falling fuel economy

[KIKER]

I have had an '07 Dually in service for a little over a year now with my Lincoln welder and tools in the bed. The very first tank of diesel went 12 mpgs. It went up from there almost immediately to a high of 14. 8, all hand calculated. I put an Edge EZ box on at about 10,000 miles and run it on 1 or 2. Couldn't tell much difference in the power between the settings, but could definitely feel the increase in performance, and maybe 1 mpg more. Back in March, at about 20,000 miles, I added a Smarty Jr. I ran it stacked with the Edge for about 3,000 miles and then disconnected the EZ to see if I could pick up mpg's with the Jr. alone. My mileage has consistently gone down and I have tried running Jr. on #1, as I had it programmed on #2 from the start. It's still going down. I set it back to stock last night and my overhead reading is still going down. My fillup today netted 12. 2, hand calculated. Any ideas? I have a 5. 9, auto, 4x4, 373, stock everything else. I'm running almost 12,000# and have been driving 110 miles a day on the highway with cruise at 65-75 mph. Is the high dollar diesel I'm buying making my mpg's go down, or do I need to take it in to the dealer and let them look at it? I was driving a '99 2x4, 5 speed, with the same tools and approximate weight and getting 16-19 mpgs with it. Shouldn't have traded? Help, anyone?

 

[Dan Simmonds]

Your mileage sounds awfully low - I have nearly the exact same rig as you, only I have the manual trans, and running around empty I am seeing peaks of 20 mpg - hooked to a light load (5,000 LB) brings it down to 17+. Maybe you picked up a bad tank of fuel somewhere along the line and your filters need replacing? Hopefully it's something that simple. I've seen horrible mileage out of other vehicles of mine, and a fuel filter change was all it took to bring it back.

 

[TFucili]

Is it smoking? Are the boost and EGT about the same as they were? Any sign of fuel in the crankcase?

 

[KIKER]

I don't have boost and egt gages to see if they changed. I have replaced the air filter with a new one about 1000 miles ago. I haven't pulled the dipstick on the engine, so I will do that. I had the fuel filter changed at the last oil change, but can put in a new one, just in case. Thanks for the responses!

 

[JDiepstra]

Wow I hope I don't buy your truck used. Running that heavy stacked with no gauges!

 

[Coalsmoke]

Wellllllll, added power, lots of weight and no EGT gauge. The first thing I'd do is be looking at your turbo as it is probably pooched. I know with my 95 welding rig I was hitting 24-26MPG on the highway but I had to be really careful about the EGTs on any hill over a mile in length. If I were running it in OD I could send those EGTs through the roof without trying too hard. That added cargo (in my case about 3000lbs worth of gear and probably the same for you), will provide enough resistance to let the truck fuel so much that it will bring the EGTs up real quick.

EGT gauges are cheap compared to the alternatives.

 

[KIKER]

I ran the EZ stacked with Jr for less than 2500 miles, maybe 6 weeks. I never tried the 100 hp program on the Jr. I thought the selling point of Smartyn Jr. was lower egts and never thought I would need to really monitor that. No hills around Odessa, real flat. 95% easy starts, with a few pedal to the metal merges. So, I guess I need to check my turbo now? A good friend of mine always says if you're going to be dumb, you better be rich, and I might be finding out why he says that. I ran an Edge EZ on my '99 for about 80,000 miles with the same load and never experienced any problems with it and didn't run gages. What is the procedure to check the turbo?

 

[MMeier]

How does the trans fluid look?

 

[Coalsmoke]

Well, if you've been nice to it then your turbo can be fine, but all it takes is shutting it off hot a few times and letting the oil coke. High impeller RPMs will do the rest to aggravate the situation. Pull your intake tube, any black residue on the aluminum intake to the turbo? Any excessive play in the impeller shaft?

 

[KIKER]

The trans fluid looks fine, transparent red. I'll pull the intake tube tomorrow and see what it looks like there.

 

[p-Bar]

I'm in the same boat single wheel drive , bed loaded with carpenter tools , 17mpg jr. on 1 . Disconnected and giving it a try. I think we should be doing better with the smarty due to the advance timing. Have you tried a Rokktech to change the crank timing I am running that .

 

[KIKER]

I have run 3-4 tanks of diesel thru it with the calculated average mpg around 12. 5, with it back to stock. On the tank before last, I noticed my overhead reading back up to 17 and 18, when I would reset the average for a new tank of fuel. The last calculated mpg was 14. 45. I did take of the intake hose off the turbo and the housing/impellers were shiny clean, but I could wiggle the impeller just a bit. I don't know how much is acceptable. I ordered gages from Geno's last night and will put them on when they get here. My mileage just went over the 25,000 mark. Maybe it's just in the break-in process? Or the broke process? I guess I will find out later.

 

[Coalsmoke]

12. 5mpg is poor, something is up. When you pulled the tube to the intake, on the inside wall of the turbo intake right by where the impeller blades travel, was there any black residue there?

 

[KIKER]

I didn't see any residue, all clean. Nothing would rub off on my fingers to show any color.

 

[Coalsmoke]

ok, that's a very good sign if it passes the white glove test. Next thing to check are all of your intake tube boots. Start at the output of the turbo, follow it through to and from the intercooler and then to the intake horn on the engine. Clean each boot and look for loose clamps, tears, etc. anything that would allow air to be lost from the pressurized side of the system. You'll need a mirror to see the backsides of the boots.

 

[KIKER]

OK, I got my gauges installed over the weekend. I don't have any idea what my boost and egt should run. The boost will go up near 35 psi on full throttle, with the egt up to near 1300. With cruise set at 70 on the interstate, boost runs 8-10 and egt around 800. Do these numbers sound normal? Also, can anyone give me some help hooking up the gauge backlights to the headlight switch and the stepper motor on the pyrometer to the ignition switch on an '07? I just hot wired the pyro to the battery to check temps.

 

[LCartier]

With cruise set at 70 on the interstate, boost runs 8-10 and egt around 800

With the load you have on the truck and at that speed those would be very normal numbers.

I used power from the cigarette lighter and found a good ground under the dash. As for back lighting, go to your headlight switch wiring and using a test light and with lights on, look for the "dash lights" to determine you have the "dash lights" wire turn dimmer up and down check test light for corresponding dim/bright.

 

[rbattelle]

OK, I got my gauges installed over the weekend. I don't have any idea what my boost and egt should run. The boost will go up near 35 psi on full throttle, with the egt up to near 1300. With cruise set at 70 on the interstate, boost runs 8-10 and egt around 800. Do these numbers sound normal? Also, can anyone give me some help hooking up the gauge backlights to the headlight switch and the stepper motor on the pyrometer to the ignition switch on an '07? I just hot wired the pyro to the battery to check temps.

Your numbers for boost and EGT seem normal to me.



Here's a good thread on gauge installs.



Ryan