See all Motoring NewsIf you ever needed proof that diesel is on the way back out, just take a look at the kind of technology that Toyota is pumping into its new 1.5-litre four-cylinder petrol engine, which will make its debut later this year in the Yaris.
It replaces the ageing 1.33-litre VVTi engine (which has always been a decent and very frugal unit) and bucks the modern trend for downsized turbos by being both naturally aspirated and having a larger swept volume than its predecessor. From 1,496cc it develops 111hp, and 136Nm of torque at 4,400rpm - decent figures and both improvements on the old 1.33-litre engine.
It's also one of the most thermally efficient engines on the market according to Toyota. Thermal efficiency is the measurement of how much of the car's fuel is burned for power and how much is wasted as heat, and the 1.5's 38 per cent efficiency rating makes it one of the best, barely behind the best hybrid models in fact.
Toyota claims that the engine meets both the latest round of Euro 6 emissions regulations and the upcoming Real World Driving Emissions (RDE) regs. Partly that's down to clever electronics and valve control, which allow the engine to switch from normal four-stroke Otto cycle to deeper-breathing (and more efficient) Atkinson Cycle without the driver ever noticing. To do that, the camshaft has to be controlled both electronically and hydraulically - quite something for a small supermini engine.
Toyota is also debuting a new water-cooled exhaust manifold system, which cools the gases leaving the engine and means that the engine can be run on a leaner fuel injection programme at motorway speeds, which should improve long-run economy. Toyota says that the engine will hit 64mpg on the combined cycle, and allows a Yaris to accelerate from 0-100km/h in 11 seconds.
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