EBS' strategy starts with a gas engine that would be smaller than a diesel or gas engine designed for the same power application. So a V-8 becomes a small V-6 or even a four-cylinder. A monster 11-liter diesel engine usually found in an 18-wheeler would become a 7.0-liter gas engine.
"The technology applies across the board," Cohn said. "It works with higher rpm motors as well."
The smaller engine provides better fuel economy during normal operation, is less expensive to produce and reduces vehicle weight.
These small engines are designed with high compression (12:1 or 13:1) and turbocharged, with boost pressures around 35psi to provide power when needed. Normally that combination is a grenade waiting for the pin to be pulled; such a design leads to massive detonation under most loads, and certainly at wide-open throttle, even with premium 91-octane fuel.
Detonation occurs in the cylinder when abnormal combustion leads to an instantaneous and unwanted spike in cylinder pressure. Basically, there’s an explosion of the air-fuel mixture — often setting off at different places in the cylinder — instead of a controlled burn or combustion. When these separate pressure waves collide — especially if the piston is forced backward against its will on the compression stroke — they create a sonic symphony of metallic chatter referred to as "knocking" or "pinging."
Higher-octane fuels reduce knocking because their burn properties help control or challenge abnormal combustion. Powertrain engineers can also address knocking with a lower compression ratio or by backing off the ignition timing, all of which can reduce power. A traditional pre-treatment remedy was an injection of water mixed with ethanol, or methanol, into the intake manifold. Water in the air-fuel mixture helped cool the cylinder, and the ethanol/methanol increased the fuel’s octane rating to reduce knocking. This solution is very maintenance-heavy, though, because the water/ethanol bottle had to be refilled often because there was no precise injection strategy.
EBS discovered that injecting ethanol directly into the cylinder allows a higher cylinder pressure to produce torque and horsepower when needed, but without the detonation. The engine-management computer uses sensors to monitor the knock level, then injects only as much ethanol as needed to cool the cylinder and increase the gasoline’s octane for that particular rpm and load.
Cohn estimates that ethanol consumption during normal driving would be about 3 percent to 5 percent of gasoline consumption because full power isn’t needed for cruising or light city driving.