I've done a search on this, but haven't found many answers.

I'm considering straight piping my 6.0 and was curious what some of you noticed from it:

Did you mileage increase? Decrease?

Are you running a hot or mild tune?

Aside from more noise and less back pressure, did you notice anything else?

 

Mine is with 4" turbo back. Here that 03 turbo good and really can't tell on mileage. Drops temps maybe 100 or so degrees. Running hot tune from Matt

 

Notice no difference between straight piped or running a kitty. I swap back n forth for "noise ordinance" aka "when I feel pity on the neighbors".

Josh

 

I have stock pipe but deleted muffler and cat. Good sound, not very loud. No difference in mileage or performance that I noticed. I run SCT trans only tune.

 

My muffler has been loooong gone, and I have a bolt in cat delete pipe. Race tunes/local driving=no cat. Long distance towing=the cat is in. A good 6.0l cat isn't very restrictive as it has a huge surface/cross sectional area. I do notice a bit lower EGT's when towing with it removed, but it's not worth the noise on long trips. The change from stock to AM downpipe made a more noticeable difference in EGT's/general performance on mine than removing the cat. I see no mileage changes with, or without.

 

Nope, mines stock all the way back. I have owned the truck for 13 months and the mileage hangs around 15 to 16 when not towing and most all of my driving is on secondary roads. I don't know my EGT's but my deltas don't reflect a hot running engine, 188* to 200 water temps and the hottest I've ever seen my oil is 208*

 

4" inch turbo back. No tunes, Atlas 40, truck is stock otherwise.

Sounds great, plenty of power, better mileage for my style of driving.

My previous mileage averaged 14.7- 15.2 pre-FICM, pre-straight pipe.

Current mileage averages 16-16.1.

Mixed driving, towing, highway, traffic,etc burning through 150 gallons a month.

Wish I had done it sooner. Noise is not an issue.

 

I have a straight pipe as well I didn't own the truck long enough to calculate fuel Eco before and after. The exhaust came off after a couple days of owning it.

My avg is 19.8 with the canned performance tune from SCT.

I do hear a drone from the exhaust when I'm at a low RPM-which was not there before I replaced the exhaust

 

Did the larger down pipe make it louder too?

 

4" straight piped turbo back, hot tune from Matt. 15 towing and 18-19 daily driving. I can tell it's louder while towing and my Brother-in-law who followed us up to the camping spot a month ago confirmed it's LOUD. Not very loud in the cab, even my wife likes the sound.

 

Based on what you guys are saying and between the SRL+ and Atlas 40 I figured my truck could use a little more breathing room, so I just ordered the MBRP muffler delete pipe.

I'll report back on my findings, but lets keep the ball rolling for others who may have the same question.

 

Mines a early 04, so it's a screamer. I didn't notice much in the way of power or fuel maybe a little. But it sounds amazing and my egts are lower. Still my favorite mod though.

 

I went with the Diamond Eye 4" turbo back SS duals and put the Hi flow muffler on. Got 1 to 2 mpg's better.The noise factor with the skinny pedal to the floor is great!

 

I put the Magnaflow 4" Turbo back system on it, sounds good outside (don't think it is too loud), actually seemed a little quieter inside when I first installed it, now after about 9 months it is worn in and it sounds great. Running the Atlas 40 and SCT Performance tune and getting around 16.5 in town and 18-19 on the highway....

 

Stock system cut off under the cab, straight through. Just because the stock muffler/cat isn't "very" restrictive doesn't mean it's not hurting your performance. Straight pipe will always be best. I noticed slight mileage gains, in the winter when i got it fully stock was seeing 16.5mpg highway, summer straight piped i can see 20 mpg on flat highway. Some of that gain was definitely from the switch of winterized to summer fuel though, and warm up times. Under the cab stock system also competes with the 2003 turbo whistle in loudness have myself a sinister 5' turbo back kit coming in because i'd rather have the throaty growl of the high rpms a bit lower with whistle between fewer rpm ranges