Lotus Exige (Series 2) 2004-2011

[Gt1Street]

Lotus Engineering, the world renowned automotive consultancy division of Lotus, unveils its latest development towards carbon neutral road transport at the 78th Geneva International Motor Show. The Lotus Exige 270E Tri-fuel is the most powerful road version yet of the Exige (0-60 mph / 96 kph in 3.88 seconds, a top speed of 158 mph (255 km/h), 270 hp (201 kW / 273 PS at 8000 rpm) and it runs on any mixture of gasoline, bioethanol and methanol. Emerging technologies will allow alcohol fuels such as methanol, already a proven internal combustion fuel, to be made synthetically from CO2 extracted from the atmosphere.

The Exige 270E Tri-fuel is part of Lotus’ research to understand the complex combustion process involved in running on mixtures of alcohol fuels and gasoline, which will be important for a successful transition from today’s fuels to the sustainable, synthetic fuels of the future.

This research is just one aspect of Lotus Engineering’s ground-breaking work on environmentally-friendly vehicles. It is involved with a number of electric vehicle projects, has successfully integrated hybrid technologies into vehicles such as its EVE demonstrator, and recently announced results on a collaboration with Continental Division Powertrain on the Low CO2 downsized three-cylinder engine. The research into sustainable alcohols is progressing at Lotus’ Hethel headquarters in Norfolk, UK and involves input from the Royal Society of Chemistry’s Alternative Fuel Symposium Series, the Low Carbon Vehicles Innovation Platform, developed by the Technology Strategy Board and direct discussions with the University of Sheffield.

Methanol (CH3OH) can be produced synthetically from CO2 and hydrogen. Ultimately, emerging processes to recover atmospheric CO2 will provide the required carbon that can entirely balance the CO2 emissions at the tailpipe that result from the internal combustion of synthetic methanol. The result is that a car running on synthetic methanol, such as the Exige 270E Tri-fuel would be environmentally neutral.

Lotus Engineering’s Lotus Exige 270E Tri-fuel technology demonstrator illustrates how easy it is for synthetic methanol to be embraced over time as a future fuel for road transport. The Exige 270E Tri-fuel, with its supercharged 2ZZ-GE VVTL-i engine, could be the forefather of a new generation of conventionally driven cars that have the potential to be environmentally-neutral.

Synthetic methanol – a green fuel?
Synthetic methanol’s green credentials arise from its potential to be completely CO2 neutral. The most likely future mass-production of the fuel is by using electrochemical techniques to combine oxygen, hydrogen and carbon:
· Carbon could be sourced from carbon dioxide recovered from the atmosphere using either large scale extraction facilities or biomass.
· Oxygen would be taken from the atmosphere already contained in the CO2 molecule.
· Hydrogen would be acquired through the electrolysis of water; challenges remain in the electrical power required; in a green future, this could be supplied from renewable sources, an issue already being addressed by supporters of hydrogen as a fuel.
· Synthetic methanol can also be supplemented by production from biomass sources where properly sustainable.
· Methanol can be produced easily from a wide variety of feedstocks.

Synthetic methanol – How to make it?
Techniques for the production of synthetic methanol through the extraction of atmospheric CO2 are well developed and understood but are not being employed on an industrial scale. An early solution would be the co-location of a nuclear or hydroelectric powerplant with a conventional power station – the hydrogen generated by hydrolysis of water would be combined with CO2 from either fossil or biomass sources to make liquid methanol. In the future, large volumes of CO2 could be extracted directly from the atmosphere.

Synthetic methanol – easy to adopt?
As well as being green, another crucial advantage of synthetic methanol is that it can be introduced relatively simply. As the Exige 270E Tri-fuel demonstrates, only small changes to engines are required, such as:
· Sensors to detect alcohol content
· Modified software for engine management control driving alcohol/gasoline, flex fuel and fuel systems operations.
· Fuel lines compatible with alcohol fuels
· Higher flow rate fuel pump and injectors
· Fuel tank material, compatible with alcohol
In addition, as a liquid, which is miscible with gasoline, synthetic methanol can be transported; stored and sold to motorists exactly as today’s liquid fuels are, with only minor modifications.

Synthetic methanol – a performance fuel?
Synthetic methanol is better suited to spark-ignition combustion than today’s liquid fuels, delivering better performance and thermal efficiencies, due to its higher octane rating giving it better resistance to ‘knock’. As a result, it is a fuel that will benefit the motorists in terms of driving experience. For example, the Exige 270E Tri-fuel is quicker to 60mph from standstill and has a higher top speed when using 100% synthetic methanol fuel than with conventional gasoline. Synthetic methanol is also ideally suited to pressure-charging, a trend already well underway as car makers look to downsize engines to reduce fuel consumption.

Synthetic methanol - the way forward
Lotus Engineering regards sustainable alcohols as the third step in a process towards carbon neutral driving. The current E85 (85% ethanol and 15% gasoline) based movement represents the first stage in building momentum towards sustainable fuels. The valuable learning from the current bioethanol vehicles on the market means that synthetic methanol would easily be managed technically and within the existing transport, storage and distribution infrastructure. The steps towards a synthetic methanol economy for transportation fuels could be as follows:

1st Generation: there is a handful of current bioethanol models on sale around the world. These cars run on E85 bioethanol, which is produced from valuable arable crops (food). This is unsustainable in the short and medium term as global demand for fuel will outstrip the supply available from farmland to the detriment of food production, but is a necessary step in the evolution of the market.
2nd Generation: the next generation bioethanol fuels will be based on biomass waste, for example crop stubble, waste vegetable-based oils and any biodegradable waste matter. This is thought also to be unsustainable in the medium to long term as the required volume of biomass increases beyond that which can be supplied.
3rd Generation: sustainable alcohols such as synthetic methanol can be introduced due to its miscibility with ethanol and gasoline. This fuel can be produced from entirely sustainable, readily available inputs, with an environmentally neutral overall impact.
4th Generation: Direct Methanol Fuel Cells: over the longer term, sustainable alcohols in internal combustion will facilitate the soft introduction of direct methanol fuel cells as a long term sustainable future fuel. This will only be possible with pure methanol pumps on the forecourt which internal combustion engines can bring forward due to their ability to consume a mixture of fuels.

The Lotus Exige 270E Tri-fuel
The Lotus philosophy is all about performance through light weight. The Exige 270E Tri-fuel is built to the lightest specification possible without resorting to expensive and rare materials. The performance improvements of using synthetic alcohol have been made through increasing the power of the engine without increasing its weight and therefore the overall weight of the car.

The Engine
The heart of the Exige 270E Tri-fuel 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 270E Tri-fuel has peak power of 270 hp (201 kW / 273 PS) at 8000 rpm, 184 lbft (260 Nm) of torque at 5500 rpm, up by 51 hp (38 kW, 52 PS) or 19% and 25 lbft 45 Nm or 14% over the standard gasoline Exige S. Maximum engine speed is 8000 rpm (8500 rpm transient for up to 2 seconds).

The low carbon number alcohol fuels methanol and ethanol give more power when burned in the engine than conventional gasoline (petrol) fuel. The performance benefits come largely from the high heats of vaporization of methanol and ethanol, which give strong charge-cooling effects, and the increased octane ratings. There are other secondary thermodynamic effects. Methanol's higher heat of vaporization leads to a slightly higher performance relative to ethanol. 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 turned by the crankshaft, and has an integral bypass valve for part load operation.

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. This gives the Lotus Exige 270E Tri-fuel a smooth and linear surge of power from idle speeds all the way to the maximum 8500rpm. 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. Six fuel injectors have been fitted to increase fuel flow to the engine at normal and higher engine speeds and loads.