Quote:
Originally Posted by cRiPpLe_rOoStEr
About 10 years ago there were some rumors about either Mercedes-Benz or GM being in a hurry to release an engine with that feature, which had been evaluated by GM using some Opel Insignia and Saab 9-3 test mules and was featured in the Mercedes-Benz F700 concept. GM claimed that it could run without the spark plugs at all, but they provided a smoothier and quicker cold-start ability. Anyway, I wonder how such engines would perform with ethanol or gaseous fuels such as biomethane.
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Same concept. The problems identified at the time were the cost and complexity of the acoustic sensors needed to properly control combustion (when the mix explodes at the right time, that's combustion. When it doesn't, that's engine-killing knock!) and the narrow range they could successfully implement HCCI in.
From my talks with engineers, yes, the sensors are expensive, but the benefits of not having to run a gazillion psi in the injection system, as in diesel, means that cost overall should be lower.