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Old 09-12-2016, 02:26 PM   #1 (permalink)
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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.
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Old 09-12-2016, 09:56 PM   #2 (permalink)
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I did a lot of dirt and gravel road driving in small rear-wheel drive sedans back in the 70's and 80's (I really needed some small truck tires, as the passenger tires always found a sharp rock). I cannot think of anything that would work well today, other than a compact 4-cylinder pickup, but those are hard to find now.

A Suzuki Samurai or Sideckick (Geo Tracker) seems to be the best overall choice. There are also diesel conversions that give power where it is needed and tremendous range. It is hard to find vehicles that have not been butchered for rock crawling, but they do exist.

You might also try a Baja bug. A Thing would be nice, but they are collector's items now.
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Old 09-12-2016, 10:35 PM   #3 (permalink)
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Both GM and Ford wisely required at least a 2.8L V6 for their 4x4 mini pickups, and those v6s were a bit crap, but the GM 2.5 and the Ford 2.3 were even more crap for 4wd use. Ford soon replaced their 2.8 with a 2.9 which was no better, and GM added the excellent 4.3 before Ford poked and stroked the 2.9 to a 4.0, but at least they revised the head castings for slightly less cracking.
Dunno about the other minis, all the others i drove were 2wd with 5 speed manuals, the Isuzu had more potential for a street sport, the Toyota drove more carlike but the 22R isnt torquey enough. The Nissan was decent but no standout. And none of them had a frame competitive to the GM.
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Old 09-13-2016, 03:51 PM   #4 (permalink)
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Quote:
Originally Posted by cosmick View Post
Both GM and Ford wisely required at least a 2.8L V6 for their 4x4 mini pickups, and those v6s were a bit crap, but the GM 2.5 and the Ford 2.3 were even more crap for 4wd use. Ford soon replaced their 2.8 with a 2.9 which was no better, and GM added the excellent 4.3 before Ford poked and stroked the 2.9 to a 4.0, but at least they revised the head castings for slightly less cracking.
Dunno about the other minis, all the others i drove were 2wd with 5 speed manuals, the Isuzu had more potential for a street sport, the Toyota drove more carlike but the 22R isnt torquey enough. The Nissan was decent but no standout. And none of them had a frame competitive to the GM.
All depends what your off road targets are. I've owned two 22RE Toyota's and both were great off road. Climbing a dune at 50 mph? No. Turning 40's thru chest deep peat bog? No. Rock climbing? Snow wheeling? Climbing legal hills and mud holes? Great little trucks.

I also had a TJ with the 4.0. Dismal highway mpg, but would probably run all year off road on 1 tank. So it sometimes seemed.
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Old 09-13-2016, 04:43 PM   #5 (permalink)
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So are you solely looking at engine options that would fit in your existing Jeep? What MPG are you getting now and what tires/transmission to you have now? What MPG would you like to achieve?

My expedition type off-roading vehicles have evolved from a 1991K2500LD with 350 NV4500 NP241 3.73 on 255/85R16s to a 2005 Toyota Tacoma with 2.7L R155F 4.10 4x4 on 235/85R16. Mild (<2”) height adjustments on both, with several other mods for MPG/off-roading on both. I got maximums of 18MPG highway with the first rig, and 28 MPG highway with the second rig. Both were very capable offroad for moderate trails. My next high MPG on/off road vehicle is going to be based around a 90’s model GMC Diesel Suburban, 6.5 NV4500 NP241 3.42 rest TBD.

I wouldn’t be so quick to dismiss aerodynamics for expedition style off-roading (which I think is what you meant by your title, ignore this if it wasn't). When I think of expedition style offroading, I think of plenty of driving on paved backroads between stretches of light to moderate offroading. The idea is more of sightseeing and going places than running trails in a dedicated rig.

This totally wouldn’t be that practical and I don’t know about $250 at self-service yards, but given your basic requirements I would find a 2ZZ-GE from a Celica/Corolla/Matrix and figure out how to adapt it to one of the Toyota R15X transmissions which should be doable. For four wheel drive then pair that to a stock whatever transfer case was available behind the R- series transmission that works, preferably one with aftermarket 4.xx:1 low range gear sets available which is almost as good as a doubler. The 5 speed in some jeeps is an AX-15 which is the same thing as a Toyota R, General Motors AR-5 , Jeep AX-15, NV3550, and Isuzu AR5, all the same family of Aisin transmissions with minor differences. Gear it low and don’t be afraid of RPMs as the 2ZZ likes to spin, but has fairly high BSFC so MPG should still be good. (For gearing reference the factory 2zz transaxle came with 4.56 final drive gears in a car with 24" tires turning out in the 30s for MPG.)

Once again, I wouldn't suggest actually doing what I just suggested above, I would rather suggest re-looking at your starting vehicle and perhaps find a capable offroader that would put out more MPG stock (like a 1999-2000 4Runner with 2.7l, 5 speed, 4x4).
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Old 09-13-2016, 09:41 PM   #6 (permalink)
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Try a GM LE5 EcoTec, commonly found in Malibus, G6, Cobalt, etc... It's 2.4 liters, and 175hp... A company makes off road harnesses designed to run them, and they usually come with a tuned PCM... Fairly efficient engine that makes good power, and they're plentiful and cheap... The engines in stock form will handle 8-10psi of boost just fine and make more power than you could ever really need for off roading, except maybe in the sand... Bolt up a Colorado transmission and find a transfer case doubler to gain that double low range, and run 3.55 or 3.73 gears with a 235/85-16 tire... Plenty of clearance for mild trails and enough gearing range to handle both highway driving and some tight technical off-roading... Might maybe get 20mpg highway depending on aero...

Only reason I suggested a doubler over, say, an Atlas transfer case, is the potential of running in 2wd, single low on light trails where traction isn't an issue so much as power is...




But, if you don't need a Jeep, why not lift a Subaru? How much ground clearance do you need? I imagine an older Impreza based Outback, lifted enough to clear a 215/75-15 tire, would be fine for all the off-road I have around here...
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Old 09-18-2016, 04:34 AM   #7 (permalink)
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Seems like the 2.4 that came in the Wrangler would be the obvious way to go.

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