Among the more significant changes over the existing turbocharged 1.4-litre four cylinder TSI engine is a smaller 74.5mm bore and longer 80.0mm stroke – something that suggests there will also be larger capacity variants of the EA211, too. The compression ratio has also risen.
What’s it like?
With 138bhp and 184lb ft of torque at 1500rpm – some 34bhp and 55lb ft more than the existing Polo 1.2 TSI, the four-valve-per-cylinder engine provides the Polo 1.4 ACT with spritely off-the-line qualities, a satisfyingly flexible in-gear character and, thanks to long gearing, a relaxed cruising nature.
Nothing is official just yet, but expect on a 0-62mph time around 8.0sec and top speed around 125mph for seven-speed DSG (dual shift gearbox) equipped versions like that tested. Creditable performance, then.
However, it is the engine’s ability to seamlessly switch from four to two cylinder operation that impresses the most. It takes a steady application of throttle at engine speeds above 1250rpm to make the transition, but when it does the only hint two cylinders have been deactivated is an advisory in the instrument panel and slightly raw exhaust note – something Volkswagen’s development engineers say will be altered before production begins. There’s no loss of momentum, as the revs are immediately matched to take into account the lower capacity.
Ease into the throttle gently and it is immediately obvious there is less power on tap in two-cylinder mode. But at city speeds and at a constant cruise it does not hinder progress. Push beyond 4000rpm and it automatically switches back into four-cylinder mode, instantly providing the full level of performance.
Volkswagen denies the deactivation of the middle two cylinders could lead to a potentially disastrous cooling of middle section of the aluminium block engine, saying the internal water and oil system has been conceived to heat the middle two cylinders even when they are shut down.
Should I buy one?
The Polo fitted with ACT technology is still at the prototype stage, but it’s clear that the new cylinder deactivation system brings lower consumption and emissions without spoiling performance or the potential for fun.
Overall, the new system is claimed to bring a claimed 0.4 litres per 100km reduction in consumption and 8g/km lowering of CO2 emissions – figures that are likely to see the upcoming Polo 1.4 TSI ACT come close to matching its 1.6 TDI sibling for overall economy and efficiency.
Volkswagen Polo 1.4 TSI ACT (prototype)
Price: TBC; Top speed: 125mph (est); 0-62mph: 8.0sec (est); Economy: TBC; Co2: TBC; Kerbweight: TBC; Engine type, cc: 4 cylinder, inline, 1390cc; Power: 138bhp at 4500-6000rpm; Torque: 184lb ft at 1500-4000rpm; Gearbox: seven-speed DSG