Gas Fed

(From Lotus Life Club)

Alternative energy sources for vehicles are increasingly being sought so, in response, Lotus engineering has developed the Bi – Fuel Elise, which can be powered by compressed Natural Gas ( CNG ) as well as petrol.

The whole point of using the Elise for the research project is that a high profile car will attract people’s attention towards this important alternative fuel, use a van as the development vehicle and people’s attraction tends to drift off elsewhere.

CNG is methane based gas and had been discovered in huge quantities all over the world. Furthermore, being methane, it can be easily manufactured on a sustainable basis, if needs be. Its great advantage is automotive applications is that it produces only a fraction of emissions of petrol and diesel fuels and yet can be used in existing internal combustion engines with only minor modifications. Its reduction in emissions is particularly significant when starting from cold, a situation where petrol and diesel engines are at their dirtiest.

There are some disadvantages too, many with storage – the Elise’ 40 litre tank gives a range of about 90 miles, where as the car will travel around 200 on it’s 25 litre tank of unleaded. Also CNG gives 10 – 15 % less power than petrol.

Which is why the Bi Fuel Elise runs on both types of fuel. Cruising along the motorway or puttering about town, it runs on CNG. If you need rapid acceleration or are running constantly at high revs then the petrol supply automatically cuts in to provide you with full power.

Until now the problem with CNG has been that it requires much larger fuel tanks than petrol or diesel fuel and that has meant eating up either cabin or boot space simply to accommodate the tanks. The challenge to the Lotus Engineering Powertrain team was to fit the tank without sacrificing interior or boot space.

This was achieved by fabricating a very slender 25 litre petrol tank to fit in a narrow enclosure behind the seats and in front of the rear bulk head, and using the existing petrol tanks space to store the 40 litre CNG tank.

To ensure the project has real relevance, the Lotus Engineering Powertrain Team made the Elise as close as possible to a vehicle that could be put straight into a show room and sold to the public.

Unless you have an extremely intimate relationship with an Elise, chances are you won’t even notice the slightly reduced cabin length. If you were able to lift out the boot liner for a better view of the engine and the rear cross members, you might spot a few additions to the engine bay. There’s an extra set of fuel injectors for the CNG, a pressure regulator on top of the engine, a single stand alone ECU to manage the automatic switch between gas and petrol power on the move and a few additional pipes, But frankly there’s little to see.

Which is just the way it’s meant to be to demonstrate that with just a little ingenuity and effort, the most likely cars can be converted to run on CNG.

Having driven the Bi-fuel Elise, I can assure you the system works well, despite being in the early stages of development. On this prototype you have to switch the CNG system, but once you’ve done that the electronics imperceptibly switch between fuel sources. Actually there is a big give away and that’s the amount of noise the gas injectors make - they’re bigger bore than petrol injectors and operate ‘ dry ‘ (remember they are injecting gas not a liquid) so they’re naturally louder. Work is already underway to quieten them down.

You can feel that the Elise’s performance isn’t quite as crisp when running on CNG, but then it kicks into petrol power and you’ve got all the punch and response you could want. In terms of ride and handling the Bi-fuel Elise feels pretty much the same as the standard car, which again was part of the engineering brief.

The Bi-fuel Elise, which is purely a research tool and won’t be for sale, is being developed in conjunction with British Gas and the project is part of the government funded power shift programme, designed to get big business, the oil companies and end users such as fleet managers, more interested in alternative energy sources.

Until there’s a national infrastructure to supply CNG it won’t be a viable fuel for general public. Never the less, Lotus Engineering Powertrain team is continuing to develop the bi fuel Elise to further refine its derivability and to completely mask the change between fuels, So by the time you start buying CNG from your local filling station, there should be no reason for your car to be any less practical or enjoyable to drive than it is now.