Virtually every engine component was designed and refined to aid the quest for high revs, from the straight port intakes, which sharpen engine response, to the low back-pressure exhaust and the light, race-influenced valve springs. Particular attention was paid to ensuring efficient combustion through advanced combustion chamber design, making full use of the knowledge gained from the company's racing activities. Key features in realising a 9,000 rpm maximum are a relatively short-stroke design (short-stroke engines have the ability to rev higher, while connecting rod length is kept to a minimum), low friction valve gear, and a very efficient oil pump.

Certain components also feature a low-friction plating technique on bearing surfaces, a technology adapted directly from Honda's Formula 1 experience.


Keeping things compact

Efforts to reduce engine dimensions have been just as important as those aimed at increasing power output and starting with a clean sheet approach provided the opportunity for Honda's engineers to create a remarkably compact engine. Length, width and height are all reduced relative to Honda's conventional 2.0-litre DOHC VTEC engine and this has made it possible for the HONDA S2000's power unit to be located behind the front axle in a 'front midship' position to the benefit of handling. The engine is also exceptionally light - lighter than the 2.0 Prelude unit by around 10 per cent, in fact.

During the development period, Honda engineers discovered that a number of the key features aimed at performance enhancement such as the short stroke design, forged pistons, and lightweight connecting rods, also played a role in reducing NVH. Further refinement comes from the adoption of a liquid filled front engine mount and a liquid filled differential mount. Balancer shafts have not been used, since their marginally higher levels of operating friction would adversely affect the quest for high revs and high output.


VTEC: the next generation

At the heart of Honda's new engine is the latest incarnation of the renowned Variable Valve Timing and Lift Electronic Control (VTEC) system which so successfully provides volumetric efficiency at all engine speeds to achieve good low to mid-range torque and vivid top-end output - all the more important given the high-revving nature of the HONDA S2000's engine.

VTEC works by maximising the amount of air-fuel charge entering, and the exhaust gas leaving the cylinders over the complete range of engine speed. Ideally, the valves should remain open for a longer duration and with greater overlap at high engine speeds to give the gases sufficient time to overcome their inertia and to enter and depart from the cylinder.

For each pair of inlet valves and each pair of exhaust valves, there are three rocker arms and three corresponding lobes on the camshaft. From idle to around 5850 rpm, the valves are operated by the two outboard cam lobes, their short duration and low lift ensuring good cylinder filling. Above 5850 rpm, pins in the rocker arms lock the two outboard rockers to the centre one which is operated by a high-lift, long duration cam lobe. Valve opening now matches the timing required for good output at high engine speeds.


Roller-type rocker arms

In its latest guise, the DOHC VTEC system uses new roller-type rocker arms to cope with the high engine speeds of the HONDA S2000. This is the first time Honda has chosen such an approach on its DOHC VTEC design, and a roller in contact with the camshafts substantially helps to reduce friction losses.

previous page | go to page 6