British Racing (Very) Green Lotus
August 24, 2006 Lotus has always danced to a different drum. When the rest of the world was building muscle cars in the sixties and seventies, it went the other way. Light weight, superb handling, miniscule frontal areas and svelte aerodynamic efficiency became the hallmarks of Lotus roadsters which always did more with less. Now the Lotus brand is further extending its values towards the responsible use of resources with the Lotus Exige 265E which runs on environmentally friendly bio-ethanol E85 - 85% ethanol alcohol and 15% petrol! As the Exige uses a supercharged and intercooled engine, Lotus engineers saw the opportunity to prove the point that green sportscars can offer high performance by exploiting the performance characteristics of ethanol. Ethanol has a high octane rating, which allows an optimum timing for engine ignition and has a fast flame speed in the combustion chamber, so the fuel burns faster, increasing the efficiency of the engine. Ethanol has less stored energy per unit volume than gasoline so the fuel economy is less, however as E85 ethanol is 85% sourced from renewable bio matter, there is a net reduction in carbon dioxide (CO2). The beauty of using ethanol though, is its ability to produce more power in the engine than with conventional petrol and the Exige 265E is the most powerful road Exige ever. The Exige 265E now produces 264 bhp at 8000 rpm (up 21% over the petrol Exige S), and 184 lbft of torque at 5500 rpm (up 16%). The performance figures are pretty healthy for a green machine: 0-60 mph in 3.88 seconds, 0-100 mph in 9.2 seconds and a top speed of 158 mph!
The research vehicle is a true Lotus (it weighs just 930 kg unladen) and is called the Lotus Exige 265E. 265 indicates the approximate horsepower and is consistent with the naming strategy of other one-off and limited run Lotus variants such as the Lotus Sport Exige 240R; the E indicates the environmentally favourable bio-ethanol E85 fuel (85% ethanol alcohol and 15% petrol / gasoline) that powers this extremely high performing sportscar. Key to this performance is a slightly modified version of the 2ZZ VVTL-i supercharged and intercooled high revving 4-cylinder engine from the standard Lotus Exige S. This now gives an estimated set of performance figures that would thrash the majority of “Super-Unleaded” performance cars: 0-60 mph in 3.88 seconds, 0-100 mph in 9.2 seconds and a top speed of 158 mph! In fact, the Lotus Exige 265E is probably the world’s quickest road-legal E85 bio-ethanol car.
Key changes have been made to the fuel system, the engine calibration and the four fuel injectors mounted on the inlet manifold have been enlarged. Two additional fuel injectors have been fitted at the supercharger inlet to increase the amount of fuel being injected in to the engine under higher engine loads and to further cool the charge air prior to combustion.
What is Bio Ethanol E85?
Bio-ethanol E85 is a fuel which is a mixture of 85% ethanol (an alcohol) and 15% petrol / gasoline. The bio-ethanol can be made from bio-mass plant crops such as cereals, sugar beet, sugar cane and wood. As these plant crops grow, they absorb carbon dioxide from the atmosphere, which then partly offsets the carbon dioxide (CO2) emissions produced during the burning of the bio-ethanol fuel in the car’s engine.
Different bio-fuels were considered for this research project, bio-methanol, bio-ethanol and biobutanol. E85 bio-ethanol was the finally chosen as the fuel as its characteristics allowed the engineering project team to enhance the engine performance. The fact that this vehicle uses a pressure charged engine provided even more opportunity to exploit the performance characteristics of a high-octane fuel. Ethanol has a high octane rating, which allows an optimum timing for engine ignition and has a fast flame speed in the cylinder, so the fuel burns faster, increasing the efficiency of the engine.
The beauty of ethanol is its ability to produce more power in the engine than with conventional petrol / gasoline fuel. The Lotus Exige 265E now produces 264 hp (197 kW, 268 PS) at 8000 rpm, and 184 lbft (249 Nm) of torque (at 5500 rpm), up by 46 hp (34 kW, 47 PS) or 21% and 25 lbft (34 Nm) or 16% over the standard petrol / gasoline Exige S. With the total weight of approximately 930 kg (unladen), the power to weight is approximately 283 hp / tonne (211 kW / tonne, 287 PS / tonne).
Ethanol has less stored energy per unit volume than gasoline so the fuel economy is less, however as E85 ethanol is 85% sourced from renewable bio matter, there is a net reduction in carbon dioxide (CO2). Geraint Castleton-White, Head of Powertrain for Lotus Engineering explains the rationale behind the Lotus Exige 265E technical demonstrator: “We wanted to prove the point that green sportscars can also be very high performing sportscars. The fact that we have produced a research version of the Exige that is more powerful than the standard road car is a testament to the benefits of going green. We are also pleased that this vehicle demonstrates our engineering capabilities, our understanding of flex fuel vehicles and our knowledge of emerging fuel technologies. It also promotes bio-ethanol as a fuel of choice for the enthusiastic driver as well as the environmentally conscious driver.
Mike Kimberley, Chief Executive of Group Lotus explains the Lotus ‘Green Strategy’: ”Lotus Engineering is actively pursuing technologies that will improve the efficiency and environmentally friendliness of engines in the future. Carbon dioxide reduction is a priority, as is anything that can reduce our reliance on fossil fuels. We are one of the world leaders in powertrain engineering especially in the internal combustion sector and we are researching into all areas of alternative and conventional fuels to get greater efficiencies, power, performance and reduce net emissions and Bio Ethanol research is one area where we are expert. The problems that are facing the automotive industry at the moment are challenging, and these solutions fit with the Lotus culture and expertise.”
Mike Kimberley continues: “We have decided to develop a thorough understanding of the techniques and technologies of what alternative fuels can achieve, to produce vehicles that are both fun to drive and environmentally friendly. We are also working, globally, on hybrid and electric vehicles together with governments and universities and as an engineering organisation we have a duty and a desire to promote these ideas to a worldwide customer base.”
Rapid Project Delivery for a Rapid Car!
The final sign-off test drive was completed just 5 weeks after the project was instigated and has resulted in a demonstration vehicle that not only excites the driver but also is at the forefront of environmentally friendly vehicles.
The next phase for the vehicle is to upgrade the calibration to a flex fuel spec to allow use with initially gasoline, followed by the possibility of a multi fuel flex calibration to use fuels such as bio-methanol and bio-butanol in addition to the conventional gasoline / petrol and bio-ethanol. The Lotus Exige 265E is purely a research vehicle for Lotus Engineering and Lotus does not intend to put the car into production or sell aftermarket kits for Lotus Cars.
The Lotus philosophy is all about performance through light weight. The Exige 265E is built to the lightest specification possible without resorting to expensive and rare materials normally found in the rarefied environment of Formula One or Aerospace Industries where weight reduction is often considered more important than cost. The performance improvements of using bio ethanol have been made through increasing the power of the engine without increasing the weight of the engine and therefore the overall weight of the car.
The heart of the Exige 265E is a Roots-type supercharger (with a sealed-for-life internal mechanism meaning that it does not require the use of the engine’s oil) and air to air intercooler attached to the tried and tested 4-cylinder, 1.8 litre 2ZZ-GE VVTL-i engine. Using a development of the supercharger and intercooler package from the Exige S, the Exige 265R has peak power of 264 hp (197 kW, 268 PS) at 8000 rpm, 184 lbft (249 Nm) of torque (at 5500 rpm) up by 46 hp (34 kW, 47 PS) or 21% and 25 lbft (34 Nm) or 16% over the standard gasoline Exige S. Maximum engine speed is 8000 rpm (8500 rpm transient for up to 2 seconds). Ethanol produces more power in the engine than with conventional petrol / gasoline fuel. This is due, in part, to the additional oxygen atom attached to the ethanol alcohol molecule so helping the combustion process in the cylinder to burn more effectively, efficiently and with more power.
The roof scoop ensures that the air-to-air intercooler works as efficiently and effectively as possible in all climates and environments. All charge air ducting has been kept as short as possible with large diameter pipes making sure that the bends in these ducts are not too tight, to the benefit of throttle response and efficiency. The Roots-type Eaton M62 supercharger is run from the crankshaft, and has an integral bypass valve for part load operation. A “Stage One” sports exhaust exits from the centre of the undertray.
The 2ZZ VVTL-i engine has two cam profiles – a high speed cam and a low speed cam. The seamless switch point between these two cams is completely variable depending upon driving conditions and engine load, and the driver will not know which cam is being used at any point. This gives the Lotus Exige 265E a smooth and linear surge of power from idle speeds all the way to the maximum 8500 rpm.
An electronic drive-by-wire throttle ensures the quickest engine response possible whilst keeping the emissions as clean and as low as possible, to meet relevant legislative demands. Four enlarged fuel injectors have been fitted to increase fuel flow into the engine under normal operating conditions. Two additional fuel injectors have been fitted at the supercharger inlet to increase the amount of fuel being injected into the engine under higher engine speeds and loads. This has also enabled the engineering project team to take advantage of ethanol’s higher cooling effect to further cool the charge air prior to combustion, which in turn reduces the amount of power required to operate the supercharger. A true Lotus solution where the ethanol does more than just provide energy for combustion!
The Lotus T4e Engine Management system is used in the Lotus Exige 265E. This engine management system has been programmed to optimise the ethanol in the supercharged and intercooled engine. The lightweight C64 six-speed gearbox is fitted with the closest ratios and gearset afforded by the transmission. The gearbox offers a fast, precise and light gearshift, ensuring drivers have total control and flexibility to apply the power exactly as and when required.
The Lotus Exige 265E uses the same aerodynamic package as the production Exige. Like all Lotus cars, the Lotus Exige 265E isn’t all about straight-line performance. The Lotus Exige 265E is probably the world’s quickest road-legal E85 bio-ethanol car. Not only is the engine important to the performance but also so is the aerodynamic package, which creates 41.2 kg (90.64 lbs) of downforce - 19.3 kg (42.46 lbs) at the front and 21.9 kg (48.18 lbs) at the rear - at 160 km/h (100 mph). This downforce ratio between front (47%) and rear (53%) is balanced and remains constant at the speeds of which the Exige 265E is capable.
This class leading aerodynamic package is provided through the contribution of the following components:· Completely flat underside of the car – provided by the elegantly simple, strong yet light weight extruded and bonded aluminium tub· Anodised rear diffuser which helps promote the “Venturi effect” underneath the car· Deep front splitter, which sits just 108 mm (4.3 inches) from the ground (giving just enough ramp angle clearance) whilst still maintaining the aerodynamic properties and, of course, the aggressive stance.· Fixed rear wing that is set at the optimum 11.5 degree angle for the best compromise between downforce and drag.
The Lotus Exige 265E is built around the revolutionary and award winning extruded and bonded aluminium tub, with a light weight steel rear subframe, as used in the Exige. The chassis tub itself weighs just 68 kg (150 lbs) and has a torsional stiffness of 10,500 Nm per degree.
The body of the Lotus Exige 265E remains unchanged from the Exige as it is already a winning formula that is both effective and stunning to look at.
To further differentiate the Lotus Exige 265E from its production cousins, two bold stripes (in yellow to symbolise the bio-ethanol fuel and green to demonstrate the environmental considerations of the vehicle).
Lightweight Lotus Sport five spoke forged alloy wheels have a slightly wider section, when compared to the standard Exige wheel, to accommodate the optional extra track use only specification slick tyres. These wheels, with Lotus Sport etched on one spoke of each wheel, are painted in “High Power Silver” colour.
Brakes and the Suspension
The brake system has been upgraded to 4-piston AP Racing calipers with sport brake pads and increased diameter 310 mm drilled and vented discs at the front. Brembo single-piston sliding rear calipers with 282 mm diameter discs are fitted at the rear. High grade silicon brake fluid, metal braided brake hoses are all linked to the proven Lotus track tuned servo-assisted fourchannel ABS system that enhances braking performance and minimising stopping distance without taking over from the skill of the driver.
To suit different driving styles and road conditions, the Lotus Exige 265E has been fitted with Ohlins two-way adjustable dampers and ride height adjustment to reduce the ride height from 130 mm to 120 mm and an adjustable front anti-roll bar. An oil “Accusump” is included as an oil reservoir backup for extreme track use. Cornering speeds and the lateral forces generated within the car when driven on the track are far higher than what can be experienced safely on the road and the “Accusump” ensures that, under these extreme conditions, the engine oil pressure remains constant.
A “Stage One” sports exhaust is fitted with the bifurcated exhaust pipes exiting from the centre of the anodised-finish 3-piece rear diffuser. Front driving lamps, twin oil coolers, central door locking, alarm (with immobiliser) and air conditioning (weighing in at a minimal 15 kg, 33 lbs) completes the equipment package.
The unique interior trim takes the black, green and the yellow theme of the exterior paint colours by using predominantly black trim with green and yellow highlights on certain components including the padded leather door inserts and the seats.
Summary of Equipment on Lotus Exige 265E (in addition to the standard equipment on the Lotus Exige):
· Wider section lightweight Lotus Sport 5-spoke alloy wheels painted in “High Power Silver”.· Upgraded brake with 4-piston AP Racing calipers with sport brake pads and 310 mm diameter drilled and vented discs at the front. Brembo single-piston sliding rear callipers with 282 mm diameter discs at the rear, high grade silicon brake fluid and metal braidedbrake hoses.· Ohlins two-way adjustable dampers with ride height adjustment· Adjustable front anti-roll bar· “Accusump” oil reservoir backup· Sports exhaust – “Stage One”· Anodised-finish 3-piece rear diffuser· Front driving lamps· Twin oil coolers· Air conditioning