2006 Honda Civic Powertrains
8/31/2005 7:42:55 PM
Civic: i-VTEC Valve Control System
To achieve more performance and more fuel economy, the Civic's 1.8-liter i-VTEC engine uses an innovative and new valve control timing to minimize pumping losses during cruising and low engine load situations, an important factor in creating more efficient engines. Pumping losses are lowered when the variable valve timing allows an intake valve to remain open for a brief time period as the piston begins its compression stroke. By keeping an intake valve open during part of the compression stroke, some of the volume of unburned air/fuel mixture in the cylinder moves back inside the intake manifold and lowers the volume being compressed, or "pumped."
The pumping loss reduction yields enhanced fuel economy similar to an engine with a smaller displacement (the equivalent of a 1.5-liter engine) during cruising.
During cruising or other stable, low-load driving conditions, the new engine utilizes a dedicated set of cams to close one of the intake valves and retard that valve's timing, exerting backpressure on the air-fuel mixture.
This reduces the actual intake air volume. Meanwhile, the throttle is opened wider to provide optimum control over engine output.
Opening the throttle valve, in other words, widening the path that the air flows through - reduces pumping losses to result in a significant improvement in engine efficiency.
During high load situations, the VTEC system provides high output valve timing for maximum power. Gone is the normal valve timing, replaced by two fundamentally greater extremes. A dual-stage air intake, a lightweight powertrain and optimized gearing further add to the performance character of the vehicle.
Whereas traditional VTEC operation changes valve opening duration based on higher oil pressure during high rpm operation at one side of the valvetrain's rocker arms, the Civic's i-VTEC system can switch valve timing duration at low rpm and low oil pressure using two hydraulic actuators on both sides of the intake rocker arm. This engagement method is similar to that used on the Civic Hybrid, Accord Hybrid and Odyssey i-VTEC systems.
This Civic's i-VTEC valve timing reacts to driving conditions related to throttle opening, vehicle speed, engine rpm and gear selection. A sophisticated drive-by-wire throttle control, air flow meter and dual-stage air intake allow the Engine Control Unit (ECU) to create seamless transitions between the two modes of engine operation.
Civic: Lightweight Composite Intake Manifold Chamber
The engine's intake manifold chamber is constructed of composite resin instead of aluminum alloy in order to save weight. The individual pieces that make up the manifold chamber are permanently connected with a die-slide welding technique.
A composite resin dual-stage intake manifold utilizes two intake runners for each cylinder, one longer than the other. Below 5200 rpm, only the longer of the two runners delivers air to the cylinder-taking advantage of the inertia effect of the long intake path. Above 5200 rpm, however, a rotary valve in the bore of the short runner opens to allow the passage of additional air to the cylinder. This has the effect of boosting midrange and high-rpm power by utilizing the inertia effect at both low and high rpm.Civic: Drive-by-Wire Throttle Control
An electronic drive-by-wire system helps enhance the driving character of the Civic. With smart electronics connecting the throttle pedal to the throttle butterfly valve in the intake system, the engine response can be optimized to suit the driving conditions and to better match the driver's expectations. Combined with the dual stage air intake, the drive-by-wire throttle control system is an important component to the new i-VTEC system that makes switching between the low pumping loss mode and the high performance mode seamless to the driver. By eliminating the direct throttle cable connection to the engine, the ratio between pedal movement and throttle butterfly movement can be continuously optimized. This adjustable "gain" between throttle and engine is a significant step forward in drivability. A highly responsive DC motor moves the throttle butterfly position in the intake system to change actual throttle position. To establish the current driving conditions, the system monitors pedal position, throttle valve opening position, vehicle speed, engine speed, and engine vacuum. This information is then used to define the throttle control sensitivity.
The throttle system also works to enhance the available 5-speed automatic transmission's ability to make shifts faster and smoother. By coordinating the throttle opening with the transmission's shifting functions, engine power can be precisely tailored to the needs of the transmission at every point during the shifting process. That means less shift shock and delay, no matter the driving situation.
Civic: Exhaust System
The Civic is equipped with a stainless steel, low heat-mass exhaust system integrated into the cylinder head that eliminates the need for a separate exhaust manifold, contributing to the engine's compact design and light weight. The system employs a high-density catalytic converter for improved light-off performance and reduced hydrocarbons and NOx. For emissions performance, the exhaust manifold is positioned on the front of the engine-which shortens the distance that the exhaust gases must travel to the catalytic converter, resulting in faster light-off and more complete conversion of the exhaust gases.
A composite resin dual-stage intake manifold utilizes two intake runners for each cylinder, one longer than the other. Below 5200 rpm, only the longer of the two runners delivers air to the cylinder-taking advantage of the inertia effect of the long intake path. Above 5200 rpm, however, a rotary valve in the bore of the short runner opens to allow the passage of additional air to the cylinder. This has the effect of boosting midrange and high-rpm power by utilizing the inertia effect at both low and high rpm.Civic: Maintenance Minder and Tune-Up Intervals
The Civic's engine tune-up schedule is calculated by the Maintenance Minder system. The Maintenance Minder system automatically indicates when to have standard service performed based on actual driving conditions (tracked by the ECU) and minimizes the guesswork related to whether the vehicle is being used in standard or severe use conditions for maintenance interval purposes. The display indicates when to change the oil, air cleaner, transmission fluid, spark plugs or coolant, as well as when to rotate the tires. Under normal usage, a tune-up is not required until typically more than 100,000 miles (only routine inspections and fluid changes are required up to this point). Credit for this longevity goes to long-wearing iridium spark plugs, a long-life timing chain, and careful engineering of the precisely manufactured SOHC valvetrain-which reliably maintains proper valve tappet clearances until the first tune-up.
Civic: 5-Speed Manual Transmission
The 5-speed manual transmission has also been redesigned into a more lightweight and compact unit that minimizes power-robbing rotating mass and adds a rotating select link for quick and direct gear changes. Additional features include a low friction design with single cone synchronizers in all gears and high capacity bearings throughout. From a performance standpoint, the new manual transmission has a higher torque capacity and a shorter, firmer and more direct shift feel.Civic: 5-Speed Automatic Transmission
The Civic Sedan and Civic Coupe are available with an electronically controlled 5-speed automatic transmission. The 5-speed automatic transmission - a first for the Civic - is all new for 2006 and improves on the previous 4-speed automatic design with a wider overall ratio that maximizes acceleration in gears one through four and optimizes fuel economy in its overdrive fifth gear. The computer controlled direct control transmission provides amazingly smooth shifts.
The direct control coupled with gear ratios that are closely matched to the output of the engine help extract more power from the engine at just the right time to provide overall vehicle performance competitive to vehicles with 4-speed automatic transmissions and more horsepower.
The 5-speed automatic transmission uses a wide variety of technology that provides smoother shifting as well as reduced friction for enhanced efficiency. Those technologies include a low-friction clutch and a special super-thin torque converter. The thin torque converter results in a compact transmission unit. Other space saving measures include a double-row idle gear and a tightly packaged second-gear clutch.
To improve powertrain smoothness and reduce gear "hunting" on steep grades, the 5-speed automatic transmission is also equipped with a standard Grade Logic Control system. Using sensors that monitor throttle position, vehicle speed, and acceleration/deceleration and then comparing these inputs with a map stored in the transmission computer, the system is able to determine when the vehicle is on an incline and adjust the shift schedule for improved climbing power or downhill engine braking.
To improve fuel economy while maintaining a high level of drivability, the 5-speed automatic transmission includes an active lockup torque converter. With the precise control afforded by a linear solenoid, the system expands the speed and throttle setting range in which lockup can be engaged.