18 February 2000

NOT A MANUAL OR AN

AUTOMATIC, BUT A CVT

In this months Country Car,

Geoff Ashcroft tries Nissans

CVT Primera, while Andrew Pearce

experiences an ex-army

Citroen Buggy

THE idea of a car transmission that uses a belt and two variator pulleys – more commonly found in a combine – seems almost a backward step in technology. But thats how CVT (continuously variable transmission) operates.

Nissans CVT box in the latest Primera range is called Hypertronic CVT. It uses a torque converter to give the car that "creeping" feeling when drive is engaged, and an auto box gear selector with P-R-N-D-L provides familiarity.

Compared with a combines transmission, this is refined and compact and uses a segmented steel belt running between the variable diameter pulleys. Electronics and hydraulics manage the pulleys according to engine output and driving style.

The 2-litre Primera estate in Sport+ trim tested by farmers weekly was equipped with the M6 sequential version of Nissans CVT, offering the enthusiastic driver the opportunity to manually shift the transmission through six predetermined gears. Here, electronics control the variable diameter pulleys to give the impression of fixed ratio gears.

Left to its own devices in Drive, Nissans CVT M6 is much smoother than a conventional auto box. But its mode of operation takes some getting used to. It pulls away like an auto, and driven gently, behaves very similarly too. But put your foot down hard and revs climb almost instantly to put the engine on maximum power – in this case 5800rpm – but without instant acceleration from the car. Its just like a slipping clutch – all noise and little drive. Then, with motor wailing at almost full chat, the transmission gathers itself up and starts to accelerate the car, using the engines full power to gain momentum.

Backing off the throttle when the desired speed is reached sees transmission and revs settle at a happy medium and engine braking is available during deceleration.

At all times Nissans CVT remains seamlessly smooth – theres no jolting nor the interruption normally associated with a conventional auto box where cog swapping takes place.

Its not quick out of the starting blocks. The same 2-litre Primera estate with 5-speed manual box gains 1.5secs in the 0-62 dash. And those constantly high revs when accelerating hard did little to help fuel economy.

The verdict: Ultra smooth CVT box makes for easy driving and manual mode should suit the enthusiast, though mode of operation is reminiscent of a slipping clutch. Engine noise is intrusive under hard acceleration, and fuel economy suffers too.

NISSAN DATA

Model: Primera estate Sport+.

List price: £20,100 OTR.

Engine: 140hp, 2-litre 16v petro.

Transmission: Hypertronic CVT M6.

Top speed: 122mph.

0-62mph: 12sec.

Test fuel consumption: 26.6mpg.

Insurance group: n/a.

Above and left: Latest version of Primera builds on strengths of the previous one, but CVT transmission takes some getting used to.