After much anticipation following the global introduction of Mazda’s diesel proposition, the new Mazda SkyActiv-D twin-turbocharged diesel powerhouse has finally arrived on our shores, a few short years after its global debut. Initially featured globally in the pre-facelift CX-5, the SkyActiv-D 2.2-liter turbodiesel engine is the first of its kind developed by Mazda with many key notable features unheard of before in oil-burning production cars.
For Malaysia, the SkyActiv-D 2.2 will initially be featured in the Mazda CX-5 and Mazda 6, while a smaller 1.5-liter SkyActiv-D engine is undergoing evaluation in a yet to be launched CX-3. Bermaz Motor has indicated that this is but a first of many SkyActiv-D launches to come, and we wait with bated breath to experience the full range of gut-wrenching, ball-busting torque that only a turbodiesel, and in particular, a SkyActiv-D engine can deliver.
In the morning before its local unveiling, us lucky journos were given the opportunity to lay our greasy palms on the turbodiesel variants of the CX-5 and 6 on a short media drive down south, with enough time behind the steering wheel of each model for us to provide an initial field impression.
First off, some background info on SkyActiv-D and what makes it so groundbreaking and truly one of a kind. Initially, when Mazda created SkyActiv-G (G for Gasoline engines, D for Diesels), they featured never before seen astronomically high compression ratios of up to 14:1, which would cause ordinary petrol engines to detonate or crumple up in a big lump of metal and nasty byproducts due to the explosion. Mazda’s engineers cleverly bended science and physics to do their bidding to create some of the most efficient engines the world has ever known, without resorting to forced induction. For diesel though, the reverse is what they did. A typical diesel engine needs between 15:1-23:1 compression ratios in order to compress the fuel enough to start the combustion process autonomously (without requiring a spark plug to ignite the fuel).
If a diesel engine’s compression ratio is too low, combustion cannot happen. Too high and a lot of inefficiencies start to occur due to heat, not to mention the inability to rev up the engine beyond 4,000 turns. So why bother with diesel altogether, given the many physical roadblocks, aside from earning a bad rep over the decades as a smoke machine and soot generator? Two words. Thermal Efficiency. In layman’s terms, thermal efficiency refers to the efficiency of the fuel to generate mechanical power. A typical gasoline engine (petrol) is said to be about 30% efficient while a typical diesel engine gets to around 45% efficiency, meaning you get more miles to the gallon, liter for liter. And considering the current price per liter of diesel (Euro 5) which is cheaper than RON 97 (Euro 4M) petrol, suddenly it all makes sense doesn’t it? The typical range of a 2.0L petrol engined car is around 400-550km to the tank, while an equivalent diesel powered car will easily have a range of around 800-950km for every tank! So in other words, even if petrol and diesel were to cost the same at the pump, you’d still be visiting the fuel station a lot less if you were running a SkyActiv-D.
The other thing that makes sense to go with diesel is the huge amounts of low end torque that consumers can measure with their derrieres, a.k.a. butt dyno. Diesel fuel has great thermal expansion which translates to a larger energy potential with which to turn the engine over, resulting in more work done at a lower rpm. What the layman feels is instantaneous and exhilarating acceleration which is now only starting to be emulated by turbocharged petrol engines with a broad powerband, thanks to variable geometry turbos and other forms of variable boost control. To such laymen, the initial accelerative force gives them the impression of a very powerful engine under the hood. Having said that, the party ends a little too early, as traditional turbodiesels tend to redline around the 4,000rpm mark. Clever engineering has allowed Mazda to push the envelope by a massive 25%, giving SkyActiv-D turbodiesels a very respectable 5,000rpm redline which matches a typical turbocharged petrol engine in terms of powerband range.
One other notable feature of the new SkyActiv-D engines is their inherent quietness, which Mazda claims to rival petrol engines. Diesel chatter is one of the banes of diesel engines, and has resulted in many lost potential sales as consumers didn’t want to be associated with clunky old diesel taxis. The lower compression ratio of Mazda’s SkyActiv-D engines allowed them to build said engines with lighter materials that do not need to withstand the tremendous pressure associated with standard diesel engines with higher compression. The benefits are two-fold; lighter components (pistons, connecting rods etc) produce less diesel chatter while being more efficient due to the decreased rotational mass. Put in practice, we noticed the diesel chatter to be very much subdued and closely mimicking the pulse of direct injection petrol engines. Having said that, diesel chatter is still present but once the hood is closed, the chatter is kept to an absolute minimum, and once inside the cabin, the only giveaways are the gobs of low end torque and insane traveling range.
For more details on Mazda SKYACTIV-D feature, please follow Part 2 of the article…