomC on July 20, 2010, 08:15:38 AM
1- I'm using a Donaldson 10"x15" oval muffler that is 20" long with both inlet and outlet on the same side-5" pipe. It is a bit big for a 6V-71, but will work. It puts out a nice exhaust tone (my engine is a 8V-71TATAIC).
2-Stainless is REALLY expensive in 4" or 5". Even big rig diesels do not use that. They make aluminized steel-that works well.
3-I would suggest doing what many GMC transits had-up exhaust out the left small panel of the rear window. I have an up exhaust on the left side through the roof (it was stock on the AMGeneral) and I like it that I can see the exhaust through my rear view mirror.
4- I would make the entire exhaust system 5", using the suggested above muffler. Then when you finally get fed up with the feeble power of the 6V-71, you can easily change it to the more robust 6V-92TA without having to again change the muffler system. Good Luck, TomC

TomC, can you get me a part number for that muffler? No worries if you can't. I've ordered it from my truck parts dealer and received the 4" in 4" out muffler..... three times!! They can't get it right. Thanks!

Mark

TomC · July 20, 2010, 09:49:46 PM

Donaldson part number- M120131. 5" inlet and outlet same side, 10"x15" oval, 30" long over all, 30lbs. It's not a quiet muffler-really rated for turbocharged engines, but it does put out a nice sound. Good Luck, TomC

OneLapper · July 21, 2010, 03:54:24 AM

Quote from: TomC on July 20, 2010, 09:49:46 PM
Donaldson part number- M120131. 5" inlet and outlet same side, 10"x15" oval, 30" long over all, 30lbs. It's not a quiet muffler-really rated for turbocharged engines, but it does put out a nice sound. Good Luck, TomC

Thanks! I ended up using the 4" muffler because, at the time, I had no alternative. The back pressure is too much and it has popped off several times. That was made only worse with the bad cylinder on my old engine because the unburnt fuel/oil gummed it up, making it useless.

buddydawg · July 22, 2010, 05:05:25 AM

I am going to take the bus over to a shop and let them look at it next week. Whoever repaired the exhaust last time really botched it up. On one side they reduced the pipe from 4" to 3" then back to 4" where it connects to the other side. then out of the muffler they reduced it back to 3" again. To top it off most of the bends are distorted as well. I think I may just but the muffler I want and have them do the rest if they come with a resonable price.

DMoedave · July 22, 2010, 08:46:38 PM

can you run duals? we have them on our 6V71 but its not a stock configuration by any means.

TomC · July 22, 2010, 10:14:08 PM

On a V drive, running duals would be hard-there is hardly enough room for one muffler, let alone two mufflers. A T drive is a different story. Good Luck, TomC

buddydawg · July 30, 2010, 04:19:09 AM

I am taking the bus in next week to have the exhaust work done. I ordered a Donaldson M120154 muffler (the one TomC recommended but with 4" inlet & outlet) I will let ya'll know how it turn out when I get it back.