[ausias]

Originally Posted by orbywan

Thank you ausias. So let me see if I understand this right. You're getting 30 mpg gallon out of 24 foot van at 50mph, from a vehicle with 177 bhp?
Yes
So that would make it about 3.0L, is that right?
Yes, Iveco 4L F1C engine 3.0 HPT, with 380.000 milles, and 200 thousand more expected.
If you don't mind me asking, what are the dimensions of your box and how much does your rig weigh when you're doing this?
Wheelbase: 12.96 ft. 3950 mm
External=> Long: 23.01 ft. Height: 8.76 ft. Width: 6.55 ft.
Cargo Area=> Volume: 15.6 m3 (550.68 cu ft.) L: 14.96 ft. H: 6.23 ft. W: 5.91 ft.
3500 kg overall weight on average (legal maximum), 7716 lb.
Top speed: 112 mph (but I was a little afraid driving >100 mph on German Autobahn and I did not reach or exceeded that speed)

If my guesses about your vehicle are correct, I can only imagine what kind of gains you would get with a boat tail. If reducing the rear drag on my 7.3L boat anchor gives me 25 - 30% + improvement, so far, I can only imagine what your motor of half or less displacement would see. I realize you have to open your back doors. Could you make the tail in two halves that would swing away to allow access to the box doors?

The IVeco Daily with full Load consumption at cruise speed of 107 kph (66.5 mph) is 10.5 L/100 km or 22.4 us mpg.
In same condition Volkswagen LT 35 2.8 TDI 158 cv, 23.5 mpg@66.5 mph, 230.000 milles ODO.

My first attempt will be underbody drag.
I have a partner with the same Iveco Daily and 585.000 mi on the clock. and he have not plans on buying a new one yet.
Maybe first conversion in usa will be put a small eficient turbo-diesel engine,
I did some calculations and getting cd=0.32 on that van will reduce consumption in about 9 %, (sorry I think in I.S. units and not in milleage,) that is 11 % milleage improvement at full load.