The general sentiment associated to the word diesel has been a long but ineradicable stigma in Malaysia, to say the least. Let’s face it. How many of you are put off by the idea of driving a car that clatters louder and smells no better than your granduncle’s good ol’ Isuzu Trooper? Fortunately, times (and people) are changing, but many still chafe at the thought of a diesel powered daily runabout, pickup trucks not withstanding.
Now, just days after BHPetrol introduced their Infiniti Euro5 diesel fuel to the Klang Valley, we leapt at the opportunity to sample one of Mazda’s finest, the Mazda2 1.5L Skyactiv-D. Our last stint with the very same car had a full tank of Euro2m diesel, but that did more than a good enough job in convincing us that it’s the Mazda2 to have. With Euro5 now in place, let’s help Bermaz Motor shed some ‘green’ light on the matter at hand.
i. All about that torque
A diesel engine is best known for its fuel efficiency (more on this below), but the main reason behind its suitability in powering heavy duty industrial vehicles, busses and utility trucks is because the diesel fuel is much denser or richer in energy, therefore providing greater pulling power (torque) that’s accessible at low engine speeds. Just how quick is a diesel powered car, you ask? Well, click to watch a video of an Isuzu D-Max blaze across a quarter mile strip in 8.2 seconds. Yep, an Isuzu D-Max with a four cylinder diesel engine that’s capable of humbling Dominic Toretto and co.
So, imagine having 270 Nm of torque in a Mazda2, all harnessed from the turbocharged 1,499cc Skyactiv-D engine. In comparison, the 1.5-litre petrol (Skyactiv-G) engine delivers 114 hp and 148 Nm of torque – a full 102 Nm lesser than its equal sized diesel counterpart! On the subject of compression ratio, Mazda engineers ambitiously took both these Skyactiv engines a few steps beyond the conventional.
The gasoline engine operates at a ratio of 14.0:1 (that’s really, really high for petrol powered vehicles), whereas the oil burner cranks at a relatively low 14.8:1 when some diesels go as high as 22.0:1. In justifying this, Mazda cited that their pursuit of an ideal combustion resulted in the creation of an all-aluminium, low compression turbodiesel engine. In short, it’s not just more powerful, it burns leaner than the petrol as well.
ii. It’s still that much fun to drive
Despite being nearly 80kg heavier on the front end, the Mazda2 Skyactiv-D’s fun-to-drive character remains surprisingly intact, if not made better by the low-rev torque surge. Trust us, there’s not a single time where we weren’t caught smiling sheepishly when flooring the throttle upon exiting a corner. Granted, there is a discernible dive during hard braking, but that came to light only after spending weeks driving the petrol variant. Imagine had we not!
The fact that the brakes weren’t as grippy as we’d like had very little to do with its poor stopping performance, but rather because the discs were of the exact size as the petrol. With all that additional power – and more importantly weight up front, the only thing that’s missing from what is otherwise a complete package is better brakes.
iii. Sure, it rattles, but does it really matter?
Diesel engines, for as long as they’ve been around, rattles. The reason behind this lies in its combustion process. During an intake stroke of a gasoline engine, both air and fuel is injected into the cylinder before being compressed and subsequently ignited by a spark plug. This tiny explosion drives the piston downwards, creating what is known as the power stroke, a motion which sends torque to the crankshaft.
In a diesel engine however, there are no spark plugs at all, and ignition occurs simply by compressing air, and just air alone. The higher the compression ratio, the more heat (up to 260°C) is created during the compression stroke. What happens when you inject fuel into this extremely hot pocket of air? Ignition. And it’s this very process that gives a diesel engine its characteristic knock or clatter. Who’s to say that they don’t rattle now? They still do, in fact very distinctively as well, much like a sewing machine on loudspeaker, but hardly discernible from inside the cabin thanks to progressive insulating technology.
iv. Diesel engines are generally tougher, more robust and longer lasting
Contrary to popular belief, the clanky nature of oil burning engines does not mean that they wear out much faster, but instead have extremely long lifespan, in most cases even longer than gasoline engines if given appropriate care. Website pieced together nine cars whose owners drove past the million-mile mark (that’s 1.6 million kilometres, all with the original engine!), a feat only so few can achieve in a lifetime.
So what makes a diesel engine robust? Well, this goes back to its nature of combustion. Because they operate at such extreme ratios, the mechanical components of the engine have to be made of denser steel. This in turn require the use of heavier pistons, crankshaft, bearings, rings and what have you.
Again, Mazda’s 1.5-litre diesel engine has a low compression ratio of 14.8:1, which is one of the reasons why the entire engine can be made out of aluminium. This not only reduces weight by a significant margin, Mazda also claims that it makes the engine more dynamic, allowing for a greater rev range because the moving components are so much lighter. We can attest to that.
v. Exceptional fuel efficiency
As mentioned earlier, the diesel fuel contains more usable energy than gasoline, sometimes up to 50 percent in a single drop of diesel. In a real-world scenario, that translates to superior fuel economy, covering between 30 to 40 percent more tarmac than comparable gasoline engines. There’s nothing quite like a diesel engine’s fuel economy when cruising on freeways, as they rack up more kilometers per litre as opposed to gasoline, hybrids or even electric vehicles. To prove this, Mazda specifically flew us to Bangkok, dumped us in the Mazda2 diesel and had us drive over 1,000 km in a single tank of fuel because you know, they were certain we’d make it. What if we didn’t, guys?!
A key contributor in the Skyactiv-D’s remarkable fuel efficiency is the use of Piezo injectors (connected to the fuel rail, typically a common rail setup in diesel engines) which are far more precise than traditional fuel injectors. They for one, act really quickly and can inject fuel as many as seven times during a single combustion cycle, but only when needed. Such level of precision yields better fuel economy and reduced emissions. Win, win, win.
With the cleaner Euro5 diesel making its slow entry across the country, we’ve reached a point where we could finally see a new wave of vehicles making its way here. Sources from Bermaz Motor have not completely dismissed their plans to introduce the diesel-powered CX-5, Mazda6 and Mazda2, but whether or not they make it here remains to be seen. If anything, chances are they might already be well in the planning stages of introducing the highly anticipated CX-5 Skyactiv-D. Until then, let’s keep our fingers crossed in hoping that these cars will find their way here.