Small but mighty

Bigger means more power. Right? Wrong. A new generation of compact petrol engines could help transform the car industry, and help the environment too. Jamie Merrill reports

Essex is Ford country. Park at the company's technical centre in Dunton and you'll see just about every model the American giant produces. Don't breathe too deeply though; it's 28 miles from London's diesel-guzzling black cabs, belching red buses and thirsty Chelsea tractors and only six miles along the busy A127 to the gyratory of gridlock that is the M25. It's no wonder that down the road the once-gleaming Basildon town sign (erected in the style of its more famous Hollywood rival) has taken on a slightly grey hue. For Essex, like the rest of the country, shows little sign of falling out of love with the car as new sales, and particularly sales of diesels, defy the recession and continue to grow.

With diesel sales soaring (they now make up the majority of sales) it might seem like a risky moment for Ford, which is struggling to make a profit in Europe, to launch a new small petrol engine in the form of its 1.0-litre Ecoboost. Especially when just 15 miles from the Fiesta and Focus-packed car park at Dunton is Ford's Dagenham plant, which produces one million diesel engines a year. Diesel and Dagenham has been central to Ford's dominant market share in the past (it still sells one of every seven new cars), and like most other major manufacturers its diesel engines have been "downsized" and fitted to smaller models – many diesels emit less than 99g of carbon per kilometre (g/km) and are rewarded with vehicle excise duty and congestion charge-free motoring.

This economy has come at a price. While smaller cars and diesel engines have helped average vehicle CO2 emissions drop since 2009, figures from the Department for Transport show that harmful oxides of nitrogen (NOx) emissions for diesel cars are twice that of petrol engines, while particulate emissions, which can be inhaled deep into the respiratory system, are 22 times higher. The two emissions contribute significantly to air pollution and breathing difficulties, Simon Birkett, founder of the Campaign for Clean Air in London, says. And, according to a survey released last week by the Massachusetts Institute of Technology, they help cause around 5,000 premature deaths from road pollution in the UK each year.

"The Government has failed catastrophically to tackle harmful emissions from diesel vehicles. Some leaders, like Boris Johnson, have actually given strong financial incentives to buy diesel vehicles in cities," Birkett says. "The health impact of long-term exposure to invisible particulate emissions is of the same scale as the problem we thought we had from short-term exposure to the Great Smog of 1952 but, unlike then, the Government and London's mayor are doing nothing about it."

Back at Dunton, Ford's technical engineers think they have part of the solution, with the new Focus fitted with the 1.0-litre Ecoboost engine. The new model, which is now rolling off Ford dealership forecourts, only uses three cylinders and just 999cc to produce 123bhp and a fuel economy and emissions normally associated with a less powerful vehicle. It does this by reducing the engine capacity and adding direct fuel injection, a turbocharger and variable-cam timing to outperform larger engines.

"The technology is complex and borrows from performance cars," Andrew Fraser, who heads Powertrain Development for Ford at Dunton, says. "The key liberating factor, though, has been the turbocharging of a smaller engine, which is the use of exhaust gases to drive a turbine to force more air through the engine, which gives the power and torque... that traditionally only a much larger engine would have had."

Fraser's team also worked on the engine to make sure it used direct fuel injection – fuel sprayed at high pressure into the cylinder, something "you'd normally expect to find on a Ferrari 458" – and a twin variable cam shaft configuration. "One of our goals is to make the technology cost-effective for the average customer," he says. "Companies like BMW are doing brilliant things with two or three turbochargers but that drives up prices."

Of course, Ford has a lot to gain by portraying itself as a "green" car company, but the company expects to shift the Ecoboost in serious numbers (800,000 by 2015). And other manufacturers are not far behind. Vauxhall is replacing its petrol engine line-up in the next 12 months and pretty much all the major manufacturers have smaller engines planned or on sale. Even the luxury behemoth Bentley is offering its £140,000 Continental GT with a smaller 4.0-litre V8 engine. Petrol heads and Clarkson might have a fit, but when it comes to petrol engines, less is more.