A collaboration between Lotus Engineering and Fagor Ederlan will develop the Lotus Range Extender Engine for series production.

Lotus Engineering, the automotive consultancy division of Lotus Cars Limited,  and Fagor Ederlan, part of the Mondragon Corporation Cooperativa, the biggest co-operative group in the world, have completed a joint technical and market study analysing the best route to production for the Lotus Range Extender Engine. The study has culminated with an agreement for Lotus Engineering to develop the engine for series production and sale by Fagor Ederlan for the global automotive market.

The three-cylinder, 1.2 litre Range Extender engine from Lotus Engineering has been designed specifically for series hybrid vehicles and the production engine will offer a fast route to market for manufacturers wanting to source a dedicated range extender. The high efficiency, low mass design will enable low emissions vehicles to be produced cost effectively across a wide range of hybrid vehicle applications, as already demonstrated in both the Lotus Evora 414E Hybrid and the PROTON Emas concepts, which were shown at the 80th International Geneva Motor Show this year.

Lotus Engineering designed, lighter weight 2020 Toyota Venza

Lotus Press Release and full report below

• Study by Lotus Engineering concludes that a vehicle mass improvement of 38% versus a conventional mainstream vehicle can be achieved at only 3% cost.
• Efficient design and lightweight materials significantly reduce CO2 emissions.

Lotus Engineering has conducted a study to develop a commercially viable mass reduction strategy for mainstream passenger vehicles. This study, released by the International Council on Clean Transportation, focused on the use of lightweight materials and efficient design and demonstrated substantial mass savings. When compared with a benchmark Toyota Venza crossover utility vehicle, a 38% reduction in vehicle mass, excluding powertrain, can be achieved for only a 3% increase in component costs using engineering techniques and technologies viable for mainstream production programmes by 2020. The 2020 vehicle architecture utilises a mix of stronger and lighter weight materials, a high degree of component integration and advanced joining and assembly methodologies.

Based on U.S. Department of Energy estimates, a total vehicle mass reduction of 33% including powertrain, as demonstrated on the 2020 passenger car model, results in a 23% reduction in fuel consumption. This study highlights how automotive manufacturers can adopt the Lotus philosophy of performance through light weight.

Dr Robert Hentschel, Director of Lotus Engineering said: “Lighter vehicles are cleaner and more efficient. That philosophy has always been core to Lotus’ approach to vehicle engineering and is now more relevant than ever. Lightweight Architectures and Efficient Performance are just two of our core competencies and we are delighted to have completed this study with input from the National Highway Traffic Safety Administration and the U.S. Environmental Protection Agency to provide direction for future CO2 reductions. We believe that this approach will be commonplace in the industry for the future design of vehicles.”

The study investigated scenarios for two distinct vehicle architectures appropriate for production in 2017 and 2020. The near-term scenario is based on applying industry leading mass reducing technologies, improved materials and component integration and would be assembled using existing facilities. The mass reduction for this nearer term vehicle, excluding powertrain, is 21% with an estimated cost saving of 2%.

A benchmark Toyota Venza was disassembled, analysed and weighed to develop a bill of materials and understand component masses. In developing the two low mass concepts, Lotus Engineering employed a total vehicle mass reduction strategy utilising efficient design, component integration, materials selection, manufacturing and assembly. All key interior and exterior dimensions and volumes were retained for both models and the vehicles were packaged to accommodate key safety and structural dimensional and quality targets. The new vehicles retain the vision, sight line, comfort and occupant package of the benchmarked Toyota Venza.

Darren Somerset, Chief Executive Officer of Lotus Engineering Incorporated, Lotus’ North American engineering division which led the study, said “A highly efficient total vehicle system level architecture was achieved by developing well integrated sub-systems and components, innovative use of materials and process and the application of advanced analytical techniques. Lotus Engineering is at the forefront of the automotive industry’s drive for the reduction in CO2 and other greenhouse gas emissions and this study showcases Lotus Engineering’s expertise and outlines a clear roadmap to cost effective mass efficient vehicle technologies.”

The 2020 Passenger Car Technical Detail

Body
The body includes the floor and underbody, dash panel assembly, front structure, body sides and roof assembly. The baseline Toyota Venza body-in-white contained over 400 parts and the revised 2020 model reduced that part count to 211. The body-in-white materials used in the baseline Venza were 100% steel, while the 2020 model used 37% aluminium, 30% magnesium, 21% composites and 7% high strength steel. This reduces the structure mass by 42% from 382 kg to 221 kg.

The low mass 2020 body-in-white would be constructed using a low energy joining process proven on high speed trains; this process is already used on some low volume automotive applications. This low energy, low heat friction stir welding process would be used in combination with adhesive bonding, a technique already proven on Lotus production sports cars. In this instance, the robotically controlled welding and adhesive bonding process would be combined with programmable robotic fixturing, a versatile process which can be used to construct small and large vehicles using the same equipment.

Closures/Fenders
The closures include all hinged exterior elements, for example, the front and rear doors and the rear liftgate. One alternative approach included fixing the primary boot section to improve the structure, reduce masses and limit exposure to high voltage systems. A lightweight access door was provided for checking and replacing fluids.

The closures on the baseline Toyota Venza were made up of 100% steel. The low mass Venza closures/fenders would be made up of 33% magnesium, 21% plastic, 18% steel, 6% aluminium with the other 22% consisting of multiple materials. The mass savings are 41%, a reduction from 143 kg to 84 kg.

Interior
The interior systems consist of the instrument panel, seats, soft and hard trim, carpeting, climate control hardware, audio, navigation and communication electronics, vehicle control elements and restraint systems. There is a high level of component integration and electronic interfaces replace mechanical controls on the low mass model. For the 2020 model the instrument panel is eliminated replaced by driver and passenger side modules containing all key functional and safety hardware. A low mass trim panel made from a high quality aerated plastic closes out the two modules. The air conditioning module is incorporated into the console eliminating the need for close out trim panels; heated and cooled cupholders are integrated into the HVA/C module. The audio/HVA/C/Navigation touch screen contains the shifter and parking brake functions and interfaces with small electric solenoids. This eliminates conventional steel parking brake and shifter controls and cables as well as freeing up interior space.

The front seats mount to the structural sill and tunnel structure eliminating conventional seat mounting brackets (10 kg) and the need to locally reinforce the floorpan. The composite front seat structure utilises proven foam technology; the seat mass is reduced by up to 50%. The rear seat support structure is moulded into the composite floorpan eliminating the need for a separate steel support structure. The front and rear seats use a knit to shape fabric that eliminates material scrap and offers customers the opportunity to order their favourite patterns for their new vehicle. Four removable carpet modules replace the traditional full floor carpeting; this reduces mass and allows cost effective upgrading of the carpet quality. The floorpan is grained in all visible areas. The 2017 production interior mass was reduced from 250 kg to 182 kg with projected cost savings of 3%. The 2020 production interior mass was 153 kg with projected cost savings of 4%.

Chassis/Suspension
The chassis and suspension system was composed of suspension support cradles, control links, springs, shock absorbers, bushings, stabilizer bars and links, steering knuckles, brakes, steering gearbox, bearings, hydraulic systems, wheels, tires, jack and steering column.

The chassis and suspension components were downsized based on the revised vehicle curb weight, maintaining the baseline carrying capacity and incorporating the mass of the hybrid drive system.

The total vehicle curb weight reduction for the 2020 vehicle was 38%, excluding the powertrain. Based on the gross vehicle weight, which includes retaining the baseline cargo capacity of 549 kg and utilising a hybrid powertrain, the chassis and the suspension components were reduced in mass by 43%, with projected cost savings of 5%.

Front and Rear Bumpers
The materials used on the front and rear bumpers were very similar to the existing model to maintain the current level of performance. One change was to replace the front steel beam with an aluminium beam which reduced mass by 11%. The use of a magnesium beam was analysed but at the current time exceeded the allowable price factor.

Heating, Ventilation and Air Conditioning
The air conditioning system was integrated into a passenger compartment system and an engine compartment system. This section addressed the under hood components which included the compressor, condenser and related plumbing. The under hood components were investigated for technologies and mass.

The study showed a relatively small mass difference for the underhood air conditioning components based on both vehicle mass and interior volume. Because of the highly evolved nature of these components, the requirements for equivalent air conditioning performance and the lack of a clear consensus for a future automotive refrigerant, the mass and cost of the Toyota Venza compressor, condenser and associated plumbing were left unchanged for both the 2017 and 2020 models.

Glazing
The glazing of the baseline vehicle was classified into two groups: fixed and moving. The fixed glass is bonded into position using industry standard adhesives and was classified into two sub groups: wiped and non wiped.

Factors involved in making decisions about glazing materials include the level of abrasion it is likely to see during the vehicle life, the legislative requirements for light transmissibility, the legislative requirements for passenger retention and the contribution it will make to interior noise abatement.

The specific gravity of glass is 2.6 and the thickness of a windshield is usually between 4.5 mm and 5 mm, therefore the mass per square metre of 5 mm glass is approximately 13 kgs. The high mass of glass provides a strong incentive to reduce the glazed area of the body, reduce the thickness of the glass and find a suitable substitute that is lighter. Fixed glass on the side of the vehicle offers the best opportunity for mass reduction.

The mass of the baseline glazing was retained for both the 2017 and 2020 models; this was a conservative approach. It is possible that coated polycarbonate materials may become mainstream in the 2017 – 2020 timeframe for fixed applications.

Electrical/Lighting
The estimated mass savings for using thinwall cladding and copper clad aluminium wiring, as used on the 2017 model was 36% versus the baseline model. The lighting technologies section reviewed included diodes, xenon and halogen. The study also reviewed a variety of wireless technologies under development for non-transportation applications that could be used in this time period pending successful development for mobile applications.

63 page PDF detailing the VVA platform

The Versatile Vehicle Architecture (VVA), used on the Lotus Evora, is a low volume evolution from the architecture used on the Lotus APX concept and allows for the development of a range of vehicles up to a gross vehicle weight of 1,900 kg. This VVA approach has been designed to be applicable to low and mid-volume applications by utilising low capital investment manufacturing processes. It progresses the Lotus technology from the Elise family of vehicles, using bonded extrusions and folded panels, whilst now incorporating contemporary ease of ingress/egress, build modularity and improved, lower cost repairability.

[Source: The Lotus Forums]

Lotus Range Extender

News from Autocar today reports that Lotus Engineering is putting the wheels in place for mass production of the Lotus Range Extender.

Series hybrids and the Lotus Range Extender

More on the Lotus Range Extender

Negotiations with an unnamed supplier are underway to produce the engine.

While this supplier does not currently manufacture internal combustion engines, plans call for 50,000 units per annum for several auto manufacturers interested in incorporating the Lotus Range Extender in extended-range electric models.

Autocar has also quoted Lotus management as saying the Evora 414E Hybrid’s technology is “very close to being production possible”.

Proton EMAS Concepts

Proton Press Release

PROTON Showcases Concept Global Car Series at Geneva Motorshow

GENEVA, Switzerland, 2 March, 2010 – Malaysian car manufacturer PROTON today unveiled a series of concept global cars at the prestigious 80th International Geneva Motor Show. The three concept global cars – EMAS, EMAS Country and EMAS3 – signal PROTON’s long-term plan to expand its footprint in the global automotive market.

EMAS – which means gold in the Malay language – stands for Eco Mobility Advance Solution, and is a result of the joint collaboration between PROTON, its subsidiary Lotus, and Italian design house, Italdesign Giugiaro (IDG).

The cars were unveiled at IDG’s booth by PROTON Advisor and former Prime Minister of Malaysia Tun Dr. Mahathir Mohamad and will be displayed throughout the exhibition from 4th to 14 March 2010. PROTON Holdings Berhad Chairman Dato’ Mohd. Nadzmi Mohd. Salleh and Group Managing Director Dato’ Haji Syed Zainal Abidin Syed Mohamed Tahir as well as Italdesign Giugiaro Chairman Giorgetto Giugiaro and Co-Chairman Fabrizio Giugiaro were present to witness the unveiling.

Speaking on the collaboration with IDG, Dato’ Mohd. Nadzmi said, “We constantly strive to acquire and jointly develop new knowledge, skills and technologies that will ultimately benefit our customers. While we continue to gain progressive technology from our subsidiary Lotus, our design collaboration with IDG will further strengthened our position within the global automotive industry.”

He added that PROTON wanted to work with the best and IDG topped other styling and design houses with their credibility and flair. “We undertook a careful process of benchmarking and a thorough point-by-point analysis of strengths and weaknesses in our decision. With IDG, we have good design and more, as they would contribute in our brand-building initiatives as well as provide knowledge-transfer to accelerate our learning curve in car design.”

Dato’ Syed Zainal Abidin said that the EMAS concept global car project signifies PROTON’s “golden” opportunity to stand in competence with the global automotive market.

“The unveiling of the concept cars today reflects the long-term strategy we have in matching global automotive standards as we expand and reinforce our presence worldwide.”

Dato’ Syed Zainal Abidin pointed out that the concept cars are the yardstick to gauge public opinion. “We strive to listen to our customers to ensure the development of a global car that meets customer’s requirements and expectations. The aim is to produce the global car for world market in the future,” he said.

The PROTON Concept car, to be unveiled at the Geneva Motor Show, showcases an advanced series hybrid drivetrain, designed and developed by Lotus Engineering.

Lotus Engineering, the world-renowned automotive consultancy division of Lotus Cars Limited today announces its latest series hybrid vehicle technology application in the PROTON Concept, which will be unveiled at the 80th International Geneva Motor Show. The complete hybrid drivetrain in the PROTON Concept city car has been developed by Lotus Engineering and it includes the Lotus Range Extender engine, designed specifically for series hybrid vehicles.

The PROTON Concept, a plug-in series hybrid city car, has been styled by Italdesign and will be unveiled on the Italdesign stand at the Geneva Motor Show. Lotus Engineering has designed and integrated the complete drivetrain, including the electrical drive system with single-speed transmission, which delivers low emissions, optimised performance and acceptable electric-only operating range for city use. For longer journeys, when the battery charge level falls, the 3 cylinder, 1.2 litre Lotus Range Extender engine is used to replenish the charge in the battery and provide electrical power for the drive motors. The battery can also be recharged via an AC mains domestic outlet to achieve initial electric-only operation.

Dr Robert Hentschel, Director of Lotus Engineering said: “The hybrid drivetrain of the PROTON Concept is another example of Lotus Engineering’s expertise in electrical and electronic systems and efficient performance engines. The high efficiency Lotus Range Extender engine, which we unveiled to great acclaim at the IAA Frankfurt Motor Show last year is perfectly suited for the advanced series hybrid we have created for the PROTON Concept city car.  It is an exciting example of the diverse range of highly efficient total propulsion systems that Lotus Engineering continues to develop for its partners and clients.”

PROTON Holdings Berhad Group Managing Director, Dato’ Haji Syed Zainal Abidin Syed Mohd Tahir said, “Our collaboration with Lotus and Italdesign on progressive technology and design will further propel our competitiveness in the world market. Through this association, we strive to acquire and jointly develop new knowledge, skills and technologies that will ultimately benefit our customers.”

[Source: Lotus]

Larger version

The Lotus Omnivore engine is a flex-fuel 2-stroke HCCI engine concept design to maximise fuel efficiency on renewable fuels or gasoline.

The Omnivore engine concept features an innovative variable compression ratio system and uses a two-stroke operating cycle with direct fuel injection. It is ideally suited to flex-fuel operation with a higher degree of optimisation than is possible with existing four-stroke engines.

Key Features of Lotus Omnivore Engine

Monoblock

The engine concept features a monoblock construction that blends the cylinder head and block together eliminating the need for a cylinder head gasket, improving durability and reducing weight. In this case, the application of a monoblock is facilitated by the absence of the requirement for poppet valves. A novel charge trapping valve in the exhaust port allows asymmetric timing of exhaust flow and continuous variation of the exhaust opening timing.

Direct Injection

The Omnivore engine uses the Orbital FlexDI fuel injection system which produces fine in-cylinder fuel preparation irrespective of fuel type and, together with air pre-mixing, allows efficient two-stroke combustion and low-temperature starting, whilst offering singular opportunity for advanced HCCI control.

Variable Compression Ration

The variable compression ratio is achieved by the use of a puck at the top of the combustion chamber. This simple, yet effective system moves up and down effecting the change in geometric compression depending on the load demands on the engine.

[Source: Lotus Engineering]

Dr. Robert Hentschel - Director of Lotus Engineering

Lotus Press Release

Lotus Engineering starts the New Year strongly, announcing significant new contracts and welcoming a new Director of Lotus Engineering.

Major new projects with three Chinese clients ensure an excellent start to 2010 for Lotus Engineering, the automotive consultancy and technology division of Lotus Cars Limited. These projects result in a fourth consecutive year of growth in new orders for Lotus Engineering’s global third party consultancy work, with a quarter of the financial year still to go.

To continue to build on the success of both the Lotus Engineering and Lotus Cars divisions, Lotus has also made changes to the senior management structure. Dr Robert Hentschel joins Lotus as Director of Lotus Engineering. Dr Hentschel’s task will be to lead the expansion of Lotus Engineering’s third party consultancy work and to further develop its position of technology leadership in lightweight architectures, driving dynamics, efficient performance and electrical/electronics. Dr Hentschel will have full responsibility for Lotus Engineering worldwide, reporting to Dany Bahar, CEO of Group Lotus plc. Dr Hentschel brings a wealth of experience from the automotive industry and engineering services sector, most recently from positions at EDAG as Chief Operating Officer for North American operations and previously as Head of the Electrical/Electronics Business Unit.

Paul Newsome, previously Managing Director of Lotus Engineering, takes up a new role as Director of Product Engineering for Lotus Cars to develop an exciting range of new Lotus cars.

Dr Hentschel commented: “This is a fantastic opportunity for me to contribute to the continued success of this outstanding business which boasts talented engineers and an iconic brand. Lotus Engineering has an exceptional heritage with an exciting array of future products, technologies and services that will further enhance its position as a pioneer in the new automotive era. Our key areas of expertise allow us to deliver exciting vehicles and sustainable transport solutions that are exactly aligned to the needs of the global automotive industry.”

[Source: Lotus]

Lotus dual-clutch gearbox

Lotus has submitted a patent application for a more compact, lighter, and less complex dual-clutch transmission.

While the patent application was submitted by Lotus Cars rather than Lotus Engineering, sources told Autocar today that the transmission is in fact being developed by Lotus Engineering.

Consequently, Lotus plans to sell the technology to its Lotus Engineering clients as well as fit the gearbox in future Lotus models. This explains why patent applications for both FWD and RWD configurations have been submitted.

The unit shown in the patent application is an eight-speed unit with seven forward gears and a reverse gear.

While a production date remains unconfirmed, the lightweight nature of the gearbox will make it a perfect match for the next Elise and broaden that model’s appeal.

Lotus patent abstract

Abstract of WO 2009156744 (A1)
With reference to Figure 2, the present invention provides a transmission unit comprising: a first set of shaft-mounted input gears (206, 207, 208, 209) each of which meshes with a respective one of a first set of shaft-mounted output gears (220, 221, 222, 223); a second set of shaft- mounted input gears (210, 211, 212, 213) each of which meshes with a respective one of a second set of shaft- mounted output gears (224, 225, 226, 227); a first clutch (215) associated with the first set of input gears (206, 207, 208, 209); and a second clutch (216) associated with the second set of input gears and the second set of output gears (210, 211, 212, 213). At least one of each meshed pair of input and output gears can freely rotate on the shaft on which the gear is mounted and a gear ratio selection mechanism (231) is provided to select a gear ratio by locking a freely rotatable gear to the shaft on which the gear is mounted. In use of ‘the transmission unit (200) either the first clutch (215) is engaged and the second clutch disengaged (216) and drive is transmitted via a selected pair of the first set of input and output gears or the second clutch (216) is engaged and the first clutch (215) disengaged and drive is transmitted via a selected pair of the second set of input and output gears.

[Source: @RacingPuma, Autocar]

Initial phase of Omnivore development achieves 10% improvement in fuel consumption compared to stratified direct injection engines, also with ultra low emissions. The research signals a potential paradigm shift with engine ‘upsizing’ for increased fuel economy.

The first testing phase of Lotus Engineering’s Omnivore variable compression ratio, flex-fuel direct injection two-stroke engine has been successfully completed on gasoline. In addition to exceptional fuel consumption results, the engine has successfully demonstrated homogenous charge compression ignition (HCCI) – where the engine operates without the need for the spark plug to ignite the fuel and air mixture in the cylinder – down to extremely light loads. Traditionally, this has been challenging but this combustion process results in ultra low emissions and has been achieved over a wide range of engine operating conditions, even from cold start.

The detailed research has so far focused on lower speed and load conditions that represent a major proportion of an engine’s operation in a real world environment. At 2000rpm and up to approximately 2.7 bar IMEP (Indicated Mean Effective Pressure), the ISFC (Indicated Specific Fuel Consumption) achieved is approximately 10% better than current spray-guided direct injection, spark ignition engines. Emissions results are an impressive 20 ppm NOx at less than 2.3 bar load and has four-stroke-equivalent hydrocarbons and carbon monoxide emissions.

Simon Wood, Technical Director of Lotus Engineering said: “These impressive results represent an important step-forward in Lotus Engineering’s strategy of developing an array of more efficient multi-fuel combustion systems. Omnivore lays the foundations for a novel and pragmatic vision of a variable compression ratio engine concept suitable for production. A multi-cylinder version is practical for a wide variety of vehicles and offers greatest benefit to C and D class passenger cars which can take advantage of the low cost architecture and significantly improved fuel economy and emissions. We are continuing our discussions with other manufacturers and eagerly anticipate the development of multi-cylinder demonstrations of this revolutionary engine configuration.”

The Omnivore engine concept achieves wide-range HCCI combustion and low CO2 emissions through the application of a simple wide-range variable compression ratio mechanism, itself facilitated by the adoption of the two-stroke operating cycle. Technologies combined in this package are all synergistic and provide a route to the efficient use of alternative fuels, accelerating the displacement of fossil fuels.

Jamie Turner, Chief Engineer of Powertrain Research at Lotus Engineering said: “The automotive industry, including Lotus Engineering, has quite rightly advocated engine downsizing for four-stroke engines. This is as a result of the dominance of the four-stroke cycle in the automotive world and its generation of throttling losses at part-load, where vehicles run most of the time. The two-stroke cycle, conversely, does not suffer from significant throttling losses and in many ways is a more natural fit for automotive use. With the thermodynamic disadvantages of throttling losses removed, the two-stroke engine is free to be sized according to its improved part-load fuel consumption. Downsizing therefore isn’t vital and, due to the improved light-load efficiency and emissions performance we see with Omnivore, this technology approach and ‘upsizing’ could permit a more efficient engine.”

The initial Omnivore programme has been in collaboration with Queen’s University Belfast and Orbital Corporation Limited Australia, with sponsorship from DEFRA/DECC and DOE NI through the Renewables Materials LINK programme. Future work by Lotus Engineering will concentrate on further investigating the operation on gasoline and alternative renewable fuels such as ethanol and methanol, with more in-depth analysis of specific test points.

Technical Detail

Omnivore Summary

The Omnivore engine concept features an innovative variable compression ratio system and uses a two-stroke operating cycle with direct fuel injection. It is ideally suited to flex-fuel operation with a higher degree of optimisation than is possible with existing four-stroke engines.

The engine concept features a monoblock construction that blends the cylinder head and block together eliminating the need for a cylinder head gasket, improving durability and reducing weight. In this case, the application of a monoblock is facilitated by the absence of the requirement for poppet valves. A novel charge trapping valve in the exhaust port allows asymmetric timing of exhaust flow and continuous variation of the exhaust opening timing.

The Omnivore engine uses the Orbital FlexDI fuel injection system which produces fine in-cylinder fuel preparation irrespective of fuel type and, together with air pre-mixing, allows efficient two-stroke combustion and low-temperature starting, whilst offering singular opportunity for advanced HCCI control.

The variable compression ratio is achieved by the use of a puck at the top of the combustion chamber. This simple, yet effective system moves up and down effecting the change in geometric compression depending on the load demands on the engine.

Engine Concept Features

Monoblock

The monoblock incorporates the cylinder head, the cylinder barrel and the inlet ports, together with mounts for the variable compression ratio system and the charge trapping valve housing. It also contains the non-moving location of one of the two possible injector mounting positions provided for research purposes. The other injector position is in the variable compression ratio puck. The monoblock is mounted on the upper crankcase, which is a common component with all of Lotus’ single-cylinder research engines. The engine carries a full primary and secondary balancer system. The monoblock is water-cooled by an electric water pump.

Computational fluid dynamics is used extensively to ensure effective cooling of the monoblock, a feature assisted by the removal of the cylinder head gasket, inherent in such architecture. The chief advantage of a monoblock construction in any engine, aside from the bill of materials and assembly benefits, is the reduction of bore distortion afforded by the removal of cylinder head bolts. This is especially important in piston-ported 2-stroke engines.

Variable Compression Ratio Mechanism

The primary component of the variable compression ratio mechanism is what is termed the ‘puck’, or a moveable junk piston in the cylinder head. In the case of the research engine, this puck is driven in and out by a double-eccentric mechanism itself comprising proprietary parts. The puck itself does not move at engine speed. In addition to the spark plug, the puck carries one of two possible injector positions. It is water-cooled and carries simple piston (or ‘junk’) rings for primary sealing, and an ‘O’-ring towards the top for final sealing.

The variable compression ratio system is controlled by an electric motor and worm drive arrangement at the front of the engine. Because there are no poppet valves in the engine, it is clear that the puck could be of a large diameter and since there is no need for valve cut-outs in the piston crown, the minimum volume of the combustion chamber can be much smaller than has been the case in variable compression ratio engines shown to date. When the puck is in its innermost position, its surface is essentially coincident with that of the combustion chamber squish band and this yields the highest compression ratio of 40:1.

The combustion chamber geometry necessarily alters as the puck is moved to vary the compression ratio. The chamber geometry in Omnivore was therefore chosen on the basis of 2-stroke experience in spark ignition operation. Consequently, the puck is positioned in the cylinder head in such a way that the non-moving squish band directs cooling flow towards the spark plug. The puck is water-cooled from the main engine cooling circuit.

Charge Trapping Valve

The charge trapping valve is caused to oscillate by a short articulated connecting link from an engine-speed eccentric shaft itself rotated by a belt drive from the crankshaft. A simple charge trapping valve mechanism provides for asymmetric exhaust timing and hence a modification of the original piston-ported two-stroke operating cycle. Fitting an articulated link between the eccentric shaft and the trapping valve actuating arm affords the opportunity independently to vary the opening and/or closing point. In this ‘variable’ form, at light load, the charge trapping valve can be made to control exhaust port opening, to maximize expansion in the cylinder, and the blowdown period can be optimised. The position of the control arm is controlled by the engine management system. All charge trapping valve components and their configuration have been analysed kinematically, and since they operate with modified simple harmonic motion, they do not suffer from jerk stresses.

Other Components

The cranktrain of the engine comprises an 86 mm stroke crankshaft, a trunk piston of 86 mm bore and a connecting rod with 195.5 mm between centres.  The piston carries four piston rings: two pegged half-keystone compression rings which traverse the ports in the upper section, and a Napier scraper ring and U-Flex oil control ring in separate grooves in the lower portion. These are not pegged since they do not have to traverse the ports. In this manner, the working chamber is completely sealed from the crankcase and hence wet-sump lubrication can be employed.

Since this is a research engine, it is cooled by an electric water pump with a separate electrically-driven oil pump used for lubrication. Scavenge air is provided externally.  For convenience, air for the Orbital air-assist DI system is provided from the factory air supply regulated to 6.5 bar maximum air delivery pressure.  Note that in any multi-cylinder application it is envisaged that all these subsystems would be incorporated into the engine in the normal manner.

Technical Specification

Indicated Specific Fuel Consumption comparison between Omnivore  and leading Homogeneous GDI and Spray Guided GDI engines

References

1.         Coltman, D., Turner, J.W.G., Curtis, R., Blake, D., Holland, B., Pearson, R.J., Arden., A. and Nuglisch, H.
Project Sabre: A Close-Spaced Direct Injection 3-Cylinder Engine with Synergistic Technologies to achieve Low CO2 Output
SAE paper number 2008-01-0138

2.         P. Luckert, A. Waltner, E. Rau, G. Vent and U. Schaupp
The new V6 gasoline engine with direct injection by Mercedes-Benz. MTZ Vol 67, 11/2006 Pages 830 – 840

[Source: Lotus]