5 MPG to 20 MPG what will it take?

[JasonG]

Years back Caterpillar 500s got 5-6 MPG hauling a full load at 70MPH.
I hate to sound down, but fixing up a NA diesel is a waste of money.
For the box, why duct it? If you don't need the space the duct will use, just chop the top level with the cab.

[autoteach]

OK, buy a bus. Mine gets 12mpg. Just a thought. Cummins, 5 speed, and some aero modding will make it much better.

[rmay635703]

A bus is actually more aero than a box truck.

And guys quit hating on NA diesel, that isn't really the problem.

A NA diesel CAN get better than a turbo varient but only if it is running in its ideal range, if its smoking a lot you obviously are not running in the ideal range.
Also the 7.3 is NOT an efficient turbo or non-turbo diesel, adding a turbo to one in my experience does not normally improve mileage. So throw the turbo always makes it more efficient out the window. That same statement was true of the 6.2, some 6.2's would do better fe wise after a turbo others were a whole lot worse. A turbo lets you burn more fuel more rapidly while using some power to force in air.

That said my 6.2 which was non-turbo got 10mpg running to the floor at 60mph pulling a 26' trailer and a 10' trailer at the same time over 10k in weight and that was with a 3 speed auto.

I know several who have a cummins that get in the 10mpg area but normally its a lot of weight or something real high. I have also encountered several ex box trucks with cummins motors that only get about 10-12mpg.

So in other words what he is DRIVING is the problem, he likely regardless of the motor is not going to exceed 12mpg without a MT transmission and extreme hypermiling with slow speeds.

A non-turbo diesel running a 22:1 compression ratio can potentially be more efficient than a 18:1 turbo'd motor if the motor is run in its efficient range.

Also my old 6.2 started a lot easier in winter than the ford and cummins versions I've encountered, likely because of its higher compression ratio.

I would love to own a properly designed naturally aspirated diesel suburban (or really any big iron naturally aspirated diesel car) of a more modern decent if such a thing existed. Pop in a 5sp manual and 30mpg craft mobile here we come. A 50mpg buick lesabre might be possible with old iron.

Cheers
Ryan

[daring4]

Just trade it in for an '04.5 to 06 Duramax, edge programmer, 4" cat back, bingo 20mpg...I get that almost every tank. 22.8 once but i pushed it into neutral alot for coasting!

As for NA diesel, they might work well in a certain rpm band, good for forklifts. ecomodding 101 is get up to speed then lug the engine, 4 seconds at 10mpg is better than 20 seconds at 10 mpg to get to the same speed. My trucks luggs along getting 30 mpg's after I get it up to speed.

My 4 cents

[usergone]

Well, if you're in California, you might just get some medals and whatnot for running biodiesel. Although if it is SoCal, you might have trouble finding a place that has any fry grease at all

A peterbilt 375 gets 4 MPG. Your box truck should not get 5 MPG. As the previous posters have said, it is likely your engine's fault.

Make sure it is running as well as you can possibly make it. Then, for the transmission, find a 5 speed, then put that on your 7.3. If you're feeling even more adventurous, go with a 9 speed non-synchromesh tranny like in semi trucks you'd have more gear ratios to chose from.


And, yes, aerodynamics play a big role if you do highway deliveries. City will be mostly the massive weight if the vehicle.

[aerohead]

John,I worked a couple years with a local moving company and the largest unit,a Ford truck-based moving van with big gasoline V-8 got over 8-mpg.Only mod was a 'Nosecone' recycled from a local wrecking lot.
I agree with the others that somethings amiss with the diesel.
A local resident owns a 'Vixen' motorhome and has reported 30-mpg with the 5-cyl diesel 5-speed( maybe 6-spd).It's probably less frontal area than your rig,certainly a lower Cd.
80,000-lb 10-wheel semis have hit 10-mpg.
20-mpg might be doable but you'd have to do 'everything' and something like a modern Sprinter might end up costing less,if those had enough interior volume.

[mechman600]

Today at work I downloaded the trip info from an ISX 550 HP, 1850 ft/lb torque in a Peterbilt 379, 18 speed. Pulls heavy haul Canadian super b-train weights (140,000 lbs) over the biggest elevation changes on this continent and cruises at 68 mph:::: 4.8 MPG (US).

Smoky old 7.3s (or 6.9s or 6.2s or 6.5s or whatever) are the result of worn out fuel system parts...pumps and injectors that need serious attention. Bluish stinky diesel smoke is fuel that never really caught on fire and did any work. The more there is, the more fuel you are basically pouring down the drain. This is completely different than black smoke exiting a heavily loaded diesel, which is caused by insufficient charge air...aka too rich. If you must, get a set of reman injectors and an injection pump. It will make a world of difference. But be sure to do a compression test first so it's not all for naught. A quick Google search has injectors priced at $28/ea and an injection pump at $415 = $639. Peanuts.

[max_frontal_area]

Originally Posted by mechman600

I think you are starting with the wrong vehicle. Seriously.

you saved me so much work
if i had had my choice of $500 vehicles it would have been a '68 Grumman-Olson

[max_frontal_area]

Originally Posted by euromodder

Recycle it.
It's obviously beyond economical reuse.
Even if you get it back in decent shape, it won't return decent MPG for only a 1 ton load.

see here in the US some states
dont have vehicle inspection, and for many
years most states didnt have smog
requirements. we can run pretty much anything we want ;-)
i got 30 year old VW A1*s to do 60 and 70 MPG respectively
and a benz to do 40.
i'll make this one shine too.

this truck was routinely carrying more than a ton. its rear leaf springs
are permanently inverted!!!

where in Belgium are you?
when i was a kid for a short while we had some real estate
in Antwerp. interesting 2 story commercial prop.
garage downstairs, residential upstairs!

[max_frontal_area]

Originally Posted by t vago

You can try the obvious aero mods. Air dam, side skirts, maybe a partial Kammback
Also, you could put some sort of dome on the top of your cab, to make the box a little more streamlined.

I don't think that ducting will work, though. You need to make your box a little less box shaped.

But be sure to fix your mechanicals first.

will do air dam, no side skirts as i am looking to implement a zero lift/mass airflow diffuser to work in conjunction with the relief duct. yes, dome is planned, and so is a kamm.

so, what is wrong with a duct?

oh. you mean like gettin it running :=)