Questions About Acura RL AWD Claim

I was watching TV last night and after one of the short
breaks to show programming I became interested in an Acura
commercial for the RL sedan. In the commercial the claim was
made that the AWD system "accelerates the outside rear wheel
in a turn to dramatically improve handling." How does the
system "accelerate" one rear wheel?

The following is from
http://www.acura.com/models/model_sp....asp?module=rl
:

"Helps steer the vehicle and enhances its maneuverability.
It helps compensate for understeer (push) or oversteer (the
rear end feels loose), when cornering. The RL feels agile
and nimble and tracks smoothly through turns without
unnecessary steering correction. It sends up to 70% of the
engine's torque to the front or rear wheels, but it can also
send up to 100% of that same rear-wheel torque to either the
left or right outside-rear wheel when cornering. It will
even accelerate the outside rear wheel to enhance handling
while cornering."

If you click on the right buttons ("Click to Experience It
Now," and then the "Control" tab) they have a little movie
illustrating the system in action. The cut away view of the
car indicates some sort of complicated rear end. An article
at
http://www.theautochannel.com/F/news...10/277071.html
indicates there are magnetic clutches in the rear end, but I
still don't see how these can accelerate one of the rear
wheels. I can see how they might selectively apply torque to
only one wheel, but not "accelerate" that wheel beyond the
other wheels. Maybe it is just the way the terminology is
used that is confusing me. Is there also a conventional
differential in the rear axle, or just magnetic clutches?

Other articles:

http://www.auto-report.net/index.html?sh-awd.html

Regards,

Ed White

Perhaps there is a computer sensing the turn, and shifting power to the
outside rear wheel, like a Mercedes?

omirix wrote:
>
> Perhaps there is a computer sensing the turn, and shifting power to the
> outside rear wheel, like a Mercedes?

"Shifting Power" seems meaningless to me. It is also not the
same as "accelerating" which implies a change in velocity.

Ed

C. E. White wrote:
>
> omirix wrote:
>
>>Perhaps there is a computer sensing the turn, and shifting power to the
>>outside rear wheel, like a Mercedes?
>
>
> "Shifting Power" seems meaningless to me. It is also not the
> same as "accelerating" which implies a change in velocity.
>
> Ed
I suspect the problem is terminology. The Acura info was probably
written by a marketing type..not an engineer.
By applying all the torque to only one of the rear wheels it would tend
to help steer the car to the opposite direction.
Stan K.

Stan Kasperski wrote:
>
> C. E. White wrote:
> >
> > omirix wrote:
> >
> >>Perhaps there is a computer sensing the turn, and shifting power to the
> >>outside rear wheel, like a Mercedes?
> >
> >
> > "Shifting Power" seems meaningless to me. It is also not the
> > same as "accelerating" which implies a change in velocity.
> >
> > Ed
> I suspect the problem is terminology. The Acura info was probably
> written by a marketing type..not an engineer.
> By applying all the torque to only one of the rear wheels it would tend
> to help steer the car to the opposite direction.
> Stan K.

Alright, so they have electrically operated clutches in the
rear axle, and they only engage the "outside" wheel in a
turn. Is there a traditional differential as well? If so,
does another clutch also "ground" or somehow modulate the
disengaged axle - which seems like it would casue a whole
other set of problems. I'd really like to see a detailed
drawing with explanations of the rear axle mechanism. It
would also be interesting to see a comaprison test of an RL
with the system and one with a traditional rear end. I have
to believe it is like quadra-steer, cool sounding but almost
worthless in the real world for most people. On the other
hand - I like cool things. Everytime I see the RL ad, I have
a strange compulsion to go buy one. This despite the fact
that I'll bet it doesn't have enough head room for me. I
guess I should just go test drive one. Do you think the
salesman would let me take it down a twisty road at high
speed?

Ed

By modulating the brakes on the rest of the wheels. Just like the
traction control on the Vette ? Left turn and it slow the left side,
that makes the differentials speed up the opposing side.

--
Steve Williams


"C. E. White" > wrote in message
...
> I was watching TV last night and after one of the short
> breaks to show programming I became interested in an Acura
> commercial for the RL sedan. In the commercial the claim was
> made that the AWD system "accelerates the outside rear wheel
> in a turn to dramatically improve handling." How does the
> system "accelerate" one rear wheel?
>
> The following is from
> http://www.acura.com/models/model_sp....asp?module=rl
> :
>
> "Helps steer the vehicle and enhances its maneuverability.
> It helps compensate for understeer (push) or oversteer (the
> rear end feels loose), when cornering. The RL feels agile
> and nimble and tracks smoothly through turns without
> unnecessary steering correction. It sends up to 70% of the
> engine's torque to the front or rear wheels, but it can also
> send up to 100% of that same rear-wheel torque to either the
> left or right outside-rear wheel when cornering. It will
> even accelerate the outside rear wheel to enhance handling
> while cornering."
>
> If you click on the right buttons ("Click to Experience It
> Now," and then the "Control" tab) they have a little movie
> illustrating the system in action. The cut away view of the
> car indicates some sort of complicated rear end. An article
> at
> http://www.theautochannel.com/F/news...10/277071.html
> indicates there are magnetic clutches in the rear end, but I
> still don't see how these can accelerate one of the rear
> wheels. I can see how they might selectively apply torque to
> only one wheel, but not "accelerate" that wheel beyond the
> other wheels. Maybe it is just the way the terminology is
> used that is confusing me. Is there also a conventional
> differential in the rear axle, or just magnetic clutches?
>
> Other articles:
>
> http://www.auto-report.net/index.html?sh-awd.html
>
> Regards,
>
> Ed White




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"C. E. White" > wrote in message
...
>
>
> omirix wrote:
>>
>> Perhaps there is a computer sensing the turn, and shifting power to the
>> outside rear wheel, like a Mercedes?
>
> "Shifting Power" seems meaningless to me. It is also not the
> same as "accelerating" which implies a change in velocity.
>
> Ed

The outside rear wheel on every car spins slightly faster in corners. So
does the outside front wheel. Both front and rear outside wheels travel a
longer distance compared to the inside wheels when turning.

On Mon, 20 Dec 2004 16:01:16 -0500, "Steve W." > wrote:

>By modulating the brakes on the rest of the wheels. Just like the
>traction control on the Vette ? Left turn and it slow the left side,
>that makes the differentials speed up the opposing side.




It's called vehicle stability assist, and is common on hondas and
acuras. it uses athe abs to apply the crakes on the other wheels
allowing the others to spin faster.

Chip

"James C. Reeves" wrote:

> The outside rear wheel on every car spins slightly faster in corners. So
> does the outside front wheel. Both front and rear outside wheels travel a
> longer distance compared to the inside wheels when turning.

I understand this. But Acura claims that they are
"accelerating" the outside rear wheel. A traditional dear
differential splits torque evenly beteen the two rear
wheels, while allowing them to rotate at different speeds.
The illustrations in the Acura RL ads show a very
complicated rear end. I want to understand what they are
trying to tell me. The rear end has electrically operated
clutches and some of the articles talk about a planetary
gearset. I want to know what they are doing back there. Are
they merely matching the speed of the outside rear wheel to
match up with the increased arc lenght (comapred to the
inside wheels), or do they really apply additional torque to
the outside rear wheel in an attempt to drive the wheel
differenty to improve handling. This is what the ads imply.

Ed

chip wrote:
>
> On Mon, 20 Dec 2004 16:01:16 -0500, "Steve W." > wrote:
>
> >By modulating the brakes on the rest of the wheels. Just like the
> >traction control on the Vette ? Left turn and it slow the left side,
> >that makes the differentials speed up the opposing side.
>
> It's called vehicle stability assist, and is common on hondas and
> acuras. it uses athe abs to apply the crakes on the other wheels
> allowing the others to spin faster.

Go look at the references. This system does not work that
way - or at least the ads and articles imply that it is
something totally different. Clutches and planetary gear
sets in the rear end have been added.

Ed