Toyota Prius c launched in US

Toyota’s launch of its new baby Prius in the US reveals substantial revisions to its Hybrid Synergy Drive, making the package smaller, lighter and more efficient.

Toyota describes the Prius c (it stands for 'city') as "striving to strike a balance between fuel efficiency, styling, intelligent connectivity and fordability to attract younger, eco-conscious buyers who may have desired, but couldn’t afford, a hybrid".

To cram its Hybrid Synergy Drive technology viable into a vehicle some way smaller than the standard Prius hatch, the company has carved 14 per cent off its overall weight. The weight loss regime includes a major overhaul to the transaxle, carving about 16 per cent from its weight and a NiMH battery pack reduced from 168 to 120 cells, cutting mass by around 25 per cent from 42 to 31kg. The power inverter is also 10 per cent lighter and 12 per cent smaller. The battery pack sits with the fuel tank under the rear seat, eliminating its much grumbled-about incursion into cargo space in the larger Prius.

The Prius c combines a 1.5-litre Atkinson cycle petrol four with a new hybrid transaxle, an air-cooled, 144V, 6.5Ah NiMH battery and a variable-voltage system using a boost converter to extend its operating voltages to 520 V DC. The company rates the hybrid package's peak output at 73.6 kW.

Toyota says the Prius c's petrol engine is "about 70 per cent new". Major revisions to the exhaust gas recirculation system reduce energy dissipation from cooling and pumping, upping heat efficiency and fuel economy.

By eliminating ancillary drive belts, they've cut losses from friction. A new electronically activated, electric powered water pump allows the ECU to monitor operating conditions and vary the rate of coolant flow to help further optimise fuel efficiency.

Tweaks to the engine's variable valve timing calibrations boost torque across the rev range while improving fuel economy and cutting exhaust emissions. Peak power is a claimed 54kW at 4800 rpm, with peak torque of 111Nm reached between 3600 and 4400 rpm.

Toyota has worked to keep aerodynamic drag down, with the addition of subtle stabilising fins, underbody covers and wheel covers over lightweight aluminium rims helping deliver a drag coefficient of 0.28. It’s more than the larger Prius’s 0.25, but they put that down to difference in size – the shorter a car, the harder it is to keep Cd down.

The net result is a claimed US fuel economy rating of 4.7 L/100 km on the combined cycle (4.4 and 5.1 urban and highway respectively).

With its bid to expand the Prius brand in new directions, Toyota has conceived the Prius c as an entry point to the range, targeting younger buyers.

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