Toyota is looking like it’s got this hybrid lark sorted. Just as it was rolling out the Yaris hybrid to European journalists came news the Prius line alone – never mind Aurion and assorted Lexus models – was the world’s third top selling nameplate in the first quarter with sales of 247,230, behind the Corolla (300,800) and Focus (277,000). More than makes up for the failure of the ‘ybrid-only Lexus HS250, eh?
Ironically, and I wonder if this will come back to haunt the Toyota Motor Europe operation in Brussels, the Prius of the moment, the Aqua, or C, which helped more than triple Prius family sales in Japan to 175,080 in the first quarter, up from 52,507 last year, isn’t actually coming to Europe where we will stick to a roster of three – hatchback original, plug-in derivative and new seven seat ‘plus’ (aka V elsewhere).
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Powertrain for Europe
The Aqua’s powertrain does, however, have a visa for Europe – it’s slotted into the newest version of the French-built Yaris instead. The downsized hybrid system combines a substantially re-engineered 1.5-litre, Atkinson cycle petrol engine with a lighter, more compact electric motor, transaxle, inverter and battery pack. It offers a claimed best-in-class balance of performance, fuel economy and CO2 emissions: official European combined cycle fuel consumption is 76.3mpg-80.7mpg depending on trim (which ups wheel size from 15″ to 16″ for the top level; CO2 output is a segment-best 79g-85g/km, well below the 100g/km annual road tax threshold here in the UK); and the ability to operate in all-electric EV mode allows for frequent running with zero NOx, particulate or CO2 tailpipe emissions.
Downsizing means the fuel tank and hybrid battery fit under the rear seat so the new hybrid has identical space for occupants and the same 286-litre luggage capacity as the standard petrol and diesel Yaris models.
Total engine, electric motor, transaxle, inverter and battery pack system weight is 201kg, 20% or 42kg less than that of an Auris hybrid.
The 1,497cc, 16-valve DOHC Atkinson cycle petrol engine with VVT-i is based on the unit which powered the second generation Prius but substantially re-engineered and is 50mm (10%) shorter and 17kg (17%) lighter than the 1.8-litre unit in other current Toyota full hybrid powertrains.
The new engine generates a maximum 73bhp (55kW) at 4,800rpm and maximum torque of 111Nm from 3,600 to 4,400rpm. With a focus on achieving lower emissions and the least mechanical friction for better fuel economy, around 70% of the engine’s components are new or have been redesigned.
Overall, the engine’s thermal efficiency has been improved by 6% compared with that used in the second generation Prius, which contributes to better fuel efficiency and environmental performance.
New technologies have been adopted, too, including exhaust gas recirculation (EGR) and an electric water pump. The auxiliary drive belt is gone and the engine uses a low-friction timing chain, a lightweight resin-based intake manifold and a compact exhaust manifold.
When used in combination with EGR, the Atkinson cycle engine can deliver significant gains in fuel efficiency and emissions performance. In the Atkinson cycle, compression and expansion are asymmetrical, and the inlet valves close late, delaying compression. This creates a high expansion ratio for less compression, converting combustion energy to engine power more effectively. As a result, the exhaust temperature is lower than that of conventional engines. The EGR system reintroduces cooled exhaust gas into the intake system, further reducing engine operating temperatures.
Using an electric water pump, and a small, lightweight, multi-function radiator, both improves engine warm-up performance and reduces cooling friction loss, strengthening fuel efficiency, while doing without a mechanical pump drive belt reduces friction, again contributing to better fuel economy.
The new resin-based intake manifold, exclusive to Toyota’s hybrids, is compact, lightweight and quiet, with reduced noise and vibration. The 12-hole atomising fuel injectors are said to be highly efficient, helping keep fuel consumption and emissions down.
The exhaust system has a new, low heat capacity, ‘maniverter’ type manifold. With the catalytic converter positioned much closer to the engine exhaust port, it cuts catalyst warm-up time by 24%, contributing to a marked improvement in emissions during shorter journeys.
A new transaxle houses the electric motor, generator, power split device and double-motor reduction mechanism in a single, lightweight, compact transmission casing comparable in size to a conventional gearbox.
Using a smaller E-CVT electric continuously variable transmission and a more compact electric motor allows for a 6% reduction in the length of the hybrid transaxle and a 11kg weight saving over the unit used in the Auris. This makes it the most compact hybrid transmission Toyota has developed.
The new electric motor generates an immediate 45kW and 169Nm of torque. It has been made smaller and lighter by optimisation of the magnet material and the winding of the coils with flat rather than round wire. The motor cooling structure has also been improved, allowing for a smaller, yet more efficient and powerful motor.
The transaxle now incorporates a multifunctional reduction gear within the power split mechanism, and a new gear deceleration mechanism does away with the need for any chains.
The downsized powertrain also features a smaller, 144V nickel-metal hydride battery with a more efficient vehicle electric power management system.
The number of cells has been cut from the 168 in Auris Hybrid’s battery to 120, made up of 20 modules connected in series. This reduces battery volume by 20% and weight by 11kg, allowing the unit to be accommodated entirely beneath the rear seats, with no intrusion into the boot.
Even though the battery is smaller and lighter, its charging efficiency has been improved, with a reduction of 67% in the pack state-of-charge recovery time compared to the Auris.
As there is a reduction in the hybrid system’s current and voltage, the power control unit has also been made smaller and lighter, by developing a more compact inverter and switching unit.
Compared to Auris Hybrid, the unit’s output current has been reduced from 120 to 80A and output lowered from 650 to 520V, saving system energy with no loss of performance or efficiency.
Unique looks
The hybrids have their own unique nose (20mm longer), wheel styles, one additional paint colour (a metallic white much like the Auris version), blue-tinged badges, blue-lit dials and blue/white interior trim highlights but are otherwise much like the petrol and diesel models launched last year.
The hybrid drove very nicely on billiard table flat Netherlands roads around Amsterdam where it was possible to spend a lot of city and country driving time with the petrol engine temporarily off in EV mode, such as when slowing as a queue builds ahead, for traffic lights, and so on. Toyota reckons zero emissions driving accounts for 66% of the average commuter journey length and 58% of the total journey time. Consequently the CVT transmission didn’t need high revs most of the time but we can’t help thinking the car would be noisier in hilly territory as the petrol engine would have to work much harder, enhancing what some writers here call the ‘rubber band effect’.
Many of the consumer writers on the launch anxiously mulled the GBP2,300 price premium over the standard petrol car (diesel is much the same extra cost) and wondered if it was worth it. Toyota’s response is it can now offer a choice unique in the B-segment – petrol, diesel, hybrid – and that the latter comes with automatic transmission (not offered with the diesel and becoming more popular in England’s congested south-east) and CO2 emissions low enough to dodge paying both England’s annual road tax and the London congestion charge.
It also claims lower maintenance costs as there’s no clutch, starter motor, alternator and timing belt so no requirement for these parts to be maintained or replaced which means lower costs over several years of ownership. The electronically controlled braking system with regeneration means brake pads can last for up to 60,000 miles.
The company estimates maintenance costs over 60,000 miles are expected to be among the lowest in the B segment while the hybrid battery is designed to last the car’s lifetime.
Prius C
So should they have brought in the Prius C instead? That’s also a small hatchback but the styling is a little quirkier and may not appeal to all tastes. The Yaris is now, in its third generation, very well established in Europe and has been built here almost from day one. Offer a Prius, and a prospective customer may not like the car and that’s that, offer a Yaris hybrid and there are standard petrol and diesel models also to consider – that may keep the prospect in the showroom longer till a sale is closed.
Toyota has high hopes – it expects the hybrid to take 8% of volume this year and 20% in the first full years of 2013/14.
Europe build
Build at Valenciennes, northern France, raised the number of different versions produced on the same flexible line to 62 – a record high.
On average, each Yaris requires the assembly of more than 2,600 parts, with around 80% common to all models. There are 400 new, hybrid-specific parts and 40% of all the assembly processes for the hybrid are either new or required adaptation. Because the plant is so compact, stock management has had to be readdressed and sequenced delivery organised for a greater number of parts.
TMMF staff underwent around 4,000 hours of hybrid assembly training with a focus on assembly techniques for new on-line parts; recognition of variety among components of a similar kind; and the meeting of key quality targets. Special attention was paid to the inverter assembly, as this component is particularly sensitive to dust and foreign body intrusion.
Around 50 staff were given specific safety training in how to handle high voltage parts, and new safety procedures were introduced to take into account the fact the new vehicle moves near-silently in EV drive mode. In addition, provisions were made for applying the pearl white paint finish at the French plant for the first time.
Nonetheless, the hybrid takes no longer to produce than the standard model.
