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Old 09-12-2016, 02:26 PM   #1 (permalink)
cosmick
Experienced UAW Mechanic
 
Join Date: Sep 2014
Location: Bear Lake
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Mpg for expedition, off- road

Found this on another forum, my local Jeeping forum actually.
Asking about combining good mpg with doing it over rough, unpredictable terrain.
My 95 Cherokee 4.0L H.O. is thirsty and underpowered in- town, but quite the opposite off-road. And sustaining 50+ mph is seldom part of it, even on the best dirt, so aero is less important. But range, miles per tank, is very important, especially when having to crawl along in first gear and low range.
They noted for the trillionth time the idea of minimal lift and more clearancing for tall narrow tires, like 255/85R16s, and the possibility of spending more building it than fuel savings can repay.
I thought i would consider an Escort 1.9L for mpg, or an Eclipse 2.0L for it cruising happily at 800 RPM at 30 MPH without lugging nor surging, or a Colorado 2.9L for being the torquiest 4-cylinder.
Off- roaders do this thing called a doubler, they take the 2:1 low range out of an old NP203 transfef case, and sandwich it between their favorite transmission and their favorite transfer case. This is often a NP241 because of strength and because it has a 2.71:1 low range. It also has an aluminum case.
Obviously, you would want a 6 speed manual, then choose the axle ratio based on 6th gear and tire size to get the cruise RPM to end up just enough over whatever was stock for the engine chosen to compensate for all the extra drag.
Any of the diesels good enough for such a build are too new, too complex, and probably still too heavy. Probably too bulky, too.
So, your responses must not call for any Honda anything, nothing less powerful than the Escort 1.9L, and nothing that isn't gasoline fueled. Last rule: nothing that can't be scored at self serve salvage yards for under $250 in one day by one man. Power tools are not permitted in such yards.
3..2..1..GO!

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