Most of you know, internal combustion engines are generally divided into two types: spark ignition and compression ignition, usually running on gasoline when we use a spark and diesel fuel when we don't, but a compression ignition gasoline engine? How does that work? Even more to the point, why bother? Engineers believe they may be able to achieve as much as 50 percent better mileage, as good as or better than a hybrid with much lower costs since there would be no huge battery or electric motor.
Diesel engines are 40 to 45 percent efficient at using the energy contained in their fuel while gasoline engines are around 30 percent efficient. That's why all of those diesel cars you see get such great mileage, but they do have a problem keeping the exhaust clean compared to the gas versions. Suppose you could get the efficiency of diesel with the cleanliness of gasoline, why not make a gasoline compression ignition engine?
Delphi, a major automotive parts supplier, is now experimenting by doing exactly that. They've taken a 500cc Ricardo Hydra single cylinder 4 valve engine and set it up to run in a gasoline direct-injection compression ignition (GDCI) configuration. Gasoline is injected in three bursts to control the too fast burning of the gasoline which reduces engine noise, while still burning faster than in a conventional spark ignition engine leading to lower emissions.
Exhaust gas recirculation is used to raise combustion chamber temperature for low speeds and soon after engine start, when it would otherwise be too low for compression ignition.
Results showed that triple injection GDCI achieved about 8 percent greater indicated thermal efficiency and about 14 percent lower specific CO2 emissions relative to diesel baseline tests on the same engine.
They are now moving to a multi-cylinder test engine, more like a production engine, to further develop the concept.
There was one interesting quote that also caught my eye:
Mark Sellnau, engineering manager of advanced powertrain technology at Delphi Powertrain, says the engine could be paired with a battery pack and electric motor, as in hybrid cars, to improve efficiency still more
Now, what were we just saying about both electric and gas together? Wouldn't an engine like this be perfect for running a generator so you could stop at a gas station for a fill up of electricity?
One takeaway of this story is developments like this would be impossible without precise computer controls, simple carburetors or fuel injection systems would never do.
High mileage, low emission, gasoline fueled diesel engines. Wow.
Thanks for the tip, Rob!
Link: Gasoline Direct-Injection Compression-Ignition (GDCI) (pdf) from Delphi via Technology Review