2002 Honda CR-V -- Powertrain
9/1/2001 5:10:21 PM
Honda engineers developed an entirely new engine for the 2002 CR-V designed to deliver a cutting-edge combination of performance, refinement, efficiency and low emissions. New technology allows the CR-V to accelerate significantly quicker and quieter than the previous model, obtain better gas mileage and reduce exhaust emissions. These engine improvements equate to increased overall acceleration, better performance on long hills and better throttle response.
The CR-V uses Honda's latest i-VTEC "intelligent" valve-control system. This technology combines VTC (Variable Timing Control) - which continuously adjusts camshaft phase - with Variable Valve Timing and Lift Electronic Control (VTEC) that changes valve lift, timing and duration. First appearing on the Acura RSX, this is the first Honda product in North America to receive the i-VTEC system. The result is impressive horsepower and high torque with outstanding fuel economy and low exhaust emissions. The broad torque range allows the 2002 CR-V to offer smooth and powerful performance in all types of driving conditions ranging from in-city to freeway driving to hilly terrain. In addition, the CR-V's transversely mounted engine block has been rotated 180 degrees. As a result, the exhaust manifold is closer to the catalyst for improved light-off and reduced emissions at startup. The engine rotates clockwise.
The 2.4-liter DOHC i-VTEC 4-cylinder design uses 16 valves, a dual-stage intake manifold, and the i-VTEC system (VTC on intake cam shaft) to deliver 160-horsepower at 6,000 rpm and 162 lb-ft. of torque at 3,600 rpm. The engine also has a dual-stage intake. The i-VTEC system represents a new, highly intelligent valve timing/lift mechanism that combines the VTEC mechanism for switching cams between low- and high-speed ranges, along with VTC, which sequentially controls cam phase based on engine speed and load. Overall, the engine's low to medium power range has improved greatly compared to the previous CR-V's powerplant - resulting in better throttle response at low engine speeds. The 2001 CR-V engine produced 146-horsepower at 6200 rpm and 133-lb.-ft. of torque at 4500 RPM.
i-VTEC VALVE CONTROL SYSTEM
The Formula 1 racing derived Variable Valve Timing and Lift Electronic Control (VTEC) system delivers abundant low-rpm torque, exhilarating high-rpm power and outstanding fuel efficiency. On the all-new 2002 CR-V, Honda unveils the latest version of this remarkable engine system: i-VTEC. The "intelligent" i-VTEC system adds new VTC (Variable Timing Control) to VTEC to provide continuously variable camshaft timing - taking the concept of variable valve timing to new heights. In short, i-VTEC = VTEC + VTC. Not only does i-VTEC provide a substantial performance increase across a broad power band, it boosts fuel economy while also reducing engine emissions.
VTEC (Variable Valve Timing and Lift Electronic Control)
Honda's innovative VTEC system is able to adjust the lift and opening duration of the valves to help the engine produce both abundant low-rpm torque and excellent high-rpm power. At low rpm, VTEC adjusts valve timing and lift for optimum cylinder filling. In addition, the timing of the intake valves is staggered and their lift asymmetric - creating a swirl effect within the combustion chambers. The result is increased burn speed with improved combustion stability. As engine rpm builds, VTEC transitions to a high-lift, long -duration cam profile for improved high-rpm engine output.
The 160-horsepower CR-V employs a new version of VTEC and applies variable timing and lift to the intake valves. The 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 causing both intake valves to open for the same lift and duration, substantially increasing airflow into the cylinder and boosting performance. When combined with VTC, a remarkably broad and smooth power band is produced with exceptional torque and horsepower.
VTC (Variable Timing Control)
The new 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 unit that monitors cam position, ignition timing, exhaust-gas oxygen content and throttle position--advances or retards the intake cam throughout the 50 degree 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, especially NOx. The reduced levels of NOx helps qualify the CR-V in the more stringent LEV-2 category. 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 advance or retard, instantly adjusting to provide additional power.
The CR-V engine uses an aluminum cylinder head and a double overhead cam, four-valve-per-cylinder valvetrain. A generous "squish" area around the combustion chambers yields increased 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 CR-V engine features a compact aluminum block with cast-in iron liners--a design known for its light weight, high rigidity, and excellent durability. The block has a one-piece aluminum crankshaft carrier that has ferrous-carbon inserts in the bearing caps for additional strength. The crankshaft is a highly rigid, forged-steel design that uses a special micro-polished surface finish for reduced friction and increased durability.
Programmed Fuel Injection (PGM-FI)
The CR-V engine is equipped with a Programmed Fuel Injection (PGM-FI) system. The system monitors such variables as throttle position, engine temperature, intake-manifold pressure, atmospheric pressure, exhaust-gas oxygen content, and intake-air temperature. It controls fuel delivery with four newly developed, multi-holed injectors. The ECU also tracks the operation of the engine with position sensors on the crankshaft and both camshafts.
The CR-V has a newly designed, stainless steel, low heat-mass exhaust system. The system employs a high-density catalytic converter for improved light-off performance and reduced hydrocarbons and NOx. Emissions performance is further improved thanks to the engine's new design, which positions the exhaust manifold on 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. A resonator before the muffler is also used to further reduce engine noise.
Engine Noise Vibration and Harshness Control
In addition to the CR-V's outstanding power and response, the engine has been engineered for class-leading smoothness and refinement. To that end, the 2.4-liter four-cylinder employs such NVH-reducing features as highly rigid, ferrous-carbon inserts in the main bearing caps for added rigidity, a one-piece crankshaft carrier, a silent chain cam drive and a balancer shaft (integrated with the oil pump). Four engine mounts (two liquid-filled) and reinforcements in the engine compartment help further reduce engine noise and vibrations.
110,000 Mile Tune-Up Intervals
The CR-V's first scheduled tune-up is required at 110,000 miles (only routine inspections and fluid changes are required prior to 110,000 miles.) Credit for this longevity goes to long-wearing iridium-tipped spark plugs, a long-life timing chain, and careful engineering of the precisely manufactured DOHC valvetrain--which reliably maintains proper valve tappet clearances until the 110,000-mile first tune-up (under normal conditions.)
4-Speed Automatic Transmission and 5-Speed Manual Transmission
Two transmission choices are available for the 2002 CR-V - a new 4-speed automatic transmission and a new 5-speed manual transmission.
The automatic transmission in the 2002 CR-V is an all-new design that delivers exceptional smoothness, economy, space savings and intuitive shift points. The smooth shifting automatic transmission features a lockup torque converter and Grade Logic Control - a system that automatically downshifts and holds a lower gear when the CR-V is climbing a steep grade. This reduces the gear hunting that can occur as the driver changes throttle position in response to changing engine load.
It is electronically controlled so there is less "shift shock." Using Honda's Active Lock Up II system, the lock-up clutch has a linear solenoid "active lock-up" system that improves the overall efficiency of the system and as a result - fuel economy. The system has a broad lock-up range depending on the driving conditions. This new automatic transmission is a compact design (35 mm shorter than the 2001 CR-V) that helps with overall packaging efficiency and improved fuel economy.
The 5-speed manual transmission brings a new level of "feel" to the shifting experience with short throws and new components that contribute to a sporty feel. The new transmission is enhanced by:
- Increased synchro capacity - fifth gear now has a carbon-faced synchro to allow for easier upshifting. In addition, thin double-cone syncronizers are used for third and fourth gear for ease of shifting and triple cone synchronizers are used for gears one and two.
- The actual amount of transmission oil has been reduced slightly - this helps reduce viscous friction, which in turn helps increase fuel economy.
Real Time(TM) 4WD
The Real Time(TM) 4WD system on the CR-V is designed to overcome the traditional drawbacks of a full-time four-wheel-drive system such as lower fuel economy, higher noise and vibration levels, higher weight and difficulty in adapting the system to ABS. The CR-V's Real Time(TM) 4WD operates automatically and only when needed. It requires absolutely no intervention on behalf of the driver for it to be engaged or disengaged.
The CR-V's Real Time(TM) 4WD system sends power only to the rear wheels when there is insufficient traction for the front-wheel-drive system. The system consists of the conventional front-wheel-drive system, a compact transfer case that distributes drive to a propeller shaft running the length of the vehicle, a dual-pump system, the rear differential, and left and right rear-wheel driveshafts.
The heart of the system is the dual-pump unit. It consists of two hydraulic pumps, one driven by the front wheels via the propeller shaft and one driven by the rear wheels via the rear differential. A hydraulically actuated, multi-plate clutch, similar to the clutches used in Honda automatic transmissions, connects the propeller shaft to the rear differential.
When the CR-V is operating with the front and rear wheels turning at the same speed, for example on dry pavement, the front and rear hydraulic pumps operate at the same speed. Hydraulic fluid circulates between the two pumps; however, no pressure is generated. In effect, the fluid fed by the front pump is absorbed by the rear pump.
If the front wheels begin to turn faster than the rear wheels, as would be the case if they were spinning on snow or ice, the two hydraulic pumps would turn at a different rate and hydraulic pressure proportional to the difference in their speeds of rotation would be generated. The resulting hydraulic pressure opens a valve body and feeds pressure to the multi-plate clutch, which engages the front propeller shaft to the rear differential. The rear differential feeds the drive torque to the right and left rear wheels.
System operation is completely automatic; no electronics or driver action is involved. The greater the degree of front-wheel slippage, the greater the amount of torque fed to the rear wheels. Real Time(TM) 4WD is also practically maintenance- free, requiring only a scheduled fluid change at 90,000 miles, like an automatic transmission. Another big advantage of the CR-V's dual-pump Real Time(TM) 4WD system is that, unlike conventional 4WD systems, Real Time(TM) 4WD automatically disengages under braking, thereby allowing the ABS system to engage.