Engine and IMA System
The CR-Z is the first car to combine a 1.5-litre i-VTEC engine and the IMA system, giving excellent fuel economy and greatemphasis on driver enjoyment. This 114 PS engine is combined with a 14 PS electric motor which also boosts torque, with an impressive 78 Nm at low to medium engine speeds. The combined power figure peaks at 124 PS with a healthy 174 Nm of torque. Performance and driver enjoyment can be seen as a conflicting need to good fuel economy and exhaust emissions levels. The CR-Z’s 1.5-litre, 16-valve, i-VTEC, petrol engine provides driver enjoyment with its enthusiastic engine note, willingness to rev and broad spread of torque. At the same time its modest capacity, boosted by an electric motor can achieve excellent fuel economy and low overall exhaust emissions, including the all important CO2 emissions. The CR-Z is the first Honda hybrid, since the original 1-litre Insight to use a four valve per cylinder head with the IMA system.
The CR-Z emits just 117 g/km of CO2 on the EU test cycle and consumes just 5.0l/100km of fuel. This CO2 figure is just 1 g/km higher than the original Civic IMA, an incredible achievement considering the over 30 PS power advantage the CR-Z has over its saloon ancestor.The CR-Z engine used is based on the 1.5-litre Jazz unit with changes to the valve timing allowing for one intake valve to be deactivated at low engine speeds. This creates an additional swirl effect which enables fast combustion and higher exhaust gas recirculation. The effect of this additional turbulence is to reduce emissions and improve fuel consumption. At higher revs, both intake valves are opened to increase power output.Numerous small changes are made to the engine to suit the characteristics of the CR-Z, integration of the IMA system and installation in the coupe body. The original engine, as it was installed in the Jazz, would not fit under the low bonnet of the car as it stood. The development engineers developed a new intake manifold and a flat air cleaner assembly, to give sufficient clearance and allow space for pedestrian impact protection.
The 1.5-litre i-VTEC engine has not been seen in an EU specification car before and was chosen for its combination of light weight, fuel efficiency and compact size. The block of the 1.5-litre engine is similar to other Jazz engine variants and the Insight meaning that integration of the IMA system is simplified. Because the basic block layout is shared with the 1.3-litre Insight engine, the sump pan that was developed for that car was adopted. This measure assisted the team in the task of reducing the overall engine height and lowering the position in the chassis.
The IMA system is shared with the Insight hybrid, but the software and settings have been altered to interact with the 3-Mode Drive System and manual transmission. Although the operating revs are quite different in a manual car, the flexibility of Honda’s IMA parallel hybrid system makes integration of different engines and transmissions more straightforward. Extensive testing was done to ensure that the impressive durability of the Insight’s IMA hardware was not compromised in any way by the addition of a manual gearbox. Particular attention was paid to the possibility of over-revving the engine due to missed gear changes and the implications this might have for the system.The electric motor provides its peak torque instantly from the start, boosting the low end torque of the CR-Z by more than 70 Nm, improving initial acceleration. The torque curve of the new hybrid is unusually flat for a naturally aspirated engine, with the peak arriving at just 1500 RPM, enabling great flexibility at all engine speeds.
The battery pack in the CR-Z is a 100.8 volt Nickel Metal Hydride unit which provides an excellent balance between output, reliability, safety and cost. As with the rest of the system, the battery pack is shared with the incredibly reliable Insight model, which has proved itself to have the lowest warranty claim rate of any Honda car sold in Europe during 2009. At the end of the vehicle life, the battery pack can be recycled through Honda dealers.
Exhaust Design and Tuning
To ensure that drivers would be able to enjoy driving the CR-Z on the open road, the development team dedicated a great deal of time and thought to the design of the exhaust. The brief was not only to create an efficient unit that allowed the optimum operation of the engine to minimise emissions and generate the target power level, but also to produce an enjoyable sound. Because of the diversity of environments, drivers and speeds that the CR-Z was designed for, engineers would not be satisfied with an exhaust that merely had less silencing capacity.
A great deal of development time was dedicated to the design of the exhaust to give it a sporty note when the engine was being worked hard, but without excessive noise during motorway or town use. To achieve this the team spent time tuning other components, including the engine mounts and noise insulation, to isolate unpleasant sounds, and allow the most pleasing acoustic ranges of the exhaust to be heard without reducing silencing too far.
3- Mode Drive System
The CR-Z has been designed to be a car that combines driver enjoyment with excellent urban driving performance and economy. The two major roles of the car can be sometimes in opposition, with characteristics like sharp throttle response and greater steering weight increasing driver satisfaction in open road driving, but possibly proving frustrating in bumper-to-bumper traffic.Honda’s engineers have developed the 3-Mode Drive System for the CR-Z, which allows the driver to alter the characteristics of the car depending on their needs and the environment the car is being driven in. By significantly altering the responses of the car, the CR-Z’s new system allows drivers to adapt to different road and traffic situations.The new feature enables the driver to choose between three driving modes which alter the responses of the throttle, steering, climate control and the level of assistance provided by the IMA system. In developing this new facility, Honda allows the driver to decide whether they wish to maximise sportiness, economy or the best balance between the two.
buttons have become commonplace, usually offering a sharper throttle response, but Honda’s 3-Mode Drive System is different. The new system alters the behaviour of the hybrid drivetrain and the power steering assistance as well as the throttle mapping between the three modes.When the CR-Z driver is away from the town or city and wanting to enjoy the open road, they can put the car into SPORT mode. This sharpens the throttle response, changes the behaviour of the IMA hybrid system to provide more electric motor assistance and increases the weight of the electric power steering.
Honda recognises that even the most enthusiastic driver may regularly experience heavy traffic, where maximising fuel economy is more desirable than the perfect line through a corner. In these situations ECON mode can be selected, which prioritises fuel economy in the operation of the drive-by-wire throttle, ECU, air conditioning and the hybrid system. For those times when spirited driving is not possible or desirable, the Eco Assist function, in conjunction with the ECON mode, allows the driver to enjoy beating their best economy score on the way to work, or in heavy traffic. The ECON mode reduces the sensitivity of the throttle to smooth out inputs and this action is assisted by the use of a different engine map that prioritises fuel economy. The climate control system is also influenced by the ECON mode, by recirculating air and reducing compressor operation in order to reduce energy consumption. The use of the motor to assist the petrol engine is redefined with the priority given to improve fuel economy, not assist performance.
At all times the car can be run in NORMALmode, which provides a balance between performance, economy and emissions and suits most driving situations.
Together with the ECON mode, the CR-Z uses a guidance function that can be used to achieve high fuel economy and thus minimise harmful exhaust emissions.During driving, there are two main elements to the system: an ‘eco drive bar' indicator within the Multi Information Display (MID), and an ambient meter, behind the digital speedometer display. Both instruments are synchronised, to give real time information on the consumption of fuel and provide guidance on how you could alter your driving style.The ‘eco guide bar' in the MID is a solid bar symbol that moves to either side of a central line. The idea is to drive in a way that keeps the bar in the centre and away from the shaded areas on either side.
When driving smoothly, and thus efficiently, the bar stays near the centre of the indicator, shifting slightly right during gradual acceleration and slightly to the left when braking gently. During these conditions, the ambient meter behind the speed display glows a green colour to show optimum economical driving performance.Under greater acceleration, or when braking moderately, the bar in the MID shifts more towards either end of the scale, showing the use of more fuel, and the ambient meter glows a green/blue colour.With aggressive acceleration, or sudden braking, the indicator bar will head to the right or left, into the shaded areas of the scale to show major fuel consumption and the ambient meter turns blue respectively.In order to achieve the best fuel consumption figures, the driver should aim to keep the bar in the centre, and the display glowing green as much as possible throughout each journey.
To help motivate drivers during each journey, another display above the bar indicator grants rewards for more efficient driving. If performing well, small leaves will ‘grow' above the bar to show the driver's eco-progress, with more leaves and eventually a flower added if the system records a ‘perfect' score. Also, by pressing the Info button on the steering wheel and scrolling through the MID displays, drivers can not only look at their average fuel consumption of the current trip, but can also retrieve their average fuel economy of the last three journeys.
The CR-Z is fitted with a Shift Indicator Light (SIL), which alerts the driver to the optimally efficient shift up or down point. Following the indications of the light, combined with following the advice of the Eco Assist function, can improve fuel consumption by up to 10%, reaffirming Honda’s commitment to improve every day fuel economy.
Once a journey is over, and the ignition is turned off, the ‘eco guide' in the MID changes to an ‘eco score' display. Now, the leaf symbols at the top, report on the driver's performance during the last drive, while the bar and symbols at the bottom of the display, show a lifetime score. This is shown in three stages with the fully grown plant and flower to the right of the bar showing the best score.If the driver's stage has improved since the last journey, a recognition symbol with wreathes is displayed. At the end of the third stage a trophy symbol appears indicating good progress.
Conversely, if the driving style is worse, and the lifetime score and stage regresses, then the recognition symbol of a withering plant is displayed.The normal mode - NORMAL -, which provides a balance between performance, economy and emissions generally suits all driving situations. NORMAL mode balances the operation of the IMA system, climate control and throttle between maximum economy and driver enjoyment, this is the mode the CR-Z defaults to on start-up. In this mode the power steering settings are the same as in ECON. All homologation tests are undertaken in NORMAL mode since this is the default mode for the car at start-up. Between the different modes, the icon of each mode is displayed on the MID for two seconds before reverting to the previously selected information.
Scramble-assist is a control strategy which detects the acceleration demand of the driver from the accelerator pedal movement and increases the amount of motor-assist. Under SPORT mode it provides proportionally greater assistance for a given pedal movement, resulting in better acceleration performance compared to NORMAL mode.The motor-assist is a control mechanism where the electric motor supports when the accelerator pedal is pressed. It can be divided roughly into four situations which are: drive-away, during eco assist, scramble-assist and 70-80% throttle. With SPORT mode engaged, there is an improvement in performance during scramble-assist.
ECON Cruise ControlWhen Cruise Control is set during normal driving, the removal of excessive acceleration when driving on the flat and when descending hills, improves fuel consumption. However, during gradient changes, it is possible for a conventional system to accelerate excessively, causing additional fuel consumption. The ECON Cruise Control minimises unnecessary throttle openings in these situations. The ECON Cruise Control softens the responses to increases in gradient and allows some variations in speed to reduce consumption. Allied with the ECON mode, this cruise control reduces fuel consumption, without sacrificing driver comfort.Cruise control operating under conventional settings, is available in SPORT or NORMAL mode since it is expected that these modes will be used in driving conditions where the vehicle’s speed will vary significantly throughout the journey.
The CR-Z is the first hybrid to be fitted with a 6-speed manual gearbox, which allows drivers maximum control over the torquey combination of the 1.5-litre i-VTEC engine and the IMA motor. For the European market a manual gearbox was considered essential and a 6-speed considered the optimum gearbox for both economy and sportier driving. As a parallel hybrid system it is easy to adapt Honda’s IMA system to work with a variety of hardware and as shown with the original 1999 Insight, a manual gearbox can work very well with the right hybrid technology.The manual gearbox will give the CR-Z a very different character from existing hybrid models and will give the driver a new level of interaction.
The gearbox has been developed with the enthusiastic driver in mind, with a short shift and a firm but light action that encourages the driver to change regularly. Tolerances of the shift mechanism components have been optimised to reduce free play in the mechanism. The detent is a component that controls the movement of the shift lever and this area was the subject of a great deal of attention to achieve a positive click with each gear change.Even with a six speed gearbox and sporty shift action, it is not essential to continuously work the CR-Z’s gearbox. The ample low end torque of the engine and IMA system means in gear flexibility is also impressive.