By Yoko Kubota
TOKYO, April 10 (Reuters) - Toyota Motor Corp is introducing a new series of engines that will boost vehicle fuel efficiency by at least 10 percent, as carmakers strive to improve performance against a backdrop of rising fuel costs and tighter emissions controls.
Toyota will introduce 14 engine models in the new series over the next two years, starting off with 1.0 litre and 1.3 litre gasoline engines, it said in a statement on Thursday.
The world's biggest car maker by sales volume has for years focused on gasoline-electric hybrid powertrains as a way of improving fuel efficiency, but outside Japan conventional engines remain much more popular than hybrids.
Rivals such as Ford Motor Co, Volkswagen AG and Honda Motor Co have focused more on small engines with added features such as turbochargers.
"We have been prioritising hybrids but there are still customers seeking cars that are not hybrids," said Shouji Adachi, an engineer in Toyota's powertrain planning department.
"Meanwhile other car makers without hybrid technology are becoming more competitive in that area and we need to do something about that," Adachi said.
The launch comes at a sensitive time for Toyota's image after it announced this week its second-largest recall ever targeting more than 6 million vehicles globally.
Hybrid vehicles, including the Prius, accounted for around 14 percent of Toyota's global sales in 2013, with most of that coming from Japan.
Toyota said the new engine range would draw on technology gained from gas-electric hybrids, but would also use a number of other innovations to improve performance.
Gasoline-driven cars currently utilise at most around 35 percent of the fuel's energy, with the rest lost mainly to heat and friction. To improve that, Toyota has used techniques such as making the engine combustion more rapid by controlling the amount and the speed of the air that goes into the combustion chamber.
In its new 1.0 litre and 1.3 litre engines Toyota improved peak thermal efficiency to between 37 and 38 percent, it said.
In future the group aims to boost peak thermal efficiency to 40 percent and more, Adachi said. (Editing by David Holmes)