Mazda SKY powertrains

Mazda SKY powertrains

What we liked
>> Linear delivery of twin turbodiesel
>> Surprising flexibility of petrol DI engine
>> Performance of new auto box

Not so much
>> Manual gearshift throw is not quite right
>> Bit too early to grizzle, really...

About our ratings

You have to award them medals for bravery if nothing else. After all, not many car companies even want journos to see their development vehicle three years out from production, let alone drive them.

But drive is exactly what Mazda wanted us to do in its groundbreaking SKY Global Next Generation Technology Forum in Berlin in the last week of August.

Two years after committing to reduce the fuel consumption of its mainstream models by 2015 via its proprietary SKY technology, Mazda made the (correct) call that it was time to put some meat on the bones of its promises. To do so it not only wheeled out its heaviest hitters in terms of R&D staff including board member Seita Kanai but it also pulled four SKY powered Technical Prove-out Vehicles (TPV) from their European development program duties and allowed them to be driven.

And the good news for Mazda is the gamble worked. Not only were the development mules returned unscathed but they performed beyond expectations. Job done.

We've covered the technical story behind the SKY-G petrol and SKY-D turbodiesel (pictured) powertrains and their complementary SKY-Drive six-speed auto and manual gearboxes via our news pages (see links below) so we won't regurgitate all the details here. The same goes for TPVs (effectively development mules for the next Mazda6 using Mazda's all-new platform) themselves. Rather, this quick drive impression is meant to convey some appreciation of how the SKY vehicles performed in their entirety.

And given they are close to three years away from on sale they were impressive.

That the SKY-D turbodiesel is the pick is probably no surprise to many. The 2.2-litre unit is terrifically refined already despite sitting in a chassis that still has a way to go regards noise vibration and harshness (NVH) fine tuning as well as production-level noise attenuation.

There's a clear diesel clatter at idle but it's not as strident as BMW's latest high-spec four-cylinder oiler. Then as the revs rise the engine has a much more sporty note to it. As it approaches its 5200rpm redline (positively stratospheric for a diesel) there's little hint of straining or harshness. It still sounds willing.

Our test route was largely autobahn -- a good portion unrestricted and therefore not exactly indicative of local Aussie road conditions. We did our best, however, to replicate the normal 80-120km/h overtaking conditions so prevalent on our own road. The news is good.

In the manual version even left in sixth gear, the engine was quick to respond and delivered positive in-gear urge. In fifth acceleration was vivid.

The SKY-Drive auto box, though still a touch coarse in its kick down, dropped straight to fourth gear and the meat of the turbodiesel's powerband and positively rocketed up to the 120km/h mark.

On the autobahn it was too tempting not too engage in some high-speed shenanigans and the SKY-D equipped car was quick to hit the 200km/h mark and happy to stay there. A real 220km/h was easy meat for the 420Nm torquer (the TPVs have accurately calibrated speedos for the engineers' use).

But the more impressive characteristic was the ability of the car to accelerate from less than 50km/h to more than 200 in the same sixth gear. Unlike most high-powered turbodiesels the SKY-D exhibits little if any lag and the power deliver is absolutely linear. Roll into the throttle from idle revs and the acceleration just builds with none of the 1400-1600rpm region surge to which most of us are familiar.

This linear nature is a clear demonstration that Mazda's engineers have got the operation of the sequential twin turbos just right. Though there is more calibration to do they say, it seems pretty good to us.

The same goes for the SKY-G 2.0-litre direct-injection petrol powerplant. Yes, we expected the diesel to be torquey and impressive in performance terms but the surprise was the onroad performance of the comparatively weedy petrol mill with its mild 210Nm -- half of the SKY-D's quotient of twist.

Possessed of a degree of refinement already, the DI petrol engine exhibits all the characteristics of a low-blow turbo engine save for the whine of a turbine or any lag twist throttle and engine response.

A resonating sheet metal exhaust shield added a timbre to the SKY-G's engine note in the TPVs that will not be there in the finished item which is a shame. That we could hear the slight offbeat sound at all indicates how quiet the engine is -- already.

In terms of power delivery it is again quite linear, not always a characteristic of naturally aspirated 2.0-litre engines. Though not as rapid as its diesel counterpart it easily coped with the bulk of the new 6. Indeed, in terms of a seat of the pants impression (always dangerous) we'd suggest that it would be close to a match for the current 2.5-litre model in overall performance.

The petrol engine was well matched by both the new manual and auto boxes. The manual especially let the engine display its flat torque curve -- which delivers 190Nm at less than 2000rpm).

Again we attempted to replicate normal Aussie highway overtaking amidst the rapid Friday afternoon autobahn traffic and can report that are no issues with lack of urge. It's no V8 beater but nor will it leave you exposed on the wrong side of the road for too long. And all the time remember it's doing so using better than 15 per cent less fuel than the conventional powertrain.

Mazda's Europe-based engineers who accompanied the Aussie drivers on the short 47km test loops reckon the TPVs represent cars that are around 90 per cent finished in terms of suspension and engine calibrations. There's still plenty of work still to be done, they say, in terms of picking tyre specs, stability control calibrations and the like, and more work to do on NVH. It's these myriad checks and rechecks that make up the four to six year program it takes to put a modern car on the market.

But again we were impressed at the level of refinement and resolution of the chassis of the new 6, err... I mean TPV. Though wearing cobbled together (literally handmade riveted front panels) current model Mazda6 bodywork and only partially complete interiors, noise levels were well controlled. And even at autobahn speeds with blustery crosswinds the cars tracked arrow straight with excellent stability.

Alas, the test route wasn't exactly replete with cornering opportunities.

We can report that at high speed on the autobahn body control was good in fast lane changes and through the one fast entry ramp we managed to score. The rest of the handling story will have to wait till a later date.

So it's a tentative thumbs up for SKY... At least at this early report card stage. We still only have Mazda's word for the fuel economy gains but if they prove to be true in the real world then the Hiroshima mob may well be on to a winner... Like you we'll watch the technology's next chapter with keen interest.

Read the latest Carsales Network news and reviews on your mobile, iPhone or PDA at carsales' mobile site