A reliable engine using this technologies would allow manufacturers to power large sedans and SUVs using small and efficient motors and at the same time rival the efficiency of more expensive hybrid systems. The biggest hurdle the designers had to overcome was in preventing ‘knock,’ a situation where too much pressure in the cylinder causes the fuel-air mixture to ignite independently of the spark and damage the engine.
The key was to reduce the boost pressure of the turbos but also to create a special fuel mixture that contains mostly gasoline but with a small amount of ethanol, which is better at preventing knock. According to their results, a vehicle using a set-up like this could operate around 25% more efficiently than a vehicle with a conventional engine. And since it’s based on current technology, it could be in production very quickly and should only cost an extra $1,000 to $1,500 more than a conventional powerplant. Volkswagen AG has been one of the pioneers in this field, already releasing its TFSI range that combines turbocharging with direct injection technology.
[Source: Technology Review]