The intake manifold used on the Insight's 1.0-liter engine is made out of plastic resin instead of aluminum alloy. The entire manifold weighs only 2.2 pounds, roughly half the weight of a comparable aluminum manifold. The individual pieces that make up the manifold, such as the intake runners, plenum chamber and throttle-body mounting, are permanently connected with a vibration-welding technique.
Additional weight-saving engine components made with plastic resin include a 0.39-pound water-pump pulley, a 0.2-pound air-intake tube and a 0.88-pound valve cover.
Much of the IMA engine's fuel efficiency comes from its newly designed VTEC-E (Variable Valve Timing and Lift Electronic Control for Economy) cylinder head and valvetrain, and advanced combustion technology Earlier versions of the VTEC-E system have been used on other high-mileage Honda automobiles, including the Civic HX Coupe and Civic VX Hatchback. The new version is more compact, operates with less friction and features an expanded stratified charge area within the combustion chamber. These features, combined with the engine's advanced fuel-injection mapping, a NOx-control catalyst and the Lean Air-Fuel Sensor (LAF), help it to achieve its high fuel efficiency without sacrificing driveability.
The engine's LAF Sensor is designed to detect air-fuel ratios as lean as 25:1. The fuel-injection Electronic Control Module uses this data, along with engine rpm, crankshaft angle, throttle angle, car mass, coolant temperature and valve position, to maintain a lean air-fuel ratio below 2500-3200 rpm (depending on throttle position and engine load).
The VTEC-E engine can burn such a lean mixture partly because of a strong air-fuel swirl created in the combustion chamber, created by the mixture's entry through only one of two intake valves during low-rpm operation. Although the overall air-fuel mixture is lean, optimized injection timing, along with the vortex, creates a "stratified" charge - the air-fuel ratio is richer near the spark plug and leaner toward the combustion chamber periphery. The richer mixture ignites more readily and creates a fast-burning, stable flame that promotes more complete combustion.
Above 2500 to 3200 rpm, the VTEC-E engine activates both of its intake valves. The additional valve area of 4 valves per cylinder (2 intake and 2 exhaust) satisfies the high-rpm breathing and power requirements of the engine.