Fibre Reinforced Metal

FRM involves an advanced metallurgical technique used by Honda in the 3.2 litre engine of the Honda NSX and it helps to increase bore size for a shorter stroked engine through its enhanced rigidity. During the casting process, the cylinder block's aluminium alloy is poured around cylinder cores composed of fibres of carbon and alumina which start to absorb the molten aluminium. Once complete, the cylinders are bored by removing most of the core material. However, the outer extremes are retained leaving a tough, wear-resistant composite cylinder wall, at least 0.5 mm thick, integral with the block but reinforced by the carbon and alumina fibres. The greater strength provided by this process allows larger bores within the same external block dimensions and bore spacing.


Forged aluminium pistons

The engine's bottom end offers a combination of strength and low reciprocating mass, vital in a high revving engine. In a first for Honda, race-style forged aluminium pistons are used for increased strength. At the same time, the adoption of a narrower oil ring and the tapering of the connecting rod's small end for a stronger piston pin boss help to reduce piston height and further increase strength.

Piston weight and friction losses are thus reduced simultaneously.

In another competition-inspired technology, the connecting rods are not only forged steel, but also case-hardened for significantly increased strength. Slimmer connecting rods can thus be adopted to reduce weight without compromising strength. Similarly, nut-less connecting rod bolts permit a smaller crankcase. On the crankshaft side, shearing resistance is increased as the source of local torsional stress is reduced by chamfering the pin's oil supply holes.


Aluminium ladder-frame

A racing-style aluminium ladder-frame main bearing stiffener, located between the block and the sump, contributes to the block's compact dimensions, and working in concert with the aluminium sump, also increases rigidity. The breathing paths between each cylinder and the oil return paths are all lengthened to reach below the baffle plate to prevent oil from churning inside the crankcase at high engine speeds and to reduce both mechanical losses and oil aeration. The engine features a compact, 'silent' low-friction chain-driven oil pump.

The cast-aluminium sump is finned to help dissipate heat, and contributes to engine rigidity and noise reduction.


High performance goes green

Despite the difficulty raised by the long exhaust manifold required for high output, the HONDA S2000's engine is remarkable for its low emissions. Close control of the engine's air/fuel ratio is achieved by the use of oxygen sensors both upstream and downstream of the catalytic converter.

The advanced emissions equipment employs a three-stage process - cold start, warm-up, and normal temperature operation - centred around an exhaust secondary air system that allows for very quick heating of the catalytic converter. When the engine is started from cold, the ignition timing is modified to give lower combustion temperatures for reduced emissions of NOx while still maintaining relatively high exhaust temperatures. Simultaneously, multi-port exhaust secondary air injection comes into operation which allows for very quick heating of the catalytic converter. An electric pump sends air into the exhaust ports to react with CO and HC particles contained in the exhaust, thus increasing gas temperature. Furthermore, the stainless steel exhaust manifold has a dual-wall design with an insulating air gap between the walls to help in the rapid warm-up of the catalyst.

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