New Clio Renaultsport V6 255 | Part Four

New Clio Renaultsport V6 255

 

A Sporting Powertrain

The 3-litre 24-valve V6 engine has been thoroughly revamped to enhance its sporting characteristics, and now develops 255bhp (187kW) at 7,150rpm. With a maximum speed of 7,200rpm, this engine loves being run at high speeds. It is, however, equally comfortable at more normal speeds with a very flat torque curve and a high maximum value of 300Nm at 4,650rpm.

The upper part of the engine, from the air intake to the combustion chambers, is new. With an intake pressure loss of just 25mb, a level rarely achieved on a production vehicle, cylinder filling is enhanced at medium and high speeds:
  • New dedicated air filter with a volume of 11.5 litres (vs. 6.1 litres) using an extra-high permeability filter cartridge.
  • Motorised throttle valve with a diameter of 74mm (40% gain in passage section).
  • New plenum with integral trumpets and short, machined intake ducts. The acoustic tuning of the assembly has been optimised for high engine speeds.
  • The camshaft uses settings which result in quicker and greater valve lift. The variable inlet valve timing is carried over.
Valves, seats and machined intake pipes have been developed for the new internal aerodynamics. New valve springs ensure optimum control of lift. The fuel supply system has been improved with a new twin-passage injection ramp and injectors with a flow rate around 50% higher. The engine management computer power has been increased and its new calibration is notable for its finer control in transient conditions and better control of response to the accelerator.

The adoption of new catalytic converters allows the IF Euro 4 emissions standard to be achieved while retaining minimum back-pressure and a low level of noise emissions.

In New Clio V6 255, the six-speed "PK6" gearbox has been specially adapted. The shorter final drive (16/67) lowers the final gearing by 10% to the benefit of response and acceleration. The internal gears are more closely spaced, with new ratios for first and second (offering a speed 0.8mph and 0.1mph higher at 1,000rpm), and for third (-0.3mph). Compact and light, the three-shaft box of New Clio, now with a final drive ratio of 4.07:1, is the ideal sports gearbox.

These developments are accompanied by a shift mechanism which has been redesigned for more sporting operation: selector movements have been reduced by 20% and the stops are more pronounced. These changes significantly improve the ease and precision of gearchanging.

The acoustics of New Clio V6 have been the focus of especially close study as customer feedback shows this adds immense driving pleasure and was one of the most favoured features of the original Clio V6. A new plenum and exhaust have been developed. The sporting exhaust note provides a heavy bass, throbbing quality up to 4,500rpm, it increases to 6,000rpm in pure harmonics that reflect the quality of the powertrain, before screaming upwards to maximum revs. To enhance comfort, noises emanating from the driveline are filtered by a twin-mass damping flywheel. A resonator modifies intake noise at high speeds and the adoption of a damped windscreen allows booming to be eliminated.

continues... | Part Five
Published 6 May 2003 Melanie Carter

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