The challenge of this project consisted of combining engine optimizations (reciprocating gears, cylinder head, etc.) and optimizing the flow of energy between the internal combustion engine and the electric motor. All of the solutions can potentially be carried over to production.

—Julien Lidsky, Manager, 208 HYbrid FE Powertrain, Peugeot Sport

The 3-cylinder engine has undergone several modifications: optimization of the engine operational cycle, reduction of friction losses and thermal management. All of these advances lead to fuel economy improvements by 10% yet with power maintained at 68bhp (50kW).

HYbrid FE concept. Click to enlarge.

The Miller Cycle is accentuated and the compression ratio modified from 11:1 to 16:1 to increase the engine’s thermodynamic efficiency. This can lead to self-ignition of the mixture (or knock), which is potentially destructive. To prevent this, the developers took several actions.

The rate of unburned fuel in the combustion chamber is reduced by valves of increased diameter, redesigned exhaust pipes and manifold, and an adapted valve lift pattern. Furthermore, the heat exchanges are optimized in the cylinder block by means of coolant passages arranged between the cylinders. The coolant now passes through the cylinder head along its entire length to recover the heat around each source: combustion chambers, between injectors and spark plugs.

The engine adopts direct injection. The variable setting at the inlet and at the exhaust extends the range of optimum efficiency to the entire engine speed range, both at full load and partial load.

However, not all of these various developments favor power at high engine speed. So, Peugeot increased the bore and stroke of the engine (75mm x 93mm) for a larger displacement of 1,233 cm³ to maintain 68bhp. This benefits the maximum torque produced, which increases by 25%.

All of the moving components are specific to the 208 HYbrid FE: nitrated steel crankshaft, the titanium con rods and the aluminium-copper alloy pistons. Weight of these is reduced in spite of the increase in capacity; the weight of the con rods and Gudgeon pins is halved.

The friction losses are a challenge as they represent approximately 1/5^th of the power consumed by an engine. On the 208 HYbrid FE, they are reduced by approximately 40% notably by the crankshaft, the pistons and the Gudgeon pins, the piston rings and the camshaft followers. These components are given a diamond-like Carbon coating and are geometrically optimized.

The weight of the cylinder head is halved due to the reduced thicknesses permitted by its design and the characteristics of the aluminium used. The coolant circuit and the inlet line are made by rapid prototyping of resins charged with glass fibres or carbon. To do this, the laser beam of a 3D printer (additive manufacturing) fuses successive layers of aluminium powder. This produces a functional component quickly and more cheaply in the context of individual specialized manufacture.

Produced using the same process, the piston base jets serve here both to cool them on use under load and to heat the oil as quickly as possible on starting.

Transmission. The base of the production piloted manual gearbox is retained for its high efficiency and its integrated actuators. To reduce friction losses, the teeth of the gears are given a tungsten carbide chrome coating.

Greasing was redesigned to reduce the volume of lubricant necessary and prevent splashing over the gears, which also consumes energy. Now, the lubricant is moved to the highest point by the final drive crown wheel before circulating through gravity over the entire mechanism.

The prototype gearbox oil, developed by Total Lubricants, is based on bio-sourced oils, of 75W grade with a very high viscosity index (higher than 250). This produces a 3% reduction in consumption, and becomes a preview of lubricants of the future.

Taken directly from a competition environment, a fluid grease of low density also reduces the quantity deemed necessary. Its longevity is enhanced by operation at a lower temperature due to a reduction in friction and finally, the hub bearings adopt a special fluid grease, which adheres but limits friction losses.

Fuel and lubricant. The 208 HYbrid FE passes the CO₂ emissions cycle with a benchmark Super 95 fuel. Excellium performance additives, developed by Total Additives and Special Fuels, would alone reduce the CO₂ emissions of this engine by more than one additional gram per kilometer.

A special engine oil of extremely low viscosity has been developed by Total Lubricants using ultra-fluid based oils and by the addition of friction reducing agents containing molybdenum. Of grade 0W12, this oil develops its properties very rapidly with a shorter temperature rise time.

Hybridization from motorsports. The electric motor and the battery are those developed for the Peugeot 908 HYbrid4 endurance race car. Weighing 7 kg (15.4 lbs), the electric machine develops 30 kW as a motor and 100 kW as a brake generator. In both modes, its torque reaches a maximum of 30 N·m (22 lb-ft). Proportional to the speed of the vehicle, its maximum speed is 40,000 rpm. The electric motor provides the reverse gear function, by inverting the direction of rotation, and the starter function. It also provides access to all-electric driving.

The Lithium-ion battery pack has a capacity of 0.56kWh; arranged in groups, the pack has the ability to isolate cells if deemed necessary. To ensure that this strategic unit is cooled correctly, Total has developed a special oil for circulating in the dedicated radiator.

Weighing 25kg, it is installed, with the 20-liter fuel tank, on a subframe which is bolted underneath the vehicle directly below the rear bench seat. Hybridization has no effect on the interior packaging, so inside the vehicle passenger space is maintained.

The principle of operation. During deceleration phases, whether by releasing the accelerator pedal or through braking, the vehicle is slowed down primarily by the electric motor. The hydraulic braking only comes into operation at the end of braking phase to maximise the recovery of the energy available. Over one homologation cycle, this recovery is 25%. Then, on acceleration, this energy is returned and assists the petrol engine according to various parameters: acceleration dictated by the driver and the gear selected.

Aerodynamics. The Cd improves by 25%, to a value slightly lower than 0.25. On the body sides, any flow-disrupting components have been eliminated to help improve the aero performance. The tires, specially developed by Michelin, are of the Tall&Narrow type, i.e.: of large diameter and narrow width. They are fitted on 19” alloy wheels on which carbon aerodynamic flaps fill the space between each spoke.

Cameras provide the rear vision, the image being reproduced on board on the interior mirror reminiscent of sporting disciplines like endurance racing. The rear track also contributes to this efficiency by being narrower by 40mm, further reducing the Cd.

The design of the roof extends in an almost horizontal movement leading into the tailgate spoiler. The rear aspect, with chamfered edges, has an air deflector in its lower section. It deflects the airflow which passes under the vehicle without hindrance due to the completely flat floor. To reduce its environmental footprint as much as possible, the LED lamps of the 208 HYbrid FE have thin vertical fins, inspired by the Onyx Supercar Concept. These features minimise the air flow turbulence.

Weight reduction. The production 208 hatchback weighs 975 kg (2,150 lbs). The engineers achieved a 20% reduction on that for the HYbrid FE concept. The 208 HYbrid FE benefits from material innovations developed by the Polymers Division of the Refining-Chemicals department at Total, as well as by its two subsidiaries CCP Composites and Hutchinson.

Taken from the end of the assembly line, the 208 retains its metal structure. Composite components replace bodywork panels and the floor, further reducing the weight of the body shell from 295 (650 lbs) to 227 kg (500 lbs). The one-piece outer skin (weighing 20 kg/44 lbs), the flat base (8 kg/18 lbs), the door panels (2 kg/4.4 lbs) and the lower front panel are made from carbon fibre. The hood (5 kg/11 lbs) and the wings (2.1 kg/4.6 lbs) are constructed from a composite VER/Carbon, a material which is half the weight but with comparable structural properties. It is obtained from a new type of resin which can be used untreated, painted or color-dyed.

With the exception of the door windows, the glazing uses polycarbonate to further save 5 kg (11 lbs). The 208 HYbrid FE innovates in its use as this material has up until now been reserved for headlight lenses. It reduces the weight by more than 50% compared to conventional glass.

Suspension and wheels. The 208 HYbrid FE rests on a novel pseudo MacPherson suspension with a glass-fibre resin composite transverse-located blade. It replaces several components: suspension springs, lower wishbones and anti-roll bar. The front blade also has varying flexibility along its length. Designed and produced by Hutchinson, using these two blades saves 20 kg (44 lbs).

Due to their dimensions, the 145/65 R19 wheels themselves reduce the rolling resistance by 20%. They also require less effort on the steering wheel to direct them, making steering assistance superfluous. The wheels are fitted onto low friction bearings assisted by special Total grease.

The wheel rims house large brake discs 380mm in diameter and 9.6mm thick. They are rigged with two-piston calipers, 44.5mm at the front and 31.8 mm at the rear. On braking, the reduced effort on the pedal and the intervention of the electric motor mean that the supplementary braking assistance can be eliminated.