Mission impossible: modding a Unimog
 

Well if not impossible, really really hard

info: 1970 Unimog 406. 110 hp 5.6L diesel inline 6 witha 6 speed transmission. 6.5:1 gears. Originally engine governed to 2500rpm, current engine to 2800 rpm. Has 40 inch tires and a top speed of 85 kms per hour. I can play with the governor to top it out at 3100 rpm max. Fuel economy? Hahahah.

So, the mission is to make it highway friendly. 8000 pounds of truck. The tires are weather cracked so I need new tires. I'm looking at 395/85r20 tires. Either Goodyear mvt ot Michelin XML. They are 46 inch diameter the Goodyear looking like more street friendly and the Michelin more offroad inspired. I like both. Not sure which to get.
The air filter is oil bath, that has to go
it would need a 4 foot airdam to get close to th ground so that is out.

Suggestions and ideas? This is so underpowered I slow down to 25mpg on hills that my passable doesn't even notice

Oil bath air filters are very effective. I've yet to see data that shows filter restriction affects fuel mileage on a diesel.

Perhaps you can decrease your rolling resistance by making sure your wheelbearings are well lubricated, and gets some good slippery synthetic lube in your transmission and differentials. Make sure your brakes aren't dragging. Get your operating temperature up to 190F, turn your fuel down if the engine smokes, get some biodiesel in the fuel tank for lubricity and improved cetane.

Those are the only suggestions I've got.

I love Unimogs! Pics?

I think the best "mod" for a Unimog is to only drive it when you really need to. :)

A Cummins 3.9L 4BT would give it a little more power and probably be more efficient as well. But I'd want to keep it all original if it was in good shape.

You're my hero.


Unimog 406 416 info

Put an aero package on it... ;)

From what I've read, the oil bath air cleaners only have one draw back and that is that people don't understand them or take the time to clean them, but as far as cleaning the air of dust and dirt they tend to be the best air filter you can get.

Are there heavy truck tires that would fit? they would tend to give you better gas mileage then off road tires, but a vehicle like that is made to be driven off road so it would be kind of like putting road slicks on a tractor and that is pretty much what you have, a tractor with a cab and a truck bed, complete with PTO and hydraulics so you can power your backhoe and front end loader.

If you can turn the fuel pressure up or swap bigger injectors, then reduce the mg/stroke of the pump it will help. If the pump isnt that adjustable, a bit more boost will help.

A full underbelly pan and axle wing/deflector should work.
Under belly pan... - Page 7 - Toyota Forums :: Toyota Nation

I never knew thew were underpowered, guess I assumed they had big Diesels.

in the subject of tyres - the more "slick" they are, the better:

so-so ones
http://www.milweb.net/classifieds/classpics/54735s.jpg

Michelin XTE2 365/80/R20 160 K
http://image.ceneo.pl/data/products/918664/product.jpg

- thread uneven, cut partially

----
best:
Uniroyal R300 365/80/R20 160 K
http://image.ceneo.pl/data/products/918573/product.jpg
Matador TH1 385/65/R22,5 160 K
http://image.ceneo.pl/data/products/918703/product.jpg

thread even, not cut, roll superbly.

Of course cut and uneven grip better, but the EF is an aim.


If the UNI is underpowered, go down with the tyre profile - that means better torque on tyres and faster gear change [EF up and lighter tyres]

you can also consider skinner tyres for smaller drag.

They are big diesels but not powerful ones. Even at 110 hp he egt temps get hot. 110 hp is not a lot with 8000 pounds, when the tires weigh 200 pounds each. As far as tires go I need something decent for offroad as well so I'll probably go with the Goodyear mvt. Looks like ordinary mud tire compare to the Michelin XML which looks like a tractor tire almost

You're right: impossible.
Case closed.
Next, please.
;)

Good luck!:thumbup:

Gasoline Fumes and I have discussed this at length,
We will be unable to help you without pictures of the subject in both mud and snow conditions :)
Poised next to a much smaller vehicle would be helpful as well ;)

HAHAHA a unimog! That's awesome! Crazy awesome. And crazy :thumbup:

You could probably increase output and decrease EGTs by upping the injection timing (advance). The way I understand that is that it makes more of the fuel burn in the cylinder and less on the turbo so the EGTs are cooler but the cylinder temps will get a little hotter. Not sure how it would effect FE.

Make sure your injectors are in tip-top shape. I'm not sure how many miles (Km?) are on the stock sticks but with an old 70's diesel, I'm sure they could use some help. Pop-off testing will let you know what shape they are in.

Those recommendations are actually from plenty of lurking over at cumminsforum.com (2nd gen) researching MY diesel engine. If yours has indirect injection... well, I'm not sure.

Of course, you could also change the rear end ratio (like mentioned in that link there) but that may or may not be practical.

Keep us updated and let us know what its FE turns out to be "stock." Should be worth a good laugh :D

Another thing I forgot: try a BHAF. It isn't as cheap as a stock filter, but it breathes so much better. I ordered one from fleetfilter.com for about $50, part number 2790

http://dodgetrucks.org/photopost/dat...talled-med.jpg

So what are you going to use this vehicle for and why do you want it to go so fast? if I was driving an 8 ton vehicle that could crush the average SUV, I would drive however slow I wanted.
If you want more power you might check in to how many of the pumps and other PTO loads running all of the time, sure it's nice to be able to hook up a snow blower or trencher, but do you have one? are you using this as a tractor or a truck?

Oil bath air filters are superior in everyway, except one.

Since they do not need replacing at regular intervals, only serviceing, there would be no need for after market sales.

(Oh dear,what would the poor air filter manufactures do...???)

:rolleyes::rolleyes::rolleyes:


I look foward to following your project...:thumbup:

>

You need either a 3.5 foot lowering kit, or a 100% smooth belly pan and some way to get the tires out of the airstream. Tires have absolutely horrible aero drag, so I'd enclose them in Aptera-style fairings.

The DoD is interested in reducing the fuel consumption of the US military. Keep an eye on the ecomods being done to our fleet of off-road capable, overweight trucks.

Also, if you're driving >25mph in a Unimog, or using one for a family vacation, you're doing it wrong.

Something I plan on doing is setting up a fuel cell unit for my engine because there is no (cheap and easy) way to electronically show fuel consumption. The fuel pump is on the side of the engine and the fuel tank just has 2 lines going to it, so volume/weight measurements should not be too hard.

I wonder what its FE would be in top gear just idling along (at 15 MPH, lol) but don't hurt your engine (don't suck a liner)

Considering how slow the vehicle is, I'm wondering if there is any benefit at all to doing aerodynamic modifications. It's just so heavy the mileage will always suck.

I vote for on top of any other vehicle!

Have you ever felt the wind load on a bicycle at 15mph?

Sure, the mileage will always suck, and it will never be the right vehicle for transporting people where there are roads, but are you interested in mileage that sucks less badly?

Yes, and it's pretty light compared to 65mph. The gains from aero mods at low speeds are minimal compared to the costs to get them. Driver adjustments, rolling resistance and engine efficiency are lower hanging fruit.

At least its a diesel.

I love Unimogs too. Just curious about the exhaust system. What is the diameter of the exhaust pipe? Could increasing the size help FE and power?

sorry about the delay gents, here is some pictures. I ordered the tires today, going from the stock 40 inch tires to 46 inches in diameter. Yes, need more hp to run them BUT the engine will run a bit over 15% lower rpms, making engine very happy.

the exhaust is stock, I believe 3 inch with a crappy muffler. there is also a kink in the pipe, maybe a new pipe is in order.

http://i36.photobucket.com/albums/e1.../IMG_1145s.jpg
http://i36.photobucket.com/albums/e1.../IMG_1142s.jpg

Yeah but the question is, how is it being used?

Daily driving this thing on the roads is an exercise in futility.

Frank,
The root of futility is utility, so I have been told. I think a unimog is a great utility vehicle. Say your driving home from work at the office, and you come upon a 2 million acre tract of rough land that is in between you and making it home with the 2 tons of building supplies that you picked up at the home depot, what vehicle are you going to take?

noit a daily driver, unless things go really right for the first time in years. I still have the passat for most driving.

This is a toy, I always wanted one. I got a real toy one after extended stay in a hospital as a child. I enjoy driving, and this thing is so very basic it's fun. I have to plan all my turns, my stops and hills, never for a minute can I sit back and relax.

I bought it a two weeks before easter, 15 hours on a rebuilt diesel. Drove it home, 305kms or 200 miles, 3 blocks away the engine spun a main bearing and some other fun damage. bought a replacement engine form a faster more powerful one and sawpped it in on Easter weekend, and the cost of the engine broek me so I had to leave it sitting for the last 6 months. Breaks my heart to see it sit. I repainted the cab interior and did some small work, but still needs some work for mechanical safety. got new tie rods coming, so maybe in a few weeks I can take it to a shop and have it on the road :turtle:

I have toys too, and fe is still a factor but it isn't at the top of the list by any means.

I just tune em up as nice as I can, run bigger tires "overinflated", and use good driving technique. I suppose if it needs work and parts anyway that the usual mods can be done but I wouldn't mod a nice original if it doesn't rack up many miles anyway.

I get about 20 with the Bel Air that way; 30 with the Corvair.

WOW!!! And you need help?! If I were you, I would be perfectly happy with 25 mpg!!!!:eek:

Make sure all your suspension component are in good working order. You'll be wasting gas with bad ball joints (king pins?) or tie rods. Swap to better rear gears if you don't have to have them. Reduce idle time. Sure listening to a diesel run is nice, but that's not just fuel your burning, it's money too!
VT247

Assuming you are getting around 4 mpg, and If your current Cd is around .75, and you decrease it by 60%, ( to .30 ) you would only boost your mileage by just over one mpg at 50 mph.
At slower speeds, like this vehicle is capable of it would be even less.

Assuming you are getting around 4 mpg, and If your current Cd is around .75, and you decrease it by 60%, ( to .30 ) you would only boost your mileage by just over one mpg at 50 mph.
At slower speeds, like this vehicle is capable of it would be even less.

hmmm. wonder if anyone ever put a unimog into a windtunnel. Would love to see the numbers...

My father has also one of those. It is for snow plowing puposes. Ours is quite scary to drive over 60 km/h because there is so much "loose" on the streering gear.

What? Oh wait a sec. 1 mpg is a 25% increase in FE... Even then, I wonder what numbers you are using???

From Unimog links:

FA (?) 48.18 sq. ft , EE .19, drive train efficiency .9, #2 diesel
CRR (?) .015

Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com

Gets 13mpg @~37mph... close to 50:50 aero and rolling resistance.

I got 9.36 mpg at 50mph with .75 Cd and a 66:34 aero to rr (respective)ratio. At .30 Cd I got 15.5 mpg, a 65% improvement in mpg and a 44:56 aero to rr ratio.

I stand by the fact that aero improvements are almost always beneficial. Would adding another axle to this vehicle cut rolling resistance by a lot?

that is a 25% improvement using your assumptions. not bad, I suspect this thing is getting closer to 6 or 8mpg while on it's way to where it is being used.

:turtle: Every little bit is gonna help...

Highway Glider (designed and patented at MIT) is "the only" product that
can actually improve your vehicle's mileage per gallon (average by about
2%-6%) at highway speeds.

Hey! Must be as good as a ScanGauge.

(Click to enlarge.)
Attachment 7574
An aerodynamic license plate cover :confused:
Hi-yer edge-a-ma-kashun; the key to arrow-die-namical x-sell-entz.

Highway Glider

:D

So far it looks like adding tires will not lower rolling resistance overall. If anyone knows if this is true that would be great.

Different tires have dramatically different rolling and aero characteristics. Tire selection WILL have a huge impact on your fuel economy, with knobby tractor tires probably delivering the worst economy, and slick big rig tires probably being the best. YMMV, HTH.

That makes sense, but what about if his truck had an extra axle and two more wheels?

Intuitively (if they were just two more of the same type of wheels) the RR would go up 50%, but he'd get 50% more traction for braking and cornering. I don't think extra traction for acceleration would help in this case.

But if he got tires that were 25% narrower (but silmilair tread and compound) his RR would be about the same, except he'd be spreading the total trucks weight across six wheels (and bearings) for some type of RR reduction?

I'm guessing it wouldn't be worth the cost, weight and work. But anything to get the RR down seems like it would be beneifical for mpg for such a heavy vehicle. I've been searching the web-but have found no real credible info so far.

If you've noticed some semi-trucks now have trailers with a single wide tire per axle instead of dual wheels and tires per axle, the reason for this is that for the load a single wider tire apparently has less rolling resistance, they are sticking to the trailers on this new single large tire setup because the drivers don't like how it handles as it is apparently not as stable.
having duel axles with tires inline would give some advantage on very rough roads but for road use? I don't see it.