Why Mazda Doesn't Turbocharge Its SkyActiv-G Engines - We Ask The Father Of SkyActiv

Every now and then, there will be rumours of a turbocharged SkyActiv-G petrol engine in the works. However, we can confidently say there will be no turbocharged Mazda SkyActiv-G petrol engines in the near-to mid-term.

We say “near- to mid-term” because we also remember that many years ago, BMW told us that they will never make a front-wheel drive car, they will never make a diesel-powered M car or an M SUV. Today BMW sells the front-wheel drive 2 Series Active Tourer and the M550d, which is a diesel-powered M5 in all but name. The X6 M50d is even more extreme. It wears the M badge, is a diesel and is an SUV: everything that BMW said it will never do just ten years ago, culminated in today's X6 M50d.

It's the same with Land Rover and Subaru, who once said that all their cars must be four-wheel drive or all-wheel drive respectively, but today Land Rover sells a front wheel drive Evoque, while Subaru sells a rear-wheel drive BRZ.

So never say never.

Anyway, back to Mazda. Earlier in April, Mazda Motor Corporation's Technical Research Centre's Managing Executive Officer for Powertrain and Electric Drive System Development Mr. Mitsuo Hitomi was in Kuala Lumpur for a conference. His job title is quite mouthful to repeat, but you can just refer to him as the father of Mazda's SkyActiv engine. He was responsible for realizing the Mazda Sky Concept engine into series production.

Mr. Hitomi explained that he does not agree with the common opinion that downsized (turbocharged or supercharged, or both) petrol engines deliver better fuel economy, and does not believe that downsizing is the right path to go in pursuit of better fuel economy and lower exhaust emissions.

However, he acknowledged that downsized engines perform better in regulatory mode fuel economy testing, which are done in controlled environment. Hitomi's says in the real-world, Mazda's SkyActiv-G engines deliver better fuel economy, citing an independent test conducted by Germany's ADAC.

Unfortunately, many governments around the world formulate their policies and incentives around regulatory mode fuel economy testing so Mazda has no choice to work even harder to improve its engines.

"NEDC fuel economy (testing) is favourable for downsized engines because low-load operation frequency is high."

Referring to an independent test by Germany's ADAC for real-world fuel economy, Hitomi said, "As you can see, the better the NEDC fuel economy is, the larger the difference between the NEDC results and ADAC test," adding that the difference for SkyActiv engines is much lower.

To further emphasise his point, Hitomi added that the downsized engines with good results in NEDC testing on the chart are smaller B- and C-segment cars, while the Mazda model used in the test is a D-segment Mazda 6.

"We believe that SkyActiv is never behind downsized engines in terms of real world fuel economy. However, unfortunately automotive tax is determined by regulatory mode fuel economy therefore we have no choice but to improve fuel economy in light-load range," he said, adding that Mazda is already working on solutions to that will see SkyActiv engines matching downsized engines in light-load operation.

"We are aiming to make SkyActiv engines superior to 50 per cent downsized engines across all operational ranges," he said.

He went on to explain that the use of downsized engines also increased the cost of producing SkyActiv engines.

"Boosted downsized engines have turbochargers and intercoolers. We are sure that the cost of SkyActiv is much less than downsized engines. SkyActiv has relatively larger displacement, however its cost is less than downsized engines and its real world fuel economy is better, we believe."  

Read the rest of our exclusive interview with Mr. Hitomi in issue 005 of our Automotive Industry Review. You can download a copy here. Past issues can be downloaded from here.