Oil & Fuel Diesel vs Gas Engines

markcg2000 · Feb 20, 2001

by doubling the voltage, the current (amperage) is cut in half.

Actually Rat, it is correct that doubling the Voltage doubles the Current. A motor is concerned with power. There, they need to keep the Watts the same, which they can do by doubling the Voltage and thereby requiring only half the Current.

E=IxR (Voltage = Current x Resistance)
W=IxE (Power = Current x Voltage)

mark

LarryT · Feb 20, 2001

Good point Todd. The Gator will be used mainly for my wife to haul stuff around the farm. We have some fairly rough terrain along a creek, both sides. Plus we will have several acres of nut trees and other stuff to take care of. The Gator seems to be a good match for what she needs to do. There are three versions; 4x2 with 10 hp 1 cyl gas, 6x4 with 18 hp 2 cyl gas, and 6x4 with 18 hp 3 cyl Yanmar diesel. The latter two are liquid cooled. These things aren't cheap, but no sense investing in something that will wear out in a few years.

Larry...

GlueGuy · Feb 20, 2001

All valid points, but remember comparing the working RPM of two motors is not necessarily comparing apples to apples. You need to dig a little deeper than that and also look at the length of the piston stroke.

For example, take two engines, one operating at 1500 RPM, and the other operating at 3000 RPM.

In this example, if the the 1500 RPM motor had a piston stroke of 2" (this is hypothitecal to make a point), the piston is moving 6000 linear inches per minute (2" * 1500 RPM * 2 strokes per revolution).

If the 3000 RPM motor had a 1" stroke (remember this is hypothitical), then it would also be moving the piston at the same rate of 6000 inches per minute (1" * 3000 RPM * 2 strokes per revolution).

So from a "wear" perspective, it's possible to have a short-stroke-high-rev engine have the same wear (or even less) than a long-stroke-low-rev engine.

BTW - That's exactly how a lot of the new gas engines achieve their magic; a really short stroke also reduces the amount of cylinder wall for gasoline to condense on when the engine is cold. It also reduces the wear that the piston/cylinder get at higher RPMs.

The GlueGuy

Anonymous Poster · Feb 20, 2001

Larry,

Also take a look at the Polaris Utility 6X6 for about $6900...

Polaris 6X6 ATV

It has a Fuji 500cc bullet-proof engine, instead of side by side seating like a gator, it's front and back, with more Standard features that cost extra on the Gator :

For about $6900. the Polaris ATV includes:
Heavy Duty AG type aggressive tires
Tilt cargo box
Composite material used for box w/ bedliner built-in
Rear hitch
Full lights
Heavy duty front and rear suspension
Switchable Full 6 X 6 Wheel Drive vs. 6 X 4

My brother has the 500 for hunting and maintaining fencing and it's been ultra-reliable. Starts everytime in below 0 weather. Never ever ever ever been stuck! Extremely manuerable... & goes fast...

Rick Jay · Feb 20, 2001

Hi Todd,

Oops....those dang metric conversions. I meant to express things in cubic centimeters, of which I think there are about 1500 of the little buggers in my B2910 and about 2000 in my Accord.

Thanks for the catch.

Rick

Anonymous Poster · Feb 20, 2001

I believe the torgue is less when operated at a given road speed. The diesel is turning slower, and has more torque on the flywheel, but at the wheel (tire) it is geared down less and therefore ends up with less torque. I ran the numbers through a spreadsheet 5 or so years ago because I doubted what ford and chevy printed in their sales lit- that the gas engines had higher towing ratings. They do look better on paper, and might even be a better choice for occasional towing.

Diesels do develop their torque earlier, an advantage to driving but almost zilch when operating a tractor.

As to my comments on the kubota, it is for practical purposes, a toy size tractor, at 1/5 to 1/10 the size or weight of an ag tractor. I didn't mean this as an insult, just that it is a scaled down ag tractor, not a scaled up lawn mower. A ford ranger pickup may have been scaled down to the size of a car, but that doesn't make it similar to a full size sedan in many ways.

And finally, I never claimed the kubota had a 14 ga frame, I just guessed at the thickness of it's body.

Pat

JATO_RaT · Feb 20, 2001

Ah yes Mark, ohms law. In our daily lives, the practical application is where I was coming from. Double the voltage to anything you own and your current would theoretically also double discounting the increased resistance from heat say in the filament in a light bulb which is practically zero when not in use and therefore has a current draw in the many hundreds if not thousands of amps. The duration however is so small that you could not measure the current flow at the instant it is turned on with conventional equipment. I guess I am looking at this in both a practical and technical sense. If I double that voltage to the bulb, my heat goes up, resistance goes up and current will be reduced to some figure less then double that of the voltage. This of course will last for but a few moments as our filament will burn out increasing resistance to the point where there is no current draw. Now I've forgotten what I was responding to and remember it was about Diesels and Gas engines, hmmm, a interesting site is at
http://www.cummins.com/na/pages/en/....cfm?uuid=93066F97-04CE-11D4-98530004AC33EA57
Rat...

paccorti · Feb 20, 2001

Toddler,

I did not intend to state that gas engines are better than diesels (or vice versa). The right tool for the right job, in my opinion. I just want to correct the misconception that for two engines of equal horsepower, the one with high torque at low RPM is (for that reason alone) more capable than the high revving lower torque engine. Once you account for the different transmission gearing requirements of the two engines you get exactly the same thing out the back end.

For whatever reason this whole discussion has reminded me of a dynamic systems engineering class from school. An automobile suspension system is an example of a spring/mass/damper system. A shock absorber (damper) resists velocity. A spring resists position. You have the same concepts in electronics. A resister is like a damper (shock), a capaciter is like a spring and an inductor (I think) is like mass. There is even a fluid equivalent. Imagine a bunch of tanks (with open tops) connect by pipes. The pipes are resistors, the tanks are springs and the fluid is mass. Crazy stuff... I love how the same concepts get used over and over.

Peter

Peter

paccorti · Feb 20, 2001

Glueguy,

Plus a large bore makes it easy to put large valves in the head for better breathing. Nice analysis....

Peter

toddler · Feb 20, 2001

Hey Pat, I grew up in NJ, 3/4 acre with 100yr old trees. My friends from there and I grew up with push mowers. Now that I'm in Vermont with 10acres, I call my Kubota b2710 a baby tractor, or even my toy tractor. (Putting it next to a JD 9000 series or a CAT Challenger would make a great picture, no? Dad and daughter or such.) On the flip side, my Jersey friends seem to think I have a big tractor. Guess it's all a question of perspective.

Still, I'm with you. Calling the BX or B series toy tractors isn't an insult. I'll bet that if anyone who took it that way thinks about it, they'll realize these are all toys to us. Toys are just something you enjoy playing with, right?? And I'll bet I have more fun with my baby bota than most of the farmers out there have in those monster tractors, plowing for hours on end.

Toy vs tool is really a fine line for most things we enjoy playing with. (hmm, wonder who's gonna run with that one)

Also, and not to belittle the rightous indignation my fellow Kubota owners, I think 14g is a bit thick. Maybe the fenders are that thick, don't know, but I'm pretty sure I could nick mine pretty well with tin snips. Could you do that to 14gauge, and do you know the thickness of 14g? My weight lifting equipment is maybe 10 or 12 gauge (gym duty stuff made for bigger men than me). Seems a LOT heavier than my fenders!! Since the body isn't really structural, the question is just academic.

Todd

putty340 · Feb 20, 2001

Glueguy , that is true the diesel does have a very long stroke which is the bad and good,there is more piston speed and sideload, but all the other parts have to be spinning at 3000 RPM - lots of wear!

GlueGuy · Feb 21, 2001

Putty,

That's only semi-valid. Biggest wear item in internal combustion engines is the piston/piston ring to cylinder walls. Mainly because they have to "scrape" the sides (well not exactly, but close). The bearings are another story. There should be almost no contact between the bearing surfaces if you have proper oil pressure. The size of the bearings can have a big impact on longevity though. And diesel engines (typically) have much larger diameter bearings because of the high compression ratios. 60psi (typical again) on a large surface is way better than 60 psi on a smaller surface.

The GlueGuy

Charliebrn · Feb 21, 2001

Ask one simple little question... [GRIN]

I love this board!!!

Anonymous Poster · Feb 21, 2001

Diesels do develop their torque earlier, an advantage to driving but almost zilch when operating a tractor.

One of the main reasons you want the diesel is because of it's "torque rise" or "torque reserve".

LarryT · Feb 22, 2001

Thanks John, I'll definitely take a look at the polaris. I'm pretty worried about the green Gator clashing with my orange tractor anyway!

Larry...

Bird · Feb 22, 2001

LarryT, have you looked at the Kawasaki Mule? My brother has one and it's sure been a fine little workhorse. And a rancher neighbor, who has 5 tractors, bought one, too, after I took him out fence repairing through the woods with my brother's Mule. Of course, they've had theirs a few years and they're gas models, but my brother has driven one of the new diesels and fell in love with it; just can't justify the cost to trade up to it.

Bird

LarryT · Feb 22, 2001

Bird, I looked at the Mule briefly, I'll look again. These things aren't cheap so I can justify spending a few extra bucks for a few extra years use. Besides, the red doesn't clash with orange as badly as the green does!

Larry...

Anonymous Poster · Feb 22, 2001

"60psi (typical again) on a large surface is way better than 60 psi on a smaller surface"

Say what?

Don't both have 60 pounds per square inch?

GlueGuy · Feb 22, 2001

I was refering to the 60 PSI of oil pressure used to support the crank bosses inside the main bearings. Assuming that two engines have the same oil pressure, the one with the larger bearings should see less wear.

Sorry about not being clear.

The GlueGuy

richfromPA · Feb 22, 2001

toys and tools??, hmmm that sounds like my ole ladys language. when i got my first welder she said "whatta ya need that toy for" well, when that got me into welding for free trees and i started haulin them home for plantin, she changed her tune. then when i bought my miller bobcat welder after plantin 8000.00 worth of them free trees, and the welder was only 3000.00 she really said "whatta ya need THAT for", well then, when i started to bring home hundreds of dollars of side money she shut up. same stuff when i bought my new ztr grasshopper 4 yrs ago. but when i made 2500.00 cash one spring(2-1/2 months) she had her darn paws out. then came the cub loboy and she didnt say much. now that the cub is gone and the grasshopper is gettin traded in for a new diesel b7500 she has started once again only to be put back into place when I said " remember how much i made with the grasshopper 2 yrs ago". anyway that is my tool and toy story and doenst have crap to do with diesel vs gas except IM GETTIN MY DIESEL SOON. haha, ya guys think it will have enuff torque or horsepower to drag her by the heels up hill with the loader full of empty beer cans? ... sorry for the stupid post and showing my room temp IQ but i couldnt help it.

really i love her and she has been very helpful and i love the cat and her potpourri

..wheww she was lookin over my shoulder
richfromPA