Infiniti pioneers variable compression engine

Infiniti has released details of a new variable compression-ratio turbocharged (VC-T) four-cylinder petrol engine that it says delivers V6 levels of performance and refinement, turbo-diesel like torque and world-beating fuel economy.

The engine is claimed to be the world’s first production application of variable compression-ratio technology. It could eventually power a range of Infiniti, Nissan and, potentially Renault vehicles, but for the moment will first be seen in an all-new Infiniti model.

Infiniti claims it has patented more than 300 new technologies for the new VC-T engine.

The engine features a crankshaft-mounted rocker assembly that can be tilted to vary the Top Dead Centre position of each piston and therefore change the combustion-chamber volume. Stroke remains constant.

Dubbed VC-T (Variable Compression-ratio Turbocharged), the new engine is production ready and is claimed to offer fuel economy improvements of close to 30 per cent when compared to conventional engines of comparable power and torque.

Continuing the trend of downsizing, the first VC-T engine is a 2.0-litre four-cylinder that is rated at 200kW and 390Nm.

It will be used in place of Infiniti-Nissan’s VQ series 3.5-litre V6 in selected models, Infiniti Corporate Vice President Product Development, Kinichi Tanuma told motoring.com.au.

The new engine features a combination of direct and port fuel-injection, an electronically-controlled wastegate and variable displacement electric oil pump and low-drag internal design. As is commonplace now in high-spec turbo powerplants, its cylinder-head features an integrated exhaust manifold.

The design also alleviates the need for a balance shaft, balancing mass or frictional deficits the new design creates.

The engine debuted as part of a two-day workshop in Japan, delivering a deep dive into Infiniti’s future. motoring.com.au was one of only two Australian outlets (and a very limited number globally) invited to the event.

One of the vehicles shown to motoring.com.au under embargo, an SUV, will be the likely first recipient of the new powerplant which to date is only engineered to suit transverse (front and all-wheel drive) configurations.

Former head of engineering for the Nissan GT-R program, Tanuma-san says the VC-T engine produces a blend of power and economy not possible with fixed-compression-ratio engines.

In effect the VC-T engine is able to maximise response at low engine revs and boost conditions by increasing the compression ratio to a maximum of around 14:1. When the engine is on song and boost levels are high, compression can be reduced to as low as 8:1 to improve combustion characteristics and emissions.

The compression-ratio change is step-less.

Low emission levels across all combustion modes and an ability to operate across a range of fuel octanes and qualities are also key advantages of the design, Infiniti says. Indeed, the company claims the torque and fuel economy characteristics are such that it could replace turbo-diesels in many applications.

With no need for after-treatment, the cost differential is also well within economic constraints, insiders claim.

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Tanuma-san confirmed that the variable compression-ratio system has been under development since 1998. The production engine is in effect the third generation of Nissan’s VC-T technology and will be introduced in selected markets in 2017, he said.

The technology was developed completely in-house.

Production versions will potentially feature economy and power modes that will significantly alter the power delivery characteristics of the engine, he said.

Infiniti global boss Roland Kruger said the world-first technology would be an Infiniti USP. He would not, however, comment on how long Infiniti would have to leverage the tech before it was gifted to the marque’s parent brands.

“We are utilising this engine first in Infiniti. It will be marketed with a new vehicle at Infiniti and we’ll be positioned as one of the leaders in this technology,” Kruger stated.

“This engine is the next step into [meeting] these [new emission] regulations but this is just the beginning. We will also announce ‘north-south’ [longitudinal versions] and we are working on other configurations that we haven’t decided on yet,” Kruger stated.

“V6s were mentioned, we can scale this down, we can scale it up... It gives us the scalability [regarding] the size of the engine and the power of the engine and hence also the opportunity to achieve new levels of fuel economy and new levels of emissions,” Kruger stated.