The new RN Engine

The new RN Engine

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The engines in the second generation of the S40/V40 are designated ‘RN’ and are totally new although their external appearance looks unchanged due to the use of the same casings. These all-aluminium DOHC engines are part of the original modular engine which began with the 850 in the early 1990s.

For the new generation, the changes focussed on reducing internal friction and making more effective use of fuel. This was achieved by redesigning the crankshaft and shaving off weight, and lengthening the connecting rods but shortening the oil-cooled pistons. Then low-friction valves in the lightened valvetrain are now mechanical and do not require any adjustment for a number of years. Inlet and exhaust manifolds have also been redesigned to improve flow characteristics.

Continuously Variable Valve Timing (CVVT), a new feature, is possible on the exhaust camshaft (on non-turbo engines, the CVVT is on the inlet camshaft). Besides enabling a broader torque band, with better torque at the low end, CVVT also lowers toxic emissions, notably the very poisonous nitrogen oxides.

The low-pressure turbocharger (the T4 operates at a higher boost) now has a ‘twin-scroll’ design which pairs up the exhaust pulses from cylinders 1/4 and cylinders 2/3 into two ducts feeding the small and light turbine. The result is that the turbine spins up to speed faster, reducing turbo-lag by as much as 50%.

These changes have boosted power output to 121 kW(165 bhp) from 118 kW(160 bhp), an increase of 2.5%, while torque has increased by 10 Nm to 240 Nm – all of which is available between 1800 and 4500 rpm. The better power-to-weight ratio, plus improved engine efficiency and a new and more advanced engine management system, have reduced fuel consumption by almost 4%.

Intent on offering the cleanest-burning cars available, Volvo has been putting in a lot of effort to bring down toxic exhaust emission levels and the S40/V40 engines have significantly lower emission levels than before. A major redesign which achieved this objective was the positioning of one of the two catalytic converters right next to the turbocharger. In this position, it benefits from the exceptionally high operating temperatures of the turbocharger which get it to working temperature within 3 minutes.

The locally-assembled models will be available only with automatic transmission and this is a new adaptive 5-speed transmission with sophisticated electronic controls. Because of the adaptive capability – the computer senses the driving style and changes shifting patterns to suit – there is no need for the Sport and Economy modes. With five speeds, the spread of ratios is even better, allowing a lower first gear without sacrificing top-end performance.

The transmission is electronically linked to the engine and its operations are synchronised with the engine to achieve smoother transitions between gears. In the long-term, this also results in less wear and tear.

Shift-lock is still incorporated in the transmission, meaning you have to step on the brake pedal in order to get out of the P position. This was introduced in the mid-1980s when a series of accidents involving cars with automatic transmissions seemed to be due to drivers depressing the accelerator pedal excessively and simultaneously engaging R or D. A related feature is the keylock which requires the transmission to be put into P before the ignition key can be removed. A bit of an inconvenience but you can get used to it.


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