PARIS – Ford Motor Co. engineers in Europe are developing a V-6 diesel aimed at meeting rigid nitrogen oxide emissions rules in Europe and North America without expensive exhaust aftertreatment.

The experimental diesel, based on the 2.7L V-6 engine Ford manufactures with PSA Peugeot Citroen in Dagenham, U.K., uses a combination of Homogeneous Charge Combustion Ignition (HCCI) cold combustion as well as ordinary diesel combustion.

But its real innovation is a new strategy for controlling combustion. Instead of adjusting the oxygen intake to match the demand for fuel, Ford has developed an engine controller that adapts the fuel injection to the oxygen available.

Changing the amount of air that reaches the combustion chamber is a slower process than altering the amount and timing of the fuel injection, says Christian Vigild, engineer at Ford’s diesel powertrain research center in Aachen, Germany.

Vigild presented research on the diesel engine, which is being developed by Ford and PSA under their Gemini project, at a 2-day academic conference here.

More than 100 international engineers and scientists attended presentations on how to better design electronic controls, mainly for HCCI engines and hybrids.

HCCI is a system that works at lower temperatures – 3,452° F (1,900° C) – than either gasoline or diesel combustion. Lower temperatures mean less NOx emissions.

By “putting the rabbit on the back of the turtle,” Vigild says low-temperature combustion is more complete even when accelerating in the HCCI mode.

One approach to getting better combustion is to measure the pressure inside an engine cylinder so the engine control unit knows what is happening. However, such sensors are expensive.

Vigild says Gemini's approach of adjusting the fuel injection to match the oxygen available provides better control during transitions.

“We tried to keep it simple from the start,” he says. “We wanted a design that did not require a pressure sensor in each cylinder.”

Without giving numbers, Vigild indicates the experimental engine had "very low" NOx output in a midsize car such as the Ford Mondeo.

But the project is unlikely to see production before 2012, when Euro VI rules are expected to be in place.

And if a cheaper system of aftertreatment for diesel NOx production is invented, it could prove to be a better economic alternative, Ford engineer Charles Tumelaire concedes.