Continued from Lexus LS Comes With New V6 Engine (2)
Sports car technology applied to Toyota's turbocharger
As in the case of the Camry, the setting angle of the LS' V-6 engine is as wide as about 40°. Many of Toyota's previous engines have a setting angle of about 30°. According to the company, when the angle increases, so does the tumble ratio, until the angle reaches a certain degree.
However, with a wide setting angle, it becomes difficult to place valve parts, etc and form inlet-exhaust pipes. So, Toyota widened the angle to a certain degree that does not affect the parts layout.
The shape of the suction port is almost linear, making it possible to reduce air resistance. Toyota developed a method to eliminate the valve sheet (to be attached to the entrance of the cylinder of the suction port as a separate part) and, instead, overlay metal powder by laser welding.
When the tumble becomes stronger, ignition becomes difficult. So, Toyota increased the amount of energy used for the ignition plug. The plug is supplied by Denso Corp.
With the high-speed combustion, it became easier to prevent knocking (abnormal combustion). As a result, the compression ratio was improved to 10.4 while a supercharger is used.
The engine is equipped with two units of a turbocharger having an electric wastegate. Toyota manufactures the turbocharger at Miyoshi Plant in Aichi Prefecture, Japan. The V-6 engine has three cylinders and one turbocharger on each of the right and left sides. The company increased efficiency by making improvements to the shape of the turbine blade.
To improve the shape of the blade, Toyota used an analysis technology developed by its motor sports subsidiary. The maximum supercharging pressure is higher than 200kPa.
The direct-injection injector is manufactured by Denso, and its maximum injection pressure is 20MPa. For the moving valve system, Denso's electric variable valve timing (VVT) mechanism and oil-pressure VVT were employed on the suction and exhaust sides, respectively.
The electric VVT system is mainly used to adjust the timing of opening/closing the valve at the time of starting up at low temperatures in the aim of quickly warming the catalyst for the after-treatment of exhaust gas. It does not perform Miller cycle operation, which other companies recently started to use frequently. Also, it does not use external EGR (exhaust gas recirculation), and internal EGR is used to address the problem of pumping loss.