Toyota Prius Mk4

	Toyota Prius
	Debut: 2015 Maker: Toyota Predecessor: Prius Mk3

Published on 31 Dec 2015

Time passes so quickly. The first Toyota Prius was launched just a few months after AutoZine. Now it is in the 4th generation. In the past 18 years, some 3.6 million units have been sold worldwide. The majority of them belonged to the Mk2 (1.2 million units) and Mk3 (estimated 2.2 million units). In good years, Toyota could sell 400,000 to 500,000 units a year, more than many big nameplates. However, since 2011 its sales performance started declining. Why? Because oil prices dropped dramatically. More people shifted to SUVs and crossovers. Perhaps Toyota should build a Prius SUV – if Bentley and Lamborghini can, why not Prius? No, it is not going to do so, fortunately. Toyota’s response is to improve its fuel efficiency further. A strange strategy it might be, I am glad to see it keeps doing the right thing even though the rest of the world gets crazy.

A few words sum up the 4th generation Prius: an adventurous styling matches evolutionary engineering. The new car looks certainly new but also controversial. Its headlights and taillights are radical to the extent of over the top. There are a lot of sharp edges and twisted surfaces so that it looks quite busy, especially around the rear quarter. However, this also makes it less MPV-like and more distinctive, unlike its predecessor. The new body profile gets lower and sleeker at both ends, while the peak of its roof is moved forward so that it forms a waterdrop shape, which explains why its Cd is improved further from the already remarkable 0.25 to a class-leading 0.24. The whole car is slightly longer (by 60 mm), wider (15mm) and lower (20 mm), although its wheelbase is unchanged at 2700 mm.

Toyota stresses that its center of gravity is lowered, thanks in part to mounting the powertrain 10 mm lower. The front seats are mounted 59 mm lower to create a sportier driving feel while improves headroom. Rear occupants are not so lucky as the battery and fuel tank take the space underneath the rear seat. Note that the battery in the last Prius was mounted in the boot. As it is moved forward, the boot floor can be lowered. In addition to the longer rear overhang, luggage space is enlarged from 446 to 502 liters. In other words, it is no longer a compromise.

As before, the Prius is powered by a 1.8 VVT-i Atkinson-cycle engine in combination with electric motors and CVT transaxle, the latter two are integrated and mounted beside the transverse engine. Toyota spent a lot of effort to improve its fuel efficiency. For example, the engine has increased EGR and reduced internal friction, boosting its thermal efficiency from the previous 38.5% to 40%, which matches diesel engines. The motor and transaxle unit is made smaller, lighter and has 20% friction removed. Likewise, the power control module is made smaller and more efficient. The battery – still Nickel-Metal Hydride on standard car, although now extra cash could buy you a 15-kg-lighter Lithium-ion pack – is also smaller and has higher energy density. Overall, Toyota claims 10% reduction of fuel consumption compared with the Mk3. In European terms this means 94 mpg and 70 grams of CO2 per kilometer. US rates it as 54 mpg city and 50 mpg highway.

On the downside, the new car fails to improve performance. The new engine produces a modest 97 SAE horsepower, actually 1 hp down from the old engine. The smaller electric motor produces 72 hp instead of the previous 80 hp. As a result, the combined output of engine and motor drops from 134 to 122 hp. The car should take 10 seconds and a great deal of patience to accelerate from 0-60 mph. Its top speed is still capped at 112 mph.

However, the new car should be still better to drive, thanks to a significantly improved chassis. Not only the torsion-beam rear suspension has been replaced with a double-wishbone setup which mirrors the Mirai, the body shell is massively strengthened by 60 percent in torsional rigidity, thanks to using more high-strength steel (increased from 3 to 19%), laser welding, structural adhesives and parts of varying thickness. The bonnet, tailgate and front crash bar are now made of aluminum to offset the weight gains of the suspension. In addition to the lower center of gravity, the car should perform swifter in corners.

Moreover, the Prius is now available with optional e-4WD for the first time. In this form, a high-power motor is added to the rear axle to provide extra power and traction. All these improvements are possible only because the car sits on the new TNGA (Toyota New Global Architecture) platform, an equivalent to Volkswagen MQB. It allows higher flexibility for different configurations hence larger scale of economy.

On the road, the new Prius is definitely better to drive. There is a new found precision in its steering and less roll in corners. The steering is more direct since it is geared 15 percent quicker, although feel remains largely absent. The combination of independent rear suspension, stronger chassis and enhanced sound insulation results in a more composed ride and a quieter cabin. Now you can finally enjoy the silent operation of its powertrain on less than perfect surfaces. Meanwhile, Toyota also manages to improve the brake feel. Now the transition between regenerative and mechanical braking is a lot more linear and natural. That said, the Prius is still hardly a driver’s car. It’s handling is more competent than the old car but still you will never call it good or exciting. Its performance is mediocre, and the CVT’s rubber-band effect, although reduced a bit, is not going to disappear as long as its main objective is to save fuel.

In the cabin, the Mk4 Prius keeps its traditional central instrument and minimalist design, so it is hardly inspiring. Plastics and switchgears remain on the cheap side, falling behind the class norm. Although the amount of space is about the same as before, it feels larger, thanks to an airier atmosphere created by the slimmer pillars, lower windscreen cowl and the deletion of floating console.

Apart from the more radical exterior styling, the new Prius is perhaps too predictable. It follows closely the format set by its predecessors and only improves things bit by bit. That’s not enough to win new customers. No wonder Toyota forecasts it will sell 300,000 to 350,000 units annually. In other words, it won’t be as popular as the last generation. The Prius nameplate deserves a bigger step forward.

Verdict:

Published on 7 Oct 2016

Prius Prime (Prius Plug-in)

The plug-in hybrid version of Toyota Prius is called Prius Prime in America or simply Prius Plug-in in Europe. It sounds a simple conversion that hardly raises our interest, but look again and you will find plenty of interesting changes. First of all, the car looks different. To accommodate the larger battery, its rear overhang is extended by 80 mm and this necessitates a styling overhaul. Toyota takes this opportunity to inject more style, giving it a Zagato-style double-bubble rear hatch, whose frame is made of carbon-fiber to save weight but the screen is real glass, unlike the polycarbonate items on many Aston Martin Zagatos (considering its production volume, Toyota has no problem to afford the cost of bespoke glass). Up front, the Prius’ nose is also smartened up with a black fascia and Mirai-style quad-LED headlights. This car still looks strange – perhaps even stranger – from my conservative taste, but it does stand out from the crowd.

Under the rear seat and cargo floor, there is now an 8.8 kWh lithium battery, versus 0.7 kWh of the regular Prius or 4.4 kWh of the last generation Prius Plug-in (which was a sale flop, btw). It gives the car an EV-range of 25 miles or 40 km before needing the intervention of petrol engine. The 1.8-liter engine remains the same, as are the hybrid system’s 2 electric motors. However, while the regular Prius uses only the larger motor for propulsion and the smaller one for starting and regeneration, the Prime can use the latter for propulsion also, thanks to the addition of a one-way clutch. As a result, the electric power is boosted by 20 hp, although combined maximum output remains unchanged at 122 hp because the smaller motor gives up working earlier. The car can run on stored electricity alone at up to 84 mph, covering the majority of driving situations. Nevertheless, as the car gains 150 kg of weight, its 0-60 mph acceleration gets slightly worse at about 11 seconds.

On the road, as long as the battery is not depleted, the Prime provides enough punch and performance to satisfy most driving needs. Built on the TNGA platform, its ride and handling are also much more decent than any previous Prius. In fact, with more time to fine tune the chassis, it drives better than the Prius hybrid. The steering feels more naturally weighted. The ride seems more compliant. Although there is still more pitch and roll than desired, the car feels agile enough to go head to head with most family cars.

Inside, the Prime loses the middle rear seat and 142 liters of luggage space due to the larger battery. It is not as practical as the regular Prius, of course, but in return you get a more upmarket, 11.6-inch portrait touchscreen at the center console. Moreover, the plug-in hybrid remains economically viable like all Prius do. It is significantly cheaper than Chevrolet Volt yet returns lower fuel consumption. The only concern is how much Toyota will charge for repairing the carbon-fiber hatch in case it is damaged by rear collision. This is the best Prius so far, if still not something we would choose over a Passat, a Fusion or Mazda 6.