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smlranger · 06-04-2012, 07:11 PM

The tailpipe on my 2002 Journey has rusted out and is rusted fast in the muffler. So, I am getting a new muffler and tailpipe. My factory set up is 4" pipe into the muffler and 5" coming out to the 5" tailpipe.

I plan to use a local, family owed shop that has a great reputation and does a lot of RV's. He is proposing to use a smaller (smaller than the huge OEM muffler) free flowing muffler, 4" in, 4" out. He advises the OEM is more restrictive to make it very quiet and his 4" set up will provide as much, if not more, flow than the current set up. He says the muffler he will install will be a bit more loud but not obnoxious.

I'm inclined to trust him but do wonder why CAT/Winnebago used a 4" inlet and 5" out.

Any advice from any CAT experts is appreciated.

jauguston · 06-04-2012, 08:40 PM

I am no way a Cat expert but my Freightliner chassis C-7 350 has 5" from the exhaust brake all the way back. I would not want 4".

If your mechanic is talking about a Aero muffler they are LOUD.

Jim

wb7auk · 06-06-2012, 12:30 PM

I just had mine done by a fellow I have been doing business with for 25
years and he has never given me bad advise.
My factory exhaust is 4 inch to the muffler then 5 inches out but reduced
to 4 inch and connected to the tail pipe, don't ask me why they did that.
My friend like yours said and showed me just how bad the OEM muffler
was in design. Lots of back pressure at the inlet not to mention a lot in
the muffler.
He installed a 5050XL 5 inch but reduced the input and output to 4 inches
for the following reasons. Reduce back pressure to the turbo allowing faster spool up time and less heat. He also said reducing back to 4 inch
will provide some back pressure and help the noise figure. He also said
I would see a increase in performance from the stock muffler.
He said a straight 5 inch install would add a little performance but a lot
of noise and I found that to be true sitting along side a twin to my MH
with the 5 inch system that was loud and mine about half his but a little
more than stock. As to performance that also proved to be true and the
EGT dropped an average of 300 degrees.
I am happy with the install and would do it again.

Quote:

Originally Posted by smlranger

The tailpipe on my 2002 Journey has rusted out and is rusted fast in the muffler. So, I am getting a new muffler and tailpipe. My factory set up is 4" pipe into the muffler and 5" coming out to the 5" tailpipe.

I plan to use a local, family owed shop that has a great reputation and does a lot of RV's. He is proposing to use a smaller (smaller than the huge OEM muffler) free flowing muffler, 4" in, 4" out. He advises the OEM is more restrictive to make it very quiet and his 4" set up will provide as much, if not more, flow than the current set up. He says the muffler he will install will be a bit more loud but not obnoxious.

I'm inclined to trust him but do wonder why CAT/Winnebago used a 4" inlet and 5" out.

Any advice from any CAT experts is appreciated.

smlranger · 06-09-2012, 08:06 PM

I ended up with a straight thru flowing Magnaflow muffler, 4" in/out. He welded a 5" chrome tip on the 4" tailpipe since a 4" tip looked lost in the fairly big opening in the coach body. It is more 'throaty' sounding than the OEM set up but not really loud. Subjectively, the coach seemed to have more giddy-up on the drive home from the shop. Also, the operating temp dropped based on the dash temp guage.