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profi Tractor Test: Big and Mighty (2008)

August 25, 2008
 
 


The brawny MT865 is muscular and built to work

Challenger MT865
Data Sheet

The sheer size of the Challenger MT800 Series, launched with four models ranging from 340 hp to 500 hp, is impressive. The granddaddy of them all—the 500-hp MT865—stands more than 11.5' tall from the ground to the top of the cab. Access to the cab involves a bit of a climb—up seven steps and along a 22.9' catwalk that runs from the front to the back of the machine.

Under the hood, power for the test tractor was abundant thanks to a six-cylinder Caterpillar C16 engine, which boasts 15.8-liter piston displacement, four-valve technology, and a pump and nozzle injection system.

Since profi tested the MT865, it, along with the other tractors in the series, have received an engine upgrade. Power for the MT865B (notice the addition to the model name) now comes from a Tier 3, Caterpillar C18 ACERT engine. This engine uses 18.1-liter piston displacement, with a mechanical electric unit injector to opiti- mize fuel delivery. The B series gained a model, for a five model lineup ranging from 350 hp to 570 hp. Claimed PTO output at rated speed (2,100 rpm) is 425 hp with a gross engine output of 570 hp.

Back to the test tractor, the profi team was eager to verify the bold horsepower claims. However, the test station's PTO power kit couldn't handle this level of output.

On to plan B. In reality, only a limited number of customers choose the PTO option. With that in mind, the test team focused on what the MT865 is really about—lugging power. At rated speed, the test station's brake wagon recorded 380 drawbar hp of the tractor's claimed 500 engine hp; at maximum output, the same lugging power scaled to a notable 460 drawbar hp. (The Nebraska Tractor Test Lab tallied 444.1 PTO hp at rated speed and 523.6 PTO hp at 1,750 rpm.)

These drawbar results suggest AGCO's maximum engine rates are realistic and unexaggerated.

Translating these figures into useful power is key to the MT Series, hence, the reason for tracks, rather than wheels. The test tractor was outfitted with 27.5"-wide belts (9.8' runs along the ground). The result is a more-than-25-ton machine with massive output potential, minimal wheel slip and little power loss. All of this is achieved at a ground pressure of slightly more than 7.1 psi.

At 2,100 rpm rated speed, the MT865's specific fuel consumption at 0.472 lb./hp/hr drawbar power was on par with high-horsepower wheeled tractors. However, the more important parameter is fuel consumption at 1,700 rpm, the engine revolutions per minute at which the MT865 produces its maximum drawbar power. Here, consumption drops significantly to 0.411 lb./hp/hr, which suggests that there is little point in running this tractor at full throttle; not only does the operator go through more fuel, but he or she looses up to 80.5 hp of engine power, too.

To describe the MT865 as economical would be a little far-fetched; at maximum output, the engine drinks 26.4 gal. of diesel per hour from its 330-gal. tank. However, the tractor proved itself capable of accomplishing much in an hour.

The tractor's transmission offers a somewhat limited choice of 16F/4R speeds, which translates into a minimal seven gears in the primary 2.5 mph to 7.5 mph working band. This isn't a significant problem, though, because the gears are evenly spread, which allows the operator to comfortably work within the most economical 1,700 rev to 1,800 rev band, a task further simplified by the option of tapping into three auto modes:

Maximum output mode: The transmission automatically shifts to the gear that allows the engine to rev for maximum output. When the MT865 faces sticky soil, it downshifts; once through the conditions, it shifts up. The operator can program the highest gear to be selected automatically, so in easygoing conditions, the MT865 doesn't build up surplus speed. In summary, the electronic system automatically keeps engine speed between 1,500 rpm and 2,000 rpm.

Constant travel speed mode: The operator chooses the target groundspeed and travel speed, and the tractor responds by altering its engine speed and gear ratios. This is ideal for light draft applications.

Constant engine speed mode: For PTO work, the operator can preselect a specific engine speed, and the transmission shifts according to the load to maintain that engine and PTO speed.

Moving up and down the transmission via the armrest-mounted lever is simple. To put the MT865 in park, hold in the front-locking button and shift the lever to the right. To select the direction of travel, pull the lever toward the seat, and then slide it forward or backward. Once that's done, two buttons take the tractor up and down its available speeds.

When it comes to acceleration, the pedal acts as a decelerator, dropping the engine revs, rather than increasing them in conventional fashion. As a result, most operators use the hand throttle to set the engine revolutions per minute for field work, and then knock them down at the headland on the decelerator pedal. This works fine in the field, but it would be handy if the operator was able to switch the pedal to a more traditional accelerator mode when on the road.

While on the subject of on-road performance, it is worth noting that the MT865 is capable of zipping along at a lively 24.6 mph and, more important, it does so in a smooth fashion thanks to the Mobil-trac system's Opti-Ride suspension system.

When it comes to rear linkage, the MT865 linkage is an option. The standard alternative is to outfit the tractor with the beefy floating drawbar—and its 6-ton tongue load.

One of the most important features on a high-horsepower tractor like the MT865 is a powerful hydraulic system to drive the steering motors. On the MT865, this consists of a swash plate pump and four standard hydraulic outlets. The test station measured a flow of 56.3 gal./min. and a colossal output of 70.8 hp at the rear couplers.

Also worth mentioning is the MT865's Load-Independent Flow Division system. When demand exceeds supply, the Challenger slows flow proportionately to all circuits, rather than shutting down one completely.

Hydraulic output operation comes via easy-to-work rockers, and the couplers connect under pressure and drip into leak-collecting containers. However, the electronic timing and setting cannot be separately programmed for the two directions of flow.

The MT865's cab is a quantum leap forward in almost every respect compared with the accommodations of its predecessor. The cab receives excellent test scores for space, visibility and its climate-control package.

The biggest eye-catcher in the cab is the Tractor Management Center and display screen stationed at the front of the right-hand armrest. The operator can use a dial to monitor primary tractor functions on the screen, a design that, unlike some, retains its visibility under most conditions.

Another neat feature is the one-touch headland management system. This allows the lifting and lowering needed to complete a headland turn to be recorded with, as the name suggests, the touch of a button. The system takes getting used to, especially the programming procedure, which has to be carried out in real time, rather than according to distance traveled. Auto-Guide is the automatic steering system option.

Further details of the MT865 worth mentioning:

  • If the operator holds the activation button in for too long, there is a danger of deleting a sequence.
  • Rubber track width options are 30" and 36", which push the MT865's width to more than 9.8'.
  • Life expectancy of the tracks is 3,000 to 5,000 hours.
  • Tracks on the MT865 are pretensioned and use 4.9'-diameter drive wheels for better grip.
  • An engine oil change is needed at 250 hours and requires 9 gal. Access to maintenance points is OK.
  • An ISO bus socket, 12 work lights and heated and electrically adjustable mirrors are standard.

There is little doubt that the MT865 is a worthy successor to the 95E Series. It builds on the base advantages of a high-horsepower tractor and adds a smooth-riding undercarriage, comfy cab, a headland management system and automatic steering.
 

Challenger MT865

 

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FEATURED IN: Farm Journal - December 2008

 
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