What's preventing Lexus from combining torque vectoring and rear wheel steering?
#16
Lexus Test Driver
Yeah, most AWD cars have had some sort of a side-to-side torque splitting function where it shifts from one side to the other for a long time now. Nissan GTR and Subarus, EVOs all use such mechanisms.
Heck, even Acura with its lowly SH-AWD does something similar, but it actually applies brakes on the inner wheels to get the car to rotate (which in turn helps the car fight centrifugal forces).
However, TVD is a rather new concept in RWD cars.
Heck, even Acura with its lowly SH-AWD does something similar, but it actually applies brakes on the inner wheels to get the car to rotate (which in turn helps the car fight centrifugal forces).
However, TVD is a rather new concept in RWD cars.
Now I want to get a really fast car with toque vectoring so I can feel what that straight-line acceleration enhanced by torque vectoring is all about. Doesn't Subaru use torque vectoring in their Sti and Wrxs? They also have a CVT-turbo with TV too. I was mildly interested in forking over 28k for the MT or 31k for the CVT but liked the idea of spending a paltry sum of 4800 for my little SC3.
#17
Lexus Champion
Acura also has rws but only on fwd. They drop the system on sh-awd because they can control the rear with a differential. In their case there is no driveshaft (with the rlx) so they control it electronically and individually by wire. If the NSX ever comes out itll feature a system like that but reversed (hybrid driven front wheels). Itd be interesting to see if Lexus goes this route with awd hybrids in the future. Maybe soon.
#18
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From what I've read in the past regarding rear wheel steering and F models, it's not likely to be included with the new TVD. This was pointed out in an interview with chief engineer Junichi Furyama:
http://lexusenthusiast.com/2014/03/2...ailable-japan/
http://lexusenthusiast.com/2014/03/2...ailable-japan/
“All-wheel drive tends to be heavier and the behaviour tends to be understeer,” he explained via an interpreter. “Also in the cornering, the vehicle doesn’t respond to the driver’s intention.
“So I think FR (front-engine rear-wheel drive) base is better and with this system you can turn the steering wheel at the corner more naturally.”
Intriguingly though, while DRS and LDH was judged suitable for F Sport models, Furyama said it wouldn’t feature on future higher-performance cars such as the next IS F.
“The objective of LDH is for a certain level of drivers who are enthusiastic drivers, but not necessarily professional drivers, and they should be able to drive well with LDH. On the other hand the drivers of F like to do the drifting while driving on the circuit. So what we are targeting is different.”
“So I think FR (front-engine rear-wheel drive) base is better and with this system you can turn the steering wheel at the corner more naturally.”
Intriguingly though, while DRS and LDH was judged suitable for F Sport models, Furyama said it wouldn’t feature on future higher-performance cars such as the next IS F.
“The objective of LDH is for a certain level of drivers who are enthusiastic drivers, but not necessarily professional drivers, and they should be able to drive well with LDH. On the other hand the drivers of F like to do the drifting while driving on the circuit. So what we are targeting is different.”
#19
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^Thanks for the very relevant post. Sounds to me that the chief engineer purposely avoided DRS because he wants the car to drift better, instead of gripping better and posting faster lap times. So it was a design decision and not a technical issue or that DRS wouldn't have helped (in grip driving) after all. It would be nice if it could be made an option (and with a button to be disabled at will) just so people can set up the car differently for different driving situations though.
Last edited by ydooby; 08-08-14 at 03:59 PM.
#20
Lexus Test Driver
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Well, the two technologies are kind of at odds.
Torque vectoring is intended to cause a controlled oversteer, and rear wheel steering is intended to maintain stability while decreasing turning radius. I imagine there's a lot of weight gain with minimal advantage in performance by combining the two. I also imagine the packaging is difficult to fit both underneath the car. Here's a pic of the GS with DRS.
The TVD is going to be quite a bit larger than that rear differential. I find it challenging to imagine ways to fit both.
Torque vectoring is intended to cause a controlled oversteer, and rear wheel steering is intended to maintain stability while decreasing turning radius. I imagine there's a lot of weight gain with minimal advantage in performance by combining the two. I also imagine the packaging is difficult to fit both underneath the car. Here's a pic of the GS with DRS.
The TVD is going to be quite a bit larger than that rear differential. I find it challenging to imagine ways to fit both.
#21
Now I want to get a really fast car with toque vectoring so I can feel what that straight-line acceleration enhanced by torque vectoring is all about. Doesn't Subaru use torque vectoring in their Sti and Wrxs? They also have a CVT-turbo with TV too. I was mildly interested in forking over 28k for the MT or 31k for the CVT but liked the idea of spending a paltry sum of 4800 for my little SC3.
Where is the bloody final spec for this F?
#23
Lexus Test Driver
That is a huge red flag. Something has seriously gone wrong. Never seen a car officially unveiled in a press conference 9 - 10 months before the specs were out. Never happened in the past.
#25
Lexus Test Driver
Because I don't think that is happening. The prototypes are already out and already shipped to the US that will used for press events. So there is no work being done that could potentially change the specs. Maybe, some small tweaks here and there, but the specs already had been decided a while back.
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Because I don't think that is happening. The prototypes are already out and already shipped to the US that will used for press events. So there is no work being done that could potentially change the specs. Maybe, some small tweaks here and there, but the specs already had been decided a while back.
Just have to wait for the "Official Specs" release date...
Joe Z
#27
Lexus Champion
Its not a big deal. Pre orders are doing well from everything were hearing. Excitement is there. The magazine/website tests will come around the same time figures on power/weight is released. Theyre not in any rush so its not a top priority. Driving feel is more important than lap times anyway.
#29
Well if you look at the cut-away that came out a few months ago, the RC F DID appear to have both rear wheel steering and the TVD.
So they can clearly package both technologies.
As for why have them, as a former Toyota Engineer, I can see that it may help agility and turn-in (RWS) while also having a very neutral stance (between over/under-steer) from the TVD.
I too am highly disappointed by the lack of final specs on the RC F.
Should I just buy the M4 because it's already here? I may do that.
It seems like either Lexus has an inferior performer to the M4 on their hands, and they are trying to figure out what to do, or there's some other problem we don't know about. Either way, not good.
So they can clearly package both technologies.
As for why have them, as a former Toyota Engineer, I can see that it may help agility and turn-in (RWS) while also having a very neutral stance (between over/under-steer) from the TVD.
I too am highly disappointed by the lack of final specs on the RC F.
Should I just buy the M4 because it's already here? I may do that.
It seems like either Lexus has an inferior performer to the M4 on their hands, and they are trying to figure out what to do, or there's some other problem we don't know about. Either way, not good.
#30
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Well if you look at the cut-away that came out a few months ago, the RC F DID appear to have both rear wheel steering and the TVD.
So they can clearly package both technologies.
As for why have them, as a former Toyota Engineer, I can see that it may help agility and turn-in (RWS) while also having a very neutral stance (between over/under-steer) from the TVD.
So they can clearly package both technologies.
As for why have them, as a former Toyota Engineer, I can see that it may help agility and turn-in (RWS) while also having a very neutral stance (between over/under-steer) from the TVD.
http://lexusenthusiast.com/2014/01/1...he-lexus-rc-f/