Efficient 4WD Jeep
 

New to the forum and I thought I'd share my plans to make an efficient Jeep.

my plans are to start with a 1992 Jeep Comanche 2wd, I love Jeeps and will only own Jeeps (except maybe an air cooled VW), my goal is to make a realistic, functional truck that I can use as my daily driver, to replace my current thirsty lifted Cherokee. I figured the Comanche would be the best Jeep platform to start with as it is one of the few somewhat aerodynamic models, plus they got decent mpgs stock, with torque minded motors made when mpg ratings were a practical way to fill up empty space on window stickers.

1986 Jeep Comanche 2.1 4cyl Diesel 2WD 5spd Manual-24 city 29 highway
1986 Jeep Comanche 2.5 4cyl 2WD 5spd Manual-19 city 24 highway
1992 Jeep Comanche 2.5 4cyl 2WD 5spd Manual-18 city 22 highway

My plans are:
Engine-VW 1.9 TDI, equipped with a hydrogen generator, maybe a veggie oil/ used oil conversion later.

Drivetrain-5spd Manual from a Geo Tracker (cant adapt Jeep trans to TDI without custom work) and two auxiliary overdrives. With the gears in the spare axle I have laying around I'll be doing 70 at roughly 1700 rpms

Aeromods- Remove fender flares and smooth out mounting surface, fill grill (I'll be upgrading the cooling system to utilize less airflow), a 3" chop top, a coroplast slantback bed cover, 2" lowered and many more here & there aero mods

My naive, mpg hungry heart is aching for 40 MPG.

With the 1.9 tdi you will see 40 mpg, easy.
I bet you could throw that motor in a full size pick up or your Cherokee and get 40 mpg.
I say that because my beetle gets 62 mpg on the hwy with that motor.

I think I'm going to use My Jeep M38 instead, it's less aerodynamic but quite a bit lighter, it weighs a little more than a Metro. After more research on the hydrogen generator I think 60 MPG is attainable.

Now your title says 4 wheel drive... is that going to work with that engine and transmission set up?
After seeing an electric front wheel drive, gasoline rear wheel drive pickup truck last week, I really like that as a home built hybrid design and you get your 4 wheel drive as well, not that most people need it but it works.

Yes it will be 4WD, it is a must in Minnesota, we had over 100" of snow last year and it's supposed to be significantly more this year. Front wheel drive is useless in our winters, especially on the highway. I was considering a Geo but want something that I can drive year round that will get me there alive on long winter trips.

Are you up to building new aerodynamic body onto the frame? Yes you'll need steering and suspension spring movement clearance to match the Jeep's specs but the body doesn't have to be a box with protrusions.

I'm assuming the Jeep is a body-on-frame construction?? So removing the body doesn't affect the base structure??

Uni-body

http://jeep-parts.uneedapart.com/ima...nche-parts.jpg

The idea of building my own body is making me think about building a sand rail, I have enough drivetrain, suspension, etc parts laying around and I could "borrow" steel tubing from my friends farm. I also discovered that HPA Motorsports makes a Jeep TDI swap kit so I could use a Wrangler 6spd, I thought the only RWD adapters were for Suzuki samurai/sidekick trans which are better suited to the VW 1.6td, the TDI has too much torque for them. The Jeep trans has a wider gear spread as well.

Does anyone have pics of a aerodynamic sand rail or similar vehicle?

I'm thinking a lightweight, low profile frame with a coroplast and fiberglass body.

knowing what my mid size suv gets, id say 40 is really up there.

looking at major aro mods to get that.
doable yea, but no cake walk.

mine is about 4,300LBs with 4.55 gears, 450LB engine and really bad aro. 33mpg is as good as ive gotten.
that's in flat land in warmer temps....with no cargo.
its old school diesel with a turbo added at the factory, so its not ideal as far as the power band, its rather narrow.....2,300 to 2,800rpms its very much suited to the gearing they put in the autos....and the fed 55 speed back in the day..

29 mpg is common as a year round avrege, running at 60 or less, with many steep roads day in and day out.

its rated at 28 city 28 highway

un like your jeep, im limited to 4.55 or 4.11s with the stock axils in a 87 or older ZOO.
my aveter is one of my loads, it sucked mpg down to 17. CGVW was about 9,000LBs, thus why i stay with the 4.55s


for the jeep if i remember right there's many different 3rd member gears that fit the dana 35 that the jeeps are common with.

I'm thinking of a lifted Zoltanbod with Monster Mudders.

If you can have an aerodynamic shape, reduced weight, and reduced displacement and rpms, you should be able to produce really impressive mpg in a 4WD beast. IMHO (in my humble opnion).

So far in this thread, I think the only fixed requirements are 4WD and hopefully 40 mpg or better. If the other project definers are still open then weight, aerodynamics and power train specifics will determine the mpg. The 4WD drivetrain will reduce mpg from what it would be if that weren't needed - but it's NOT a show stopper.

Nearly all 4WD's on the new/used market are relatively boxy and not lightweight. Those that aren't, tend to be built for "performance" (Subaru WRX and Audi Quattro/S4).

People + cargo capacity, shape, and other requirements may still be open - but SOURKRAUT may have some requirements in mind there.

Subaru could make such a car but they don't seem to be interested. Their stuff is all either heavy, or go-fast, if not both. And their bodies are not built for low drag.

I'm leaning towards the sand rail, space isn't an issue, all I need is a two seater with enough cargo area space for a couple duffel bags for weekend drill (proud weekend warrior, upcoming vaction to Afghanistan will fund this project). Check out the 2nd post in the link below.

First EV - Sandrail, low range low speed, for now... - DIY Electric Car Forums

Something similar to this but with a full body would be perfect, I could go for a rear engine and use reverse cut gears in the axles, shifter would be trickier though.

On a side note, all of the people on this forum are great. I'm used to off road forums where the users can be rather... Unpleasant

I can see why you would want one.

Link with 2nd post mentioned above, has this pic below.
It's a UVA Fugitive, a sand rail kit car made by a now defunct company. Main Page - UVA Fugitive Kit Car UK Owners Club

(I'm reading between the lines that your project needs to be highway-capable, right?)

http://www.shining-wit.net/rick/bugg.../fugitive0.jpg

Yes sir. A similar frame to that with a lower top, slightly more aerodynamic shape, modified to run a regular 4WD drivetrain but backwards for rear engine mount + a TDI.

I think I could build the frame around the drivetrain then strip everything and stretch fleece over the frame then fiberglass over it. I could use foam pipe insulation when molding the body to keep a little space to make it removeable then build some body mounts when the body shell is complete. I could use coroplast for the belly pan and have a cutout for the transfer case to protrude out of (the transfer case I'm using angles down and to the right (left in rear engine).

The only exposed parts would be the suspension components.

The UVA is pretty narrow. A belly pan of about that width probably wouldn't need any bracing/framing to keep it from sagging. I have no welding/fiberglassing skills so you're way ahead of me in those areas.

Now that you're thinking about an aerodynamic design for your vehicle, I think it's important to reference two key articles.

Our member basjoos modified his 5th generation Civic to a very slippery shape indeed, and was one of the first - if not THE first - to do so. Have a look at his thread: http://ecomodder.com/forum/showthrea...ight=aerocivic. Of course your project is pretty much a ground-up effort, vs. basjoos' modded car, but I think it's well worth a look.

Our very own aerohead, aka Phil Knox, has provided a template which can be scaled to guide the design of a low drag vehicle. Have a look here: http://ecomodder.com/forum/showthrea...rt-c-9287.html

That's the "Part C" thread, which has the template. You can find parts A-B-C-D-E by searching on these combined criteria:
- In the "Aerodynamics" forum
- "Aerodynamic Streamlining Template" in the thread's TITLE
- Posts by "aerohead"

You have a huge amount of work ahead, on any version of this project - good luck with it!

I like the idea of the diesel swap. There's good science behind that.

The hydrogen generator belongs in the unicorn corral.

Yeah, I had heard about the hydro generator at NAPA and was all excited then after some real research I was gravely dissapointed.

My version will be a little bit wider and a little bit lower than the one in the picture.

Are diesel swaps still a good idea? Will diesel still be relevant in 30 years?

I've wanted a Jeep Comanche for a really long time. I found this article today:
https://www.dieselworldmag.com/featu...jeep-comanche/
A guy swapped a 3.9 Cummins engine into a Comanche. The build included a 4.5" lift and 33" tires. He recorded an all time low of 24 mpg, and a high of 36 mpg. Would it be within reason to get 40 mpg or more with this engine? I think that is reasonable if you drive like an ecomodder and perhaps built the truck with fuel economy in mind. Like putting in a NV3500 transmission in lieu of the NV 4500, using a tonneau, etc...

The fuel savings from this setup would make the cost of the build and the time invested well worth it. With the current cost of diesel fuel, it would just about halve my yearly fuel cost. edit: Not to mention having an awesome custom off road vehicle with great fuel economy.

If you aren’t making an income BECAUSE of 4WD (unlikely, we built the entire country without it) its a mistake.

I get it about wanting “both” drab commuter and exciting weekend toy.

Go back to basics.

1). How long will you keep it?
2). How many miles will it accumulate?
3). As it will eventually be the same out-of-pocket as a three year old vehicle (accepting unreliable transportation is a non-starter. Entire vehicle must be COMPLETELY re-Wired. This is not optional. This is before the complications of a drivetrain swap), what is the annual cost of the latter per AAA or Edmunds “True Cost of Ownership” expressed as cents-per-mile over X period.

4). What will be the additional costs? Offroad is especially high maintenance.

5). The cost of fuel is half or less of a brand-new vehicle at 5-years and 60k miles. Purchase, depreciation, finance, etc, all add up hard.

Go find the three year old nice JK and run TRUE NUMBERS.

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https://www.youtube.com/watch?v=zZmzGYANZvI

Eco off roading.

It's not just about the money, but I get your point. Those are all good things to consider before undertaking such a project. It is also about the thrill about creating something unique. A vehicle that is not only capable but economic too.

Off road vehicles cost about the same to maintain as a regular car, with the exception of much faster tire wear. If it is a budget build then it will be more expensive as stuff will break all the time.

At 60k miles the fuel costs in a JK would be about 9k or so. Depreciation really hits hard.

The cost of my build would not be that much in relative terms. It would vary a lot based on where I would source parts from. A crate engine is as cheap as 3k. I could get the truck itself for as cheap as $500. Other mods would likely be around 4k-6k. So I would need to drive around 120k miles to recoup the cost of the build in fuel savings, which is probably unlikely to happen. But it isn't just about that

That video is pretty great, haha.

edit: Now that I think about it, the cost of other mods would probably be closer to 6k to 8k.

Regular road vehicles don’t have transfer cases or all the changes from the 2WD version first, second, the differences between on and off road vehicles of any sort. It’s a weight penalty, an aero penalty, and a mechanical/electrical penalty. Plus shorter life before replacement or overhaul.

Sure, it could use less fuel. But it won’t ever use less money or even the same. The penalties are inherent.

So come up with the numbers. Against a three year old sedan of some sort. It’s one thing to dive in. But how deep is this pool (my pockets) versus an alternative?

The reliability or lack thereof which threatens my income right down to how do I get to work today — not just other goals scaled back or foregone for what is pleasure-seeking — warrants a plan. An inventory.

There’s the teenager within us trying to persuade Dad. And there is the man who’s supposed to be husband & father who we are or will be. Protector & Provider versus Pleasure Seeker.

Spending money to save money is harder than it looks.

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I like that you're making me give a thorough rundown of the cost of this project, rather than an estimate. I will provide the actual cost of things I expect to buy for this project to get an accurate estimate.

1988 Jeep Comanche 4.0L 4wd - $2k
Could be talked down to $1400 due to condition and mileage
-500 from selling the engine, transmission, and transfer case
Net cost: $900

2003 Volkswagen TDI - $2k
(This was cheaper than any sources of a 3.9l cummins engine I could find)

NV3500 - $57 from Pick n Pull on a half day

Wiring harness- can be used from the volkswagen

NP241 transfer case- $144 ebay

Custom driveshafts- ~$600

Front and rear air lockers $1700

Air compressor: $300

Tires and wheels: $1100

4.5" lift kit: $500

Steel for custom rockers: $400

Skidplates: ~$500

That comes out to ~$8200. I would expect to spend at least another $1000 for mating the engine to the transmission, and other things depending on the condition of the engine. So $10k would be a better ball park estimate.

A comparable 3 year old vehicle would be the 2016 Toyota Tacoma or Jeep Wrangler. Those are currently selling for around 30k. A basic 3 year old sedan is around 9-12k right now.

If done correctly, this can be a reliable vehicle. Diesel engines can last a very long time. If I hypermile the truck, it can probably get better mpg than the 10k Corolla. Other Jeep owners report getting an average mpg in the 30-range.

TLDR:
Will it save money? Not compared to buying a sedan, but the fuel cost will be about half of what driving a gasoline Jeep is.

Will it be cool? Yes it will

I would like to add that this would end up being the 3rd-- or even 4th vehicle in my household by the time I am finished. So reliability isn't exactly the greatest concern, though I do expect it to be reliable.

I’d still add a couple thousand for miscellaneous and the unexpected.

That it’s not primary transportation changes things. If I missed that earlier, sorry.

I’d still recommend the use of a CPM calculator. AAA or EDMUNDS (True Cost of Oenership) as multiple vehicles figure just as much to family budget.

Perspective.

I think it would be foolish to have a vehicle like what I'm describing to be my only mode of transportation.

I'll check out that calculator. It would give a good perspective on my vehicle cost

Oh, I understand why men want to do it. I just was angling for perspective.

A CPM calculator is a basic business tool. You’ll REALLY like how it sharpens focus. Each pony, then the herd as a whole. Take solace that it’s nearly always more than we expect when extrapolated over a lifetime (major phases thereof).

I zeroed out the full expense of my pickup as a business vehicle (whew, plan worked) as otherwise something this expensive (to buy and to own) would have been foolish. The plan to make the most of it was centered on low fuel cost per mile (diesel was still cheaper per gallon then; tremendous energetic content per gallon advantage) coupled to business use. Squeaked by on that last part. Today I would NOT buy diesel. That window shut.

It’s been a long-tenure faithful servant. But still expensive as 1T pickups are greatly oversized for the majority of use, thus no repairs of consequence are cheap. (A new set of injectors will likely run $5k after pro installation; etc).

As book value declined $3k in 12-years from what I paid, it still makes sense to keep.

It’s the long-term CPM based on actual figures which keeps emotions at bay. Even at 19-mpg overall average annual MPG. (A gasser from a few years before with similar capacity for work would average 8-mpg. The diesel only really shines past 200k with the delay of engine replacement ).

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tdi swap trucks on facebook is the place to be if you're considering a swap. But the only possible way to do a swap is to buy say an entire 99 golf tdi and tear it apart.

Mercedes Turbo Diesels.
 

I'm not sure how it is in your neck of the woods, but here in Southern California they are plentiful. You can pick up a runner for 1000 dollars.

Our laws allow you to swap a diesel into your pre-1997 inclusive, Jeep and not have to run smog checks. With the older, robust pumps on these diesels, you can run waste oils to reduce your fuel costs. There are several companies that make adapter kits for the Mercedes OM617 and OM602-3 line of engines. I make my own as I have a fabrication capability and CNC equipment. These diesels have good RPM capability so they cruise on the freeway comfortably. The Cummins 3.9 does provide more torque but they weigh much more.

Look into it and see the availability in your area.

There are no mercedes turbo diesel cars in my area. There seems to be a lot in California though. That would only be a couple hour drive, so it may be worth it. It might be easier than finding a TDI engine to swap in, though I didn't find any here either. We have a big food truck culture here, so finding a box van with the Cummins is a possibility.

Also CPM calculators seem to be more of a marketing thing. I could not find anything for cars.

1). Edmunds “True Cost to Own” (TCO)

2). AAA’s Your Driving Costs
“How Much Does It Cost To Drive?”

You’d be correct in assuming no one wants you shifting from feelz to brains in re cars.

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