2014 New Verso DPL: Driving performance

New 1.6 D-4D

The 2014 Verso features an expanded line-up which introduces a new 1.6 D-4D (Direct injection — 4-stroke Diesel) engine to the range for the first time.

Diesel engine sales continue to dominate the European market in the C-MPV segment, and 1.6 litre variants currently account for over 50% of sales.

The engine for the 1.6 D-4D is sourced from the BMW Group, and is mated to a Toyota 6-speed gearbox. 20 kg lighter than the 2.0 D-4D powerplant, this Euro 5 compliant engine develops 112 DIN hp/82 kW at 4,000 rpm and 270 Nm of torque from 1,750 to 2,250 rpm. It accelerates the Verso from 0-100 km/h in 12.7 seconds, and on to a top speed of 185 km/h.

The engine delivers an 8% improvement in fuel efficiency over the 2.0 D-4D unit, equating to fuel consumption of 4.5 l/100 km in the combined homologation cycle. Simultaneously, CO₂ emissions have reduced from 129 to only 119 g/km.

These figures are supported by the first ever adoption of a Stop & Start system in the Verso range, in accordance with the principles of the Toyota Optimal Drive philosophy.

Several engineering challenges were key to the successful integration of the new 1.6 D-4D engine. All electrical interfaces were redesigned, and a newly-developed dual-mass flywheel was fitted to optimise noise and vibration.

New engine mounts offer particularly low vibration characteristics, especially under Stop & Start operation, minimising Noise, Vibration and Harshness (NVH) and offering quiet running at cruising speeds.

The engine itself has been tuned to deliver a fast throttle response throughout the rev range. It generates good initial response at low rpm, then, as turbo boost develops, provides a linear torque build-up. The availability of torque has also been stretched, so the engine will happily rev beyond 3,000 rpm without running out of breath.

With ride quality already assured on the existing Verso, spring settings have been modified for the new 1.6 D-4D version to replicate the same levels of body control and ride comfort.

The addition of the 1.6 D-4D unit to the model range increases the engine line-up to a choice of 6 powerplants —150 DIN hp and 177 DIN hp versions of the 2.2 D-CAT diesel, a 124 DIN hp 2.0 D-4D diesel, the new 112 DIN hp 1.6 D-4D, and a choice of 1.6, 132 DIN hp and 1.8, 147 DIN hp Valvematic petrol engines.

Interview

Gerald Killmann, Vice President RandD2 at Toyota's RandD centre in Belgium, discusses the new diesel, key development goals, the main project challenges, and the RandD required to develop a true Toyota D-4D engine.

Why did you decide to source an engine, rather than to develop a 1.6 diesel from scratch?

Considering that diesel sales for passenger cars are mainly concentrated in Europe, and that a new diesel engine requires significant development work, we came to the conclusion that in this instance, the best solution was to cooperate with another OEM (Original Equipment Manufacturer) rather than develop a unit ourselves. 

The next step was to fix the selection criteria. We went looking for candidate engines that delivered our required level of performance — torque, power, fuel consumption. And of course, we also had to take into account whether the geometry was compatible with our car. 

But the engine hardware wasn't our only driver — we also wanted to find a partner that is, like us, a technically oriented company, and which thinks in similar ways to us. 

So, all in all, the BMW Group turned out to be the ideal partner for us.

What was Toyota's development on this engine?

The engine is maybe the most interlinked component in a car — it interacts with a huge number of systems. In this case, we developed a host of new elements: a new dual-mass flywheel, an adapted gearbox housing, new engine mounts, new electronic interfaces… 

When you install an engine in a car, it is not only a mechanical, but also an electrical marriage. 

This matching of electronics was a major task, because the engine control unit contains elements from both partners in this project, and they all needed to be integrated to the car's electronic system through our interfaces.

External components of the unit were adapted to meet our geometrical requirements. And, to cope with the thermal stress that comes from powering a relatively large and potentially heavily loaded car, air flow through the engine compartment was optimised.

Has the use of a Toyota gearbox primarily to do with the packaging?

No. The key point was that we started with a very good car. We wanted to preserve as many elements as possible, and only change what was really necessary. 

What were your main targets when adding this engine to the line-up?

First of all, being a family car, an MPV has to remain comfortable to drive. On the other hand, based on the vehicles that were already on the road with this engine, we recognised its dynamic performance. So we wanted to bring a combination of these key aspects to our car.

With a low displacement engine in a relatively big car, it's essential that the engine delivers. So that was one of the key engineering targets. We had to make sure that torque was available from low revs, but also that it was spread over a wide rev band. 

This 'stretchiness' was one of our key goals — it allows the driver to stay in the same gear for longer, at higher rpm during acceleration, without getting the feeling that the engine runs out of steam.

A second item was fast engine response, delivering sufficient torque even before the turbo cuts in. And not just a fast response but also a natural torque build-up, so it doesn't feel like small engine… small engine… small engine… and then suddenly the turbo comes in with a whoosh. Rather, we wanted a more natural, linear torque build-up. 

As a result, the driver gets access to very decent performance, without upsetting the comfort of his passengers with sudden bursts of acceleration as he goes through the gears — important in a family car!

The target on NVH was to be as good as the 2.0 D-4D and, in some areas, perform even better. 

And of course, one of the key objectives was efficiency. We managed to cut back CO₂ emissions by 8%, from 129 to 119 g/km, compared to the 2.0 D-4D engine. And due to the smaller engine size and the adoption of a Stop & Start-system, the fuel consumption advantage is noticeable, especially in urban conditions. 

How was Toyota quality guaranteed?

The car is engineered like any other Toyota. The engine was subjected to all our durability tests, even though it comes from another OEM. From the RandD viewpoint it's just a different engine manufacturer supplying the unit, but our standards don't change. 

We have checked that it complies with all our durability requirements, and we have done all necessary component re-development and testing. 

What elements are you most proud of?

Our goal was to ensure that the 1.6 D-4D version would deliver improved CO₂ without sacrificing comfort, driving pleasure and real-world usability. Three elements contribute to achieving that:

Firstly, we managed to control the transmission of engine vibrations into the body very well. Especially under Stop & Start operation, I'm extremely happy with the level we achieved. 

Secondly, the response of the engine, the linear torque build-up and the high torque availability over a wide rpm range. Often with a diesel, once beyond 2,700-2,800 rpm, the torque decrease hits you like a barrier. The 1.6 D-4D, on the other hand, allows you to happily continue well beyond 3,000 rpm, almost like a petrol engine. As a driver, it is nice to have that option, especially when you have to pull into heavy traffic and need power to catch up with the traffic flow. 

Thirdly, we've also worked on gear ratio selection to combine dynamic performance with good fuel consumption and low noise levels at motorway-speeds. That's why we made 6^th a highway cruising gear, while lower gears like 2^nd and 3^rd are designed to give good acceleration, using the stretchiness of this high revving engine.