2001 Honda CR-V -- Engine

9/15/2000 6:43:08 PM

Honda engineering goals for the CR-V drivetrain centered around developing an engine with the following performance characteristics:

  • Excellent power and appropriate torque characteristics for both on and off-road use
  • Good fuel economy
  • Compact dimensions, for maximum maneuverability
  • Quiet, smooth operation

In order to achieve these goals, Honda engineers developed an entirely new engine, with the following features:

  • A 2.0 liter displacement, generating 146 hp @ 6200 rpm and 133 lb.-ft. @ 4500 rpm
  • The external dimensions and weight of a 1.6 liter engine. A new cylinder block-casting process was developed in which all four cast-iron cylinder bores are one compact (siamesed) unit with the aluminum-alloy block cast around it. Conventional engine manufacturing uses individual cylinder liners, resulting in a longer engine
  • Dual overhead camshaft, 16-valve cylinder head
  • Newly designed, compact intake manifold that fits in the CR-V engine compartment, yet has the long intake runners necessary for generating good low-rpm torque

The CR-V engine is a 4-cylinder, transverse-mounted engine, with a high-pressure die-cast aluminum-alloy, open-deck engine block. The sides of the block extend well below the crankshaft center line for added rigidity. A cast-bearing cap carrier forms an exceptionally rigid main bearing support. The connecting rods and single-plane crankshaft are of drop-forged carbon steel.

Additional weight-saving features of the engine include a stainless steel exhaust manifold, a die-cast aluminum power steering pump bracket and a planetary gear starter.

The cast-iron cylinder liners are an integral (siamesed) unit, instead of individual bores. The result is a very compact 2.0 liter engine block (external dimensions are length: 16.14 in., width: 15.47 in., and height: 8.34 in). The bore-stroke ratio is 3.31 in. x 3.50 in. (undersquare) and a 1972 cc displacement. The CR-V engine's total weight is 321.7 lbs. (145.9 kg).

Honda wanted the design of the CR-V to reflect the long-standing Honda design philosophy of Man Maximum, Mechanism Minimum, meaning there should be the most space for people, while the automobile and its systems should physically intrude the least amount on the human space. In the case of the CR-V engine, this meant developing a 2.0 liter engine with the compactness of a 1600 cc powerplant.

In addition, a compact -- and therefore lighter-weight -- engine would help maximize performance, maneuverability and fuel economy. Since the engine block can account for as much as 15 - 20% of the engine's overall weight, Honda's goal was to produce a 2.0 liter engine with the external dimensions and weight of a 1.8 liter engine.

Most Honda engine blocks are made of cast aluminum with cast-iron cylinder liners. The minimum amount of aluminum between individual, adjacent liners for sufficient bonding and dimensional stability is 9 mm. However, if the distance between the liners could be reduced to 6 mm, then the bores could be increased sufficiently to yield the desired 2.0 liter displacement.

To achieve their goal, Honda engineers perfected the technique of casting all four iron liners as a single unit with a 6 mm spacing between the cylinder outer walls.

Honda has applied for 13 patents comprising 44 items for the quad-sequential cylinder block and casting process.

The CR-V cylinder head is low-pressure die-cast from aluminum alloy. The individual combustion chamber's pent-roof configuration and centrally located spark plug promote rapid, complete burning of air and fuel.

Each cylinder has four valves (two intake and two exhaust). Since the individual valves in a four-valve combustion chamber are smaller and lighter than the valves in a two-valve combustion chamber, there is less reciprocating mass. This allows the engine to be revved safely to higher rpm levels, helping to extend the engine's power range. Four-valve combustion chambers also have greater valve area, so they offer less restriction to intake and exhaust flow, better exhaust-gas scavenging and greater volumetric efficiency.

Valve actuation is via dual overhead camshafts and direct-acting rocker arms located under the camshafts. Direct-acting rocker arms permit the use of screw-type adjusters for easier valve adjustment. The camshafts are driven by a Kevlar-reinforced toothed belt.

The fuel-induction system uses Honda Multi-Point Programmed Fuel Injection (PGM-FI). PGM-FI is a timed, sequential system with sensors for throttle position, coolant temperature, crankshaft angle, intake-manifold pressure, atmospheric pressure, intake-air temperature, vehicle speed and exhaust-gas oxygen content. Information from these sensors is fed to an Electronic Control Unit, which then decides when to activate each injector. PGM-FI can alter fuel delivery to match the engine's needs under varying environmental and engine-load conditions.

Because the CR-V is an SUV, Honda engineers designed the engine to have a broad torque curve that would serve it well in all applications. The engine's 2.0 liter displacement, 4-valve, DOHC cylinder head and 6300-rpm redline would serve it well on the highway; however, high-revving engines tend to have peaky torque curves, unsuitable for the low-rpm pulling power required in many off-road situations.

To extend the CR-V engine's torque curve into the mid- and lower-rpm ranges (the torque peak is 133 @ 4,300 rpm), Honda engineers designed an intake manifold with exceptionally long (14.5 in.) intake runners for a 2.0 liter engine. The runner's long, tapered length has the effect of amplifying intake-tract sonic waves around 4,000 rpm. This in turn creates a positive pressure pulse in the air-fuel mixture as it enters the cylinder. The pressure pulse rams more air and fuel into the filling cylinder, resulting in a more powerful explosion and greater torque.

In addition, the intake manifold's runners are carefully tapered. This, combined with their long length, accelerates the air-fuel charge as it approaches the cylinders. The mixture's high velocity translates into greater turbulence as it enters the combustion chamber, which in turn improves mixing and combustion efficiency. And the mixture's higher velocity also gives it added momentum, which tends to increase the amount of charge filling the cylinders.

The large-capacity air-cleaner chamber used in the CR-V's induction system serves to muffle intake roar, and it also incorporates a Helmholtz chamber to damp unwanted resonances. In addition, another resonance-damping chamber is located upstream, between the intake tube and the air-cleaner box. The intake tract from the air cleaner to the fuel-injection throttle body has also been optimized to muffle intake roar and incorporates an anti-resonant side-branch.

The CR-V engine, like other Honda automobile engines, uses an innovative inertial-axis engine-mounting system. In this system, the engine mounts are located on the axis of the engine's principal inertial moment (the axis about which the engine vibrates). At these points, the least amplitude of force is transmitted from engine to frame, which significantly reduces engine-idle vibration.

A liquid-filled engine mount is used at the engine-body inertial-axis mounting point. The mount has two internal chambers, separated by a metered orifice. Liquid in one of the chambers vibrates in response to engine vibration and acts as a damper. As engine rpm increases, vibration pumps the liquid into the other chamber, which changes the dynamic-spring constant of the mount. The mount is very effective in absorbing engine vibration in the 200-500 Hz range.

The CR-V engine features an On-Board Diagnostic System (OBD-II) that monitors the status and efficiency of the engine's fuel and emission system.

The OBD-ll system used on the CR-V engine expands the control and diagnostic capabilities of Honda Programmed Multi-Point Fuel Injection to include emissions-system components and operation.

The components of the system include an Electronic Control Module, a charcoal-canister purge-system monitor, an engine misfire detector and a set of oxygen sensors that monitor the efficiency of the catalytic converter.

The engine misfire detector uses a magnetic sensor that reads cylinder-firing information from the toothed, cam-drive pulley on the end of the crankshaft. The sensor is capable of reading the minute angular accelerations of the crankshaft that accompany individual cylinder firing. This data is sent to the ECM. If a cylinder is not operating efficiently, the ECM will take appropriate action.

Since Honda engineers anticipated extended operation in cold climates, they equipped the CR-V with a large 95-amp alternator.