Lexus Engineers Explain the LC500h's Twin-Transmission System - Lexus LC500 Forum
 
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post #1 of 6 (permalink) Old 03-07-2016, 02:03 PM Thread Starter
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Lexus Engineers Explain the LC500h's Twin-Transmission System



The Lexus LC500h is the vessel for Lexus' brand new transmission set-up, a four-speed gearbox connected to the CVT. This unique transmission set-up takes away the "rubber band" feeling of CVTs. Lexus chief engineer for the Lexus LC500h Koji Sato explained the twin-transmission set-up to Automotive News at the Geneva Motor Show.

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The idea behind this technical solution was to eliminate the “rubber band feeling” that comes with all conventional CVTs. If you are unfamiliar with the phenomenon, it goes like this: you press the gas pedal hard, the revs go up and they stay there while the car accelerates.

On a regular car, you might think that your clutch is slipping, or that there’s something seriously wrong with the automatic transmission, but that is how CVTs respond to hard acceleration.

Lexus wants to change this and stop it from happening to their new cars fitted with a multi-stage hybrid system. The solution was not to introduce a twin-clutch gearbox or an eight-speed automatic, but to keep using the CVT transmission with a four-speed automatic gearbox.

The idea behind the mating of the two gearboxes is that the four-speed automatic modulates the CVT’s output and creates an intentionally perceived gearshift. The pair of gearboxes simulates the shifting of six gears in total, but the trick is that the driver will not be able to tell if the car shifted a gear through the automatic gearbox or the CVT did the work. It is improper to say that the CVT transmission shifts, as these units continuously change their ratios instead of actual gears.
Lexus is planning to use the twin-transmission set-up for many other vehicles. Next in line may be the next LS, which is expected to go on sale last year. Other Lexus models with longitudinally mounted engines could also get this hybrid system.

The twin-transmission set-up was an apt solution for Lexus engineers who sought to mate the electric engine of the LC500h with its naturally aspirated 3.5-litre V6 unit.

Lexus Engineer Details the Twin-Transmission Setup of New LC500h



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post #2 of 6 (permalink) Old 03-08-2016, 12:23 PM Thread Starter
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I found an even more detailed explanation of the twin-transmission system. Here is a quote from the article and I've put a link to the full article at the end of this post.

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Multi Stage claims to improve the relationship between car and hybrid. Multi Stage is still a continuously variable transmission, and there is potential for a dramatic disconnect between engine rpm and throttle inputs, the so-called “rubber-band” effect that is a relationship killer. LC chief engineer Koji Sato says the goal is to eliminate this disconnected feeling. In normal driving modes he admits the trans will perform much like a conventional CVT because it is more efficient to keep the engine in optimal operating conditions (load and rpm). In the new “M” mode, Multi Stage will mimic a 10-speed automatic, creating discrete ratios through a combination of HSD and planetary reductions. If you’re so inclined, you can shift with paddles located behind the steering wheel.
Details of the New Lexus Multi Stage Hybrid ? Feature ? Car and Driver | Car and Driver Blog



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post #3 of 6 (permalink) Old 03-08-2016, 05:49 PM
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Hopefully that will shut up the typical crowd of people that moan and complain about manual not being an option although I can see where they're coming from, some applications just call for advanced transmission tech like this and only this.
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post #4 of 6 (permalink) Old 03-11-2016, 05:00 PM
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There's still going to be die hard manual fans but the twin-transmission system may be enough to convert some. I've never really thought about the “rubber band feeling” when I accelerate but I'll have to look for it the next time I hard accelerate.
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post #5 of 6 (permalink) Old 03-12-2016, 02:53 PM Thread Starter
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I can see how some people just like the activity of driving a manual but when it comes to optimal performance, it is obvious that manuals are not the best out there.



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post #6 of 6 (permalink) Old 03-17-2016, 04:28 PM
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Quote:
Originally Posted by ToyoLex View Post
There's still going to be die hard manual fans but the twin-transmission system may be enough to convert some. I've never really thought about the “rubber band feeling” when I accelerate but I'll have to look for it the next time I hard accelerate.
Have you looked at the stats? The percentage is so small it's not even worth having as an option. Fact is doing away with the clutch and shifter is the way to go for consumer and for the car makers own bottom line.
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