Published on June 28th, 2015 | by Subhash Nair0
Lexus IS Gets a 2-litre Turbo Variant
Lexus is expanding the range of vehicle equipped with its new 2.0-litre turbo engine. Following the launch of NX 200t in early 2015 and the announced arrival of RX 200t by the end of the year, IS is the third Lexus model to be fitted with this new engine.
Powered by a new 2.0-litre petrol turbo engine – with innovative D-4ST fuel injection technology for both fuel economy and instantaneous torque – the Lexus IS 200t sports sedan delivers 245 DIN hp (180kW) with a maximum torque of 350 Nm. Capable of rapid acceleration up to a top speed of 230 km/h, its 8-speed Sport Direct Shift transmission was developed for the high-performance RC F.
Featuring a breakthrough combination of water-cooled cylinder head, integrated exhaust manifold and twin scroll turbocharger, this all-new Lexus 2.0-litre turbo engine delivers fast throttle response, performance and high torque at low engine revs. For enhanced fuel economy, innovative valve timing (VVT-iW: Variable Valve Timing intelligent – Wide) allows the engine to switch between the Otto and Atkinson cycles.
The IS 200t returns a 0-100 km/h acceleration time of 7.0 seconds and an average fuel consumption of 7.0l/100 km.
This innovative, combination of engine technologies has been designed to provide a high level of responsiveness with minimal turbo lag and enhanced low speed torque, and yet return an improved fuel economy.
The four-into-two exhaust manifold system pairs cylinders according to their expansion or compression stroke. Acting in conjunction with the highly-efficient, twin-scroll turbocharger, this innovative manifold structure prevents interference between the exhaust gasses from each cylinder, generating high torque across the widest possible rev range.
The engine further employs an air to liquid intercooler mounted directly to the engine to significantly reduce the intake volume downstream of the turbocharger, minimising turbo lag for a highly responsive performance.
The twin-scroll turbocharger itself features variable waste gate valve control. This minimises pumping losses by reducing back pressure during low engine loads when the turbo is not required realising good fuel economy.
In addition, the integration of the exhaust manifold within the cylinder head enhances exhaust gas cooling without sacrificing catalyst warm-up performance. This not only helps to suppress catalyst deterioration, but also expands driving range at the optimum, stoichiometric air-fuel ratio.
D-4ST (Direct injection 4 stroke gasoline engine Superior version with Turbo) combines a high pressure fuel system for injection directly into the cylinders with a low pressure system for injection into the ports. Injection is split between the direct and port injectors according to the engine load, optimising fuel combustion in all driving situations to enhance both low speed torque and fuel economy.
This advanced fuel injection system works in combination with turbocharging technology to create a high level of compatibility between the ‘high tumble ratio’ achieved by optimising the shape of the cylinder head intake ports and the piston tops, and turbo ‘boost control’.
Optimising torque throughout the engine rev range and allowing the engine to start in the Otto cycle and yet run in the more fuel efficient Atkinson cycle, the new Lexus turbo features innovative dual variable valve timing technology which adopts VVT-i to the exhaust valves and VVT-iW to the intake valves, but also delivers wide open throttle performance.
The late intake valve closing of the Atkinson cycle reduces pumping losses and boosts fuel economy. VVT-iW incorporates a mid-position lock which not only enables the Atkinson cycle to be maintained without sacrificing starting performance in cold weather.
The IS 200t also received the 8-Speed Sport Direct Shift transmission with paddle shifts, originally developed for the RC F high-performance coupe. The rear wheel drive IS 200t is the first Lexus sedan to vary gear shifting in accordance to G-forces.
The transmission automatically downshifts during hard braking before a corner then holds a lower gear through the corner for best control and then selects the most suitable gear on corner exit to give the driver greater throttle response. The IS 200t will be available from September 2015.