Big pickup mpg ability - stock and modded
 

Does anyone have any rules of thumb for the approximate aerodynamics of full size pickups, primarily chevy/ford/GM, but not only including the latest/newest ones? I'm curious how much things have improved from say the 80's to today and whether any of them stand out or if they are all about the same. What little i've seen suggests the aerodynamics of a brick for dodges, i've seen Ford windtunnel tests designed for efficient tailgate up towing - and wondered whether the truck itself is a bit swoopier because it actually is better aero... or if that's just styling.

I'm sure there's lots of other posts and I will search - this is strictly brief info/rules of thumb/suggestions for further research. :) Like someone following trucks better than me if they could share any useful info they know.

I'm specifically wondering if there's any full sizes that can get 30mpg or higher at 70mph normal road speeds, whether through teardrop bed covers or whatever, but without excessive focus on extremely numerically low gearing. (future project to research will be a tow vehicle for 5 tons and up loads either 5th wheel or preferably gooseneck, main goal being to boost mileage while unladen or with empty trailers, and while moving low dense heavy material on flatbeds) As an interesting story of point I once met a guy (with previous owner claiming the same) who had a 44mpg Suburban... it was some modified isuzu diesel in it and still had enough power to pull a horse trailer. He probably drove it real slow but I still find that mindblowing if it's even possible despite hearing good things about cummins/isuzu 4cyls approaching 30mpg without any aeromodding at all.

Good questions sir. I too share your general curiosity about trucks and SUVs. There are so **** many of them on the road. I'd love to see some real numbers to see what models have the best aero designs right out of the box. Seems like it would be smart to buy something that starts out with an advantage.

most likly engine is the 3.9L isuzu I-4
about the only engine used in Isuzu cab overs in the 80s early 90s

the 2.8 and 3.1L where never sold state side rigged for road use...there more of a car engine with a 4,200rpm top end when in road config.

its more or less size wise the same as a cummens 4BT engine,
same size, same 750LBs and same 2,800ish rpm limit..

its the one that's in the dodge trucks with two less pistons.


difference being the Isuzu was sold in many different flavors over the years,
DI and IDI injected with and with out turbo.

the early ones have HP numbers on par with my Isuzu SUV 80hp just its a 3.9L not a 2.2L so way more torque.

where the 4BT are all DI injected and turbo-ed as far as i know, for the ones made for road use.....



id say 30 is quite possable, but 44 hmmm.....need real lonnnnnnnnnnnnng legs as far as gearing.
problem is a 2.73-3.08 non full floating diff don't work real well for big loads......
i know more then one person that as blown light diffs up moving big loads in half tons...

Interesting stuff guys...most of my towing needs are served by my subaru wagon. 5x8 garden trailer for moving the bike or lawnmower. So far so good :-)

I'm specifically wondering if there's any full sizes that can get 30mpg or higher at 70mph normal road speeds . . . .

This contains your first of several mistaken assumptions (stated and implied).

.

Yeah, if you call 70 mph "normal road speeds" and you're looking for 30+ mpg out of a full size pickup that's akin to asking for a diet pill that's going to make you lose weight while eating lots of bacon and donuts.

FWIW I figure most late model full-size pickups have about 39 square feet of frontal area and Cds of .45. My guess is there wasn't a whole lotta change in aero between the '70s through, oh, the mid '90s, when there may have been wee lil incremental improvements in Cd (airdams, thick tailgate edges, etc.) which were probably more than offset by bigger frontal areas from bigger cabs, running gear, and tires.

However there was a recent EM post about the new Ram which has aero tricks that bring Cd down to .36, which sounds like one helluvan accomplishment.

Yeah I want to be able to drive faster than 45mph pulling a trailer.
A turboed isuzu 4 cylinder only makes like 130-150hp.
Thats close to what my N/A 6.5L diesel made.