Honda VTEC

(Variable valve Timing and lift Electronic Control)

The Honda VTEC engine came around because Honda believed that Turbo engines had too much lag. So they built a lightweight engine with all the lightweight valve gears which reduced the friction inside the car engine. The engineers working on the engine ruled out balancer shafts as part of the quest for minimal friction, because even the tiny drag and incremental power loss of turning the two shafts would be too great a compromise to place on such a precision-built engine. Although stiffness is aided hugely by the material used for the block, the engineers added an aluminium ladder frame to increase the rigidity of main bearings in the bottom end of the engine.

 The key to the engine's extraordinary performance is the unique VTEC (Variable Valve Timing and Lift Electronic Control) system. Put simply, VTEC gives the engine a dual personality, changing the timing and lift of the valves to combine good torque characteristics at low revs with high power at high revs. For the Honda S2000, a new method was developed to manufacture the rocker arms. Usually they are machined into complex shapes from a solid block, which is time consuming and expensive. With the new method, liquid metal is injected into a mould, creating the rocker arm in a simple, one-shot process. It is then heat treated for increased strength. To reduce friction in the valve gear, these new rockers are mounted on smooth-running roller bearings, which are also the cylinder head lubrication system to be simplified. Certain engine components are also coated with a special low-friction plating, a technology taken straight from Honda's Formula One engine programme.

The massively high speeds sustained by a valve train designed for an engine running beyond 9,000 rpm led to the adoption of lightweight valve springs using materials derived from Honda's CART ChampCar racing programme. Other components that use competition materials and construction techniques include the pistons and connecting rods. Forged pistons are seen for the first time in a Honda road engine, as are the specially heat-treated steel con rods. Another feature is the use of chain-driven (instead of belt-driven) camshafts for greater reliability at the higher potential speeds of the Honda S2000 engine.

As well as the physical size of the engine, the engine's ancillaries - the alternator, water pump and air conditioning pump - have been cleverly packaged to reduce the bulk of the powerplant. These are all known as a serpentine drive, a single belt driven by the camshaft. The belt does not drive a bulky power-sapping (up to 5 ps) power steering pump, because Honda opted for EPS - electric power steering, similar to the system used on the NSX. The main advantage of this system is that it can be programmed to offer greater steering feel at all speeds, something much more difficult with conventional hydraulic power steering. To optimize the weight distribution by mounting the engine as far back as possible, a conventional distributor was dispensed with. In its place comes individual coils sitting on top of each spark plug, a layout which also improves ignition performance at high revs.

Clear breathing - both inhaling and exhaling - is vital for a high-performance engine, especially one capable of such high speeds. To this end the Honda S2000 features both a low-restriction intake manifold and air filter system. The engine's intake manifold is a straight-through, large bore design as is the air filter set-up which is mounted in the nose, ahead of the engine. Free-flowing exhaling is helped by a low back-pressure exhaust. This feature an unusual metallic honeycomb catalyst, which is much less restrictive than conventional ceramic types. Emission performance is enhanced by an exhaust valve air pump which reduces emissions on start-up and an insulated exhaust manifold which shortens the time needed to get the catalyst up to operating temperature.

          Engine Cutaway - Torque/Power Graph

Click on the Pictures to see more detailed versions!

All info and pics provided by Honda UK.