Class B passenger car results – FIAT 500X

Content

Motivation for the solution

Environmental and social mobility challenges are becoming more relevant. To pave the way to this green, clean and efficient mobility vision, towards the long-term goal of a sustainable completely zero emission future, electrification is one of the most promising solutions. In the short and mid-term, to support a wider diffusion of electrified vehicles, it is essential to find solutions able to satisfy the typical customer expectations, in terms of costs, higher performance (fun to drive), better driveability and comfort, improved usage flexibility, and new functionalities.

The hybrid architecture selected for the B Class passenger car aims to give an answer the environmental requests and the private user needs, through a plug-in solution (enabling a pure EV mode for tens of kilometres), an improved regenerative braking strategy and an electric 4WD capability (with higher dynamic and efficiency in comparison to a mechanical system) plus a wide impact (not only for zero to near-zero speeds (depannage)).

The Class B passenger car developments performed can be summarised as follows:

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Table 1 Main technical targets for the city car demonstrator

  • identify the hybrid architecture
  • define the hybrid powertrain subsystems and components specification
  • design and size the selected new plug-in hybrid architecture with a modular approach and considering its potential scalability to lower and higher size cars and light commercial vehicles
  • integrate, at a functional level, the hybrid powertrain in a B class passenger car demonstrator vehicle
  • define and implement the optimised thermal and energy management
  • assess through vehicle level test (dyno. bench and track) the developed solution, optimising fuel efficiency as well as driveability and safety (enhanced as result of the e-AWD capability).

The key components implemented on the demonstrator are:

  • the new downsized FCA gasoline engine (in place of the donor vehicle 1.4 gasoline engine)
  • the FCA Dual Clutch Transmission (in place of the donor vehicle Automatic Transmission)
  • the Bosch 400V front e-machine (in place of the standard alternator)
  • the rear electric axle made of the Bosch 400V e-machine plus the GKN fixed speed transmission with integrated differential and disconnect (in place of the donor vehicle mechanical AWD unit)
  • the Bosch 400V inverters with the integrated HV-12V galvanically insulated step-down DC/DC converter
  • the 400V Li-ion based Battery System (initially planned by JMBS)
  • the Brusa 400 V battery charger (with the charging socket)
  • the thermal systems (included an HV electrical PTC heater and the Denso HV electric air compressor of the passenger air conditioning also in EV mode and the Battery System cooling-heating)
  • the HMI devices (tablet display, mode selector, buttons etc)
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Table 2 Main targets for the end user requirements for the city car demonstrator.

where:

  • best in class SoA (HEV for B segment): Toyota Yaris Hybrid 2013
  • baseline: FIAT 500X 2015 with 1.4 l MultiAir gasoline engine, ZF AT9 gearbox and GKN mechanical AWD
  • hybrid powertrain: internal combustion engine, mechanical transmissions, front & rear e-machines and power electronics

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Key innovations

The CRF demonstrator is based on a FIAT B/C segment passenger car (donor vehicle) in which the hybridized plug-in powertrain has been installed in place of the current normal production one (FWD pure thermal engine based with mechanical 4WD capability). The developed architecture additions are:

  • high efficiency (engine downsizing and high voltage e-components (included the Li-ion batteries))
  • add-on approach for the front axle hybrid powertrain and the integrated rear electric axle (with favourable impact on the costs)
  • hybrid architecture able to exploit the advantages of the front dual clutch transmission and compensate its limitations through the hybridization
  • wide flexibility in the usage (engine only, parallel (with torque assist), split (with power looping) or series hybrid and pure electric modes)
  • pure electric range based on the proper battery sizing
  • advanced energy management
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Figure 1 Ghost view of the car showing the installation of the hybrid powertrain components

The key components implemented on the demonstrator are:

  • the new downsized FCA gasoline engine (in place of the donor vehicle 1.4 gasoline engine)
  • the FCA Dual Clutch Transmission (in place of the donor vehicle Automatic Transmission)
  • the Bosch 400V front e-machine (in place of the standard alternator)
  • the rear electric axle made of the Bosch 400V e-machine plus the GKN fixed speed transmission with integrated differential and disconnect (in place of the donor vehicle mechanical AWD unit)
  • the Bosch 400V inverters with the integrated HV-12V galvanically insulated step-down DC/DC converter
  • the 400V Li-ion based Battery System (initially planned by JMBS)
  • the Brusa 400 V battery charger (with the charging socket)
  • the thermal systems (included an HV electrical PTC heater and the Denso HV electric air compressor of the passenger air conditioning also in EV mode and the Battery System cooling-heating)
  • the HMI devices (tablet display, mode selector, buttons etc)
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Figure 2 E-AWD distributed complex plug-in hybrid architecture.

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Figure 3 Some of the main hybridized powertrain components

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Key results

The plug-in hybrid demonstrator vehicle, based on the FIAT 500X, meets near all the ECOCHAMPS targets despite severe issues with the supply of the JMBS traction battery (in the vehicle validator replaced with a Li-ion A123Systems based solution CRF had to develop in house). Due to the significant delays, CRF had to complete a comprehensive part of the final evaluation after the end of the project (April 30th, 2018). The final assessment was carried out between the second half of March and the end of April 2018 on closed test tracks within FCA facilities in Orbassano (Centro Sicurezza) close to Turin (Italy), partially under the supervision of the Golden Engineer.

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Figure 4 City car demonstrator

As reported in the two previous tables, the developed prototype vehicle was assessed against:

  • Toyota Yaris Hybrid 2013 for the powertrain efficiency and vehicle consumption/CO2 emissions
  • FIAT 500X gasoline mechanical 4WD for the weight & volume plus delta cost impact and many of the EUR

For noxious emission, the EURO standards have been considered, while for the remaining EURs, standards (for instance for safety) and industry practice (Noise Vibration and Harshness and Reliability) have been used.

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Table 3 Main technical results for the city car demonstrator. * tested after end of project

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Table 4 Main results from the end user requirements for the city car demonstrator. * tested after end of project

The EV Battery Life target has been defined according to the future product (but not verified in the project due to the already mentioned JMBS problems). Moreover, the following results have been achieved through integrated component bench activities combined, where necessary, with 3D CAD virtual installation and calculations:

  • Enhanced Thermal Management through an innovative multi temperature coolant circuit concept to better cope the high efficiency targets with the passenger comfort in the different vehicle modes (engine on and off, pure EV etc) thanks to a 4-way valve and its proper control.

BClass-Fig4

  • Smart Energy Management (e-horizon based): adaptive‐predictive control strategy designed and implemented to pre‐calculate the total trip energy needed and the remaing energy needed for the trip. Adaptive predictive backward Quasi‐Steady State (QSS) Vehicle model to predict on board the energy consumption of a real trip by using trip information and driving styles.

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  • Thermo Electric Generator (TEG) novel solution applied to the engine exhaust pipeline to recover part of the gas’ heat and convert it into electric energy (power: 450 W, weight: 4.5 kg and volume: 7.9 litres)

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Further potential

The main improvements to be considered/investigated towards the production level can be summarised as:

  • Powertrain Architecture: evaluate for the front e-machine a position between engine and transmission (or inside the transmission) also to avoid limitations in the power transferred to the rear axle
  • Traction e-Drives: one unit (integrated e-motor & inverter; for the rear powertrain also the transmission)
  • Battery System: different position to increase luggage compartment area and increase safety during crash
  • Thermal Management System: simplified 4-way valves layout and battery direct refrigerant cooling
  • Engine: replace the standard aftertreatment to include a GPF (Gasoline Particulate Filter)
  • Vehicle Control Unit: integration of e-horizon based algorithms
  • Charging port: better positioning.
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