Archive Article: 2001/11/30

30 November 2001

First time around

Our results show all the CVTs pretty close on efficiency, but they didnt start out that way. The Fendts initial values were 2-3% lower below 7kph (4.3mph) (range 1) and 12kph (7.5mph) (range 2), though elsewhere its curves were the same as the re-test. The factory changed an overpressure relief valve, bringing the 714s results back in line with a previous DLG test.

Cases CVX 150 started with a particularly bad dip in the 14kph-17kph (8.7-10.6mph) area where efficiency bottomed out below 71% – thats 8% worse than the powershift. Changes to the control software lifted and partly ironed out that dip while generally smoothing the rest of the curve. Average efficiency improved by 1%.

John Deeres 6910 AP started by posting the worst results. Efficiency hovered around 72% in the 4kph-6kph (2.5-3.7mph) band (11% under the powershift) and although values perked up with speed, the green machine didnt better the Case until 14kph.

JD engineers pulled the box apart to find worn hydrostatic drive components, damage put down to low oil flow during pto power testing. For the re-test, internal oil supply was increased and the boxs lubricant level lowered to reduce drag. The result was a 4% efficiency improvement on average, the lifting of the low-speed blues and a small advantage over the Case beyond 14kph. Production tractors now have this set-up.

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