2002 Honda Civic Si -- Powertrain
10/26/2001 5:02:34 PM
The new high-output DOHC, 2.0-liter i-VTEC engine in the Civic Si incorporates a host of innovative features designed to deliver a combination of performance over a wider, more accessible power range, efficiency, and low emissions. A new close-ratio 5-speed manual transmission has also been developed. The combination is designed to provide more power at lower rpms than past VTEC engines.
The latest version of Honda's acclaimed valve-control technology, the "intelligent" i-VTEC system combines Variable Timing Control (VTC)--which continually adjusts intake-camshaft phase--with Variable Valve Timing and Lift Electronic Control (VTEC), which changes valve lift, timing, and duration. The result is 160-horsepower at 6500 rpm, 132 lbs-ft of torque at 5000 rpm (a 20 percent torque increase over the previous Civic Si), and exceptional operating efficiency.
VTEC (Variable Timing and Lift Electronic Control)
The Si's VTEC system uses two roller arms per pair of intake valves. During low-rpm operation, intake air is drawn almost exclusively through the primary intake valve, thereby creating a very strong swirl effect to maximize combustion. At higher rpm, the secondary rocker arm engages the primary roller, opening both intake valves for the same lift and duration, substantially increasing airflow into the cylinder and boosting performance.
VTC (Variable Timing Control)
The i-VTEC system adds a new camshaft VTC (Variable Timing Control) system to VTEC for continuously variable camshaft phasing across the engine's entire power band. As engine rpm builds, a VTC actuator--controlled by an engine-control union that monitors cam position, ignition timing, and throttle position--advances or retards the intake cam throughout the 50-degree timing range, optimizing engine output and reducing emissions.
During typical operation, the intake camshaft timing is almost fully retarded at idle to help provide more stable idling while reducing exhaust emissions (NOx). As rpm increases, the intake camshaft is advanced, opening the intake valve sooner and providing additional valve overlap. This results in increased fuel economy (by reducing pumping losses) and a further reduction in exhaust emissions (by creating a large, internal exhaust gas re-circulation effect).
Also, to generate additional power throughout the rev range, the intake camshaft is continuously varying the amount of advance or retard, instantly adjusting to provide additional power as required by the driver.
Cylinder Head/Valve Train
The Civic Si engine features an aluminum cylinder head and a double-overhead-cam, four-valve-per-cylinder valve train. A large combustion chamber "squish" area increases gas turbulence for faster flame propagation and excellent efficiency. The camshafts are operated by a silent-chain drive that helps provide smooth, refined performance while also being maintenance-free.
The powerplant has a compact aluminum block with cast-in iron liners--a design known for its light-weight, high-ridigity and excellent durability. The block has a one-piece aluminum crankshaft carrier that has ferrous-carbon inserts in the bearing caps for additional strength.
Programmed Fuel Injection (PGM-FI)
The advanced Programmed Fuel Injection (PGM-FI) system of the Civic Si monitors such variables as throttle position, engine temperature, intake-manifold pressure, atmospheric pressure, exhaust-gas oxygen content, and intake-air temperature. Fuel delivery is controlled by four newly developed, multi-holed injectors mounted in the cast-aluminum intake manifold. The ECU also tracks the operation of the engine with position sensors on the crankshaft and both camshafts.
The exhaust system on the Si is a stainless-steel, low heat-mass design. Emissions performance is improved thanks to the engine's design, which positions the exhaust manifold to the rear 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. The system also employs a new, high-density catalytic converter for improved light-off performance and reduced hydrocarbons and NOx.
Remarkably, given the impressive power output of its DOHC 2.0-liter engine, the Civic Si reduces NOx by 25 percent compared to the previous model and is designed to meet strict 2004 Low Emissions Vehicle II (LEV II) standards.
Noise, Vibration and Harshness (NVH) Control
In addition to its outstanding power and efficiency, the Civic Si engine has been engineered for class-leading smoothness and refinement. To that end, such NVH-reducing features a balancer shaft (integrated with the oil pump); highly rigid, ferrous-carbon inserts in the main bearing caps (for added rigidity); a one-piece crankshaft carrier; and a silent chain cam drive are incorporated.
A sophisticated engine mounting system plays a key role in limiting noise and vibration in the interior space. Four engine mounts (two liquid-filled) and reinforcements in the engine compartment help further reduce engine noise and vibrations.
Centrally mounted at the front of the engine bay is a lightweight, extruded aluminum mount. At the rear engine bay is second mount made from resin that is designed to shear off in an impact, limiting the rearward movement of the engine. The two liquid-filled mounts (one fitted to the transmission) are positioned for maximum absorption on the 2.0-liter's NVH characteristics.
110,000-Mile Tune-Up Intervals
The Civic Si's first scheduled tune-up is required at 110,000 miles (only routine inspection and fluid changes are required during this period). Credit for this longevity goes to long-wearing platinum-tipped spark plugs, a long-life timing chain, and careful engineering of the DOHC valvetrain--which reliably maintains proper valve tappet clearances until the 110,000-mile first tune-up (under normal conditions).
5-Speed Manual Transmission
The standard and only transmission offering on the driver-oriented Civic Si is a close ratio 5-speed manual designed to optimize the performance characteristics of the i-VTEC engine. It is equipped with a short-stroke shift linkage for superb shifting quickness and feel. By employing multiple large-capacity synchronizers (triple cone on gears 1 and 2; larger diameter single cones on gears 3-5), the 5-speed offers an exceptionally light and positive shifting effort.
For enhanced sportiness and shifting ease, the shift lever is mounted "rally style" within easy reach of the driver on the Civic Si's center console.