By Dave Abrahams
Brussels, Belgium - Lexus has dropped its new two-litre dual-cycle turbopetrol four, already seen here in the NX200t, into its sporty IS sedan.
The resulting IS200t model - which will be released in South Africa towards the end of the year - should be less expensive (no Lexus is ever cheap), less thirsty and with less power loss at altitude than the current IS350 V6, if the numbers are anything to go by.
In this application, says the maker, the new engine is tuned for 180kW at 5800 revs and 350Nm from 1650-4400rpm, and drives the rear wheels through an eight-speed paddle shift transmission that was originally developed for the high-performance RC F.
Lexus quotes 0-100km/h in seven seconds flat and 230km/h flat out, at a nominal cost of seven litres per 100km.
That puts it squarely up against established premium compact competitors such as the new BMW 330i (due here in the third quarter) at 185kW an 350Nm, and the Mercedes C300, with 180kW and 370Nm, each of which is also a two-litre turbopetrol four, despite what the model designation says.
To push that comparison a little further, both the current BMW 328i and the new C300i are already more expensive than the entry-level IS350 EX.
HOW DOES IT WORK?
To recap as briefly as possible, the Lexus 200t engine has exhaust manifold and twin-scroll turbo housing built into the liquid-cooled cylinder head, to get them as close as possible to the seat of power and keep exhaust-gas temperature down. It uses variable valve timing with a very wide range, so that it can swop from the conventional Otto four-stroke spark-ignition cycle to the more efficient but less powerful Atkinson cycle as and when necessary.
In this cycle the inlet valve stays open longer than would be optimum in an Otto engine, so that the compression volume is smaller than the expansion volume, and every last joule of energy is sucked out of the combustion process - which is great when you're cruising but not so great when you need to overtake a 22-metre truck, hence the dual-mode set-up.
GEARED FOR PERFORMANCE
The special RC F paddle gearbox makes this the first Lexus sedan to vary its shift points according to G-forces. Under hard braking into it automatically downshifts, holds the lower gear through the corner for more accurate control, and selects the most suitable gear for optimum response on the exit.