Published on October 25th, 2016 | by Daniel Sherman Fernandez0
How Mazda Reinvented The Diesel Engine With Skyactiv Technology
Diesel is the world’s most efficient internal combustion engine. It provides more power and more fuel efficiency than alternatives such as petrol, compressed natural gas or liquefied natural gas. Advanced Diesel engine from car manufacturers like Mazda are changing the mindset of car buyers and giving diesel powered cars more credit.
The biggest problem for a diesel engine has been insufficient heat for complete combustion during cold start, and misfiring during warm up. The conventional solution has been to increase the compression ratio. This, however, results in too high a temperature and pressure, causing incomplete combustion (the formation of NOx and soot). The solution to this has been to delay ignition, which causes fuel economy to worsen.
Mazda’s solution is to precisely control the fuel injection and improve the exhaust valve’s opening and closing mechanism. Multi-hole piezo injectors are used for variable injection patterns. The precision in the amount and timing enables optimum mixture control, thus maximising combustion. A variable valve lift (VVL) system is used for the exhaust valves – a single combustion cycle is sufficient for temperature to rise; exhaust gas is channelled back into the cylinders, to raise temperature further, which improves cold start.
The new-generation diesel engine comes with a 2-stage turbocharger for smooth and linear response from low to high engine speeds, and greatly improved low- and high-end torque. One small turbo and a larger unit are selectively operated to suit driving conditions. The system offers high torque and good response at low speeds, and high power at high speeds, as well as clean burn throughout the entire cycle.
The reduction in compression ratio to 14:1 and pressure has made it possible to significantly reduce the weight of the new engine. It comes with an aluminium cylinder block, lighter cylinder walls, as well as integrated exhaust manifold; the weight of the pistons has been reduced by 25%. There is also a dramatic reduction in friction, to the same level of an average petrol unit. Fuel economy has been improved by 20%.
Specifications Mazda6 Diesel Skyactiv
Engine 4-cylinder Diesel DOHC 16 Valve
Transmission 6-Speed Skyactiv Drive with Manual Shift
Max Output 173bhp @ 4500rpm
Max Torque 420Nm @ 2000rpm
Top Speed 250km/h