I am going to be putting exhaust on my truck and I was going to go with 5" straight pipe kit and add a Donaldson 51" muffler or a Farmboys kit/muffler. But I am now wondering if maybe I should only go 4"? I have not read much about it but I did see that one guy put 5" on a stock rig and LOST a bunch of power and hated it...Is this common or what? I know that 5" is way overkill unless your making big power or just want it stupid loud.I want it because I think it sounds the best (with the right muffler) But will it actually kill the power above 2500rpm? Anyone have any suggestions? Should I just go with 4" with the Donaldson? Keeping in mind that my truck is '03 standard output with no mods.

 

the power lost is minimal the sound will definitly be different. if you are running over 700 horse i think 5 inch helps but under that you will loose a little hp but nothing to worry about

 

I have the 5 inch on mine and I like it alot. Its not to bad with noise/drone at cruising speed, but mash the skinny pedal and the thing roars to life!!

 

This other dude said his truck was just a pig with the 5" wouldn't get out of it's own way....I think he was going to take it off and he only had it on for a bit he hated it so much...I don't want to hate my exhaust that much. Is the HP loss noticible? Does it affect spooling?

 

I'm confused too...How could dispersing exhaust gas more efficiently after it's done its job in the turbo cause lack of power?......Ben

 

I don't know what my dyno numbers are... but the good old butt dyno cannot tell a difference

 

No noticable difference from stock to 5"? Straight pipe or with muffler? Do you have any other mods (smarty etc)?

 

Nothin besides the 5 in straight pipe... Well, it does have a "muffler"... more like a glass pack

 

I went from stock to 5" turbo back Expandit kit with muffler. I noticed a little bit of loss on bottom end but top end improved. No loss that made the truck a dog by far, just barely noticeable. Decreased probably 200 deg on EGT too. My truck's stock except for a Quadzilla Mileage Module, & air filter. I recently went straight pipe - sounds awesome but horrible drone in cab. Just put a 30" muffler back on & like it much better. Almost stock sound. No difference in mileage or power between muffler or straight pipe. Really only reason I put 5" on my truck is the look, sure looks good.

 

Maybe I'll stick with the idea and go with the 5" then. There doesn't seem to be any drawbacks...

 

I don't understand how a bigger pipe could rob low end power on a turbo'd diesel. Its not like it needs to be set up to scavenge back through the cylinders like a carb'd engine. Anybody have any idea?