Oil & Fuel CUT/SCUT fuel consumption?

[284 International]

I think those guidelines are good baselines when there is no other frame of reference, and the tractor is used in generalized utility applications. That is, it isn't exclusively used for heavy tillage, thick mowing at high ground speeds, etc, or barely loading the machine for the lightest tasks, light towing a garden cart, easy loader work, and so forth.

I have an array of older compact machines dating from the days when the test lab DID publish data for smaller machines. I can say that the usage of the tractor really makes a vast difference.

I have two compact tractors with the same engine, but one has a loader and is used for light loader duty: smoothing driveways, carrying mulch or wood chips from piles, etc. The other is ballasted far beyond what is advised in the manual, and is used almost exclusively to pull the heaviest disk possible. The loader tractor very rarely sees half throttle, and quite literally sips fuel. I have put 30 hours of meter time (so under-representing the clock hours, since operation is at low RPM) on less than 5 gallons of fuel, while I have emptied a 5 gallon tank discing with the other machine in a single afternoon.

I have 3 sets of Nebraska data available for compact diesel tractors I own. I own 4 machines of those tested, one of which is a loader equipped machine, and the other is a bare tractor used for disking, tilling, and mowing, mostly. I have one compact gasoline powered tractor with Nebraska data available, and one utility diesel tractor. Another pair of loader equipped and non-loader tractors I own supports the fuel consumption disparity between tillage and loader work (accurately, light vs heavy demands on the power plant).

I have compared my experience using the tractors with the Nebraska data, and they tend to confirm non-empirical but attentive measurements. Running hard, my usage is about 1.5 gallons per hour in a 20 PTO horsepower tractor. Doing basic loader work with the same model machine burns about 1/2 gallon per hour clock time.

My gasoline compact burns more fuel than the 0.06 gph/PTO horsepower suggested. I suspect this is because even at idle, the gasoline tractor consumes more fuel per unit power output. Operating the gasoline tractor at idle, as when I run the cement mixer or post hole digger, the gas consumption is noticeably more than a diesel machine doing the same work. Mine increases more than the diesels under heavy loads, but doesn't decrease as much under lighter loads.

Comparing the Nebraska data, the figures of 0.044 and 0.06 correlate well to their average PTO horsepower readings for average power produced vs fuel consumed per hour. If I took my tractors and averaged their fuel use, it would fit well with the guideline, but I think a tiered model may be more useful to the average compact tractor owner.

If one is doing light duty work (clearing horse stalls, smoothing gravel with a drag, etc,) I would suggest a preliminary number of something like 0.037 GPH/PTO horsepower. For average use, I think 0.044 is good, and for heavy use (Running a high powered generator often, very heavy mowing, rototilling, heavy disking, etc) 0.050, all for diesel engine tractors. For gasoline versions (And there are a very scarce few; all are old that I'm aware of, and actually DO have Nebraska test histories) corresponding guesstimates would be 0.056, 0.060, and 0.072, based on my machines, memory, and calculations.

I am interested to hear other responses to this.

 

[smstonypoint]

<snip>


Comparing the Nebraska data, the figures of 0.044 and 0.06 correlate well to their average PTO horsepower readings for average power produced vs fuel consumed per hour. If I took my tractors and averaged their fuel use, it would fit well with the guideline, but I think a tiered model may be more useful to the average compact tractor owner.

<snip>

Thanks for your informative post.

Estimates of fuel consumption are available by type of field operation for ag. tractors (e.g.,Estimating Farm Fuel Requirements ,Fuel Required for Field Operations A3-27 October 2005), but only a few of the operations are likely to be performed by a CUT on a custom basis. I will try to illustrate alternative operations if I decide to proceed with my primer.

Thanks again.

Steve

 

[ruralruss]

I had estimated that my Kubota B3200 used about 1 gallon per hour during heavy to medium hogging with a 5 ft cutter. The formula says 1.012 gallon per hour. Pretty close.

 

[jinman]

Steve, my 45 eng/39 pto hp tractor has to be pushed hard to burn 1 gallon per hour. That puts it around .7 gal below the formula (39 x 0.044 = 1.716 gph). I'm thinking that the larger tractors would all be turbo-charged and that would make them use more fuel under load. Of course, a turbo-charged engine is very efficient if you stay out of the boost curve.

 

[Baby Grand]

After 368 hours I am burning fuel at a rate of .54 gal/hr (all the fuel loaded/time on the clock) with 26.5 POT HP. When it's running, it's usually working at snow plowing, tilling, chipping or hogging.

 

[dodge man]

I have a BX2350, a pretty small SCUT, and have about 17 to 18 pto horsepower. That computes to about 0.75 gal/hr, and when its working hard, such as mowing, thats a pretty accurate number.

 

[JDgreen227]

Deere lists gph consumption rates for full load at pto speed. The problem is that almost nobody ever runs full load all of the time. The only way to project your true usage is experience. But one can use the rated consumption to get a worst case scenario idea. Anything less than that would just be gravy.

If you are doing a job for hire start with a full tank and then top off. Measure the amount burned and if you are really honest you can pass along any fuel savings to the customer (assuming you bid the job by running the math at full load usage rates).

I keep seeing the term "full load" here but don't quite understand what it means. Suppose I am running the MMM at the 2600 rpm PTO speed in heavy grass, is that considered full load? Or suppose I have a 800 pounds of sand in the FEL bucket while running the MMM as outlined above, is that full load? Or maybe I am doing both, plus pulling a 4,000 pound trailer, maybe that is full load?

 

[284 International]

For the Nebraska tests, at least in the older ones I'm familiar with, full load is rated RPM (or peak power RPM if higher) and maximum load that can be sustained at that same RPM. Attached is the version for my IH 284. There is a section called "VARYING POWER AND FUEL CONSUMPTION" where you can see they run the machine at 0 horsepower, and 2962 RPM, for a certain fuel consumption per hour. That is how much fuel it takes simply to run the engine at nearly 3000 RPM, with no load. Just above it is a rating at 23.36 hp at 2774 RPM, so the engine is applying 44 foot-pounds of torque to a brake at that RPM (Technically it would be much higher torque applied to the brake, somewhere around 200 foot-pounds at whatever the PTO shaft speed is, but it's all the same)

Really, it is the maximum output of the engine. So if cutting in heavy grass can achieve that, it is full load. Data I find especially interesting is the horsepower-hours/gallon. It measures the efficiency of the engine at turning some amount of fuel into power. A bigger number is better in this case. It allows comparison of small, lower horsepower engines to bigger ones, because it is a measure of efficiency, not only quantitative data. I wish this information were available for newer compact and subcompact machines.

 

[rsewill]

Steve, my 45 eng/39 pto hp tractor has to be pushed hard to burn 1 gallon per hour. That puts it around .7 gal below the formula (39 x 0.044 = 1.716 gph). I'm thinking that the larger tractors would all be turbo-charged and that would make them use more fuel under load. Of course, a turbo-charged engine is very efficient if you stay out of the boost curve.

Hmmm, I'd rather also pour more air than just more fuel into my engine to get the same HP. Or, to put it another way, a lighter, smaller turbo engine will be more fuel efficient at continuous full turbo boost than a larger NA engine putting out the same HP. Correct me if I'm wrong.

 

[JDgreen227]

I belong to a truck/trailer/towing forum elsewhere and in one thread I started maybe 15 years ago about being sure your new tow vehicle had enough power plus a reserve, somebody asked "why should I buy a bigger engine that has reserve power when the smaller engine has enough for my purposes?"

He was convinced that a smaller engine running at 80-90% output while towing would be more economical in the long run than a bigger engine that had enough power not to require operating at near full output. The thread was back before turbocharging became available in tow vehicles and I wonder sometimes how that situation would play out today.

Sorry if this is off topic. I got to thinking about this because of the comparison of turbo vs. non-turbo engines rsewill mentioned in the previous post.