Leave it to the engineers at Honda to make an engine for the 2006 Civic that is physically smaller and lighter, has a larger swept area, has more power, and that consumes less fuel than its predecessor. As if that wasn't enough, they followed this feat with a revised hybrid powertrain that is smaller, more powerful, and more fuel efficient. Both engines debut this fall.
Honda claims its new 1.8-liter four cylinder has standing-start acceleration equal to a 2.0-liter; fuel economy approximately 6% better than the Civic's current 1.7-liter; and cruising fuel economy on par with a 1.5-liter four cylinder. Engineers focused on reducing pumping and friction losses in the new engine to boost power and economy.
Under low-load conditions, the drive-by-wire throttle is kept wide open to reduce pumping losses, and the closure of the intake valves is delayed to control the air-fuel volume entering the cylinder. Pumping losses, Honda claims, are 16% lower using this system. It works in unison with a two-stage plastic intake manifold and Honda's "intelligent" VTEC variable valve timing system to smooth torque and horsepower fluctuations so the driver and passengers aren't tossed around as driving conditions change.
The engine borrows an idea from Honda's 2.2-liter diesel (HONDA Coming Full Circle ) in its use of a highly rigid aluminum girdle to stabilize the closed-deck aluminum block. This is coupled with an aluminum cylinder head that includes an integral exhaust manifold that places the dual-bed catalyst just after the manifold for improved light-off performance and low start-up emissions. Each block is "plateau honed" to create a smooth surface that improves oil film retention and reduces friction by 10%. Plus, each die-cast aluminum piston is infused with molybdenum disulfide and fitted with ion-plated oil control rings to further reduce friction.
Other technology used on the new engine include piston oil jets to suppress engine knock with the 10.5:1 compression ratio, aluminum rocker arms, cracked connecting rods, a narrow cam chain, an oil pump integrated into the cam chain case, and plastic valve covers. The result is an engine 13-mm shorter and 5-kg lighter than the 1.7-liter four it replaces.
The 1,339-cc four-cylinder engine mated to Honda's Integrated Motor Assist (IMA) system sounds exceedingly complex. It has three hydraulic pathways to couple/decouple five rocker arm assemblies to provide three stages (low-speed, high-speed, and idle) of valve control. The valves can be on the normal cam lobes, the high-output cam lobes, or on no cam lobes (valves closed). The latter reduces pumping losses during deceleration, and increases energy recovery during braking by 10% over the current Civic hybrid.
The Honda-developed IMA unit uses a new DC brushless motor with high-power magnets that packs 1.5 times the power into the same package size. It also uses a dissolver-type rotation sensor that allows energy production to be more efficient by knocking the edges off the previous unit's square-edged, on/off wave. The inverter used to control motor speed is integrated with the motor's ECU for greater efficiency, and battery output is increased by nearly 30%. A hybrid dual-scroll air conditioning compressor is powered by both the engine and electric motor so passenger compartment cooling can continue even when the gasoline engine shuts down in Idle Stop mode.