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REAL TIME 4WD SYSTEM

The new CR-V continues to offer Honda’s efficient and convenient Real Time 4WD system which only comes into operation when required. It does so automatically, without any extra driver input. Real Time 4WD enables the CR-V to cope with light off-road driving – over dirt roads or slippery grass fields for example – while providing greater on-road security in slippery conditions.

In the latest system, uprated clutches, high tensile steel gears and a stronger casing allow 20 per cent more torque to be sent to the rear wheels for enhanced traction.

How it works
In normal, everyday driving conditions, Real Time 4WD operates as a conventional front-wheel drive system. But if the front wheels begin to lose traction, then it automatically starts to send power to the rear wheels.

At its heart is Honda’s innovative Dual Pump unit, which is integrated with the rear differential. This features two hydraulic pumps, one driven by the front wheels via a transfer gear and propeller shaft, the other by the rear wheels via the rear differential.

While front and rear wheels turn at the same speed, the front and rear pumps operate at the same speed. During these conditions, hydraulic fluid circulates between the two pumps, however no pressure is generated. In effect, the fluid pressure created by the front pump is equalised by the rear pump.

If the front wheels begin to turn faster because of slippery conditions, then the two hydraulic pumps turn at different rates, and hydraulic pressure proportional to that difference is generated. That pressure is fed to a multi-plate clutch that engages the front propeller shaft to the rear diff, which then feeds precisely the correct amount of torque to the rear wheels to increase overall traction.

As rear wheel drive is only engaged when it is really necessary, frictional losses are reduced and thus there’s an improvement in fuel economy.

In 2005, an additional one way ball cam and pilot clutch system was introduced, which detects slippage and provides drive transfer instantaneously. The 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, the ball cams move within the ramped grooves and create pressure to instantly engage the main clutch. This happens before hydraulic pressure is generated by the two hydraulic pumps, so driving torque is transferred without any time lag.

For 2007, the design has been enhanced further, providing better acceleration and hill climbing performance on slippery – in particular snow covered – surfaces, as well as smoother responses and improved performance when accelerating around corners or pulling away from slippery road junctions. It means the Dual Pump system matches even the best electronically controlled 4WD systems.

The body
CR-V uses a monocoque construction, rather than a separate body-on-frame, with all the benefits of improved rigidity, crash performance and weight reduction. It defines new standards for torsional and bending rigidity in the SUV market, achieving a level similar to D-segment saloons and a handling balance to match.

More high-tensile steel for lighter, stronger body
The benefits of using a higher percentage (33.5 to 58 per cent) of high tensile steel in the body of the new CR-V are threefold: greater stiffness; lighter weight; better crash protection.

Almost 32kg are saved as a result of incorporating tougher and lighter materials throughout the body. The static bending stiffness has been improved by 85 per cent. There is also a better balance between front and rear lateral stiffness, and together with excellent rigidity around the damper fixing points, the CR-V delivers greater handling stability and response to driver input.

This increase in body rigidity, together with the use of more noise absorption materials, has also made the cabin a more relaxing environment – on a par with premium saloon cars. The potential for tyre noise has been reduced by adopting passenger car tyre patterns which don’t suffer from increasing noise as they progressively wear.

Specific additional items include:
• Increased rigidity of the floor, roof, around the tailgate opening and the A and B pillars
• Torque rod-type engine mounting to reduce engine idle and acceleration noise
• Lightweight insulation applied to the dashboard, carpeting and roof lining to dampen high frequency road and engine noise
• Complete front and rear door double sealing
• Sound absorbing material applied to the inside of the roof, on the sides of the trunk, to the backs of the door panels, to the spare wheel cover and to the instrument panel
• Sound absorbing material applied to the A pillar garnish
• 5mm glass, increased from 3.5mm used in the front doors
• Sound insulating glass for the windscreen

VSA on all models
VSA (Vehicle Stability Assist) is standard across the CR-V range. It is designed to assist the driver in maintaining control during cornering, acceleration and sudden manoeuvres, by applying brake force to the right or left hand wheels as necessary and managing the throttle and ignition systems. In the new CR-V, the control software has been revised to complement the enhanced Dual Pump four-wheel drive system.

VSA monitors driver input using a series of sensors and then predicts a range of vehicle responses, while keeping an eye on the actual responses made by the car and the driver. If the actual response is outside the predicted response range, as when cornering forces exceed the tyres' performance, VSA automatically intervenes with corrective action. The system is calibrated to provide stability and predictability, without interfering with driving enjoyment.

In the case of oversteer (which may lead to a spin), VSA applies braking to the outside front wheel to counter the yaw effect. On the other hand, if understeer is detected, VSA applies braking to the inside rear wheel and reduces engine power to turn the car back on to the intended course.

Braking system
All CR-Vs are equipped with 4-channel ABS and Electronic Brake force Distribution (EBD) which adjusts front-to-rear brake effort to achieve maximum braking performance and stability.

In the event of a rear wheel locking-up on a slippery road, less braking pressure is applied to the opposite wheel to help stabilise the rear end. All models feature brake discs all round, 293mm ventilated at the front, and 302mm solid at the rear. The actual brake pedal action is now slightly shorter and lighter, for better control without being over-sensitive.

Meanwhile, a variable, speed-sensitive steering system features quick gear ratios for an agile response to driver inputs, providing greater assistance at low speeds for easier manoeuvring, and less at higher speeds for a more direct feel and stability.

Petrol-engined CR-Vs are equipped with electric power steering (EPS), while diesel-engined models use a hydraulically-assisted system.

Wheels and tyres
17-inch wheels are now fitted as standard on SE and ES models, shod with 225/65 R17 tyres, while 18-inch items are fitted to EX models. Low rolling resistance tyres contribute to the overall excellent fuel economy.

Towing
It’s now easier and safer to tow using a CR-V thanks to an increase in the towing capacity on models equipped with manual transmission. On the petrol-engined model it rises from 1500 to 1600kg, and on the diesel from 1500kg to a very competitive 2000kg (braked trailer).

All CR-Vs are also fitted with Trailer Stability Assist, which will quickly restore stability by using a combination of reduced engine torque and precisely controlled braking should a towed trailer cause snaking.

ENGINES AND TRANSMISSIONS

At a glance
• Brand new 2.0 i-VTEC petrol engine delivers high performance with maximum economy
• Renowned 2.2 i-CTDi diesel engine continues and offers even better fuel consumption
• Both engines produce emissions lower than some D-sector cars
• New 6-speed manual and 5-speed automatic transmissions on petrol models

The 2.0-litre i-VTEC engine
New, efficient engine means petrol models are faster but more frugal
Output figures for the new 2.0-litre petrol engine are around the same as its predecessor. Power output is the same at 150PS, although that’s produced at a slightly lower 6,200rpm, while peak torque is 140lb.ft at 4,200rpm.

Fuel economy is boosted due to greater efficiency from the new engine, new gearboxes and improved vehicle aerodynamics. On the Combined cycle, the manual version records an impressive 34.9mpg (34.5mpg auto gearbox), which is significantly better than the previous generation CR-V – and importantly compares favourably to other SUVs in the class (see table below).

Performance is also enhanced, with the 0 to 62mph acceleration time dropping from 10.8 to 10.2 seconds for manual models (13.1 to 12.2 seconds for the auto).

2007 Honda CR-V #12