New Ford Fiesta sketches

How to... reach 100mpg

Despite the allure of the electric vehicle the humble petrol engine will continue to be the mainstay for cars for the foreseeable future.

The rise of the electric vehicle (EV) and the acclaim it has received in the press would have you believe that it was the answer to our transportation predicament, but that is far from the case.

Despite the launch of exciting new models such as the Nissan Leaf and Chevy Volt the EV is unlikely to be much more than a bit-part player in the evolution of the automobile. Even with advances in battery technology, the range and recharging ability will confine it to local or urban driving.

The real revolution lies in the continued development of the internal combustion engine. Over the past few years there has been an unprecedented drive to improve fuel economy and that is spurring manufacturers and their extended supply chain into greater innovation in engine technology.

Stimulating this are stricter emissions targets from national, regional and global organisations. For example, the legislated current average fleet CO2 emission level of 130g/km in Europe is to be reduced to a castigatory 95g/km by 2020.

"Fleet averages are a very tough level to achieve," Andrew Fraser, manager of the gasoline engine development group at Ford, says. "My view would be unnecessarily tough on the automotive industry because it sets a very extraordinary high price of carbon abatement. But we have to work with the limits we're given so that is pushing the boundaries on a worldwide basis."

Ford's attention, along with that of other mainstream manufacturers, is moving on to two key strategies. The first is downsizing the engines, which, allied to technologies such as turbo charging, direct injection and sophisticated engine-management systems, is allowing smaller engines to deliver power usually associated with much heavier units. The second technology is hybridisation and the increased electrification on the way to the ultimate goal of an all-electric power train.

"Fuel efficiency is probably the most dominant factor of the moment," Fraser adds. "The noxious gas emissions, the nitrous oxide and hydrocarbons, are very well controlled on petrol engines so it's a reasonably well understood control issue. Ford used to have a slogan in the 1990s that said 'Everything we do is driven by you', but that mantra now reads, 'Everything we do is driven by CO2'."

Over the past five years it has come into prominence with all major manufacturers and it dominates day-to-day discussions and activities both in the power train and in the complete vehicle arena.

Improved emissions

In 2000, the average car fleet when sold had 181g of CO2 while last year it had 138g, a 23 per cent reduction. That advance has largely come from power-train improvements, but'also from enhanced aerodynamics and tyres as well as the adoption of electric power steering systems instead of hydraulic ones.

"Virtually every car has power steering, but until recently had a hydraulic pump which churned all the time to have a reserve of pressure when you want to turn the steering wheel," Fraser explains. "It was turning mechanical work into heat and then taking that heat away when you didn't need it via a radiator. Now that they have largely shifted across to electric ones that only assist the steering when needed, they are significantly more efficient."

As part of its 'downsized engine' strategy, Ford recently launched the Focus Studio with a one-litre, three-cylinder, turbo-charged engine - the one-litre EcoBoost ' which delivered 135 horsepower, considered to be a sensible mid-range power output for a Focus-sized car. "It has a fantastic torque of 200nm, so it really doesn't ask the customer to give up anything on performance and yet it is a big step forward in fuel economy for the consumer and CO2 rating for road tax," Fraser says. "With the Focus, virtually every engine that you can buy in Britain is turbo charged, which would be almost unthinkable even five years ago.

Optimum performance

These engine advances may have prompted greater fuel savings, but they are delivered by new dynamic engine-management solutions with software modelling controlling the engine. These model-based controllers are constantly modelling what the engine is doing and predicting how much fuel it is using.

"There are nine different variables all going into the combustion chamber on each stroke now," Fraser says. "It used to be fundamentally what speed, how much fuel and what spark time we are putting in. We still have those, but now we can inject quantity and timing of the fuel because it's direct-injected ' you can choose when to inject the fuel in each stroke and you can sometimes inject it two or three times during the stroke to get the best performance.

Fraser adds: "The spark timing is variable, both intake and exhaust cam shafts are variable, but you can swing those through about a 55-degree range of operation to vary the air flow into where the exhaust exits the cylinder for optimum performance. The engine management has been a real enabler in doing that."

The move to a three-cylinder engine breaks many of the conventions that car buyers have traditionally valued. Multi-cylindered, high-capacity engines have long been viewed as a hallmark of quality cars. "It is a big shift in perception and I think for a lot of people it's still a bridge they have to cross," Fraser admits.

"We think people are looking at their cars [and asking] is it quiet? Is it refined? Is it fast enough for me and how little fuel will it use? How often do I have to refill it? And they're starting to see past how that's being achieved and the results. The traditional focus on engine displacement and number of cylinders is starting to diminish quite significantly."

Traditionally the more cylinders you have the fewer gaps there are between each firing of a piston ' the ultimate being a V12 in a Jaguar or a Bentley ' which makes a car smoother. However, by isolating the engine from the vehicle through advanced engine-mounting systems and carefully-tuned fly wheels, Ford has managed to eliminate a lot of the concerns that a low number of cylinders would have once had.

Even the luxury cars have started not only to accept but to embrace lower numbers of cylinders. BMW is a classic case. Traditionally the home of six-cylinder engines, it is now happily selling four-cylinder engines and its is bringing out a three-cylinder one next year, which will' probably go into the Mini and possibly some of the company's own badged vehicles.

A three-cylinder engine is not a new idea at Ford; the auto-maker originally toyed with the idea over ten years ago in a programme called Fiesta Etec. In essence it took the 1.6'engine and sawed off a cylinder. "We built a fleet of 100 Fiestas with this 1.1 litre, three-cylinder, turbo-charged direct injection engine and we ran fleets in Britain, Germany and Spain and collected all the data from them," Fraser says. "Everyone who drove them really liked them. They liked the fuel economy, the sporty sound of the three-cylinder engine and the performance that the turbo gave them. But the feeling was that the market wasn't at that time ready for them and the project was put on hold."

Aside from the weight reduction a three-cylinder layout offers other advantages. The shorter and stiffer the engine is, the quieter it will be as everything becomes closer to the middle: shaking and vibration gets reduced because it's taking place within a smaller engine. Ford opted for a cast-iron cylinder block rather than an aluminium one as cast iron is very stiff and strong so it allows for a very compact engine.

"It is also very good at absorbing the noise that an engine makes," Fraser adds. "Aluminium is quite a 'ringy' metal, quite resonant, so there are lots of factors that gradually came together that convinced us to go with a three-cylinder layout."

Future moves

One indication of the future potential of the internal combustion engine came from HyBoost, a Technology Strategy Board project with the aim of delivering an extremely efficient gasoline power train with CO2 emissions below 100g/km without a detrimental effect on the car's performance. By adding an electric supercharger, and additional energy capture and storage, this was achieved successfully.

As a bench, a Ford 2.0-litre normally aspirated engine was selected. This power unit delivers 145hp at 6,000rev/min and 185Nm of torque at 4,000rev/min, with CO2 emissions of 169g/km with the standard five-speed manual transmission. Against this the HyBoost team, which counted Ricardo and Ford among its members, worked on the three-cylinder 1.0 litre turbo GDI EcoBoost engine with fixed-geometry turbocharger.

"We have pushed the engine up to close to 160 horsepower and about 280Nm of torque," Jason King, the programme leader, says. "But that was not for reasons of performance: it was to get better fuel consumption from the power train."

Focus on fuel economy

There was a four-step process to achieving this improvement: a bigger, increased torque, innovative air cooler and advanced air pack. The bigger turbo delivers enhanced performance with the added advantage that there are reduced pumping losses at part load, which benefits fuel economy. The increased torque permits the engine to be run at lower speeds. Another partner in the project, Valeo, produced an advanced water charge air cooler that reduces knock at the extremes of the operating conditions, while a novel air pack handles the inlet side, also giving better engine volumetric efficiency.

"The job of the electric supercharger in our application is to help bring the transient, real-world torque curve as close to the steady- state torque curve as possible," King says. "The electricity for the supercharger comes for free under normal driving conditions."

"We have overachieved, showing the potential to reach 90g with a standard car, with no light-weighting, aero modifications or change to Eco tyres, as you'd see on a Toyota Prius for example ' and with an on-cost over-the-base engine that's below that of a diesel and a quarter of that of a hybrid," King continues. "This enables the use of the aggressively downsized gasoline engine. If you look at the fuel economy relative to the performance and the cost, it's in quite a unique position. The fuel consumption is approaching that of a diesel, yet the overall system cost is less."

King concludes: "This highly effective combination of engine and micro-hybrid technologies is achievable at a cost that can be justified for the mass market, not just the premium end or niche hybrids. This type of solution will probably displace some conventional diesels, but at the same time the technology is equally applicable to diesel."

Fraser is just as positive about the future for petrol engines. "We think there is still a long way to go," he says. "There will probably'be a degree of mild electrification and some enabling of the engine. Our forecast is that by 2020 probably 90 per cent of the cars on the road will still fundamentally be internal combustion engine cars and that the electric or hybrid will be in the 10 per cent range.

"So I think that most of the CO2 gains over the next decade will still come from improving combustion engines," he adds.

"My vision would be cars with perhaps 20 per cent or 200kg taken out of their mass allied with engines which are 20 per cent more efficient than they are now. Putting these two together, you're probably getting close to another 30-40 per cent improvement of where we are now."

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