(Please, let's keep this thread to additions and/or relevant discussion. thx.)
Smaller+more power+ fuel efficiency topics only.
High compression, low-knock:
Design To Improve Turbulence In Combustion Chambers
"Results from a dynamometer test by the Automotive Research Association of India (ARAI) showed a reduction of 42.5% in BSFC / fuel consumption when fully loaded, producing more torque and power at lower temperatures."
Opposing-piston radial design?:
Angel Labs :: Home
"With 40 times higher power to weight ratio, low parts count, low maintenance, high mechanical efficienty, and low pollution, the MYT™ Engine will benefit airplane, big ship, 18 wheeler, SUV, passenger car, even down to carry on power generator applications."
200hp, 3 cylinder, 1.2L:
MAHLE.COM | Put to the test: the MAHLE downsizing engine
"1.2 litres, 200 hp and 287 Nm @ 2,500 rpm. The consumption has not been officially measured but gains between 30 and 40 %, compared to a NA 2.4 litre V6, has been accomplished."
Integrted hybrid and supercharger:
SuperGen
"SuperGen is an electro-mechanical boosting system which provides exceptional response even at low speed on heavily downsized engines. The system replaces the alternator and can also provide mild hybrid functions."
More links:
Engine Technologies
Fuel economy in automobiles - Wikipedia, the free encyclopedia