Lexus RX350 in Depth

Press Release

Page 1: Overview
Page 2: Engine and Transmission
Page 3: Interior
Page 4: Specifications

3.5 LITRE V6 PETROL ENGINE

The Lexus RX 350 is powered by a new, highly innovative, aluminium-block petrol engine which is the most powerful, yet the most economical, 6-cylinder petrol unit in the Premium SUV market segment.

The 24 valve, 3456 cm3, chain-driven double overhead camshaft V6 combines Dual VVT-i (Variable Valve Timing-intelligent), roller rocker valve activation with HLA (Hydraulic Lash Adjuster) valve clearance adjustment, and an electrically activated, ACIS (Acoustic Control Induction System) variable air induction system to achieve the optimum balance of high performance with low fuel consumption and emissions.

The RX 350’s 3.5 litre V6 is the first engine in this market segment to adopt Dual VVT-i, an optimised, low pressure loss, variable intake and exhaust timing system. Able to control intake and exhaust camshafts through angles of up to 40 and 35 degrees respectively, Dual VVT-i allows a greater intake/exhaust valve overlap, benefiting both low-end and high-end torque as well as contributing to a significant reduction in exhaust emissions.

The chain-driven valve system features roller rocker arms, the marked reduction in friction between the camshaft and sliding components – some 15% at 2,000 rpm - enhancing fuel efficiency. In addition, the diameter of both intake and exhaust valves has been enlarged to improve efficiency, high load valve springs and a concave camshaft profile increase valve lift to boost output, whilst a ceramic check-ball Hydraulic Lash Adjuster ensures the system requires no valve clearance adjustment over the life of the vehicle.

Refining the intake air flow of this unit has been a priority for the engineers of the Lexus Development Centre, located in Japan. As a result, the new V6 achieves the world’s largest volume of intake air amongst 6-cylinder powerplants. Along with an enlarged valve diameter and wider cam action, the shape of the intake manifold and the cylinder head intake port diameter and length have been optimised to improve output and torque, and air cleaner and duct profiles revised to reduce intake pressure loss.

• New 3.5 litre V6 - the most powerful, yet the most economical, 6-cylinder petrol unit in the premium SUV segment

• 203 kW/276 DIN hp at 6,200 rpm and 342 Nm/252 lb.ft of torque at 4,700 rpm

• 0-100 km/h in 7.8 seconds – the best mark amongst 6-cylinder luxury SUVs

• Combined cycle fuel consumption of 11.2 l/100km – an 8% improvement over the outgoing 3-litre V6 unit

• By-wire throttle and 5-speed automatic gearbox feature a new control logic benefiting a quicker response

• A viscous coupling has been added to the centre differential, creating a limited-slip effect when necessary

• Steering system has been retuned to provide a more direct and responsive feel

RX 300

Another segment-first, a high-speed electrically activated Acoustic Control Induction System (ACIS) featuring the system actuator bonded to the resin-made surge tank through an advanced laser-welding process, varies air induction by automatically adjusting the intake pipe length according to engine rpm, optimising the fuel/air mixture to further boost torque across the full rev’ range.

In addition, centrifugal cast iron cylinder liners feature a ‘spiny’ outer wall liner to improve bonding with the cylinder block, increase radiation characteristics, reduce piston temperature and suppress cylinder bore deformation. And pentroof, slant squish combustion chambers combine with a shallow piston cavity and centrally located, high-ignition, long-reach iridium spark plugs for excellent combustion and anti-knocking performance.

Gas flow within the stainless steel exhaust system has been optimised to reduce pressure loss between the exhaust manifold and silencer, enhancing engine performance. The exhaust manifold features ultra-thin-plate ceramic catalytic converters to further improve performance, significantly reduce warm-up times and, hence, reduce emissions.

Moreover, the by-wire control logic of the new 3.5 litre V6’s throttle valve has been re-configured; the ECU eliciting a more prompt engine response to any given throttle pedal angle.

Within a remarkably compact design, extensive measures have been taken to reduce engine weight and minimise noise and vibration. The new V6 employs a die-cast aluminium cylinder block, lightweight pistons, a thin-wall aluminium cast intake manifold and a resin-made surge tank.

The overall engine assembly is made lighter and more compact through the installation of the water pump, oil filter and oil pump within the chain cover. And the optimisation of the high-tensile forged crankshaft’s balance weight combines with lightweight pistons, roller rocker valve activation with HLA, and urethane foam acoustic damping to both engine and chain covers to significantly reduce engine noise and vibration across the entire power band.

Representing power and torque increases of 35% and 21% respectively over the previous RX 300, the ultra-smooth Lexus V6 generates 203 kW/276 DIN hp at 6,200 rpm and 342 Nm/252 lb.ft of torque at 4,700 rpm. This rewards the new RX 350 with a 0-100 km/h acceleration time of just 7.8 seconds, which makes it the quickest amongst 6-cylinder luxury SUVs. Top speed has been electronically limited to 200 km/h.

Conversely, specific fuel consumption (g/kWh, grams per kilowatt-hour) has seen an average 4% improvement over that of the RX 300 across the entire rev’ range, whilst the RX 350’s combined cycle consumption figure improves by some 8% to an outstanding 11.2 l/100km, making it the most economical amongst conventional 6-cylinder petrol engines in the premium SUV segment.

5-SPEED AUTOMATIC TRANSMISSION

The RX 350’s 3.5 litre V6 powerplant is mated to a 5-speed, automatic transmission. A newly developed shift control logic promotes superior performance and excellent fuel economy.

Gear downshift - for example, from 4th to 2nd gear - has been significantly improved through a new control logic. By predicting the level of engine torque developed at any given moment through a reading of engine status, the transmission ECU can instigate a 4th to 2nd downshift simultaneously to the engine ECU’s adjustment of the by-wire throttle angle, obviating the requirement for a slower, two-stage operation. This new control logic reduces downshift times by some 0.2 seconds at 60 km/h, elicits an even smoother gearshift and greatly enhances throttle response.

A further new control logic, Shift Phase Controller, has also been adopted for situations involving, for instance, a rapid 2nd to 4th to 2nd gear change sequence such as might occur during an interrupted kick-down. Through simultaneous control of clutches and torque management, this logic promotes both significantly smoother gear changes and reduces shift times by about 0.8 seconds at 80 km/h, further improving the RX 350’s rapid response to throttle inputs.

Moving the transmission’s gearshift lever into ‘S’ mode activates a 5-speed sequential gear-range selection system – forward for up-shifts, backwards for down-shifts - offering enhanced engine braking, more precise control and, hence, greater driving involvement. The gear indicator in the driver’s instrument binnacle now features an ‘S’ position, which displays each manually selected gear range.

PERMANENT 4-WHEEL DRIVE

The RX 350’s, 50:50 front-rear torque split, full-time 4-wheel drive adopts a new centre differential featuring a viscous coupling. The limited-slip function inherent in this system not only promotes the smooth delivery of the increased torque generated by the new 3.5 litre V6, but also, allied to Vehicle Stability Control (VSC), further enhances traction and stability under all driving conditions.

When, for instance, wheelspin is detected at the front of the vehicle, the viscous coupling will lock, passing more torque to the rear in order to counteract the usual differential effect. The new centre differential greatly improves the RX 350 4-wheel drive system’s efficiency in responding to momentary traction loss, whilst the action of all three differentials is further complemented by the ability of Lexus’ proven Traction Control system to reduce individual wheel speed whenever traction loss is detected.

Vehicle Stability Control and Traction Control systems have also been retuned in order to better respond to the 21% torque increase brought by the new 3.5 litre V6 engine. In addition, communication between the engine ECU (Electronic Control Unit) and the Brake Control ECU is now done through a faster CAN (Controller Area Network) multiplex network, 100 times faster than the previous connection, which allows a better interaction between the Vehicle Stability Control and the new 3.5 litre V6 engine.

IMPROVED STEERING FEEL

The steering of the RX 350 received further improvements brought by a reprogramming of the system’s Electronic Control Unit (ECU), added to a redefinition of the power steering pump’s behaviour.

The aim was to confer a more direct and responsive feel that is consistent with the more dynamic posture brought by the 3.5 litre V6 engine.

In addition, parking manoeuvres have also been facilitated by providing additional steering assist. This is complemented by the tightest turning radius in the segment – 5.7 metres – making RX 350 the most versatile luxury SUV in urban environments.

NOISE AND VIBRATION

• New 3.5 litre V6 engine and further sound proofing material reduce noise intrusion into the cabin

• Noise and vibration originating from exhaust and transmission have also been further reduced

• A new acoustic windscreen largely reduces wind and engine noise

• Aerodynamics developed at Japan’s Maibara wind tunnel, possessing one of the lowest levels of ambient noise

• Lexus RX has the lowest drag coefficient amongst luxury SUVs – 0.33 – guaranteeing low levels of wind noise

IMPROVED NOISE VIBRATION AND HARSHNESS

Within the RX 350’s highly stiff body structure, particular attention has been paid to noise and vibration reduction. Though substantially more powerful than its predecessor, the new Lexus luxury SUV sets class-leading standards in Noise, Vibration and Harshness (NVH) reduction.

In addition to the extensive NVH suppression measures inherent in the design of the new 3.5 litre V6 engine itself, the adoption of a new bonnet insulator and dashboard silencer significantly reduces the transmission of engine noise and vibration into the cabin. The new RX 350 further benefits from a variable back-pressure exhaust system. A valve incorporated within the main silencer, the latter located under the centre of the vehicle enables optimum noise reduction. At low engine revs the valve is closed, generating extra back-pressure and reducing exhaust noise. At high revs the valve opens to allow a more free passage of exhaust gases, thus improving engine performance.

The addition of damping materials to the exhaust manifold heat insulator and a dynamic damper to the exhaust pipe itself further suppress unwanted exhaust noise. Transmission noise has been reduced through the addition of a more effective transmission tunnel insulator and a sound-absorbent intermediate transmission shaft seal.

Marked improvements in wind and engine noise reduction have been achieved through the replacement of the existing windscreen laminate with a new acoustic windscreen. This is equipped with an acoustic inner film boasting high noise damping characteristics, leading to a cabin noise reduction of up to 3 dB while driving.

CLASS-LEADING AERODYNAMICS

Developed in the Japanese Railway Technical Research Institute’s Maibara wind tunnel, used in the creation of the Shinkansen Bullet Train, the Lexus RX was extensively tested at wind speeds of up to 200 km/h. This enabled Lexus engineers to develop bodywork boasting class-leading aerodynamics, with particular emphasis on the eradication of wind noise.

Lexus design engineers chose the Maibara wind tunnel not only for the very high wind speeds it generates – up to 400 km/h - but also for its extremely low background noise levels. Noise levels of 42 dB(A) at 100 km/h and just 75 dB(A) at 300 km/h make it unique within the field of wind-tunnel construction. Moreover, the Maibara facility is equipped with a high-speed belt allowing for the faithful simulation of the complex air-flow around the wheel arches of a moving vehicle.

To promote both high speed straight line-stability and excellent fuel economy, careful consideration had been given to controlling the airflow convergence at the back of the RX. An integral, roof level rear spoiler comes fitted as standard to improve the Cd value, whilst front and rear tyre fairings control wheel arch airflow to lower wind noise and enhance stability. The addition of numerous aerodynamic under-body elements further promotes vehicle stability, helps reduce wind noise to a minimum and lowers the Cd value of the RX 350 fitted with optional air suspension to 0.33 – the best value among luxury SUVs.