when i got my new to me 3rd gen i got a scangauge to monitor fuel milage and such,with the truck stock my readings were "cruising on hiway,,throtle position was at 23-30 and engine load was 25-35%.after installing the diablo predator on extreme rkl. "cruising throttle position is 12-18 and load on engine is very low 6-10%,the engine seems like its not even working to cruise,and going up hills with stock i seen as high as 70% engine load,with the tuner ive never seen much higher than 25-30%.milage is up but nothing like what it feels like it should,cruising the engine is barley working but still burning fuel i guess, any thoughts????

 

its pushin alot of wind. not much to do about the aerodynamics of a "brick" as its affectionately been called before

brett

 

The way I see it, the reason that one can not get their modded truck to achieve such mpg would have 2 factors:

1.) Aerodynamics, as stated
2.) Modded trucks = urge to mash the skinny

 

have you ever idled your truck? it burns a edited by admin of fuel even at idle... how do you expect it to get better when moving....

 

Yes I do expect it to get better mileage when moving than when sitting and idling. At a stop it's getting 0 MPG. You're talking about gallons per hour, not miles per gallon.

The engine is doing the same amount of work to move the truck at 60 MPH wether it is modded or not. But with the mods it appears to be doing less because the electronics are being fooled ito giving it more fuel so the throttle is backed off and then it seems to be doing less. This is why the mileage computer is off with mods.

Mileage numbers are an average of the fuel used over the miles tested. You can easily get 200 MPG if you just back off the throttle on a down grade. But averaging 30 MPG over a whole tank will require slowing WAY down and running on level ground at a steady speed.


John

 

I got 30...actually I got 99.9 mpg last week....oh, wait I was getting my sorry rear towed to my guy for a clutch swap since I somehow roasted my other one.....

 

Wrong Mods....Here is a formula for getting 30mpg with a Dodge Cummins

Drop the truck 2 to 4 inches in height and skirt the body all the way around to keep the air out and have a full underbelly pan to keep the air that does get under flowing cleanly. Get the compact mirrors (SRT) and the have a tonneau that is 24 degrees angle from the roof line to the top of the rear bumper...no tailgate.

Run a Smarty Beta 4.4 on SW1 and a TST PMCR R49 on 1/0 auto 6* or 9*

Have water injection for High boost times (hill climbs, etc) and propane injection at 5 to 7 psi boost.

2wd....no rotating front axle assembly. Run a TC and tranny that can lock in 1st gear, Run a 6 speed and have a Gear vendors OD.

Run 225/70/19.5 tires on AL rims or 235/17 tires on non decorative AL rims both at 80psi front 65psi rear (empty)

Drive between 55 and 65mph, 70mph on the downhills with very light pedal, let it drop to 50mph on the uphills if necessary.

Keep boost less than 8psi and generally as low as possible.

Unbelt the A/C, Keep the windows rolled up.

No extra lights or bolt on accessories.

Fluidamper

Stock exhaust with a 4" straight through muffler

Highest flowing intake possible.

Run Evans Coolant with a 220deg Thermastat

Synthetic fluids all around with the lighter diff fluid in the axles.

When driving around on flat or downhill terrain...lightly pump the accelerator on a bit then off for a bit. When you know you are going to stop or turn....let off the pedal early so you barely have to use your brakes.

IF you can't make 30mpg with these mods then get a Hybrid and get some really good mileage. KS

If this doesn't get y

 

i just took a 400 mile trip from memphis to new orleans. i got 23.6MPG (hand calculated) I stayed at 65 MPH and only used cruise control half the time. C/C kills fuel mileage because it will always keep the throttle down. When i get my new turbo/injectors/tranny i am hoping for 26-28mpg. With these trucks you have to spend $$$$ to save at the pump. In last months DP mag. replacing the stock fan assembly with a electric one added 2mpg and i might try that one when they get one made for my truck.

 

That otta do it! But I would have to say your truck would not look near as cool and would be boring to drive.

 

i guess its burning the same amount of fuel,it just seems like its barely workin at hiway speeds,and i never seen any fuel additives in abcforyew formula for milage.no ceatane or even acetone haha.

 

I've tried all the fuel additives and while they may help keep things clean....I haven't noticed a significant increase in fuel economy. ks

 

All other vehicle operating-envelope characteristics being equal (load, route, driving style, ST&P, blah blah), any mod that improves an engine's VE & BSFC (they typically have an inverse relationship on the graphs) will result in higher fuel economy.

... as stated above, the trick is to keep your foot out of it!

 

Just found a guy who is reporting 30-mpg on his 40-mile commute:

1,000-miles to the tank on a CTD

 

Third gen, 3 injection events and the stock emissions cam..........Not going to happen.

 

Don't forget that every time they re-do these things they get bigger and heavier.