I put a 5" turbo back exhaust on an 04 6.0. there is no cat just a muffler. My fuel mileage has dropped. I have heard that if you put on exhaust you need to program the engine to exhaust to get best results. Is this true? Can i run a sct with a DP-tune on stock head bolts? Please help thanks

 

You shouldn't need to do anything. Did you expect to gain mileage? How are you calculating mileage?

Everytime I've put an exhaust on anything I lose mileage the first few tanks, because I can't control myself and am harder on the throttle listening to the sweet new sounds of my truck!!! Your experience is probably similar to this.

Lose the muffler.

 

Thanks for the reply. I thought it would stay about the same mileage wise. I know what your thinkin cause i love to hear it!!! but my wife has been driving it and she is a **** on driving it easy and still not as good as it was. I fill up tank and reset trip, then when empty i refill and divide the miles by how many gallons i put in. will removing the muffler make it louder inside the cab? I am new to diesels in general so still learning. what do you get for mileage? how many horse programmer you have? are your head bolts stock? just tryin to find out whats a must. Thanks again

 

Yeah I doubt you'll notice an increase in mileage, but EGT's should be lower and the sound improved. You can lose the muffler if you want, it will get loud, but it's really only loud when you romp on it, still not that loud in the cab I guess, but that's coming from a guy with two 6" mitre stacks behind my back window, it gets real loud in my cab.

As for the drop in mileage, it could be from the way you're calculating mileage. On these trucks you can't just fill up til the pump clicks off, you have another 3-5 gallons of fuel to put in there... you need to slowly fill until you have fuel resting in the filler neck and can see it. That's the only way to do this accurately.

Aside from that, this time of year a lot of places are switching over to winter blend, which notoriously decreases mileage.

I get about 15mpg mixed driving. They're heavy trucks... I use an SCT with custom tunes, which is the only way to go IMO. Who you choose to do your tunes is another story, but I've used and currently use tunes from Innovative Diesel, GoGo diesel, and Quicktrick automotive. Will be trying some Gearhead tunes soon too. Which tune I run depends on what I'm doing and the weather too. I have a towing tune just for towing, which not only increases power a touch, but most importantly drastically changes the way the transmission works when towing. For daily driving I pretty much stick to a mild street tune, it's still a 375ish rwhp tune. Maybe a touch more. The extreme tunes I have are closer to 420-430rwhp and high 700 (780ish) rwtq. I have blown headgaskets 3 times. Twice with stock headbolts, once with ARP headstuds, but they were Ford dealer installed headstuds so they definitely didn't do the job right. I'm currently building mine right now and putting studs back in. New OEM gaskets, heads decked, etc.

 

I was pissed when I took my Dynamax 4" muffler off and my truck sounded the same. It was a giant glasspack style. Didnt loose any mileage. Currently driving in Extreme race from Innovative. (I'm light on the right pedal these days) and do ok in town. Thinkin next tank Aggressive street.
Anyway, truck runs great, all stock except the "me too" mods everyone else does. Mileage, about 13 in town, 17 highway. I live @ 4000ft and it hurts the mpg, I get 15 in town at 1500 in Phx, Az.

 

Karl,

I know a lot of guys DD the x-race, and have had luck, but I grenaded a stock torque conveter DD'ing mine. They did warn me it needed to be either driven like a grandma, or WOT, and they were right. I stick to x-street for play time, and leave my x-race for the track.

 

I drive like a grandma! Living in the sticks helps. Oddly enough, cruise control at 68 actual (62 indicated) got better mileage than Aggressive Street on road trip to Az. Gonna contact Go-go after xmas for more tunes.

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Oh yeah! Unless you re-geared for taller tires, your odometer needs to be corrected for mpg. 35s need a 9% correction. That means 300 miles indicated is closer to 327 miles traveled, on a 20 gallon fill, thats ~ 16.35 mpg not 15 mpg.

My gps confirmed my correction factor, 65 indicated is 70'ish actual. Keep in mind your speedo may be off as speed increases, mine is. I thought my 35s KILLED my mpg, then I figured it out to ~ 2mpg loss.

 

I fixed my speedo according to my GPS using Autoenginuity. Mine is almost dead on now. Good point though, most never realize this. I get better mileage with the 35's actually, it lowers my cruising RPM quite a bit.

Your better mileage with the x-race is because of the converter lock-up. It locks in 2nd gear and stays locked through everything.

 

What about adding 2 stroke oil to the fuel. i have not done this but have read a lot on this subject. 3-5% increase some say. Mdub what is your take on 2 stroke oil?

 

No harm, but don't expect anything out of it. I use Opti-lube...

Read here and let me know what you think...

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