The innovation behind Lexus and Yamaha’s V10 engine

Why “bigger” doesn’t always mean “better”

Normally, when a high-performance engine is built here in North America, it is built with an architecture that promotes immediate torque and overall response. The American recipe for performance is actually unique in this sense, because most automakers from overseas build engines around the opposite theory, that an engine should sacrifice low-end performance for high-end, because it’s the running dynamic of putting out horsepower at the top of a powerband that is the most vital in the world of track and endurance racing.
But if there is anything that we’ve learned from the Japanese about the science of engine building, it’s that building a four-stroke engine around the same principles as a two-stroke actually makes for a running dynamic that allows for a horsepower-band that is a quick-running crescendo, rather than just a swift snap. And this is where the discussion of why Toyota and Yamaha’s aluminum V10 is superior truly begins, because when Toyota and Yamaha co-developed the 4.8 liter V10 used in the Lexus LF-A, they did so with the intention of building an F1-profile motor that would rev higher than a V8 with the same displacement, while avoiding the high reciprocating mass of a 12-cylinder.1
The Lexus/Yamaha V10 is also an engineering milestone in the sense that it’s physically lighter than the manufacturer’s own, 3.5 liter, 2GR-FE V6, the same V6 used in a Toyota Camry/Lexus ES series. Also characteristic is the 72-degree, cylinder bank offset, as opposed to the 90-degree configuration such as that used in the Dodge Viper V10, which promotes a better balance of the force applied to the crankshaft from the cylinder combustion during normal engine operation, making for a smoother and more accurate response from the motor that is consistent all the way through.2
At the same time, the small displacement of the V10 allows for a torque band that begins to manifest around 3700 RPM, while peak torque of 354 foot-pounds builds at 6800. Because peak torque is produced at a relatively high RPM and the engine doesn’t actually redline until 9g, peak horsepower is around 550 BHP at 8700 Rs, and the engine’s small displacement allows for a 0.6 second rev time from idle to redline, complimented by the LF-A’s sequential gearbox, a transaxle setup that allows for upshifts as fast as 200 ms (milliseconds) in what Lexus calls the “sport” mode of operation. Because the sequential six-speed shifts so rapidly and the aluminum V10 redlines almost instantly, a full-digital tachometer is used, as an analog gauge could never keep up with the running speed of the LF-A motor.3
It’s not very often Lexus develops a platform like the LF-A V10, but the fact that they spent an entire decade on the LF-A itself is evidence that when they do build a supercar, they do it the right way, definitely a hallmark of a true, performance car builder.

- Sal Alaimo Jr., B. A.  S. J. A.