Article
Articles, Issue 51 - Spring 2014

Jaguar C-X75 | A demonstration of the Future

Introduction

The concept of the Jaguar C-X75 was born to symbolise the future of Jaguar Cars and to create a vehicle that was indicative of the future.

The timing of this automotive engineering project was to celebrate the significant milestone of 75 years of Jaguar Cars and to emphasize to the world how the innovative heritage of Jaguar and the UK car industry can lead the next generation of powertrain and vehicle development. This project was not only a showcase in technical innovation but also in rapid product development with strategic partners such as Williams Advanced Engineering and Lotus can raise the bar in project delivery technical complexity and timescales.

The platform for the launch of this vision to the world was Paris. The show car was presented at the 2010 motorshow, drawing attention from the media, competitors, suppliers and the public to its blend of classic beauty and innovation. The thinking behind C-X75 is to provide an owner with a unique car, capable of being driven as a road vehicle showing style with economy, then on occasion, take it to the race track to unleash its performance and power.

The decision was made in May 2011 to go forward to the next stage of the supercar development and engineer the concept into a production solution, based on 250 vehicles. Jaguar’s Programme and Vehicle Manager, Rob Atkin with Paul Newsome Head of Williams Advanced Engineering led the programme and engineering activities from Grove Oxfordshire under the guidance a steering committee chaired by Bob Joyce Jaguar’s Engineering Director.

To deliver this task the newly formed Jaguar / Williams project team carefully selected key suppliers that were competitive, experienced and focused on delivery. Lotus were selected as a key partner to develop two major function groups: the chassis system and the engine management system. This technical delivery was managed under the guidance of Paul Pywell, Head of Lotus.

To deliver the chassis and engine management systems meant working closely with the core programme team. Lotus brought its 60 years of motorsport, car production and engineering collaborative consultancy experience with OEMs to bring a blend of process and flexibility to meet the challenge.

The strategic fit with Lotus allowed Jaguar and Williams to draw into Lotus’s DNA and adopt some of Colin Chapman’s key values for the challenge

  • If you’re not winning you’re not trying
  • To add speed, add lightness
  • To finish first, first you have to finish
  • Adding power makes you faster on the straights Subtracting weight makes you faster  everywhere
  • The least number of parts effectively deployed

Management 

Each of the Lotus teams interfaced with other cross functional teams, managing interfaces within function groups, such as the transmission, engine and body systems. A challenge for management was identifying robust design freeze points for the teams. Each team was developing their systems in parallel and relied on robust data to meet the tight deadlines right first time. Key relationships built rapidly to ensure this worked.

A challenge for the Williams manufacturing team was to provide the designers with production input from virtual data for a unique innovative vehicle that was still a paper exercise. The Jaguar/Williams team worked with Lotus to study manufacturing processes so that design for manufacture (DFM) supercar best practice could be implemented ensuring right first time was achieved for the first build.

Focused meetings were held at key locations on a regular basis with skilled staff in a structured manner to manage progress, accelerate problem solving and keep the project on track. The mutual respect between the chosen partners encouraged an open dialogue between industry experts which allowed for technical issues to be brought to a head and resolved quickly.

Key vehicle attributes

One of the major challenges for the automotive industry is to drive down CO2 emissions. The key enablers for this are to engineer cleaner downsized engines coupled with hybrid technology and lighter vehicles to get more power per kg. It was important to think outside the box to capture the right technology content, reduce time to market and cost whilst improving performance and customer appeal. This is what the team set out to do.

After a review of the Paris concept car the technology moved away from the idea of micro gas turbines which uses jets to generate electricity for the battery and extend the range of the car. The technology direction was to develop a plug-in hybrid electric vehicle solution (PHEV) with a unique liquid and battery pack for this performance vehicle. This direction change allowed alignment with current production technology trends for CO2 reduction. Coupling boosted engine performance with additional power delivered from the battery through twin electric motor drives delivered additional performance.

The partners were challenged to deliver: “a hybrid supercar with no equal”.

Targets

  • Performance of the Bugatti Veyron, 0-160 kph in less than 6 seconds
  • CO2 emissions of a Toyota Prius less than 89 g/km
  • Electric range of a Chevrolet Volt, 60 km

Specification

  • Supercharged 1.6-litre turbo petrol, 500 bhp
  • Power output 313 bhp/litre compared to the Bugatti Veyron, 125 bhp/litre
  • Twin electric motors developing more than 175 bhp electric motor on each axle 
  • Total power more than 850 bhp
  • Torque more than 738 lbft
  • Range of up to 60 miles on electric-only power
  • Engine and rear electric motor drive coupled to 7 speed automated manual transmission
  • The vehicle can be driven electrically or as a hybrid with 4WD
  • High level of technology leveraged from Formula 1 including engine, high voltage battery, vehicle control system and aerodynamics
  • Electric front axle drive, driving through a single speed reduction gearbox

The story from the chassis team

Thanks to a small team of passionate, driven and focused engineering experts, Lotus successfully designed and released all C-X75 chassis systems in less than 16 weeks. The work scope included the design and integration of the entire vehicle suspension, steering and braking systems along with wheels, tyres and various mounts throughout the vehicle.

Defining the required attributes during the feasibility and concept phases was crucial to the success of the C-X75 production intent phase. From vehicle, system and component target setting to supplier benchmark and selection, Lotus were key partners in all the chassis engineering activities. The goal was to ensure that the foundations were in place before the start of the production intent design phase.

In addition to being a technology showcase, it was important that C-X75 delivered ride, handling and refinement befitting to the Jaguar brand. Delivering this would require the highest performance from the suspension, steering and powertrain mounting systems, achieved within minimum weight and time constraints.

The unique nature of the C-X75 powertrain and chassis composite structure meant that traditional attribute mule evaluation of the suspension targets would not be practical, and the first evaluation drive would not occur until a complete prototype was finished.

To give confidence in achieving the desired performance Lotus leveraged it’s supercar vehicle dynamics experience and employed their virtual benchmarking and target cascade process to validate kinematics and compliance attribute targets through virtual comparison with suitable benchmarks in Lotus RAVEN vehicle simulation software.

Lotus utilised its SHARK interactive simulation tool to achieve rapid development of the suspension and steering system geometries. Alternative system types were quickly evaluated and optimised within the vehicle package, enabling robust system selection decisions at the early concept stage.

The various technical challenges offered by the C-X75 programme gave Lotus the opportunity to showcase its knowledge and expertise in chassis and vehicle design while remaining true to one of our core value: “to add speed, add lightness”. From the design and optimisation of the bespoke front push rod suspension system to the exceptional stiffness and compliance compromise of the rear suspension, every single technical aspect has been pushed. Thanks to this approach, Lotus managed to design and deliver a vehicle suspension system that is 10% lighter than the original benchmark target whilst maintaining all other product attributes including stiffness.

The Lotus chassis team also developed innovative mounting systems optimised for the unique C-X75 hybrid powertrain, overcoming the packaging and performance challenges of the front drive motor and rear power unit.

Working closely with all chassis suppliers, using Lotus’s robust product development process and adopting a cross-functional approach to vehicle design were key factors to the on-target and on-time delivery of the C-X75 chassis systems.

Lotus’s experience of delivering projects across the globe for a wide range of OEMs allowed them to be flexible, proactive and responsive to change. These elements definitely helped in building a strong and successful relationship with Jaguar, Williams Advanced Engineering and other partners involved in the C-X75 programme.”

Everyone at Lotus was extremely proud of the achievement and realised that this would have never been possible without the full commitment of every single member of the chassis team.

Jag_C-X75_Image_10_270613

The story from the engine management team

Working closely with the engine developers, Lotus engineered a system that would be capable of meeting the control demands of the engine. Whilst a motorsport ECU solution could have been developed to support the initial demonstration phase, the Lotus solution was to build the required control system on an already proven production platform, assuring compliance with the emissions, diagnostic and quality standards required for a low volume production vehicle.

The C-X75 program required a sophisticated control system. The system controlled 2 throttle bodies and a supercharger bypass (effectively a third throttle), the supercharger clutch, turbocharger wastegate, the port and direct injectors, fuel pumps and pressure regulation (for the two systems), intake swirl flaps, twin cam phasers and an exhaust silencer bypass. The system was also protected for Secondary Air Injection (using the supercharger as a pump) and emissions control.

Because the Lotus EMS systems solution is developed in house we were able to react quickly to changing project requirements. An example of this was the addition of functions to limit engine speed and torque at cold oil/coolant temperatures, protecting the engine and prolong the life of development engines. This was achieved through the use of model based software with timescales from request to implementation measured in days rather than the normal weeks or months normally required.

Although the engine and initial calibration met all of the torque and power targets Lotus, working in conjunction with the engine design partner, were able to increase the low and mid speed torque above target levels whilst respecting the cylinder pressure limits which assured engine durability.

Calibration of the complex system and its interactions provided significant challenges, and Lotus used its facilities along with those at Jaguar to optimise performance, fuel consumption and emissions. Those used included the test track, dyno and emissions labs at Hethel. Significant use of cylinder pressure acquisition equipment was used in the calibration process for both basic setting optimisation and calibration of the full torque structure.

A major challenge was the management of the supercharger clutching. The supercharger is required at low engine speeds to meet the torque targets; it also needs to be clutched out at higher speeds, where the supercharger would otherwise over-speed. Lotus implemented various control strategies and techniques to manage the re-clutching of the supercharger in a way to optimise drivability.

The vehicle platform is a full hybrid system, the task for the engine was to deliver the torque requested by the vehicle’s hybrid controller. As there is no physical link between the accelerator pedal and the engine, the engine control is managed purely through torque requests behaving as a slave module to the vehicle controller.

In addition to engine calibration and development at Hethel, Lotus also supported transient development on the dyno at Gaydon. This facility allowed the transmission, rear motor, vehicle controller and engine management system to be developed and proven before the first application in the vehicle. Lotus worked closely with William’s vehicle control engineers to develop vehicle launch, gear shift and dynamic response on this rig before ramping up to the aggressive vehicle tests.

Lotus also provided significant support to vehicle testing and development and, although the EMS system was proven to be reliable throughout the vehicle development phase, Lotus were able to assist with rapid diagnosis of development issues thanks to the diagnostic functions carried over from the Lotus production control system.

The success of the program is measured not only in the phenomenal performance of the engine and vehicle, but also in the delivery of an extremely technically challenging project on time and within budget. Lotus is very proud to have supported the development of one of history’s highest specific power output engines, 313 bhp per litre and to have provided an engine control system capable of not only producing this level of performance but also to have produced a system which produced the prototype vehicles with a good level of refinement and driveabilty.

C-X75 delivered

The combined, collaborative project team delivered an outstanding fleet of five prototype supercars that has showcased many of UK car industry capabilities.

This car exceeded the expectations of many and proved throughout its development and public appearance phase to be an effective and robust demonstration of the exceptional capabilities. One of the key moments for the C-X75 was being driven up the hill with the legends at the Goodwood Festival of
Speed in June 2013. Simon Newton was privileged to be the driver.

During the Silverstone C-X75 team event in April 2013, hosted by Jaguar and Williams Advanced Engineering, Lotus were recognised by Bob Joyce, Jaguar Engineering Director, as one of the major contributors to the programme. Key points being strengths in utilising experience and, knowledge, producing high quality of work, delivered with effective communication and management.

Writers: Andy Green, Steve Williams, Fabien Dall'ara, Gareth Jones and Roger Tudor

About lotusproactive

Lotus proActive is an e-magazine published quarterly by Lotus Engineering, covering engineering articles, industry news and articles from within Group Lotus (Cars, Engineering, Originals and Racing).

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