Being able to extend the Lean/Dilute Misfire Limit can offer significant advantages in fuel consumption and emissions. Source: Etatech. Click to enlarge.

Ignition systems for spark ignited, high brake mean effective pressure (BMEP), low emissions engines have historically been a problem from a performance and reliability standpoint. Low emissions, high BMEP engines usually have high compression ratios and operate with high turbocharger boost levels, both of which help to produce high cylinder pressures at the point of ignition. This high cylinder pressure and a lean/dilute mixture require higher voltage from the ignition system to initiate combustion.

The high voltage demand required to initiate ionization at the spark plug gap puts additional stress on the secondary system, which delivers the coil voltage to the spark plug. High voltages are difficult to contain in the secondary system, and often, the secondary dielectric strength is not sufficient to deliver the energy to the spark plug gap. This problem requires that small electrode spark gaps be used to reduce the voltage demand.

Unfortunately, small spark gaps often do not deliver sufficient ignition energy to a lean air-fuel mix in the cylinder to consistently initiate a flame kernel, the beginning of combustion. Thus, the lean/dilute mixture ignitability limit is insufficient to meet emissions and efficiency goals.

—Radio Frequency Electrostatic Ignition System Feasibility Demonstration

Unlike traditional engine ignition systems that rely on heat to initiate combustion, the ECCOS generates a high voltage, low current, and radio frequency electrostatic field (corona) inside the combustion chamber to efficiently ionize the air-fuel mixture and initiate multiple flame fronts. This greatly improves combustion efficiency and speed, and consistently ignites the leanest air-fuel mixtures.

The electric field can be directed to where it is optimum for combustion; electrode, insulator and combustion chamber design all influence the geometry of the corona discharge.

With little or no heat-related electrode erosion, maintenance is virtually eliminated. To further improve engine performance, the system electronically controls various characteristics of the combustion cycle, further reducing emissions, improving efficiency and increasing horsepower. A controlled combustion rate can significantly improve engine performance by reducing emissions, improving efficiency and increasing horsepower by extending knock-limited BMEP.

ECCOS electrical schematic. Click to enlarge.

The ECCOS ignitor is physically similar to a conventional ignition system’s coil, extension and spark plug, except it is one assembly, not separate components.

BorgWarner expects to commercialize the technology, which will replace conventional spark plugs, for powertrain applications across various markets and regions in the next few years.

Our ignition experts at BERU Systems believe this will be the ignition technology of the future. The significant improvements in fuel economy and emissions provided by this technology may revolutionize the industry. Our focus on reducing emissions, increasing fuel economy and improving engine performance makes this technology a perfect fit for BorgWarner.

—Tim Manganello, BorgWarner Chairman and CEO

Resources

• Radio Frequency Electrostatic Ignition System Feasibility Demonstration

• ECCOS Combustion Characteristics and Engine Performance