Laser-clad valve seats
The UX engines feature a relatively rare innovation that Toyota pioneered on a World Rally Championship Celica race car in the ’80s. The aluminum in a cylinder head isn’t strong enough to withstand the pounding that occurs every time the valves slam shut, so valve seats of a much harder material (typically a cobalt-chromium alloy called stellite) are pressed into the aluminum head.
That piece and the aluminum required to support it tend to force the intake air runner to make a slight turn as it enters the cylinder. The WRC advance was to use intense laser light to melt a layer of steel onto the aluminum in the valve seat area. This allows the intake runner to straighten out considerably, permitting greater tumble and faster, more complete combustion.
It also means the coolant passages can be relocated closer to the valve, dropping the valve temperatures by a significant 68 degrees. This allows for greater spark advance before knock occurs.
In the ’80s, doing this required moving the head around on a turntable while a laser waggled back and forth on control springs as metal shavings were dropped onto the seat. It was so difficult and expensive that they dropped it after that program. But modern computer numerical controls and laser wire-arc deposition of the metal permit economical application of the technology in the new UX engines, in the LS 500’s twinturbo V-6, and soon in the ES.