I have a 2003 cummins with afe cold air stage 2 with lid, 150 horse injectors, raptor pump, and the bullydog E3 programmer. The exhaust is in decent shape but I feel it will need replaced by spring. They removed the muffler before I got it and it has what looks like bird poop for welds.

When I stop at a light after cruising down the road I can smell the diesel fumes in the truck and I figure it is the leaks around the welds.

Anyways.

Would you put a 4 inch kit back on it or a 5 inch?

I am looking at getting an AFE stainless kit so all my stuff will match since I am also getting the intake elbow.

 

Personally I would just go with the cheapest exhaust you can find. 4 or 5 inch is personally preferance, 5 will have a deeper tone but 4 is cheaper. To my knowledge 5 inch isn't (performance) necessary until around 500-600 hp range

 

I put a 5" on my 06, an on a run from Calif to Tenn @ 70 mph on cruise picked up 3 mpg and a lower EGT and pressure. It's slightly louder, but not to bad, at least the wife hasn't yelled yet. If your not willing to spend the cash, or put up with the increase in noise, stay with the 4".

I take many long runs seeing my kids and grandkids or the sights, and try to find anything to increase mpg. (Smarty is next) If you staying local and / or pulling loads locally, you don't need to go big. But I highly recommend stainless if it staying in the family long. Mine will be with me until it's totally worn out or I die.

 

I drive it back and forth to work with a 85 mile daily trip, so I am looking to gaim mpg's.

With that being said which is better the 4 or 5?

 

You are not going to notice a difference in mileage from a 4" to a 5"

 

i put 5 inch on mine its a notice able diff in noice but performance wise didnt see much or any

 

I just put a 5" Flo Pro, I haven't had it long enough to answer for the mpg, but I'm guessing I'll get .5 - 1mpg which works for me. You can get a flo pro for under 400 and it looks and sounds great!

 

Never said anything about major performance increase, but I did notice an increase in mpg on my 06. Performance is what your looking for. When I was a kid, I wanted performance from my old muscle cars and trucks, and that was extreme HP to burn tires off while flying at ground level. Never got good mpg, but I didn't care, fuel was cheap them. Now performance means to me ..... a great running engine, long endurance, the best mpg I can get and the HP to pull what I want when I want. (I forget mpg's when pulling, but only to have my truck stay strong).

I have a friend that was very deep in the diesel world before retiring and he said a decrease in back pressure and exhaust gas temp eases the restriction on the engine and helps her preform as she should. On long hauls, like I do when seeing my kids, I cover 2,000 miles one way. Checking mpg by hand calculation each fill up and at end of trip. I have recorded an increase in mpg's after just changing to the 5". I have also noticed that soot on my bumper and quarter panel is less verses the 4" stock setup, and the exist point it at the same place. After that last trip, I change the air intake system to a cold air induction setup, and this could have helped, there is even less each time I wash her. But don't expect increasing mpg's to 25 mpg or more.

There are many discussions on this in this forum, and with due respect, individual findings are just that, individual. Seems the main thing to do is decide for yourself on the exhaust size after researching as much as you can, (It's Not Cheap To Convert, some can be up to $800.00+ and more), keep the rpm's below 2 grand, have a light foot when touching the pedal, and maintain a constant speed once obtained. And ALWAYS maintain your vehicle when servicing is due.

 

Best deal is the Summit Stainless System if you want a 4" system.

Summit's systems are made by someone else. When I bought mine from Summit it was a rebadged 4" system from HOG Performance. I don't know if they still source from Hog Performance or not, but the pictures look identical to a Hog system. They are T-304 systems, not the lesser T-409. Summit's systems come with stainless band clamps, and a 4" slash cut tip. I called HOG to order the 5.5" Side exit tip and they sent it to me for free. I didn't ask for it for free, they offered since I wasn't pleased with the slash cut tip.

Their prices are $499.00 for the stainless systems now.

 

actually, the flo pro system at 5" is around $399

 

If it still has the OEM exhaust then it is a 4" already. You already said the muffler was replaced. Check to see if the Cat/resonator is still on it. If so, but I didn't tell you this, you can remove it and replace it with the correct pipe then you are G to G

 

Aluminized, not T-304 Stainless

2003 is 3.5" to the muffler and 4" tailpipe.

 

I would stick with the aluminized as suggested above. There is no such thing a true stainless exhaust. Call Lary in the DTR store. They had the best prices of anyone that I could find. I got the 4" Silverline Turbo back. Bolted right up with no adjustments.

 

I have the Flo Por 5" TB, it's aluminized, fit was perfect, comes with form fitted band clamps, a little louder than stock, not enough to make a real difference. I know several people who are using this exhaust, they are happy with it too.


CD

 

Dtr has good prices.

FWIW, I bought my 5" expandit exhaust from RollinSmokeDiesel for $330, the best deal i could find and for the price it is a great kit...