The Volkswagen Polo BlueGT has Active Cylinder Management to provide the petrol-engined Polo with diesel-like running costs
5 July 2012

What is it?

With car manufacturers seeking ever cleverer ways to reduce the consumption of their latest models to meet stringent emission standards we've been exposed to quite a lot of new fuel saving technologies n recent times.

Features such as automatic stop/start, brake energy recuperation, on-demand engine ancillaries and low rolling resistance tyres have gone from being exotic options not that long ago to just about universal standard today.

However, they're not the end of it. Because, as signs have it, there's another fuel saving technology that's about to go prime time: cylinder shutdown, or as Volkswagen prefers to refer to it, Active Cylinder Management (ACM), for small displacement engines.

Previewed by Volkswagen earlier this year, it is included on a frugal new version of the German car maker's latest turbocharged 1.4-litre four-cylinder direct injection petrol engine, the EA211 as it is known, fitted to a new sporting version of the Polo called the BlueGT.

The principle of ACM is simple, and a good deal less expensive than other systems already applied to larger capacity powerplants, with a set of electronic actuators sitting above the camshaft on the middle two cylinders controlling the movement of the valves and fuel injection.

At revs between 1400 and 4000rpm and torque loads between 18 and 74lb ft - a characteristic Volkswagen claims covers nearly 70 per cent of all driving states, the valves and injection process is shut down, effectively turning the engine into a 700cm3 twin for lower consumption and emissions, most noteably in city driving and at constant motorway speeds.

What's it like?

With 138bhp and 162lb ft, the Polo BlueGT is both eager and refined, with satisfying off the line accelerative qualities, a flexible in gear character and, thanks to a heavily overdriven seventh gear, a relaxed cruiser on the motorway. It always feels more enthusiastic than the Polo 1.2 TSI, as shown by its official 0-62mph time of 7.9sec and its 50-75mph fifth gear split of 9.5sec. Just don't expect Polo GTi levels of performance.

But its prime attraction is its economical nature. Volkswagen claims 62.7mpg, giving the Polo BlueGT average CO2 emissions of 105g/km. By comparison, the Polo 1.2 TSI is rated at 53.3mpg and 124g/km. On a 60 mile motorway run out of Amsterdam we managed 76.4mpg, proving both the worth of ACM and a series of aerodynamic tweaks brought to the new car, including bumpers, sills and rear hatch flaps brought over from the Polo BlueMotion.

The operation of ACM is virtually seamless with a display in the instrument being the only real indication of what mode you're in; there's a very slight alteration in engine character as it shuts down the valves and injection and switches into two cylinder mode. But as the pistons continue to operate within the second and third cylinders the reciprocating masses and inherent vibration does not change.

The engine never feels quite as strong in two cylinder mode as it does in four-cylinder mode, with tardier pick when you ease gently into the throttle. Push harder though and ACM switches the engine from two-cylinder back into four-cylinder mode, instantly providing the BlueGT with a full level of performance.

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Should I buy one?

A game changer, then? In certain respects, yes. If the promise shown by the Polo BlueGT's new engine is any guide, cylinder shutdown is set to become an integral fuel saving feature in coming years - and not just high end models but in volume offerings, too.

Volkswagen says it is already preparing ACM for the seventh-generation Golf due out in September, suggesting the new technology ill help lessen its dependence on even costlier diesel engines as buyers once again warm to the more refined  qualities of its latest 1.4-litre four-cylinder unit. Given the way it broadens the Polo's spread of scope of abilities, we wouldn't disagree.

Volkswagen Polo BlueGT

Price: £18,750 (est); Top speed: 131mph; 0-62mph: 7.9secs; Economy: 62.7mpg; CO2: 105g/km; Kerb weight: 1146kg; Engine: 4-cyl, 1395cc turbocharged petrol; Installation: front, transverse, front-wheel drive; Power: 138bhp at 5600rpm; Torque: 162lb ft at 1500rpm; Gearbox: 7-speed double clutch

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Comments
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Fidji5 6 July 2012

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I think VW should offer the 105bhp 1.6 turbodiesel engine in the Polo in the UK - it's available in the identical Ibiza, Fabia and A1. The downside to this engine is that it usually comes with a five-speed 'box, which makes motorway journeys not as refined and frugal as they could be. Nonetheless, it can emit 99g/km of CO2 in heavier cars, like the Golf and Octavia, so should manage about 80mpg in the Polo. It would also offer decent performance and loads of torque.

Flatus senex 6 July 2012

Fidji5 wrote: I think VW

Fidji5 wrote:

I think VW should offer the 105bhp 1.6 turbodiesel engine in the Polo in the UK - it's available in the identical Ibiza, Fabia and A1. The downside to this engine is that it usually comes with a five-speed 'box, which makes motorway journeys not as refined and frugal as they could be. Nonetheless, it can emit 99g/km of CO2 in heavier cars, like the Golf and Octavia, so should manage about 80mpg in the Polo. It would also offer decent performance and loads of torque.

I am always a little puzzled about this pre-occupation with the number of ratios in a gearbox. For motorway work it is the final drive ratio that matters. If the power unit has adequate torque and refinement then a four speed actually would be adequate. I have no experience of the 105bhp power unit mentioned but there are several instances where press reviewers are unimpressed by its noise and refinement levels. Six, seven or eight forward ratios would not alter this.

petegeoff 6 July 2012

Gears!

Doesn't it spread the ratios so that the power is used better with 6 gears? Why are car makers putting 6 gears in now? Iwould agree about motorway driving but around town I find it much better to have a wider spread of ratios. It's not as though they're go-faster stripes or even these rediculous low profile tyres many are obsessed with. Regards. quote=Flatus senex]

Fidji5 wrote:

I think VW should offer the 105bhp 1.6 turbodiesel engine in the Polo in the UK - it's available in the identical Ibiza, Fabia and A1. The downside to this engine is that it usually comes with a five-speed 'box, which makes motorway journeys not as refined and frugal as they could be. Nonetheless, it can emit 99g/km of CO2 in heavier cars, like the Golf and Octavia, so should manage about 80mpg in the Polo. It would also offer decent performance and loads of torque.

I am always a little puzzled about this pre-occupation with the number of ratios in a gearbox. For motorway work it is the final drive ratio that matters. If the power unit has adequate torque and refinement then a four speed actually would be adequate. I have no experience of the 105bhp power unit mentioned but there are several instances where press reviewers are unimpressed by its noise and refinement levels. Six, seven or eight forward ratios would not alter this.

[/quote]

Flatus senex 6 July 2012

[quote=petegeoff] Doesn't it

[quote=petegeoff]

Doesn't it spread the ratios so that the power is used better with 6 gears? Why are car makers putting 6 gears in now? Iwould agree about motorway driving but around town I find it much better to have a wider spread of ratios. It's not as though they're go-faster stripes or even these rediculous low profile tyres many are obsessed with. Regards. quote=Flatus senex]

I actually equate gearboxes sprouting extra ratios as being akin to low profile tyres and go faster stripes as  fashion whims. (As an aside I bought a vehicle as a "no brainer" offer which included both but got the garage to remove the go-faster" stripes to the considerable benefit of its appearance!) Perhaps these questionable three or two cylinder power units do need an extra ratio or two but, assuming a motor with a decent spread of torque, the first four speeds deal with all urban situations. From 35mph upwards top gear is selected and any further stirring of the gear lever (which has a fuel consumption penalty in itself) is rarely needed.

petegeoff 6 July 2012

Who knows?

Flatus senex. I agree about numbers of gears some autos seem to have now. 7 and 8 seems a lot. Not driven any like like that yet. Can the car make up its mind which gear to be in? Especially at low to medium speeds. I can't see car makers going back to 5 speed manuals now though.

On another point, "fake" gears on CVT 'boxes. Any point to that? I'm sure I've seen some ads saying a car has x number of gears on a CVT ! Regards.

Fidji5 6 July 2012

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Isn't this engine 1390cc, not 1395cc?

EngageSportMode 5 July 2012

I'll be very much surprised

I'll be very much surprised if it hits that 62.7mpg figure in the real world. Given how well "massaged" cars are to go through EC mpg testing, I wouldn't be surprised if it falls to mid 40s realistically.

Plus, I'm unconvinced by what message this car is giving. Is it sporty with economy, or an economy car made to look sporty? Think I'd sooner have the old 1.9 GT TDI Polo.

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