Available in the mid and top of the range Comfort and Style trim levels, the new engine boosts power to 77bhp and torque to 87lbs/ft compared to 65bhp and 73lbs/ft for the 1.1 litre.
As a result, the top speed rises from 94 to 102mph, the sprint to 62mph falls almost three seconds to 12.8 seconds, and Hyundai claim improved in-gear acceleration and better cruising ability.
Emissions and combined fuel consumption are identical to the 1.1, at 119g/km and 56.6mpg respectively, meaning it falls into the same tax group as the lower powered unit.
The engine adds £150 to the mid-range Comfort trim, with an extra £800 for the automatic gearbox, and £200 to the range-topping Style.
Buyers will also be able to add ESP for the first time, at £350.
The new engine allows Hyundai to step up production to meet demand.
More than 2,500 have been delivered in the UK, with waiting lists for across the range and some dealers advertising above list price.