Taalkeeta Mountain Scouting Trip. First time ever!
- Thread starter Mark W
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I have this theory that superior diesel economy off-road is due to idling time. Gas engines idle with an air/fuel ratio of 12-14:1. An idling diesel is 200:1. Much of off roading is idling, and this is how a diesel that might get 10% better milage on the road can get 100% better milage off-road.
I think the 13B-T is maybe the best Cruiser engine ever. Super reliable. Ample power in stock configuration - even to turn 38's, and no one I know has been motivated to even start testing the upper power limits of these engines.
But if I really needed some reliable mud churning power, I would be looking at a 12H-T, like Loewenbrau.
Peter Straub
710 days till Tippy meets Tiny.
Mark W
Yep, I really don't really care that much I guess.
- Thread starter
- #63
That sounds like a cheesy Japanese monster flick.
Wait... maybe it will be... A pair of mutant Japanese monsters scaring jeepers back to the malls.
Except that you never see jeeps up here on the trails anyway (except for the close to town playgrounds).
Mark...
There are a few other things that contribute to the diesel mileage advantage over gasoline. Diesel fuel has more btu's per gallon than gasoline - more potential energy. That greater potential energy is more efficiently extracted in a diesel engine because of higher compression ratios - often times double the compression ratio of a gas engine (the 6.2L is about 21:1)
This allows the diesel engine to generate much more torque than a gasoline engine. The Banks Turbo 6.2L diesel that Mark is gonna put in Tiny makes in excess of 350 ft lbs of torque at high idle !!!!
Theoretically - that would allow one to tractor along in a higher gear than a gasoline powered rig. Diesel mileage should be at least double the gasoline mileage in the same rig.
Marks helping me get my 74 FJ40 back up and running - I hope to make one of these treks with him.
Random, off-topic question:
Any Unimogs up there? They would seem to be well-equiped for this sort of thing.
Any Unimogs up there? They would seem to be well-equiped for this sort of thing.
Yeah, those help a bit...
Diesel engine thermodynamics are governed by the 'Diesel Cycle' which calculates maximum efficiency related to compression slightly differently than the Otto cycle calculates efficiency for gassers also related to compression. But the higher compression of the IDI diesels like the GM 6.2 doesn't overcome the realities of the pumping losses of pushing 3.1litres of air through eight itty bitty pre-cup holes a few thousand times a minute. Bottom line, Thermodynamics suggest that diesels are aprox 35-38% efficient, gassers are about 30-33%.
And sure, diesel fuel has about 40.9 megajoules (MJ) per liter, whereas gasoline is 34.8 MJ/L, about 15% less.
When you add up the thermodynamic efficiency and the fuel energy density, you account for the normal difference you see between diesels and gassers on the road. Maybe about 20%. But what makes a diesel 100% more fuel efficient in off-road situations? I suggest it is the stoichiometric ratios at idle (14:1 for gassers, 200:1 for diesel - a massive difference) that account for this large overall off-road effect.
Trails like Rubicon, where it is all idle, are comically good for diesels. Gassers often carry a can or two of fuel on that 20 mile trail. I've been across thrice, and never once had my needle come off full. I use maybe 20 liters to get across the 'con.
Anyway. Sorry to have hijacked this otherwise dreary thread.
Peter
Good points - but the guys that are towing - and Ive seen this on my Turbo 6.2L Surburban - are getting TWICE the mileage with their diesel equipped trucks compared to comparably equipped but gasoline powered trucks - 16 to 18 mpg for diesel compared to 8 to 9 mpg for gasoline powered tow rigs towing fairly heavy loads. Thats the diesel advantage when the engine is being worked.
My unloaded mpg from 55 to 65 highway speeds is 20 mpg.
lowenbrau
SILVER Star
As much fun as it is to see Peter picking on the new guys, I'm here to winch this thread back onto the trail.
Oh yeah, Oh yeah!
I'm please to report that Ratpuke has agreed to share her photos and trail report with the rest of the class. I recommend reading the first couple of chapters and then sitting back with a cold bevvy to watch the slideshow. I think you'll find it edjumicational.
Put on your gum boots and head over to the Swamp Donkey section and enjoy the show.
https://forum.ih8mud.com/showthread.php?t=169796
Oh yeah, Oh yeah!
I'm please to report that Ratpuke has agreed to share her photos and trail report with the rest of the class. I recommend reading the first couple of chapters and then sitting back with a cold bevvy to watch the slideshow. I think you'll find it edjumicational.
Put on your gum boots and head over to the Swamp Donkey section and enjoy the show.
https://forum.ih8mud.com/showthread.php?t=169796
pismojim
the Dude abides...
Thanks Bruce, I was just about say Diesel Smeasle, blah blah...
Bring what you got, wheel what you bring!
Everything is a compromise. A suitable rig for this type of "expedition" needs the following capabilities (in no particular order because they all affect the trail "experience"):
Mud Bogg'in - Get the bald bogger hook up!
Rally - Think Baja 1000! Cover big distances fast.
Water Crossings - Tall and heavy or drown and float away.
Reliability - You break it you fix it.
Fuel Capacity - Ultimately, you'll have to turn back due to fuel. Big nod to diesel here. But, extra cans, long range and auxiliary tanks, hauling a trailer full of fuel to cache are reasonable options too.
I was thinking the "Ultimate 80", bobbed, chopped, portals, links, coil overs, etc. turbo'd 80 Series would have been awesome - with some 40+ inch boggers.
pismojim
the Dude abides...
I forgot to say, the vision of Tippy and Tiny tightly strapped and winched together in a mutual recovery gone bad, all eight of their 53-inch tires buried in a bottomless bog miles from any solid ground, scares the crap out of me. At that point, Peter and Mark's demented stares for help would certainly cause any nearby rig to turn and run for its life.
Time to call the Sikorsky Sky Crane!
So at the risk of incurring Peter and Marks wrath, I'm adding another capability to the list.
Stay In the Box - Do you really want to be the Biggest and Baddest??
Time to call the Sikorsky Sky Crane!
So at the risk of incurring Peter and Marks wrath, I'm adding another capability to the list.
Stay In the Box - Do you really want to be the Biggest and Baddest??
Mark W
Yep, I really don't really care that much I guess.
- Thread starter
- #71
If we were to get both of these rigs stuck to where they could not self extract... There ain't gonna be any other rigs around unless they're in the same (or higher) class. And if they are, then extraction is not gonna be a big deal.
I won't make any stupid statement along the lines of "they won't get stuck". We had a D8 sink beneath the mud out there last year. Backwards at a 45 degree angle with only the tip of the blade sticking out! In the winter time! It took a BIG excavator to dig it out and a D9 to drag it back.There's definitely places out here that you don't want to drive into.
Just a matter of common sense and planning in advance.
I am working on a variation on the familiar Pull Pal design that should work pretty well with the larger rigs.
And the 700 feet of 5/16 Amsteel Blue that the Braden PTO winch will hold will reach across a lot of muck. Even double lined.
Anyway... "In the box" is a good place for a rig that will be spending weeks on the road in the third world. I don't consider it particularly important for a few days in the back country if you are up to wrenching and repairing if need be. Although I am not fond of my bad habit of minimal shakedown time with a newly modified rig before a run like this.
"Out of the box" can bring enough increased capability to justify the extra effort. (Assuming that you've got the shakedown all dealt with first).
You don't see too many "in the box" Moose buggies on the trails.
Mark...
I won't make any stupid statement along the lines of "they won't get stuck". We had a D8 sink beneath the mud out there last year. Backwards at a 45 degree angle with only the tip of the blade sticking out! In the winter time! It took a BIG excavator to dig it out and a D9 to drag it back.There's definitely places out here that you don't want to drive into.
Just a matter of common sense and planning in advance.
I am working on a variation on the familiar Pull Pal design that should work pretty well with the larger rigs.
And the 700 feet of 5/16 Amsteel Blue that the Braden PTO winch will hold will reach across a lot of muck. Even double lined.
Anyway... "In the box" is a good place for a rig that will be spending weeks on the road in the third world. I don't consider it particularly important for a few days in the back country if you are up to wrenching and repairing if need be. Although I am not fond of my bad habit of minimal shakedown time with a newly modified rig before a run like this.
"Out of the box" can bring enough increased capability to justify the extra effort. (Assuming that you've got the shakedown all dealt with first).
You don't see too many "in the box" Moose buggies on the trails.
Mark...
Mark W
Yep, I really don't really care that much I guess.
- Thread starter
- #72
Not many Unimogs around here. A few, but not many. I've only encountered one on the trail. He was not running tractor tires, but instead had some heavy duty "mine" tires. Sort of a cross between a snow tires tread and a mud tires tread, in a size of about 1100x20. It was pitiful. With the small and underpowered engine he could just barely spin them. And his traction was minimal. When I first caugt up to the rig he was stuck on a level surface covered with a thin layer of slick/sticky mud. The tires were sitting in hollows about 3-6 inches deep each and he was just sitting there slowly spinning without moving. I yanked him out and we went our separate ways. A couple of hours later I came across him again. He was stuck frame down in a bogged out mud hole. I rigged a double line, using his buddy's F350 on 44s as an additional anchor. We still had to get his engine running again (steep tilt and no baffles in the aux fuel tank and let him suck air) before we couple pull him over the clay bank at the edge of the bog (it was over the mid-point of the tires and we were just pulling him into the bank rather than over it.
With some decent sized tractor tires a 'mog might do well out there. But I haven't seen one set up that way around here yet.
Another thought just came to mind. Seeing how effectively we were able to extract the 'mog with my little '40, Iam not real concerned about getting Tippy or Tiny out with a non-buggied Cruiser if we do get them stuck. At least not with a pair of them anyway.
Mark...
I just dug into the Excel sheet Clarence made to track fuel mileage for our trip in 2006. BJ74, weighed in around 3 ton on the trail, steel wheels and 35" SSR's, Marks under/unders, and we averaged 9.2mpg on the trail. Which is around 30L/100kms. On the road it was around 21/22MPG which is approx 12.5L/100kms.
It would have been nice to have a 6th gear, so the stop to go out of low range did not have to happen for the short bursts where one could speed up.
Stephen, your figures are gps adjusted?
gb
Greg, I just went off of the odometer as I did not keep my gps running all the time. The best I get on the road is about 19-20mpg with 33". Thats empty, or mostly empty. I don't like 65mph anymore as the rpm's are right at 2400 which seems a little high since doing the Marks gears swap. Probably need some 35" tires to get the rpm's down more at highway speeds. Just not much options in a skinny 35" good wear tire.
Mark W
Yep, I really don't really care that much I guess.
- Thread starter
- #76
For the folks who have been wanting a little better idea of jst where we went on this run, this map will give you a better idea of the area we are talking about. You can use the lat longs I have included to find it on Google Earth or whatever mapping software you might have so that you can get a closer look.
Mark...
Mark...
dmc
SILVER Star
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I will have to admit I am rather envious of the chance to wheel in the Alaska backcountry. Looks like ACT 2008 will be a special event.
dmc
dmc
