Unusual Transmission Solution in 2018 Lexus LC500H
Three years ago, at the Geneva auto show Toyota Motor unveiled its hybrid Lexus LC500H model. At first sight, there is nothing special about this grand tourer, but when you take a look at the powertrain specification, you may be surprised by its unique and innovative transmission setup. The thing is that Lexus engineers decided to equip this hybrid coupe with 2 transmissions coexisting in one package. In this article we will have a closer look at this miracle of engineering named as the Multi-stage Hybrid System.
Lexus LC500H
This remarkable gear shifting design for the LC500H
model includes an e-CVT with 2 e-motors that Lexus combined with a 4-speed
automatic transmission (mounted at the rear of the e-CVT) that regulates the
CVT’s output. The e-CVT is supposed to ensure enhanced efficiency, while the
automatic part has to expand the capacity of the whole unit, thus providing an
exciting driving experience.
Lexus LC500H powertrain
The goal of this innovation was to get rid of
the “rubber band feeling” that comes with all traditional CVTs. For those who
don’t know about this thing it happens as follows: you hit the gas pedal , the
CVT initiates the RPM rate growing, and then forces the driver to wait while the
car speeds up, producing the buzzing sound that CVT critics really hate.
Drivers who are used to automatic transmissions may think that there is
something really wrong with the transmission unit, but that’s how CVT’s react
to rapid speed ups.
Multi-stage Hybrid
System
Lexus wanted to eliminate this issue by providing the LC500H with a multi-stage hybrid unit. The automaker didn’t want to develop a dual-clutch transmission or an 8-speed automatic, but pursued the aim to try something new. The idea to design such an unusual project was motivated by Toyota's push to enhance Lexus sophistication and operating characteristics. The LC500H gear shifting system is paired with a 3.5-liter V-6 engine, ensuring 354 hp of power.
With two transmissions in its structure, it can be said that the LC500H has a total of 10 speeds. How’s it possible? The thing is that the 4 speed automatic unit is directly connected to the e-CVT, so with every mechanical gear the Lexus LC500H goes through 3 gear ratios simulated by the e-CVT. That's how you get 9 speeds. The last mechanical gear of that automatic unit is an overdrive gear intended for highway cruising. To put it simply, this sophisticated hybrid system simulates a 10-speed automatic system.
Check out cool videos
about the Multi-stage Hybrid System
The great thing about this transmission system
is that it's capable of delivering very smooth shifts without the drawback of traditional
CVTs described above, and the engine can also run at lower rpm on the highway. It's
all thanks to those fixed gear ratios, and it's surprisingly simple. This
transmission shifts really quickly (approx.100 ms to shift from one gear to the
next one) and smoothly, as this system is really smart and it knows when the
gear shifting should take place.
The main drawback of this transmission is that
the concept of gear shifting gets lost, and changing speeds by means of
paddle-shifters turns out to be quite complicated. The thing is that if you
want to switch from common highway cruising to "overtaking" mode,
you'd have to manually downshift 4-5 times before getting to the sufficient RPM
rate for taking other cars over. Thus, it is better to let the transmission
system deal with this complex gear shifting process and enjoy the ride.
