CIVIC TYPE S ENGINES
Technical details


1.8 SOHC i-VTEC

The 1.8-litre SOHC i-VTEC engine contains the finest of Honda's VTEC technology and control systems expertise and introduces a further innovation to boost environmental performance - by combining delayed intake valve closure with a wide open throttle valve during low-load driving conditions, pumping losses are reduced to the benefit of fuel economy. 

In conventional petrol engines, the accelerator pedal is directly connected to a throttle valve that opens and closes, adjusting the volume of intake air. Under low-load conditions (i.e. when the driver is pressing lightly on the accelerator pedal) the throttle valve is opened just slightly. This narrowing of the intake passage causes resistance, pumping losses and has a negative impact on fuel economy. 

The 1.8-litre i-VTEC engine adopts a different approach. Its two sets of cams - one designed for high output, the other fuel economy - intelligently adjust valve timing and lift. During acceleration and other high-load conditions, the high output cams help deliver a superior driving performance. During cruising and other stable low-load driving conditions, the fuel economy cams retard the closure of the intake valve and the throttle valve is opened wide. In this position, the output would normally be very high but since the intake valve closure is delayed, some of the air/fuel mixture is momentarily expelled back out of the combustion chamber, minimising unnecessary output and thus improving fuel economy. 

Thanks to this synchronised operation of the intake and throttle valves, output is optimised and pumping losses are minimised. Meanwhile, the drive-by-wire throttle works together with the switch between high output cams and fuel economy cams, to provide highly precise throttle control for smooth driving with minimal torque variation.

The cruising mode is detected if the water temperature is over 60 degrees C, if second or a higher gear is in use, if the vehicle speed exceeds 6mph and if the engine is revving between 1,000 and 3,500rpm.

In pursuit of even higher fuel economy, the new 1.8 i-VTEC engine also incorporates the latest friction reducing technologies. The piston skirts are shot with a solid lubricant, molybdenum disulphide, while an ion plating process is used on the piston rings to ensure reduced friction. Plateau honing of the cylinders results in a smoother surface and improved oil film retention. Friction is reduced by approximately 10 per cent as a result. 

Through this combination of new VTEC technology and comprehensive friction reduction measures, the new engine realises a six per cent improvement in fuel economy compared to a 1.7-litre engine and during cruising it delivers fuel economy on a par with that of a 1.5-litre engine. Performance is improved at all engine speeds to ensure lively response, while special attention has been paid to increasing low to mid-speed torque.

For the intake system variable length intake manifolds are implemented. Controlling the effective length of the intake manifold - making it longer at low rpm and shorter at higher rpm - ensures that the optimum intake ram effect is maintained to deliver torquey driving performance throughout the rpm range.

Also introduced with this engine are piston oil jets, more normally associated with high performance engines. The resulting superior cooling ensures improved durability against knocking, allowing the engine to run with a high compression ratio of 10.5:1.

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