Improving fuel efficiency, emissions and power of engines while maintaining their low cost and simplicity, has been a worldwide challenge. No one knew this better than CEI did, which pursued lean burn for 30 years. CEI saw lean burn as essential for fuel economy, which it solved through several breakthroughs in ignition and engine design. This report summarizes the many advances which are described in two Design News feature articles “Rebirth of Lean Burn Technology” and “Lean Burn Lives”, supported by the “Exec Summary” and the “Engine of the Future”.

1. The Production Ready Ignition System

In a classic paper SAE 750348, General Motors showed that 150 mJ spark energy (vs. 30 mJ) was required for lean burn. CEI confirmed this, and further showed that a spark with a 20 m/sec flow velocity versus the standard 4 m/sec, optimized lean burn. But it wasn’t until CEI was able to develop a system that met these goals that spark ignition was revolutionized. CEI developed and patented a coil of equal weight but with 5 times the energy (150 mJ) and 5 times the flow-coupling capability (20 m/sec) of other ignitions. It also has a 5 times faster rise time and 5 times faster charge time. During cold-start, especially of difficult to ignite fuels such as ethanol and natural gas, it can provide 10 times the energy for rapid start-up with low hydrocarbon emissions. The ignition offers many other advantages, including twice the efficiency compared to current OEM ignitions.

During the five years 2002 to 2007, CEI made further improvements to its ignition, with three patents issued in 2007, with two of them being master patents. The coil existed in block coil and pencil-coil form with a voltage of up to 45 kV, and peak current of 350 ma. A key improvement included adding two low-cost biasing magnets to achieve high energy density. Plug erosion was reduced through selective use of electrode materials. The ignition was tested by Champion on a 2005 Ford Focus and shown to increase engine fuel economy by 5% with EGR over the double-spark Visteon ignition. For ulra-lean operation, the ignition can deliver the needed 150 mj of energy and the 20 m/sec flow-coupling capability. The ignition ECU and Ignitor have been recently simplified with two low-cost micro-controllers. For car makers who adopt the ignition for 2-valve or 4-valve engines, they can provide the best ignition at the lowest cost.

2. The Prototype Lean Burn Engine

CEI’s second technology is a prototype 2-valve, 2-plug, squish-flow lean-burn engine, which uses CEI ignition to attain a record level of leanness and a 30% better fuel economy. The test engine was seen to operate at 30 to 1 air-fuel ratio, never seen before in a 2-valve, homogeneous charge engine (see SAE Paper 2001-01-0548). A 2-valve, 2-plug engine, similar to the early Nissan NAPS-Z engine, is having a revival at Chrysler and Honda, setting records in efficiency and power. Chrysler referred to CEI’s ignition “as the enabling technology for the lean burn engines of the future”, not anticipating that a successful single cylinder prototype engine would be developed in 2000 that would represent the final solution of lean burn.

3. Progress in the Variable Compression Ratio Piston Engine

CEI plans to demonstrate a variable compression ratio (VCR) system at the more optimum 14:1 compression ratio, discussed in a 2004 GPC paper. It should be noted that even when fully implemented, the CEI technologies would not require an engine change. By combining the ignition with the 2-valve, 2-plug squish-flow lean burn engine, one can achieve the 30% better fuel economy of the diesel without the weight, cost, emissions, and other problems of the diesel. When one uses the VCR system made up of steel or titanium disc springs, stacked in a piston, to provide 14 to 1 CR at light load and lean burn, one can achieve a 45% higher efficiency at the lowest cost. At full load, one obtains the highest power by overcoming the basic problems of the Otto cycle through the actions of disc springs, i.e. by relieving the excess pressure at WOT as the spring compress and then relax, giving energy back to the piston. When one combines the above three technologies, i.e. ignition, the lean burn engine, and the VCR piston, one achieves the optimal in efficiency, emissions and power.