Although a V8 diesel engine was investigated, the V6 format was identified early on as the ideal layout for the unit, providing the optimum balance between overall performance, refinement and volume potential across the three Alliance brands. Target performance was 238 PS (175 kW), 500 Nm of torque and early compliance with forthcoming Euro 5 emission legislation.
At the same time, the engine bay architecture of the EX and FX models – designed initially as petrol models only – called for a compact engine which, if it were to be used in both transverse and longitudinal positions, would need to have a comparatively narrow vee angle as close to 60 degrees as possible.
Engineers decided that 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 degree angle wide enough to allow the single turbocharger to be neatly mounted within the vee.
But perhaps the key element to the success of the new V6 is the material chosen for the engine block. While some rivals tend towards aluminium-alloy cylinder blocks to reduce the weight of their diesel engines, development engineers felt that to achieve the desired levels of refinement an aluminium block would need extra material added to increase its stiffness and reduce noise levels. It might also need extra complexity added in the form of balancer shafts to boost refinement, but all these additions negate the weight advantages of an alloy block.
Conventional cast iron, however, would place too much weight over the front wheels and lower the levels of driving pleasure offered by all Infiniti vehicles. In its place, the 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 per cent stronger and up to 75 per cent 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 per cent lower than an equivalent cast iron block.
To manage the high loads on the engine structure commensurate with the impressive power and torque outputs, the overall stiffness of the engine structure was optimised at the design stage by incorporating a number of specific features. These included a large and stiff coupling face between the converter housing and the engine; the CGI cylinder block with semi-deep skirts; direct bolting of ancillaries on the crankcase; an integrated engine bracket in the upper timing covers; a structural oil pan; a stiff torque converter housing and an axial driveline bearing on the gearbox side.
At the same time, to reduce vibrations inherent in a diesel engine and avoid unwanted resonances in the rev range, intensive structural optimisation during the preliminary design stage used finite element calculation to identify both the source of vibrations and to establish the ideal structural form of the block.
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At the same time, the engine bay architecture of the EX and FX models – designed initially as petrol models only – called for a compact engine which, if it were to be used in both transverse and longitudinal positions, would need to have a comparatively narrow vee angle as close to 60 degrees as possible.
Engineers decided that 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 degree angle wide enough to allow the single turbocharger to be neatly mounted within the vee.
But perhaps the key element to the success of the new V6 is the material chosen for the engine block. While some rivals tend towards aluminium-alloy cylinder blocks to reduce the weight of their diesel engines, development engineers felt that to achieve the desired levels of refinement an aluminium block would need extra material added to increase its stiffness and reduce noise levels. It might also need extra complexity added in the form of balancer shafts to boost refinement, but all these additions negate the weight advantages of an alloy block.
Conventional cast iron, however, would place too much weight over the front wheels and lower the levels of driving pleasure offered by all Infiniti vehicles. In its place, the 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 per cent stronger and up to 75 per cent 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 per cent lower than an equivalent cast iron block.
To manage the high loads on the engine structure commensurate with the impressive power and torque outputs, the overall stiffness of the engine structure was optimised at the design stage by incorporating a number of specific features. These included a large and stiff coupling face between the converter housing and the engine; the CGI cylinder block with semi-deep skirts; direct bolting of ancillaries on the crankcase; an integrated engine bracket in the upper timing covers; a structural oil pan; a stiff torque converter housing and an axial driveline bearing on the gearbox side.
At the same time, to reduce vibrations inherent in a diesel engine and avoid unwanted resonances in the rev range, intensive structural optimisation during the preliminary design stage used finite element calculation to identify both the source of vibrations and to establish the ideal structural form of the block.
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