So Im under my 2004 CTD changing my oil today and start looking at my exhaust system. All i can see is a muffler. Is the CAT combined in the muffler? I bought it new and Ive never had anything done to the exhaust. I was thinking about straight piping it.Any advice would be helpful.

 

if you have an early 04, the 305/555 motor you dont have a cat, the cats were installed on the 04.5 models with the 325/600 engine to make them CARB "Legal"

now, if you have a 325hp motor with no cat. I would say your truck had a Cat-ectomy

 

Drew, would straight a straight pipe help or hurt fuel economy? I know it will be loud as H#%$# but I think they sound cool. Especially louded down passin those PSD's.

 

the lack of back pressure from removeing the mufflerwould hurt your low end torque more than anything. I would say around .5mpg. however the coolness factor may be worth the extra to fill the tank

I know some that say straight pipeing is the best, then you have those that straight piped it, got annoyed and tossed in a MBRP muffler or a donaldson 51"

 

Straight pipe don't hurt nuthin'. LOL.

Especially if you are trying to make more hp/tq. I have a 4 inch downpipe, then when it makes the bend at the bottom, it goes right to 5 inch. No cat, no muffler. Just a reflective resonator, Helmholtz style. Has aboslutely no restrictions in it.

I move so much air it's not funny. Any turbocharged engine beit gas or diesel, benefits from a larger exhaust system. Even though the exhaust is restricted through the manifold for a short distance, it's the larger pipe that allows that compressed "pulse" of exhaust gas to expand.The benefit of that expansion is the exhaust gas temperatures drop rapidly. As much as 300 dergrees some claim.


Bigger is definitely better in this situation.


Just my 2 cents.


Good luck with your ride.

 

i think the straight pipe will be fun ......It will be fun to **** of the tree humpers that just moved in across the street and screwed up my deer huntin I leave the house at 330 in the morning, you think they will hear me

 

Dude, I am so attuned to my truck. When I leave my apt every day I climb up a moderate hill. I can show the neighbors courtesy, and give them a low rumble with slight turbo whistle. I can maintain the rumble and increase the turbo boost with the slighest amount of throttle increase.

If I choose, I can bark out a wake up roar that will make the dead rise up from their graves.


It's a riot, you can use it to entice the local yokels, get a country girls attention, or let that Ford know that he's barkin up the wrong tree. I use my pipe for intimidation, AND instigation......lol.


Adios!

 

I like my straight exhaustgreat, it is 4" from the turbo back. It is loud and my wife keeps asking if it ever is going to be quieter, but I say never. It sounds great and the cab noise is a little much cruising down to the Husker game in Lincoln, NE doing 80mph. But it is sure nice to get everyone out of your way in traffic. The 18 wheelers I pass just give a thumbs up. Everyday driving is fine and cruising at 60or 65 you can hardly notice on the highway. I here the turbo more at his speed than anything.

 

I straightpiped my truck, I got headers coming down into a 3 inch pipe and it bends and goes right out the side. No cat, No muffler. Im allergice to cats anyways

 

so whatcha useing to fool the computer since you dont have a cat, or do you not have a downstrream O2 sensor?