Infiniti is plugging plug a big gap in its European luxury vehicle line up with the launch of its first diesel engine. The move will make its range more competitive with local rivals such as BMW, Audi and Mercedes-Benz, which all offer a vast choice of diesel engines and Toyota’s Lexus, which offers entry-level diesels and fuel-efficient petrol-electric hybrids higher up its range.
The newly-developed three-litre V6 is the first diesel in Infiniti’s 20-year history (it was launched first in the US where diesel was not a priority) and will be available initially in the EX and FX crossovers and, later, in the Infiniti M luxury performance sedan.
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The diesel engine option is a key element to Infiniti’s growth in Europe. Launched here a year ago, the Infiniti range has five established model lines – G37 saloon, coupé and convertible, plus the EX and FX ranges – over 2,000 vehicles have been sold across 15 markets.
Infiniti Europe vice president Jim Wright said: “The sales success enjoyed by Infiniti in Europe against a backdrop of financial uncertainty proves the cars’ appeal. We have established Infiniti as the luxury performance brand thanks in part to the VQ petrol engine (shared with parent company Nissan Motor) that powers most of the models in the range.
“We were aware from the outset, however, that, for Infiniti to offer a complete range, a powerful diesel engine was a must, especially in the European premium SUV market where diesel represents the bulk of sector sales.
“Although we did investigate the possibility of adapting an existing large capacity diesel for Infiniti, we quickly established that nothing on the market met our exacting requirements. We needed an engine that delivered not just stunning performance but exemplary refinement too. For that reason, with the [Renault-Nissan] alliance we decided to develop our own engine, a performance diesel worthy of the Infiniti badge.”
Developing 175 kW (238 PS) and 550 Nm of torque, with standard seven-speed automatic transmission, the new engine accelerates the new EX30d crossover from rest to 100km/h (62mph) in around 7.9sec and the FX30d in 8.3sec.
Designated V9X, the new V6 diesel was developed in Europe by Infiniti engineers working with colleagues at Renault and Nissan. It is made at Cleon in France, about 100km (60 miles) west of Paris.
The new engine will also be used in other Nissan and Renault cars, allowing both brands to broaden the appeal of specific model ranges as well as usefully boosting volume of the new V6 diesel. Unusually, the V9X will power front-wheel drive, rear-wheel drive and four-wheel drive models.
Renault already shares its small I4 turbodiesels with Nissan which uses them in models such as the UK-built Note and Micra.
Although Infiniti considered using a V8 diesel, a V6 was identified early as the ideal layout for the news engine as it provided the optimum balance between overall performance, refinement and volume potential across the three alliance brands. Target performance was 238PS (175kW), 500Nm of torque and early compliance with forthcoming Euro 5 emission legislation.
Engineers decided the ideal vee angle for the unit would be an unusual 65 degrees. This offered an excellent compromise between crankshaft balancing, crankshaft and cylinder block reliability and engine packaging with the 65 degrees wide enough to allow the single turbocharger to be neatly mounted within the vee. BMW uses a similar turbo mounting position on its 4.4-litre petrol and also managed to queeze in a second turbocharger and a catalytic converter.
For their V6 diesel, the alliance engineers chose compacted graphite iron (CGI), a material that offers all the benefits of cast iron and more – it has higher levels of stiffness and noise absorption – but without the weight penalty. And while CGI is heavier than a pure aluminium block there is no need to add stiffening ribs or extra sound deadening material so the weight gain is comparatively modest.
CGI was patented in 1949 and its first commercial application was for the brakes of Europe’s high-speed trains. It is 75% stronger and up to 75% stiffer than grey iron, the most common form of cast iron found in engine cylinder blocks. It also performs better than aluminium at higher temperatures when it is up to five times more fatigue resistant. Best of all, the weight of a typical engine block can be more than 20% lower than an equivalent cast iron block. Two design goals were high levels of refinement and no loss of chassis balance and, in tests, engineers determined the V9X engine had the lowest 250Hz and 500Hz vibrations of all the benchmarked engines.
To ensure it fitted under the bonnet of both the EX and FX models, there are a number of significant differences between the Infiniti engine and its ancillaries and the version used in front-wheel drive applications. A number of changes also had to be made to the engine bays of the EX and FX.
