Oil & Fuel Fuel Efficiency

[fordpowerstroke]

I was reading that a tractor with a bigger engine could be more fuel efficient than a comparable tractor with a smaller engine. Something about the bigger engine might not be working so hard and therefore might be more fuel efficient compared to an overworked, smaller engine. Here's where it talks about fuel efficiency of compact tractors . Do you think the reasoning here is true? Seems like in terms of automobiles, a smaller & harder working engine will usually get better fuel economy than a bigger engine that doesn't have to work so hard. Maybe it's different with tractors.

 

[slowrev]

Perhaps, but it also depends on what you are doing with the tractor. If you are running PTO implements at PTO speed then I would think in almost all situations the bigger tractor would suck more fuel.
Of course I was assuming that both tractors would use the same implement. You might get better fuel efficiency on the biggwer tractor by using bigger implements and getting more done in less time.

Ben

 

[JoeR]

Interesting question. This is more a work vs time analysis. Where the work and time equates to fuel consumption. If you have a 30HP tractor, you may need 2200 RPM's to pull a disc at 3 mph, whereas, a 50HP tractor may only need 1800 RPM to pull the same disc at 3 mph. Of course, the lower the RPM, the less fuel you are burning. If you properly size your equipment and task, then you should not burn more fuel than a larger tractor. The savings should come in the form of time. A 50HP tractor should be pulling a larger disc than a 30HP, which means the 50HP should do the job quicker but would burn more fuel per hour, but the time savings should reduce overall fuel consumption for the job. Overall, when we start to exceed the rated task for the tractor we end up spending more time and fuel on the job. I can mow 2 acres in 1.5 hours with a 60" deck and a 27HP tractor (Deck is almost too big) or I can do it in 35 minutes with a 72" deck and 50HP tractor. Fuel consumption on the 50HP is about the same as the 27HP for mowing the 2 acres.

What's funny, is I decided to read the link after I started typing, and I find that I am saying the same thing. /forums/images/graemlins/smile.gif Sorry for restating it in a different form.

Joe

 

[JerryG]

There has been a lot of talk about this in the Ag world. If you do a search for "gear up, throttle down" you will find a lot of it. There have even been some universities that have done studies on it.

 

[MadDog]

Isn't it, at least in large part, a question of mechanical efficiency? A given task (like disking or mowing a 1 acre field requires (assuming no "overlap") the same amount of physical work and, if both large and small engines run at the same efficiency, should require the same ultimate amount of energy (fuel) to perform that work.

Of course, there are two catches; first, the efficiencies of large and small enginges may NOT be the same and second, the "work" analysis does not consider that the amount of energy necessary to propel the larger, heavier machine around the field is obviously greater and this may, or may not, be offset by the shorter amount of time that the machine needs in the field to complete the work.

It is because their engines are not running any longer to go the same distance that explains, as I understand it, why smaller cars get better mileage, even though their engines generally run at higher rpm and thus are "working" harder. Propelling a lighter, smaller load (with less wind resistance) over a given distance is less work.

I'd be interested in what any engineers or physicists in the group have to say about this.

 

[fordpowerstroke]

That's some good food for thought. Thanks for replying.

 

[Soundguy]

</font><font color="blue" class="small">( Isn't it, at least in large part, a question of mechanical efficiency? A given task (like disking or mowing a 1 acre field requires (assuming no "overlap") the same amount of physical work and, if both large and small engines run at the same efficiency, should require the same ultimate amount of energy (fuel) to perform that work.
)</font>

Here's what i observed. For about 3 ys I cut 10 ac with my NH 1920 (33hp ) and 5' mower. Took me 5-5.5 hours to cut, and about 5g of diesel.

I now cut it with my NH 7610s (90 hp ) and 10' mower. Takes me 2.5-3 hours and used every drop of 5g, if not maybee 5.5 g of fuel.

Net result is I only loose a morning to cutting the pasture, vs pretty much blowing the day with it.

Soundguy

 

[hbaird]

I am sceptical of all generalizations on this subject. Most if not all internal combustion engines have max efficiency at torque peak RPM. When you can, run at torque peak or horsepower peak RPM's for the lowest fuel use. Studies done in the 1930's and later have shown 500CC cylinders were about optimum all round. Larger cylinders have lower surface area to volume ratios, so may lose less heat when running. Tests can be run to prove just about anything. Auto makers are again making engines that are V8's when starting off and going to V4's at cruise to save fuel. I have found best economy at very constant RPM.
Harold

 

[IH3444]

Lots of considerations with a thread like this, but if I was a farmer, and trying to be fuel efficent. I would select a late model tractor with late model piston, cylinder design tier II emission certified engine, direct injection perfered, gear drive. Bigger engines running lower RPMs, but larger injectors, where do you draw the comparisions except as Soundguy states, run'em side by side. I'd much rather spend another $2 in fuel, and have the afternoon to do other things.

 

[3RRL]

</font><font color="blue" class="small">( I'd much rather spend another $2 in fuel, and have the afternoon to do other things.)</font>

How true that is...
There's a lot of value in that for sure. Some that can't be measured by dollars.

 

[MadDog]

Ah, Soundguy, now we're talking about YOUR efficiency (which takes time into account) rather than fuel efficiency.

Your own experiential data suggests pretty much of a tradeoff, i.e., the heavier machine and larger fuel consumption/unit time was about offset by larger implement and shorter time to do the job.

Plainly, in the real world, where time is $$, that's a big saving even though you burned about the same amount of fuel.

This proves (and it is reassuring that it does /forums/images/graemlins/wink.gif ) that it won't be an extravagance for any of us to move up to larger and more powerful tractors. /forums/images/graemlins/grin.gif

I'll flag this thread to show it to SWMBO when the time comes.....

 

[stevenf]

MadDog, You won't want to show this to your SWMBO whatever that is and I have very little and not very good experience in the tractor world having used my dads old ford years ago to move dirt and rock with a loader and now owning a M9000 but something that I haven't seen and something that should probably be considered is the equipment cost new is substantially more in the big stuff plus parts, lots more fluid volume, implements if you size them for the machine and completely guessing but they probably cost more to work on. Mines still in warranty so I haven't experienced the repair side yet, its a Kubota maybe it'll never see a wrench turner but Oh wait I'm awake again it most likely will at some point. I think my wayroundabout post boils down to its probably best to size your machine and be happy that it doesn't need to be bigger, although I'll have to say my 90hp machine is fun and awesome and all its also very expensive when something breaks. Also somebody posted their M9000 used 3.? gallons an hour I guess I'm not using mine hard enough at this point I've got a pretty accurate usage record I bought a 300 gallon tank and had it filled its the only thing on the ranch that uses diesel, the tractor had 3hrs or so when I got it, it has 211hrs on it now and I have over 75 gallons of fuel left so I'm thinking for mine its more like a gallon an hour. Many of my projects don't require full pto 540 rpms and I'm sure that is where the difference is but so far I'm very happy with fuel consumption.
Steve

 

[Soundguy]

For me, the time savings was the important part. i work 6 days a week usually.. and need to mow, during season, about 1 time a month. that leaves me about 3 days a month to have a life.... With my old setup.. it really blew a day, and then i had to finish the day by doing the undone weekly chores around the farm. Now.. mowing can be done by 10am if I get a good start.. and cores done by late lunch.. and then still have tme to relax or take the wife out.

Course there was an up front cost to that.. I had to trade that nice new 1920 in, plus another 3ys ofpayments to get the bigger tractor... Havn't regretted the bigger tractor.. though do miss the 1920...

The extra 3$ of diesel was low on the priority list... finishing in half the time was a major plus!.. course.. looking at total cost of ownership... the 7610s takes about 3x the fluids in quarts than the 1920.. and the 10' mower was about 260$ per foot /forums/images/graemlins/shocked.gif

Soundguy

 

[Volfandt]

Heres an example of what I've personally observed.

BX23 SubCUT, 22hp 3cyl liquid cooled diesel, 60" MMM, approx weight 1700lbs.
Mow's 2.5 acres in 1.75hrs and uses approx 1.5gals of fuel.

JDL130 lawn tractor, 23hp 2cyl air cooled gasoline engine, 48" MMM, approx weight 600lbs. Mowed 2.5 acres in 2.5hrs and used approx 3gals of fuel.

Both engines were run at full throttle and both were HST's.

In this case a much larger & heavier tractor w/a similar hp rateing as the smaller & lighter gasoline powered lawn tractor mowed the same area in less time and at approx 1/2 the fuel usage.

Perhaps the diesel to gasoline comparison isn't apples to apples but I thought I'd throw it out there anyways /forums/images/graemlins/grin.gif

Volfandt

 

[Soundguy]

I'd have to say that the lawnmower engine vs diesel tractor engine was a raisin to watermellon comparison.

The 22hp diesel tractor engine is probably exactly that on a dyno, as equipped. that 23hp lawnmower engine hp # was probably the bare engine run on 0w5 oil, on special fuel with special carb settings.. no air filter or parasitic belt / pump devices, run at an rpm range outside of normal user range, and that was the dyno number that was clocked at the last 1/8 second before the engine detonated on the stand... I.e., the engine probably puts less than half that advertised hp to the blades or ground.. whereas your diesel will probably put 90% of it's hp tot he blades.. and at least 50% to the ground even in bad conditions... that lawnmower engine is like weedwhacker technology compaired to your diesel tractor. their carbs are so simple.. that is one reason they run so ineficiently.. less fine tuned metering... I had some brigs engines... the carbs between 8-10-12.5 hp models were 100% identical, down to the main jet... neat huh? A closer comparison would to use an antique tractor in the 23 hp range as a test case.. etc..

Soundguy

 

[Volfandt]

</font><font color="blue" class="small">( A closer comparison would to use an antique tractor in the 23 hp range as a test case.. etc..
)</font>

OK, I used to occasionally bushhog the same area w/a 48 Ferguson TE20 and a Howse 5' rotary mower. I've read where the TE20 had anywhere from 20 to 24hp which varied from different sources. The Continental engine in the TE20 was a 4cyl inline overhead valve powerplant and mine ran pretty good. It used your basic updraft carb.
The fuel tank held around 10 gals. Usually I finish mowed that area but I'd bushhog it on occaison if I let it get to long between mowings so these results are skewered a bit.
The time frame would be similar to the BX23, maybe alittle longer but it would drink the gas. Almost 1/2 a tank. I'll guesstimate it at 4 gals to mow 2.5 acres.

1st thing I noticed after working that diesel for the 1st time was how much more fuel efficient it was over the 4 different gasoline powered machines I have mowed that field with.

As for those B&S carbs, I wouldn't doubt it. But Kohlers are a differnt beast. The carb off of my K181 won't run a 10hp K engine and a 10hp carb would run way too rich for the 8hp.

 

[Farmwithjunk]

Back in 1969, John Deere introduced a tractor designated the model "4000" It was essentially a stripped down 4020. It employed some components from previous models. (i.e., tranny/rear end parts from the 4010) No battery covers, no sheet metal covering seat suspention, less available options, and less over-all weight than the 4020. BUT. . . It had the SAME 96 HP 404 cu. in. diesel engine.

The purpose was twofold. One (probably being the MAIN reason) was to compete with the IH model 706. Bigger than Deere's 3020, and smaller than the 4020) It was quite a few bucks cheaper than a 4020. It filled a void in Deere's arsonal. #2 reason, and what Deere's advertising centered around was this. They claimed that a buyer who owned a 3020, and was ready to step up to more power, could buy a 4000, use the same implements as they were using with the 3020, and run FASTER in the field, at a lower throttle setting. That would get more work done, save a lot of cash on implements, and would be as productive as pulling bigger imlements at a slower speed, therefore, saving some money there. They also claimed field tests proved this concept (Gear up/throttle down) would save fuel.

The entire Deere line at that time was the "New Generation" tractors. They replaced the old 2 cylinder line. Their claim to fame was it's "HIGH HORSEPOWER TO WEIGHT RATIO". A typical 4010 was just a few pounds heavier than the 730 it replaced, but nearly double the available HP. They were both rated to pull a 5-bottom plow, only the 4010 would pull it almost twice as fast. Big fuel savings as well as higher productivity.

Also to consider, some engine manufacturers are better than others at fuel economy. And within those brands, some particular engine sizes are more economic.

The "standard" for the AG tractor industry has always been "The Nebraska Test". They rate HP hour per gallon for fuel economy. The big winners and big loosers in that area come from all sizes, big or small.

 

[Soundguy]

The te and to 20 were more along the lines of 27hp.. just like the flathead 4 cyl ford 8n. PTO hp was 25, and drawbar was 20. 129CID.. vs the 119cid for the flat head 4 that a ford N used.

Soundguy