2007 Honda CR-V - Powertrain

Advanced Technology for Performance, Economy and Low Emissions

Overview

The 2007 Honda CR-V provides a cutting-edge combination of performance, efficiency and low emissions with a 2.4-liter, i-VTEC 4-cylinder engine, standard 5-speed automatic transmission and available Real Time™ 4-wheel drive. Drive-By-Wire™ throttle control smoothly choreographs shift points with the transmission, while Honda's Grade Logic Control helps the CR-V intuitively hold the most appropriate gear on hilly roads. Compared to the previous CR-V, the new 2007 CR-V accelerates faster, drives quieter with more smoothness and has a lower CARB emission rating.

CR-V New Powertrain Technology

• Enhanced engine design with more power
• Maintenance Minder System added
• Enhanced Real Time 4-Wheel Drive
• Torque rod engine mount system

Powertrain Summary

• 2.4-liter DOHC i-VTEC 4-cylinder engine
  • 166 horsepower @ 5800 rpm (+10 horsepower)
  • 161 lb-ft. of torque @ 4200 rpm (+ 1 lb-ft. and broader torque curve)
• Standard 5-speed automatic transmission
• Real Time 4-wheel drive (available)
• Estimated fuel economy of 23/30 city/highway (2WD) and 22/28 (4WD)
  Honda in-house estimate, final EPA stimate not available at time of printing. Use for comparison purposes only.
• CARB Ultra Low Emission Vehicle-2 (LEV II ULEV) rating
  Federal Emission Rating Tier 2/Bin 5

Aluminum 2.4-liter DOHC i-VTEC 4-Cylinder Engine

The 2007 Honda CR-V engine is a dual overhead cam (DOHC) all-aluminum, 2.4-liter inline four-cylinder design that uses 16 valves and a high-volume intake manifold. The engine produces 166 horsepower at 5800 rpm and torque is rated 161 lb-ft. at 4200 rpm. Primary enhancements for 2007 include a slightly higher compression ratio (9.7:1 from 9.6:1) along with optimized valve timing and higher flow rate intake and exhaust systems. The broadened torque output allows the 2007 CR-V to offer smooth and spirited performance in all types of driving conditions whether it is city, freeway and hilly terrain.

A host of innovative features are designed to deliver a cutting-edge combination of performance, fuel efficiency, and low emissions. Most apparent is the i-VTEC "intelligent" valve-control system, a technology that combines VTC (Variable Timing Control) - which continuously adjusts camshaft phase - with Variable Valve Timing and Lift Electronic Control (VTEC) - which changes valve lift, timing, and duration. The combination of these two systems results in impressive horsepower and torque - with good fuel economy and low exhaust emissions. The engine redline begins at 6500 rpm. In keeping with Honda's proven commitment to the environment, the CR-V engine meets strict California Air Resource Board (CARB) Ultra Low Emission Vehicle-2 (LEV II ULEV) tailpipe emissions standards and Federal Tier 2-Bin 5 emission standards. Engine, fuel tank and catalytic converter enhancements help the 2007 CR-V lower evaporative emissions by 75 percent.

Engine Block, Crankshaft & Oil Pan

The 2.4-liter engine uses a two-piece, die-cast aluminum block and bearing cap design that helps maximize strength and rigidity while minimizing noise and vibration. The compact upper element features cast-in iron cylinder liners for outstanding durability and the lower element consists of a single-casting crankshaft carrier fitted with ferrous-carbon bearing-cap inserts that add to its overall structural rigidity. Each journal on the forged-steel crankshaft is micropolished to help reduce internal friction and improve durability. For those keeping score, the crankshaft rotates clockwise.

Aluminum Cylinder Head

The i-VTEC engine uses a compact, lightweight cylinder head made of pressure-cast aluminum alloy. Its 4-valve-per-cylinder design has double overhead camshafts activated by a silent chain drive to ensure extremely precise control of the cam phasing. The cam drive is maintenance-free throughout the life of the engine. The combustion chamber is designed with a relatively large "squish" area that promotes faster flame propagation on the ignition stroke. This results in more complete burning of the air-fuel mix and subsequently, low emissions.

i-VTEC Valvetrain

As a technology cornerstone, Honda's original VTEC (Variable Valve Timing and Lift Electronic Control) reaches a new plateau in i-VTEC form. This "intelligent" version of the highly effective VTEC package has Variable Timing Control (VTC), which provides for continuously variable phasing of the intake camshaft. The pairing of VTEC and VTC results in excellent drivability, including more horsepower and torque at lower rpm levels, along with enhanced fuel economy and significantly lower emissions.

The i-VTEC system on the 2.4-liter DOHC employs two rocker arms with friction-reducing roller followers for each pair of intake valves, along with an intake cam that has separate lobes configured to optimize both low- and high-speed operation. Depending on engine load and rpm, an electronic controller determines which cam profile will be used and exactly how each intake will operate.

At low revs, where low lift and shorter duration provide optimal operation, the timing of the two intakes is staggered and the lift asymmetrically skewed in favor of the primary valve. This helps to create a swirl effect within the combustion chamber that increases the efficiency of the burn process. At higher rpm, a hydraulically actuated spool valve causes a locking pin to engage the secondary rocker arm with the primary one, transitioning the secondary valve into a high-lift/long-duration mode that improves output on the top end.

VTC allows the timing of the intake camshaft to be continuously varied throughout the engine's entire rpm range. Along with helping boost power, VTC also provides a more stable idle (allowing idle speed to be reduced) and reduced pumping losses by effectively creating an internal EGR effect at low and mid engine speeds, which is also supplemented by an EGR valve. The result is increased fuel economy and lowered NOx emissions. Operation of the VTC is electronically controlled and is determined by input from sensors that monitor rpm, timing, throttle opening, cam position and exhaust gases. Depending on conditions, VTC can vary the phasing of the intake cam (change its position relative to the crankshaft) by +/- 25 degrees. VTC activation is accomplished hydraulically via a spool valve that sends high-pressure oil to passages in the cam's drive sprocket.

At idle, the timing is almost fully retarded to minimize valve overlap. In normal highway driving, the intake camshaft is advanced to provide overlap for EGR effect. With the throttle wide open, valve timing starts in an advanced condition at lower RPM and continuously changes to a retarded condition when redline is approached. This allows optimum cylinder scavenging and pumping efficiency and provides outstanding power and torque throughout the rpm range.

Drive-by-Wire Throttle Control

An electronic drive-by-wire system helps enhance the driving character of the CR-V from both a throttle pedal feel (good tip-in with direct response) and a transmission refinement perspective (less shift shock with short gear change intervals). With smart electronics connecting the throttle pedal to the throttle butterfly valve in the intake manifold, the engine response can be optimized to suit the driving conditions and to better match the driver's expectations. By eliminating the direct throttle cable connection to the engine, the ratio between pedal movement and throttle butterfly movement can be continuously optimized.

The CR-V uses a DC motor to control the throttle butterfly position in the intake tract. To establish the current driving conditions, the system monitors pedal position, throttle 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 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.

Torque Rod Engine Mount System

New for the CR-V, a torque rod engine mount system further enhances the vehicle's quiet and vibration-free operation. Previous CR-V engine mounts that attached the engine and transmission to the subframe and body utilized the engine mounts in front of and behind the engine in a vertical orientation, to resist the rotational effect seen when the engine is started, or accelerated. The torque rod engine mount system replaces these two engine mounts with an upper torque rod connected to the body, and a rear lower torque rod connected to the subframe, resisting the engine's rotational torque inputs to the chassis in a longitudinal orientation, reducing inputs that cause idle vibration, and mid and high frequency engine noise during acceleration. The CR-V's engine mounts consist of a rubber side mount integrated with the upper torque rod, lower torque rod, and a transmission mount. The torque rods isolates engine vibrations with solid rubber dampers located at the attachment points to the engine, the body, and the subframe.

Internal Balancer Shafts

To improve smoothness throughout the rev range and help lower noise levels, the CR-V is fitted with an internal balancer unit. Consisting of a pair of chain-driven counter-rotating shafts located in the oil pan, the balancing system helps quell the inherent second-order harmonic vibrations that normally impact in-line 4-cylinder engines.

Exhaust System

A high-efficiency exhaust system and a high-density catalytic converter help the CR-V engine meet stringent LEV II-ULEV emissions certifications in California and Federal Tier 2 Bin 5. Exhaust gases pass through a low heat-mass/dual-wall stainless steel manifold as they now exit the "downstream" side of the engine via a new double-walled pipe that also helps limit heat loss. The combination of higher relative temperatures and a more direct path to the catalytic converter yields quicker light-off, which contributes to lower levels of hydrocarbon and NOx emissions.

Maintenance Minder

The CR-V's vehicle maintenance 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. As calculated by the Maintenance Minder system, the CR-V has an engine tune-up interval of 100,000 miles or more. (See Interior section for more details on the Maintenance Minder display.)

5-Speed Automatic Transmission

The CR-V comes standard with an electronically controlled 5-speed automatic transmission. The 5-speed automatic transmission uses a wide 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 variety of technologies to provide 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 (closely emulating the benefits of a manual transmission design).

Real Time™ 4WD

The CR-V's 4-wheel drive system is designed to best match the majority of driving situations that SUV's realistically encounter. The fully automatic Real Time 4WD system (available) enhances the CR-V's all-weather and light duty off-road capabilities when driving in rain, snow, dirt roads and sandy conditions - without the significant weight, fuel economy and handling performance drawbacks of a conventional four-wheel-drive system. For 2007, enhancements have been made to the system for improved performance by optimizing materials and construction, resulting in 20 percent more torque transfer to the rear wheels.

The CR-V's Real Time 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 torque to a propeller shaft running the length of the vehicle, a dual-pump system with a multi-plate clutch, a cam unit mechanism, the rear differential, and left and right rear-wheel driveshafts.

The core 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 rate. Hydraulic fluid circulates between the two pumps; however, no pressure is generated. In effect, the fluid pressure created by the front pump is equalized 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 then feeds the drive torque to the right and left rear wheels.

To provide a quick torque transfer response time for transparent 4-wheel drive operation to the driver, the multi-plate clutch is supplemented by a one-way ball cam unit mechanism. The cam unit mechanism consists of two plates separated by six ball cams (large bearings) that move within ramped grooves. When a slight difference in rotation speed exists between the rear wheels and front wheels when driving forward, the ball cams move within the ramped grooves and create pressure that instantly begins the engagement of the main clutch (prior to the build-up of sufficient hydraulic pressure). By engaging the main clutch at a sufficient force even before the hydraulic pressure is generated by the two hydraulic pumps, the driving torque is transferred without a hint of time lag.

Overall 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™ 4WD is also low maintenance. The Maintenance Minder system will indicate that the dual pump fluid should be changed at about 60,000 miles.