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I was wondering if anyone who has put on a straight pipe or muffler delete saw an improvement in fuel economy?
 

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It will theoretically give you an increase in each.

I personally think that anybody who sees a difference has a placebo wedged in their butt dyno, but there are people who are sure to say that it made a major difference...
 

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I didn't see it at all. I have an 07 5.9 and have decided that I am gear bound and that is why I am not getting better mileage. I put in an amsoil drop in filter, no change, I put in the muffler delete, no change, I bought a smarty, no change. I got some better mileage when I tripped 15k and I am now at 20k and it is still pretty well leveled off. I got some more power with the smarty but I didn't get anymore mileage with the muff delete.
 

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I did not get calculated fuel economy increases on either of my trucks when I upgraded the exhaust systems but I did get improved turbo spool out of both. It may be that I just drive them harder now. If I hauled trailers more (cruised more at higher boost levels) I might notice an economy improvement. Removing or replacing a clogged catalytic converter would probably make a difference. Back pressure after a turbo is a bad thing (as is air filter restriction on the suction side of one).
 

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I made a point to compare the difference and yes, it improved noticeably on the overhead computer. Haven't done the hand calcs yet.
 

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I just had edge chip and 4" single system installed. I got 15.5 prior to the chip and exhaust. I got 17.5 with chip on 1 and muffler in. I got 19.6 with chip on 2 and muffler delete. this is on a 99 24v with and auto trans.
 

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Disclaimer: My mileage went up *if* I was keeping my foot out of it...
 

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i have to bring this up again. i have read all kinds of opinions on this matter. does anyone have any real numbers? I have been thinking real hard and if will give me mileage i will do it but I have read that some people have lost mileage. I can't understand why unless they have a heavier foot just to hear the pipe scream. theoretically the turbo give the motor all the back pressure it needs and turbos need no back pressure. I am so confused.
 

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After I took my muffler out, I thought they dropped a new engine in it. I got an ungodly amount of power and awesome sound. As for the fuel mileage, I couldnt tell ya, because as I said, it sound awesome!
 

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anyone else care to chime in? I still would like some more input.
 

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Just did a muff delete last weekend on mine. I've driven only about a half a tank of fuel since then. I'll track mine and report back. My wife is watching closely... I told her it would gain me a mile or two a gallon. It certainly sounds better and I have to be careful to stay out of it when I'm going up an on ramp... with 4.10s and factory 245/70/17s I'll be doing 80 in a blink. Used to be alot slower from 45 to 70.

MDL
 

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I know for sure that I gained low end power when I went 4" straight pipe. My very first tank I actually did make more MPG until I realized how cool it sounded and that I could accelerate faster (than normal) and then I couldn't keep my foot out of it anymore.
 

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i really don't think i got any better mileage with straight pipin but thats prolly cuz i like listening to my turbo whistle so much :lol3: i'm currently running a 4in turbo back to a 5in t pipe into dual 7" bullhauler stacks:thumbsup:thumbsup
 

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i get better milage. prob like 15 in city and 22 on highway. its better for your motor. better flow. more smoke. and awsome sound
 

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definitely better mileage... got 23 mpg on half a tank the other day driving country roads on a trip where I would only see 20-21... yes I hand-calc'd it...

but either way I did it for the sound lol
 

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Can't really say I saw very much milage change with the straight pipe. The best milage improvement I saw was the airaid intake system. I got a hand calculated 2 MPG increase with the intake. Programer and straight pipe was not noticable because of the fun to drive factor:lol3:
 

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I hand calc my mileage every tank, and I saw decent improvement when I did the 5" straight, however I did an Icebox, CFM, and torque tube all at the same time, so it's hard to say which is contributing to the increase. It did bump by about 1.5 on an average tank, but I don't know if we're on summer blend fuel either...
I dont' think you'll regret a straight pipe though, sound is unreal!!:thumbsup:hyper:
 

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well i did it today. cost me 45 bucks. so I now have 3.5 pipe front to rear. sounds like a petercar. I guess i need to track the next tank carefully. As for hwy drone...I never get that fast,lol.
 

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i saw about 2mpg but also went to runnin a k&n open element at the same time
 

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hi all i am new to the forums and noticed this lil question i got a 06 5.9turbo no mods no nothing all stock when i got it i got 13.2mpg in the city mountain driving kills mpgs period i took it apon myself to free up the exhuast knowing that back pressure after a turbo is killer to it removed the cat and the muffler and it 4in from the turbo back with in 2 days the lil onboard pc said i was getting 15.7 in the city..hand figured it out the pc was off just a lil worked out to 16.3 city so just freeing up the flow did wonders thinking of pulling th ebaffles out of the stock torque tube for a lil more air flow in not sure yet BUT YA THE TRUCK SOUNDS GREAT KILLS YA IN THE DRIVE THREW...
 
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