Study Touts “Pulsed Energy” Spark Plugs for Lean-Burn Engines

Capacitor-enhanced ignition plugs could clear the way for the mass production of ultra-clean "lean-burn" engines, according to Albuquerque-based Enerpulse Inc. and researchers at Texas A&M University.

Enerpulse says its plugs, marketed under the Pulstar brand, are a direct swap for conventional spark plugs but deliver 20,000 times as much energy. The key to their performance is a built-in peaking capacitor that boosts energy transfer efficiency to 50% from about 1% for conventional spark plugs.

The company developed the technology with the help of Sandia National Laboratories eight years ago and commercialized it in 2008 in a line of aftermarket replacement spark plugs.

The company says the higher energy level of its plugs more than 1 million watts with a standard automotive ignition system improves combustion and thus fuel efficiency and emissions by reducing cycle-to-cycle ignition variation.

Working with Texas A&M, the company has demonstrated that its technology also could be used to more consistently ignite stratified-charge lean-burn engines a challenge that has made such combustion strategies unfeasible in mass-produced powerplants.

The tests indicate pulsed energy plugs have a lean flammability limit about 14% lower than a normal spark plug. This means they could be used to consistently ignite leaner air-fuel mixtures or improve combustion in engines that burn natural gas.

Enerpulse and Texas A&M reported their findings in technical papers presented at the SAE World Congress in Detroit in April and last week at ASME's internal combustion engine conference in Vancouver, B.C.