natnut

Prime Cuts: Lexus Variable Gear Ratio Steering
From March 2012 issue of Car and Driver

The ability to change a vehicle’s steering ratio has many advantages. A quicker ratio (fewer turns lock-to-lock) can give a vehicle a deft feel. At high speeds, switching to a slower ratio (more turns lock-to-lock) imparts a better sense of stability.

Lexus is not alone in using a computer-controlled system to change ratios, but its approach is pretty trick. Note that this type of active steering is far more involved than the variable-ratio units with rack teeth cut at differing angles; they can’t make ratio changes on the fly over the full range of lock. The more complex Lexus (and Audi) approach is essentially a gearbox built into the steering column between the steering wheel and the pinion gear.

Unlike BMW’s active steering system, which employs a planetary gearbox, Lexus’s Variable Gear Ratio Steering (VGRS) uses something called a wave generator and a flexible gear. Lexus claims its system is more accurate and quicker acting than others. VGRS can be found on the LS sedan, the LX SUV, and the new GS F Sport. We sliced into the unit to get an idea of  how it works and because we wanted to find out what a wave generator is.

(My thoughts : I wonder what the differences between Audi's and Lexus' systems are. The F-Sport has been praised for feelsome steering feedback while the A6 has been panned for its lifeless steering.)

rlj4246

Thanks for posting this. I had it on my LS and always wondered how it worked.

rominl

iTrader: (4)

yup, vgrs works very very well

MY13GS350

Great post... There are so many hidden details in these cars!

In any event, I showed this to my wife, an engineer who described it as a modified planetary gear probably to avoid a patent on the same concept from another manufacturer.

She theorizes that when active, as you turn the wheel the motor turns the gear opposite to your input a little bit to effectively change the ratio.

My brain is still jello on the whole thing, I'm just glad it works and I like it.

btw that part is $3085.12 on Sewell

Hoovey689

iTrader: (16)

wow so cool! thx for sharing

natnut

That alone justifies the price premium the F-Sport has over the normal GS.
(Hint : Dear Rominl, are you listening )

LexusNN

iTrader: (5)

Very cool to see the inside workings, good find

rominl

iTrader: (4)

you aren't much into driving i suppose, have you even driven cars with and without vgrs?

if you have to pick out a single part price and try to win an argument, power to you. didn't even have to come this far, just look up the msrp on the fsport brakes and you are there already but ask those who are more into racing, ask if they care more about better spring rate / dampening / rear steer, vs stuff like vgrs.

i am so glad my ls460l has the vgrs that normal ls460 don't, coz' it makes the car one hell of a driving machine (not).

i am not dinging on vgrs (read post #3), it makes overall driving a lot more compliant and easier imho. but does it affect things drastically from a performance point of view? probably. but it's not that high up on my list.

now if they make vgrs an option while making drs standard on fsport? i will be first in line to give props to lexus.

natnut

Haha. Sorry I didn't mean to be argumentative. I was just pointing out that just based on MSRPs of the additional individual parts alone (F-Sport brakes, 19 inch wheels,VGRS), that alone might justify the price of the F-Sport over the normal GS.

Not saying that VGRS alone makes a huge difference to the handling or driving experience.Haven't driven the base GS yet but the fully equipped F-Sport I drove was a revelation. I hadn't enjoyed driving as much ever since I borrowed my friend's E39 for a spin.

spwolf

I dont think it makes any difference in handling per say... what it does it adjust the steering so it is more comfortable on the highway and faster when you need it in twisties... without out, they would probably leave it somewhere in between that would make it either twichy on the highway or too slow for twisties.

rominl

iTrader: (4)

i should have made it clearer too. i don't think i am trying to say the fsport package is not worth the price. but all along i am trying to say if lexus puts on a fsport badge on the car, i personally expect something more "extra" to differentiate with the luxury package when it comes to suspension.

fwiw, having fsport is great and fantastic for lexus imho. just like bmw has the msport. it creates variation and people like that. bigger brakes is big no matter how you look at it. it's likely subjective, but to me i just feel it's funny that the fsport hast he same springs / shocks as luxury. or put it this way, i probably talked to 6-7 random people about the new 4gs, and they were all surprised when i told them the cars (fsport vs luxury) have the same suspensions. in some way, that shows the kind of expectations people have.

spwolf

i dont see that a problem - someone decided that Luxury should end up with same suspension as F-Sport, minus the big brakes, bigger rubber/wheels and DRS.

F-Sport lost nothing.

So what is the reason to complain? F-Sport has great suspension. Luxury got great suspension. If you want DRS, pay extra for it...

The whole idea that it should be different just because it should be different... I dont get it.

rominl

iTrader: (4)

no worry, i don't expect you to get it, and i have tried to explain it in my post, as well as what people around me got surprised about. you can argue all day with your points, and i am just stating mine