Strong and clean diesel power with Mazda6 SKYACTIV-D

By Lee Pang Seng

THE progressive availability of Euro5 diesel is beginning to see the introduction of more advanced diesel cars and vehicles. Mazda is among the few who see this as an opportunity to introduce its advanced diesel range to cater to the growing confidence and acceptance of such cars.

Sole distributor Bermaz Motor brought in two alternatives, one in the Mazda6 and the other in the CX-5 SUV (sport utility vehicle) or Crossover. We had a go in the Mazda6 and came away duly impressed with the performance of the SKYACTIV technology that was applied to the 2.2-litre turbodiesel engine (which also powers the CX-5).

Having been introduced to this SKYACTIV technology during a visit to Mazda Japan more than three years ago, and having enjoyed it in some petrol versions of the Mazda range, we were looking to more of the same with SKYACTIV-D. Of course, it has to be said that this latest technology from Mazda works best with the more refined Euro5 diesel, with performance tailing off if the less refined diesel fuel is used as well as the higher maintenance that would be required to clean the fuel feed system.

Mazda is understandably proud of its efficient and environmentally friendly SKYACTIV diesel power, which is said to qualify for tax rebates for eco-cars in Japan. It also complies with strict exhaust gas regulations (Euro6) without the need for costly NOx (nitrogen oxides) after treatment systems. Mazda says it has also achieved a breakthrough in overcoming very inefficient cold starts.

The biggest problem in diesel engines is the insufficient heat for complete fuel combustion during cold starts. The conventional solution is to increase the engine’s compression ratio. This, however, results in too high a temperature and pressure, causing incomplete combustion and the formation of NOx and soot. The solution to this is to delay ignition, which causes fuel economy to worsen.

Mazda’s approach 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 fuel feed. The precision in the amount and timing enables optimum air-fuel mixture control, thereby maximising combustion. A variable valve lift (VVL) system is used for the exhaust valves; a single combustion cycle is seen as sufficient for the temperature to rise. Exhaust gas is channelled back into the cylinders to raise temperature further to improve cold start.

This has allowed Mazda to introduce smaller displacement diesel engines that are lighter, yet deliver higher output. The 2192cc engine with double overhead camshafts and 16 valves has a low compression of 14.0:1, much lower than older diesel engines with the SKYACTIV technology. Power-wise, it delivers 127kW (173hp) at 4500rpm and a huge amount of torque at 420Nm at 2000rpm, easily comparable to that delivered by a 4.0-litre V8 petrol engine.

The reduction in compression ratio to 14:1 and pressure made it possible to significantly reduce the weight of the new engine. It comes with an aluminium cylinder block (with iron liners), lighter cylinder walls as well as integrated exhaust manifold; the weight of the pistons is reduced by 25 per cent. Mazda says there is also a dramatic reduction in friction, to the same level of an average petrol unit. Fuel economy is said to be improved by 20 per cent.

While the typical diesel clatter is obvious when the engine is started, it is a lot quieter than older diesel powered cars. It sounds about the same as much older petrol engines and it is not something that one would be bothered about. After all, diesel power is a lot more respectable these days and its benefits are not merely limited to good road mileage and reliable motoring. The humongous torque ensures plenty of get-up-and-go performance to ruffle your feathers.

On starting the car, we noted that a full tank would take us more than 750km via the information offered on the instrumental panel. Later, we also observed that our average fuel consumption was easily above 15km/l (except for the time we did some full-bore runs when that dipped noticeably but it was quickly restored as we went back to ‘normal’ driving).

What we really enjoyed was the near turbo lag performance on take-offs and passing manoeuvres. With all that strong torque coming in early and quickly, we looked forward to the thrill of strong acceleration when opportunity allowed. One could easily believe it was a sportier car and not some ‘mundane’ executive sedan. On a full bore run, this Mazda6 SKYACTIV-D took us to 210km/h (engine speed was about 3700rpm) before we eased off into a sweeping turn.

This strong performance is best explained by the fact this 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. Mazda says 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.

So there you have it; all the technical speak that gave us a nice driving experience over the weekend. This was helped further by the Mazda6’s high level of standard equipment and features to make driving that much more comfortable, enjoyable and hassle-free. We have always liked the start/stop push-button facility and pressing a button on the front door handles to lock and unlock the car.

We also liked being pampered with the Head-up Display (Mazda calls it the Active Driving Display) for ‘level-headed’ safe driving, auto-dimming rearview mirror, driver-side only one-touch (up and down) power window with anti-pinch, 11-speaker Bose surround system, electronic parking brake, leather upholstery, multi-function commander control (as in some of the premium German brands), land departure warning, blind spot monitoring and rear cross traffic alert function, steering paddle shifts for the six-speed automatic transmission, to name just a few in the long list of standard items.

In dynamic performance, we could still recall the drive we enjoyed on the way up to Genting Highlands when this Mazda6 was first introduced here a few years ago. And we continued to find its dynamic qualities confident and likeable as we matched a Volkswagen Golf GTI for pace through some tight sweepers at above 150km/h.

The Mazda6 is not a small sedan; it is 4865mm long, 1840mm wide and weighs 1525kg kerb, which is about average. The front-wheel drive executive sedan is independently sprung all round with MacPherson struts in front and a multi-link suspension at the rear. It runs on 19x7.5J alloy wheels with 225/45 R19 Bridgestone Turanza tyres and has Electric Power Assisted Steering (EPAS).

Directional feedback via the EPAS is reasonably good and the suspension is nicely tuned to provide some good and stable driving through winding roads (we reconfirmed its likeable cornering prowess at pretty good road speeds through our favourite twisty stretch). The understeer though corners is mildly progressive and body lean is nicely checked when driving through the tighter bends.

We also enjoyed the appreciable ride comfort; the suspension did the job of absorbing all the road impacts from potholes, bumps and speedbumps to a good degree to give me and my family a well-cushioned experience. Likewise, the highway drive was equally enjoyed, with the low wind noise, fairly well muted road intrusions and a stable poise.

The SKYACTIV turbodiesel engine ran so quietly you couldn’t tell the difference to a petrol unit, except that it runs at lower revs for the given speed. At 2000rpm, the Mazda6 SKYACTIV-D is cruising at 110-120km/h and it would easily pick up road speed when you add gradual pressure to the accelerator pedal. Yes, it’s hard to stay at legal speeds with this Mazda executive sedan.

As an imported car, the Mazda6 2.2L SKYACTIV-D fetches a premium price of RM203,792.30 on the road without insurance. Then again, this Mazda6 SKYACTIV diesel easily fulfils expectations as a premium class executive sedan with strong all-round performance.

By the way, you might like to know that Bermaz Motor is evaluating two CX-3 1.5-litre SKYACTIV-D Crossovers. This smaller displacement engine is said to be equally impressive in torque and power outputs. It should be a good alternative to look forward to when this Crossover is made available here.

Link here

Mazda 6 Diesel Specification Sheet

Comparison – Mazda 6 Diesel and Petrol Specification Sheet

Mazda 6 2.2L SKYACTIV-D Price List

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