Lexus plans downsized engine

Lexus seems certain to follow the engine turbocharging and downsizing trend fairly early in the life of its just-launched third generation IS sedan ).

That's despite reservations within the company about refinement levels offered by such drivetrains in the rival BMW 3 Series and Mercedes-Benz C-class.

The compact luxury rear-wheel drive IS has been revealed with carry-over 2.5-litre and 3.5-litre naturally-aspirated V6 engines accompanied by a new 2.5-litre four-cylinder petrol-electric hybrid.

All three drivetrains will come to Australia when the IS launches in June.

But it is clear at least the 2.5 V6's future is limited, with a 2.0-litre turbocharged four-cylinder under development by Lexus' parent Toyota. The flagship 3.5-litre engine seems to have more time planned for it.

"Some time in this model cycle of this particular car we need to change engine to make it new otherwise we will lose competitiveness," admitted IS chief engineer Junichi Furuyama. "So we would like to develop a new engine as soon as possible."

Furuyama-san stopped short of confirming the IS would follow the downsizing route, but the development of the 2.0-litre turbo was confirmed by Toyota last September, including a 2014 introduction date.

The 2.0-litre engine will be based on the 2.5-litre 'AR' four-cylinder employed in the IS300H hybrid.

Whether the Lexus IS will be the first vehicle within the Toyota group to use the new engine is unclear at this point. However, it seems certain to get it, as should the larger GS, the RX SUV and many other future models such as the coupe previewed at Paris by the LF-CC concept, not to mention the compact SUV expected to break cover in Tokyo in November.

Furuyama-san said one reason Lexus hadn't already transitioned to the new drivetrain technology was concerns about its ability to match current levels of V6 refinement. He confirmed he based that opinion on testing of the BMW 3 series and Mercedes-Benz C-class turbo fours.

"By changing into turbocharged four-cylinder engines whether or not we can maintain the current excellent performance, the quietness, as well as vibration, as well as sound, we are not too sure.

"Therefore we didn't do it because what we hear current turbocharged downsized engine options, they still have quite a bit of vibration as well as noises. They are not in a satisfactory state."

The implication is that when Lexus downsizes the level of drivetrain refinement will be at a very high level!

While obviously a fan of natural aspiration and V6s, Furuyama-san admitted the encroaching CO2 and fuel consumption regulations that have forced other manufacturers to downsize and turbocharge would also impact Lexus.

"We still believe the naturally aspirated engine is the best, but I am not sure how long this happy time with n/a can last," he said. "Currently we can rely on the hybrid strategy to meet those regulations, so we still have a little more time to organise ourselves."

He also nominated another factor that will have an impact on Lexus' engine strategy – economics.

"In the Toyota Group we have cars overwhelmingly larger volume of FF (front-wheel drive) rather than FR (rear-wheel drive), and volume for FR is very small, and with that limited volume how we can effectively construct the engine that could be well utilised and still economically viable, that's something you have to be very careful in examining and making a decision."

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