With diesel engines on the nose with legislators around the world the clever engineers at Mazda have been working to make petrol engines behave like diesels – but without the pollution that comes with them.
In a world first they've created a compression ignition petrol engine that uses higher compression inside the cylinder, rather than a spark from a spark plug, to ignite the fuel. It's known as Homogenous Charge Compression Ignition (HCCI).
The higher compression of diesel engines has always made them more efficient, so that motorists can get more kilometres to the litre of fuel. But it's always come at a cost in air pollution, a fact that was revealed in all its sordid details by the VW emissions scandal. And VW was far from alone in cheating emissions figures.
Petrol engines run cooler thanks to their lower compression ratio, resulting in a cooler burn with less particulates, particularly nitrous oxide, coming out of the exhaust pipe.
Engineers have worked to increase the compression of petrol engines over the years to boost efficiency but have always been limited by "knocking," or pre-ignition, when the fuel ignites at the wrong time.
But now Mazda have cracked it, though they're being a little cagey about exactly how they've done it. According to Wired magazine they're basically using computer technology to control temperatures and pressure in the cylinders by varying valve timing and turbo boosting. It also adds exhaust gases to the fuel-air mix while calculating just the right amount of petrol to add to it.
Despite this Mazda hasn't completely abandoned spark plugs. The engine still uses them on occasions, such as cold start-ups.
So when will we see this radical new engine in cars on the street? Well Mazda is planning to have the first cars with the technology on the road by 2019.
Mazda rotary resurface
Compression ignition petrol engines aren't the only innovation happening at Mazda. It's famous rotary engine which gave its RX7 and RX8 sports cars their legendary performance is due to make a comeback in a more modest role. It's being used as a range extender in hybrid vehicles.
Unlike some hybrids, where the petrol engine plays a role in powering the car, Mazda will use a small rotary engine just to generate electricity and charge the battery pack while the car is moving. The rotary is light, quiet, small and very well suited to the role according to Mazda.