Lotus Engineering’s ‘EVE Hybrid‘ (Efficient, Viable, Environmental) technology demonstrator showcases how OEMs can introduce lower emissions variants to existing model ranges that currently only offer conventional gasoline and diesel powertrains.
The application of hybrid technology is a key route for CO2 emissions reduction. For many manufacturers, over the next five years it may remain more viable to integrate hybrid technologies into existing model ranges than to develop expensive new dedicated hybrid platforms.
Solutions that Lotus Engineering can provide to its OEM clients will help them keep price premiums for hybrid variants at a minimum, thanks to lower development costs, and are available immediately for introduction within current and next generation model lifecycles.
The EVE Hybrid programme focussed on establishing the processes for integrating hybrid technology with minimal development time and cost, overcoming many of the challenges associated with integrating hybrid technology into existing platforms through intelligent, compact and discreet packaging of additional systems.
Ultimately, it demonstrates Lotus Engineering’s ability to provide strong, viable business case propositions for clients to offer a hybrid variant of a medium-high volume production car.
The resulting EVE Hybrid demonstrator, based on a Proton Gen.2 compact midsize car with a 1.6litre gasoline engine, showcases a trio of production-representative technologies:
(1) a ‘micro-hybrid‘ start-stop system
(2) a full parallel hybrid drive
(3) Continuously Variable Transmission
Compared to the baseline Proton Gen.2, tailpipe emissions are reduced from a competitive 172g/km to just 134g/km, a reduction of 22%, while fuel economy improves from 39.2mpg to 50.2mpg, a 28% improvement.
The technologies featured in the EVE Hybrid are production-ready, employing systems deliberately sourced from established tier one suppliers to demonstrate the availability of components, to minimisation of development costs and to maximise business case viability.
The EVE Hybrid features three key technologies:
(1) ‘Micro-hybrid‘ stop-start system:
A starter-alternator system was integrated that switches the engine off when the vehicle stops, during town driving for example. The engine restarts automatically when the brake pedal is released.
As a result, noise, emissions and fuel consumption are reduced. The unit runs on the standard vehicle 12volt electrical system and combines both starter motor and alternator functionality. Fuel savings of 5% have been demonstrated with a 5% reduction in CO2 emissions.
(2) Full parallel hybrid technology:
A bespoke 30kW, 144V motor is packaged between the engine and transmission. It delivers electric drive or regenerative braking via an additional clutch linking the motor to the drivetrain.
The motor provides the same start-stop functionality as the micro-hybrid with the additional benefit of electrical drive or drive assist, either boosting the drivetrain performance or providing economy and emissions benefits by operating as an electric vehicle. The motor is powered by a 144 volt battery located in the boot.
Testing has confirmed simulation predictions of 28% fuel efficiency improvement and 22% CO2 emissions reduction.
(3) Continuously Variable Transmission (CVT)
The CVT is a transmission in which the ratio between the input and output shaft can be varied continuously within a given range, providing an infinite number of possible ratios. The integration of a CVT to give benefits in fuel consumption and emissions control. In addition, its compact package assisted in the application of a hybrid electric drive and it provides smooth acceleration and low transmission noise.
Various changes have been made to the Proton gasoline 1597cc CamPro engine. The main modification is the redesign of the front end accessory drive (FEAD). This was done to accommodate a Valeo ‘StARS’ starter/alternator, which drives the micro hybrid start-stop system.
The redesigned FEAD also accommodates a Sanden hybrid Heating Ventilation and Air Conditioning (HVAC) compressor that operates by conventional belt drive and has an additional electrically driven capability which enables continued air conditioning operation when the engine is stopped.
During the FEAD redesign the opportunity was also taken to replace the belt driven Power Assisted Steering (PAS) and water pumps with electric units to enable the investigation into the economy benefits of such units.
To accommodate the additional hybrid functionalities the Engine Management System (EMS) was updated to a Siemens VDO torque-based unit and re-calibrated by Lotus Engineering.
Due to tight packaging constraints and to minimise any loss in overall vehicle performance, bespoke electric motor and power electronics were developed in conjunction with specialist suppliers ElektroMagnetix and Turbopower Systems. The motor/generator and power electronics are water-cooled and include an auxiliary power unit to support the vehicle’s 12volt systems.
An additional clutch supplied by AP Racing is packaged inside the motor and connects the IC engine to the traction motor. This enables the engine to be switched off for electric drive only use.
A Punch Continuously Variable Transmission (CVT) has replaced the conventional transmission and a modified bell housing accommodates the electric traction motor.
The EVE Hybrid uses a Cobasys Series 1000, NiMH, 30kW 144V module that incorporates an integrated cooling system. This traction battery pack is securely mounted on the boot floor, displacing approx 47 litres of luggage space.
A sophisticated bespoke Lotus Engineering control system was developed to implement the energy management function by monitoring and controlling all sub-control systems including the engine management, motor/generator, transmission, HVAC, additional clutch, starter/alternator and battery pack.
To maintain the integrity of the braking circuit when the petrol engine is off, a Mes-Dea electric vacuum pump maintains the vacuum assist for the brakes.
An off-the-shelf TRW electro-hydraulic power assisted steering pump has been fitted, which allowed the retention of the existing steering column and hydraulic steering gear. This pump also provides hydraulic pressure for the additional clutch that engages the hybrid motor.
The instrument panel incorporates an additional LCD display developed by Lotus Engineering to show battery charge, power split between engine and motor, fuel economy and charge/discharge rate, and incorporates associated warning indicators where appropriate. Also fitted to the dash are new switches to select the car’s operating mode – micro hybrid, full hybrid or electric vehicle.