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Fendt’s Dual-Fuel Tractor

Fuel economy at typical performance -diesel

Working areas

Stand. speed pto 540rpm

Econ. speed pto 540Erpm

Stand. sp’d pto 1,000rpm

Econ. pto 1,000Erpm

Engine in top sp’d range

High output

Transport work

Low output, 1/2 speed

High output, 1/2 speed

Output

100%

100%

100%

100%

80%

80%

40%

40%

60%

Speed

1,933

1,490

1,900

Max

90%

90%

60%

60%

g/kWh

244

229

243

265

244

304

244

226

l/hr

41.3

31.0

41.4

32.8

30.2

18.8

15.0

21.0

Fuel economy at typical performance -rape oil

Working areas

Stand. speed pto 540rpm

Econ. speed pto 540Erpm

Stand. sp’d pto 1,000rpm

Econ. pto 1,000Erpm

Engine in top sp’d range

High output

Transport work

Low output, 1/2 speed

High output, 1/2 speed

Output

100%

100%

100%

100%

80%

80%

40%

40%

60%

Speed

1,933

1,490

1,900

Max

90%

90%

60%

60%

g/kWh

272

256

271

301

278

351

273

255

l/hr

38.5

34.0

38.5

30.7

28.3

17.9

13.9

9.4

For arable farmers wanting to reduce their dependence on bought-in fuel, there’s always the option of processing oilseed rape (canola) which, of course, is particularly attractive when crop prices are low. But there is a trade-off, both in terms of reduced performance and increased fuel consumption, as we find out when testing the Fendt 820 Greentec model.

With the big jump in diesel prices over recent years, much has been made of the potential for all arable farmers to produce their own fuel from oilseed rape. In response, tractor and engine manufacturers have come up with various kits that enable their particular machines to run on this “green” fuel.

In countries where there is no cheap off-highway diesel, the prospect of growing and then manufacturing your own fuel is undeniably appealing. But what of the widely quoted downsides — power loss and an increased level of fuel consumption? To gauge the practical implications of relying on green fuel, we tried out the Fendt 820 Greentec.

Firstly, it is worth noting that there are two distinct types of oilseed rape-based diesel, and they both have very different engine requirements. Mechanically extracted rapeseed oil, which is what our test Fendt 820 Greentec runs on, should not be confused with RME, a product obtained from esterifying rapeseed oil in a chemical process.

RME is more widely known as biodiesel and is used to power many of today’s engines, either as a blend with conventional diesel or as pure biodiesel.

But back to mechanically extracted rape oil and its characteristics. Fendt says that operating its 820 Greentec on rape oil can result in a 10 per cent drop in performance, depending on the engine speed, and fuel consumption increases by four to five percent, even up to 10 per cent in some scenarios. This is all due to rape oil’s energy density being lower than that that of fossil fuel diesel. In other words, you simply don’t get the same bang for your buck.

EVALUATING THE GREE NTEC

Under the Greentec-badged bonnet of our 820 is a turbocharged and intercooler Deutz TCD 2012 L06-4V six-cylinder sporting common-rail injection. Fueled with conventional diesel, this motor delivers a rated output of 140kW/190hp (ECE R24), rising up to a maximum output of 151kW/205hp, figures all backed up by our test of the conventional Vario 820 in the April 2008 issue (of Profimagazine).

Greentec-spec Fendt tractors get a pair of fuel tanks. The 100-litre capacity red diesel tank is positioned on the offside (right), while the 340-litre biodiesel tank resides on the nearside (left). Operators have the neat option of allowing the tractor to automatically switch between the two fuel supplies by selecting the auto mode on the Greentec menu in the Vario Terminal. They can also choose to stick with regular diesel when all of the engine’s power is required, or rely solely on rape oil.

The engine fires up in its regular

The 100-litre diesel tank mounts on the offside right, whereas the 340-litre rape oil vessel lives on the nearside left. Tank caps need better marking.

diesel mode, and then switches fuel once the rape oil temperature has risen to over 62 C for more than 10 seconds and engine torque has exceeded 250Nm during this time. If the rape oil temperature or torque drops below these figures for more than 40 seconds, the tractor reverts back to its regular diesel mode.

Critically, to ensure there is no disruption in the flow of fuel, the Greentec system is equipped with its own fuel pump, plumbing and main filter and pre-cleaner with a water separator. And because the rape oil becomes more viscous when it’s cold, there’s also a separate fuel pre-heater to encourage the liquid to flow. All of this extra hardware and software results in Greentec status adding 5,797 (CDN$7,975 approximately) to the price tag of a conventional Vario 820.

When it comes to operation, users need to be aware of two things for smooth running. First, it’s best to switch the tractor over to regular diesel before parking up, as this makes starting much easier the next time the tractor is called on. While we think there should be some way of the tractor doing this automatically — for example, when the handbrake is applied — Fendt says that the operator has to be able to shut off the engine immediately, if required, for safety reasons. Secondly, the engine output drops and consumption increases when in rape oil mode. Now let’s get down to profitest business.

THE RESULTS

In diesel mode our steed pretty much replicates the test results of the April 2008 Vario 820 test, with the DLG test centre mustering 129.6kW/175.8 hp from the shaft at rated speed. This heads on up to 142.8kW/193.8 hp at max output. Switching over to rape oil, stats drop to 116.3kW/157.8hp at rated speed and 130.2kW/176.7 hp at maximum output — a nine to 10 per cent difference between the two fuels. And it’s a similar story on drawbar power: 110.2kW/149.5 hp at rated speed on regular diesel and 99.2kW/134.6 hp with rape oil. Maximum output stats are 121.3kW/164.6 hp and 110.5kW/149.9 hp, so again a nine to 10 per cent reduction in power.

The DLG is also able to confirm Fendt’s figures of increased fuel consumption due to the lower energy density of rapeseed oil. Consumption rises by 10 to 14 per cent when you look at the g/ kWh and by seven to eight per cent when expressed in litres per hour due to the lower horsepower outputs. Given these results, we were keen to see how Greentec would fair in our Powermix tests (Check out the separate bar chart). Focusing on litres per hectare, fuel consumption only goes up by four per cent for draft applications, such as ploughing and cultivating, but climbs by 15 per cent for PTO and mixed work.

When doing your sums, these numbers act as a guide as to how cost effective it is to operate the dual-fuel tractor. Given that it uses nine per cent more rape oil per hectare than diesel, according to our Powermix table, then the biofuel needs to be 10 per cent cheaper than mineral diesel if running costs are to be on a par.

The valve that switches from diesel to rape oil, and vice versa, is on the right side of the engine right; the rape oil pre-heater is sited on the left.

Other considerations? There’s also the extra time it may take to carry out some operations, and more stops will be required at the fuel tank for top-ups. Should the price of diesel start to soar again and the rape price remain relatively static, then the Greentec premium could prove to be a prudent investment. It is worth noting, though, that if you head down the route of home-brewed rape oil, the end product should meet the DIN V51506 certified standard. The fuel also needs to be stored at a consistent temperature of between 10 to 15 C for no more than six months once extracted.

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