Exhaust mods

[Polar*JK]

2005 3500 quad cab SRW - she's got 122,000 miles.

Instead spending $800 to $1k for a 5in exhaust.

How much improvement would I achieve just by removing the Cat and replacing it with a straight.
Then should I just keep the muffler or remove it as well.

I always appreciate any advise I get from my fellow Cummins Owners.

8Lugs-n-Smokn

 

[seafish]

The only thing you'll get from a 5" exhaust is more drone…the 4" oem flows fine, even for moderate fueling mods, which you may to may not have. Some people DO replace the CAT with a piece of pip[e, or ream out the inside of the cat, , but that is also unnecessary and probably illegal in your state. Just my .02

 

[AH64ID]

The OEM 4" exhaust is capable of at least 600+ rwhp before it becomes an issue, don't bother with 5" unless you want the sound (and drone).

The cat will improve idle cool down temps, but that's about it under 450-500 rwhp.

 

[CToney]

Even the 4" aftermarket exhaust is too loud. My 05 came with a 3" tailpipe and muffler. It was cheaper to buy an entire system. The flo-pro system I installed had a tiny muffler or lack thereof that made towing way too loud I had to put a M085171 Donaldson on to quiet it down. Now it's fine. Stay stock or put on a donalson.

 

[AH64ID]

My 05 came with a 3" tailpipe and muffler.

Did you buy it used?

The OEM exhaust on an 05 is 4" from turbo to tailpipe.

 

[rscurtis]

The biggest restriction in the exhaust is the factory turbo.

 

[bigceltic]

Even the 4" aftermarket exhaust is too loud. My 05 came with a 3" tailpipe and muffler. It was cheaper to buy an entire system. The flo-pro system I installed had a tiny muffler or lack thereof that made towing way too loud I had to put a M085171 Donaldson on to quiet it down. Now it's fine. Stay stock or put on a donalson.

I second this. Am in the process of trying to quiet the drone from my Banks. Prob gonna put a Donaldson on it.

George

 

[CToney]

Did you buy it used?

The OEM exhaust on an 05 is 4" from turbo to tailpipe.

I bought it used. The guy I bought it from told his mechanic to fix the exhaust with something quiet as I imagine the stock exhaust was broken. He had just put it on as he was fixing a few things to sell the truck. I figured no harm was done.

I tried to fix part of the turbo restriction with a modified stock turbo. It takes less boost to accerlate now at the same rate of speed 20psi before now I'm at 15 which is a positive thing. My egt was supposed to drop but instead it went up. Im ~ 75 F higher now under full throttle acceleration. My boost dropped 2 psi which would account for the better flowing turbine. I have the JR set to tow and POD at 75. I may need UDC or to change my POD or programming to get things set right. I haven't towed yet and I'm waiting to test to see if I've had any milage improvement.

 

[AH64ID]

I bought it used. The guy I bought it from told his mechanic to fix the exhaust with something quiet as I imagine the stock exhaust was broken. He had just put it on as he was fixing a few things to sell the truck. I figured no harm was done.

Makes sense

I tried to fix part of the turbo restriction with a modified stock turbo. It takes less boost to accerlate now at the same rate of speed 20psi before now I'm at 15 which is a positive thing. My egt was supposed to drop but instead it went up. Im ~ 75 F higher now under full throttle acceleration. My boost dropped 2 psi which would account for the better flowing turbine. I have the JR set to tow and POD at 75. I may need UDC or to change my POD or programming to get things set right. I haven't towed yet and I'm waiting to test to see if I've had any milage improvement.

What was the modification? I seem to recall something about it, but that's as far as it goes.