HR/MR Engine Technology Overview INLINE 4-CYLINDER GASOLINE ENGINE

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Damon Simpson
6 years ago
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1 INLINE 4-CYLINDER GASOLINE ENGINE

Next-generation four-cylinder engines with enhanced fundamentals for outstanding acceleration and environmental performance As Nissan s next-generation global strategy engines for volume-selling

Major technologies Advantages Comprehensive steps were taken to minimize friction between pistons and cylinders, cams and valve lifters, and other moving parts.

combustion efﬁciency and superb environmental performance. We also reduced size and weight to class-leading low levels.

contents Though low-end torque is key to everyday driving pleasure, increasing this torque poses the greatest challenge to engine developers.

performance. With the aim of making the HR and MR the global strategy engines for volume-selling models, Nissan thoroughly reviewed and enhanced all basic performance parameters.

2 Next-generation four-cylinder engines with enhanced fundamentals for outstanding acceleration and environmental performance As Nissan s next-generation global strategy engines for volume-selling models, the inline four-cylinder HR and MR offer heightened consideration for the environment, while maximizing the gasoline engine s fun to drive potential. Major technologies Advantages Comprehensive steps were taken to minimize friction between pistons and cylinders, cams and valve lifters, and other moving parts. Class-leading environmental performance We minimized friction in the cylinders, pistons and other major moving parts, while reﬁning the intake/exhaust systems and cooling performance to gain combustion efﬁciency and superb environmental performance. We also reduced size and weight to class-leading low levels. Not only quiet, but music to the ears By maintaining quiet operation and minimizing discordant sonic components, we created a pleasant engine sound that adds to driving pleasure. contents Though low-end torque is key to everyday driving pleasure, increasing this torque poses the greatest challenge to engine developers. Unlike boosting torque at mid and high rpm through forced induction (using a turbocharger or supercharger), raising low-end torque requires painstaking reﬁnement of the engine s fundamental performance. With the aim of making the HR and MR the global strategy engines for volume-selling models, Nissan thoroughly reviewed and enhanced all basic performance parameters. HR15DE Competitor A Competitor B Torque HR/MR engine development focused on maximizing energy efﬁciency. We applied a variety of technologies to eliminate energy loss and maximize output for high performance and fuel economy. Friction-reduction Engine rev (x100rpm) HR15DE engine HR15DE engine torque curve Achieves plentiful low-end torque extending through mid-to-high engine speed. Bore circularity machining By making the cylinder bores as circular as possible, this technology greatly reduces friction. Mirror-like ﬁnish Crankshaft and camshaft journals are polished to a mirror-like smoothness to reduce friction. Torque Low-end torque for real-life conditions Instead of going for full-throttle performance, we sought to satisfy everyday driving needs with ample low-end torque that extends linearly through the mid- to high-speed range. Basic performance reengineered Improved combustion efﬁciency and cooling efﬁciency To achieve more efﬁcient combustion, we applied new technology to the valves, fuel injectors and spark plugs, while raising cooling efﬁciency for the combustion chamber. These measures contribute to rapid fuel combustion with minimum wasted energy. Improved intake/exhaust efﬁciency HR20DE Competitor A Competitor B MR20DE engine Engine rev (x100rpm) MR20DE engine torque curve 2.0-liter engine achieves ﬂat torque characteristics with low-end torque comparable to the 2.2-liter class. For improved low- and mid-range torque, we reduced resistance in the intake and exhaust systems to assure smooth airﬂow. Reducing friction 4 Improving combustion efﬁciency 5 Raising cooling efﬁciency 7 Optimizing intake/exhaust efﬁciency 8 Acoustic technology to satisfy the senses 9 Fewer parts for lighter weight and enhanced reliability

Reducing friction Improving combustion efﬁciency Friction has been reduced between moving metal parts such as pistons and cylinders, cams and valve lifters.

Bore circularity machining Plastic intake manifold with integrated tumble control valve In a conventional engine, the cylinder bores undergo some deformation due to axial forces when the cylinder

In the HR/MR engines, circularity machining is performed on the bores with the engine ﬁtted in a jig that reproduces conditions under which the cylinder head and block are bolted together.

This permits reduced contact pressure between piston ring and cylinder bore, thereby reducing friction.

Its use in the HR/MR engine marks an epoch-making advance in the technology of volume production engines.

The HR/MR engines incorporate an improved tumble control valve that generates optimal tumble (longitudinal vortex) of the air-fuel mixture to promote combustion stability.

This design helps optimize air-fuel mixture consumption to enhance fuel economy even under typically unstable conditions such as while the engine is warming up.

3 Reducing friction Improving combustion efﬁciency Friction has been reduced between moving metal parts such as pistons and cylinders, cams and valve lifters. To achieve more efﬁcient combustion, we applied a variety of technologies to valves, fuel injectors, ignition systems and other areas. Bore circularity machining Plastic intake manifold with integrated tumble control valve In a conventional engine, the cylinder bores undergo some deformation due to axial forces when the cylinder head is bolted to the cylinder block. In the HR/MR engines, circularity machining is performed on the bores with the engine ﬁtted in a jig that reproduces conditions under which the cylinder head and block are bolted together. Therefore, bore deformation due to axial forces on cylinder head bolts is prevented, and bore circularity is improved. This permits reduced contact pressure between piston ring and cylinder bore, thereby reducing friction. Bore circularity machining is a technology used in ultra-precision racing engines where even the slightest power loss is unacceptable. Its use in the HR/MR engine marks an epoch-making advance in the technology of volume production engines. Conventional engine bore HR/MR engine with bore circularity machining For rapid and efﬁcient combustion, the air-fuel mixture must be in a state that is most conducive to ignition. The HR/MR engines incorporate an improved tumble control valve that generates optimal tumble (longitudinal vortex) of the air-fuel mixture to promote combustion stability. The cylinder interior and piston crowns are also shaped to promote tumble swirl. This design helps optimize air-fuel mixture consumption to enhance fuel economy even under typically unstable conditions such as while the engine is warming up. Velocity high low Tumble ﬂow in cylinder Mirror ﬁnishing The crankshaft and camshaft journals are ﬁnished with a polishing tape to produce a mirror-like ﬁnish. The result is a thorough reduction in friction on these bearing surfaces of key engine components. Large capacity EGR system Surface of camshaft journal Crankshaft and camshafts Offset cylinders Cylinders in the HR/MR engines are ﬁtted at an offset to minimize friction arising from the angle of the connecting rod as a piston descends into the cylinder. The resulting smoother reciprocating motion of the pistons contributes to high power output and high torque as well as fuel economy. Also, the structure is designed so that the piston remains in the upper part of the cylinder longer than in a conventional engine (piston velocity slows down). This permits more efﬁcient use of combustion energy and effectively improves thermal efﬁciency. 4 Central axis of cylinder The EGR (Exhaust Gas Recirculation) system returns a portion of the exhaust gas to the intake side to reduce fuel consumption and minimize NOx emission. Reintroducing exhaust gas to the cylinders reduces pumping loss by allowing less energy to be used on the intake stroke to turn the engine. Owing to combustion efﬁciency improvements including the upgraded tumble control valve, the HR/MR engines can use more exhaust gas in EGR. This yields even better fuel economy with assured power delivery. EGR system Central axis of con rod Offset cylinder 5

Raising cooling efﬁciency More stable combustion results from more efﬁcient cooling of the combustion chambers. This helps enhance both power output and fuel economy.

Spray particle size is reduced by approximately 40%, and the spray range is greater, thereby raising combustion efﬁciency.

We reduced water jacket wall thickness around the HR/MR engine s combustion chambers to 4.5 mm, about 25% thinner than our previous design, while maintaining sufﬁcient strength and rigidity.

Water jacket: coolant passages in the cylinder block and cylinder head, which help maintain optimum combustion conditions and prevent parts from deforming or seizing up.

4 Raising cooling efﬁciency More stable combustion results from more efﬁcient cooling of the combustion chambers. This helps enhance both power output and fuel economy. Fine spray injectors Thinner water jacket wall The ﬁner the particle size of spray from the fuel injectors, the easier it is to attain complete combustion of the air-fuel mixture and therefore the less hydrocarbons (HC) are generated. The HR/MR engines replace the previous 4-hole injector nozzle plate (diameter: 250 µm) with a 12-hole version (diameter: 130 µm) in a multi-hole ﬁne spray injector. Spray particle size is reduced by approximately 40%, and the spray range is greater, thereby raising combustion efﬁciency. with 4 holes Increased cooling efﬁciency helps maintain antiknock capability during combustion at higher compression ratios. We reduced water jacket wall thickness around the HR/MR engine s combustion chambers to 4.5 mm, about 25% thinner than our previous design, while maintaining sufﬁcient strength and rigidity. The resulting increase in water jacket capacity raises cooling efﬁciency. Water jacket: coolant passages in the cylinder block and cylinder head, which help maintain optimum combustion conditions and prevent parts from deforming or seizing up. HR/MR engine with ﬁne atomized spray 4. 5m Thickness reduced to 4.5mm Thin water jacket wall raises cooling efﬁciency Fuel injector φ250µm m φ130µm Nozzle plate (injector head) Long-discharge ignition coil M12 spark plugs Using smaller M12 plugs allowed more leeway in water jacket design, thereby further raising cooling efﬁciency. The large capacity EGR system returns a substantial volume of inactive exhaust gas to the air-fuel mixture in the cylinders, which lowers the ignitability of the mixture. To adjust for this situation, we lengthened the discharge time of the ignition coil, thereby improving ignition performance for efﬁcient combustion even under unstable air-fuel mixture conditions. Conventional spark plug Ignition coil with longer discharge time 6 M12 spark plug M12 spark plug 7

Optimizing intake/exhaust efﬁciency Acoustic technology to satisfy the senses We reduced air resistance in the intake/exhaust systems to assure smooth airﬂow for improved torque in the low- to

Front intake/rear exhaust layout Acoustically equal length manifold branches The HR/MR engines have a front air intake and rear exhaust system layout.

The straight exhaust system reduces ﬂow-resistance, while compact packaging permits a stylish design.

For the intake manifold on HR/MR engines, we gave the four branches acoustically equal lengths.

The rough sound an engine can make during acceleration is minimized, leaving an attractively pleasing result.

5 Optimizing intake/exhaust efﬁciency Acoustic technology to satisfy the senses We reduced air resistance in the intake/exhaust systems to assure smooth airﬂow for improved torque in the low- to mid-speed range. Going beyond the goal of quiet operation, we sought a sound that would enhance the sensation of acceleration. The result is a softly purring engine that is a pleasure to the senses. Front intake/rear exhaust layout Acoustically equal length manifold branches The HR/MR engines have a front air intake and rear exhaust system layout. The system has long intake runners effective in promoting ample torque at low and mid-range engine speeds, and also achieves smooth exhaust ﬂow. The straight exhaust system reduces ﬂow-resistance, while compact packaging permits a stylish design. The impression given by an engine s sound is not determined by volume alone, but is also greatly inﬂuenced by timbre and a mixture of dull mechanical noises. For the intake manifold on HR/MR engines, we gave the four branches acoustically equal lengths. This effectively emphasizes only the lighter, clearer components, while greatly reducing those that muddy the sound. The rough sound an engine can make during acceleration is minimized, leaving an attractively pleasing result. Also, as engine speed increases, rising sound pressure acoustically dramatizes the pleasant sensation of acceleration. Intake Exhaust Front intake/rear exhaust layout Manifold branches are equalized HR/MR engine Torque Increased torque in the practical rpm range Valve C-VTC 6th harmonic 4th harmonic 2nd harmonic Frequency Frequency Silent chain drive Continuous Valve Timing Control MR20DE Engine Rev C-VTC enables variable valve timing in response to engine rpm and throttle opening. Enhanced control and reduced system friction improve response and optimize torque characteristics. While maintaining linear torque at high rpm, the system controls valve timing to raise torque particularly in the practical range around 2000 rpm. For example, to overcome slow intake gas-ﬂow to the cylinder head in the practical speed range, charging efﬁciency is improved by advancing intake valve closure timing. The C-VTC has also been made thinner to contribute to a lighter, more compact engine. Engine Rev Continuous Valve Timing Control (C-VTC) This silent chain reduces impact noise to deliver quieter operation. Impact noise is generated by the camshaft drive chain as its pins mesh with the sprockets. For the HR/MR engine, we redesigned the links so they engage the sprockets at points in addition to the pins themselves, thereby distributing impact to reduce this noise. Conventional chain Chain links Silent chain pin pin Engine rev (x100rpm) C-VTC helps optimize torque characteristics sprocket impact impact Link plate sprocket Redesigned shape (right) reduces noise 8 9

Fewer parts for lighter weight and enhanced reliability The HR/MR engines employ a range of innovative technologies for downsizing and weight reduction that are essential to improved fuel economy.

Coolant pipes built in Serpentine auxiliary drive The coolant distribution system has been thoroughly redesigned in all areas, incorporating it into the block and head.

The HR/MR engines use a single-belt serpentine auxiliary drive system to drive the air conditioner compressor, power steering pump, alternator and other components from the engine.

Use of auto-tensioners reduces belt load and extends service life.

6 Fewer parts for lighter weight and enhanced reliability The HR/MR engines employ a range of innovative technologies for downsizing and weight reduction that are essential to improved fuel economy. We reduced the number of parts by approximately 20% compared with the previous engine design, thereby enhancing reliability and manufacturing productivity. Coolant pipes built in Serpentine auxiliary drive The coolant distribution system has been thoroughly redesigned in all areas, incorporating it into the block and head. Pipe-free construction minimizes dependence on external couplings, thereby decreasing the number of parts and contributing to weight reduction. The HR/MR engines use a single-belt serpentine auxiliary drive system to drive the air conditioner compressor, power steering pump, alternator and other components from the engine. Whereas conventional engines run each auxiliary component separately, this system puts the pulleys in a single plane, thereby shrinking engine length. Use of auto-tensioners reduces belt load and extends service life. Coolant pipe built into cylinder block Pulleys are in a single plane Cracking-processed connecting rods High-adhesion FIP gasket and chamfer shape These integrally cast con rods offer lighter weight than conventional con rods, which are constructed in two parts, separated at the eye where they join the crankshaft. The cracking processed con rod is manufactured in one piece, then the lower connecting rod eye is broken in two (the cracking process) and, ﬁnally, the two parts are rejoined after mounting. Mating of the uneven surfaces created by the cracking process results in a very precise joint. Form in place (FIP) gaskets are used to improve cylinder head and oil pan sealing. These create a sealant layer of uniform thickness to improve reliability against oil leakage within the engine. In addition, we adopted a chamfer process to shape mating surfaces based upon ﬂuid dynamics. Surplus gasket material protruding from the mating surfaces ﬁlls the chamfer to improve adhesion. FIP HR/MR engine FIP High-adhesion FIP gasket and chamfer shape Cracking-processed connecting rod and cross-sections 10 11

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