getakey

I know on the RLX Sport Hybrid, the rear Electric Motors disengage at 78+mph via a clutch.
Actually 4 questions:
Would it be better to set speed control at 79+ versus 75-78 which is upper end of the range?
When the electric motors are not Regen or providing power, do they disengage using clutch no matter what the speed. If yes, question 1 does not really matter.
Is it the same config on the MDX, i.e., do not engage at 78+mph?
Can the motors Regen brake at 78+?

pcloadletter

From what I have seen, the motors provide regen and torque vectoring above 78.

getakey

I will have to watch.
Another question I posed in another thead, but it was kind of buried.

This was on a mostly interstate trip, but went through 2 mountain passes. I did not set on Sport in the passes, so maybe the torque vector behavior was different. As noted below, at 60+ mph, the torque vector was backwards. I did not push it hard through the curves, but did accelerate on some of the curves to see if the behavior would change. It did not.

I had power monitor on for most of the outbound trip and particularly wanted to watch it during the curves in the passes. I noticed that at 60+ mph, the system gave power to the inside rear wheel and sometimes even braked the outside wheel. Is this to counter over-steer? At less than 60, I see the expected power to outside wheel and/or braking on inside wheel.

RDX10

I find it interesting that you mention braking on the outside wheel. From
what I understand, this hybrid system is supposed to send backwards torque to the inside wheel during a turn, surprised to see braking. But my question to you is how can you tell it's braking? The absence of bars on the display does not mean it is braking.

AP8ESQ

To the above - when the SH system (either RLX or MDX) is regen braking reverse arrows are present on the power distribution monitor. There is no lack of bars but a visual demonstration of the braking which is occurring displayed any time regen is occurring. If there is neither propulsion or braking only then is there a lack of any indication either way (lack of bars) on the monitor.

RDX10

Oh I got you now. Thank you very much for the explanation. I was under the impression that the backwards arrow meant the wheel was being powered in the opposite direction. From videos I watched online, it stated that the system could spin one of the rear wheels in the opposite direction.

getakey

yes - they changed the visual for the Sport Hybrid. No more bars. Blue arrows toward the wheels is positive torque. Green arrows away from wheel to battery are Regen braking. At the higher speed cornering, I could see braking applied to outside rear wheel sometimes and more often power to inside. At lower speeds, the opposite which I expected.

RDX10

Then I sincerely appologize. I completely misunderstood how it works. Thank you guys for the clarification.

pcloadletter

I may have misspoke, there is torque vectoring shown on the display at 78+, not so sure about regen.

getakey

is torque vectoring shown on the display at 78+
Is or is NOT?

pgeorg

Torque vectoring and regeneration is shown on the display at 78+, but I believe it is not actually in effect. The rear motors disengage above 78mph, so its just the display showing that. I also do not feel the vectoring effect above that speed, at least on the RLX SH. I do not own a MDX SH.....

RDX10

Well there we have it! The most knowledgeable hybrid owner on the forum has spoken! Thank you for the clarification.
Just wondering, are you aware if the normal SH-AWD turns off above 78?

mqs1

What a great resource this board is.... I seem to learn something new all the time here!

Did not realize the rear e-motors disengaged above 78mph.... my experience on a drive back to Denver from CoSpgs now makes sense.... you know how sometimes a train of cars seem to form going really fast? Got caught up in one and I thought the car seemed to lose a little ooomph above 80mph. I thought it might have been the start of a rainstorm forming and the wheels were slipping a bit (I slowed down at that point), but i do recall thinking it started before the rain started, but couldn't be quite sure. I thought it was just old age messing with my memory and/or I'm finally paying the price for that truckload of ganj from college... another hazy experience, haha.

Parts of the drive to Vegas is now 80mph.... maybe time for a road trip and see for sure! BTW, I don't know if you folks are aware of Silvercar car rental. They rent only Audi A4s and recently bought by Audi. Friend sent me a referral code (plus 30% off first rental) so decided to do a roadtrip to Vegas a couple of months ago to check it out and I really enjoyed driving the car. Very good power from that little engine. The car itself is a base model A4 so the sound system really really sucked and the appointments were pretty sparse, but the seats were extremely comfortable, making that 10-11 hour drive fly by. I'll definitely use them again.

I wonder why they disengage? Tesla obviously doesn't......

RDX10

I can't really give you a definite answer as to why they disengage. However I can tell you that even on hybrid supercars (i.e. Porsche 918) the motors turn off as well. Might have something to do with overstraining or inability of the motors to keep up with the gas motor? Not too sure.

pgeorg

You are too kind sir! I am definitely not that person! Other people here are much more knowledgeable then I am....

I believe the regular SH-AWD works at any speed, as long as you are on the throttle.....
Here is a very good explanation of the regular SH-AWD system, if you guys feel like reading it.
Acura SH-AWD: A Comprehensive Analysis | YouWheel - Your Car Expert

I also found an older but very informative article about the SH SH-AWD, which mentions something about the rear motors providing torque only above 78mph (I am not quite sure what that part means). Here is the link:
http://www.roadandtrack.com/new-cars...x-coolest-awd/
The reason why the rear motors disengage above 78mph, is that at that speed they reach 11K rpm and above that they would provide too much electricity to be reliable. Here is a couple of paragraphs from the article:

"Part of the beauty of the system is that the motors are fairly small, made possible by gearing them down. A planetary gearset couples the motors to their
respective wheels at a 10.38:1 ratio. The problem with that is that at about 78 mph, as the motors reach 11,000 rpm, they begin to produce too much voltage
for the electric systems to handle reliably.

The solution is to decouple the motors from the rear wheels at high speeds—which is also a boon to efficiency. (And let's be honest—you don't actually
need four-wheel drive at high speeds. If you're spinning your front wheels at 80 mph, you may as well start dialing 9-1-1.)

Decoupling the motors from their wheels, though, would eliminate the SH-AWD's system from performing torque-vectoring—and that would change the RLX's
cornering behavior dramatically. The solution is to remove the motors' ability to assist or regen (and thus slow their rotational speeds) but not remove
their ability to remove torque from one side and add it to the other.

And that's where things get crazy. The TMU's two motors operate on a single planetary gearset with a single ring gear that's held in place by an
electrohydraulic clutch. Each motor's torque enters through its own carrier gear, is multiplied, and then heads to the axle via that side's sun gear.

At 78 mph, the clutch releases, allowing the ring gear to spin. However, thanks to the miracle of planetary gears, if the motors exert different levels of
torque on their respective carrier gears, they experience equal and opposite forces. Meaning the system can transfer torque from one side to the
other—albeit only in equal measures. Key point: torque-vectoring is still possible."

HTH

getakey

I had read the part about too much voltage above 78 mph. However, I'm not buying the following:
At 78 mph, the clutch releases, allowing the ring gear to spin. However, thanks to the miracle of planetary gears, if the motors exert different levels of
torque on their respective carrier gears, they experience equal and opposite forces. Meaning the system can transfer torque from one side to the
other—albeit only in equal measures. Key point: torque-vectoring is still possible."

Reason is that above 60, I see many times that power is supplied to the inside wheel and only sometimes braking is applied to outside wheel. To suddenly shift to an equal torque applied opposite to each wheel above 78 doesn't make sense to me. And, would it apply positive torque to inside or outside wheel as this clearly changes depending on the dynamics and speed.
I looked at monitor when I applied brakes above 80 and it appeared that Regen braking on the rear did not come on until speed went lower than 80. I want to retry this again several times.

George Knighton

Be careful, people! LOL....

I'll look forward to what you say because we none of us know the answer, I don't think, except what Honda tells us: There's torque vectoring at high speeds, but the rear motors will no longer provide forward thrust in a straight line.

The exact nature of the torque vectoring at high speeds, whether it's still push/pull, only pull, or only push, I don't think any of us knows.

I might have been in a position to look, a couple of times, but with a helmet on and under pressure, an old man doesn't have time to look at the INFO screen. LOL....

pgeorg

^^
Maybe you can ask some of your trusted Honda sources, to give us a concrete answer.......

George Knighton

I didn't buy a CTR or a TLX A-Spec. I'm not sure they're speaking to me.

pgeorg

I am sure they don't mind.......Although you can still buy one.....

RLX-Sport Hybrid

So people here is my take:

Today I was engaged in some aggressive driving in which I was traveling between 75-85 on some technically challenging hilly highway portions and observed something I had not previously. I noticed that in long sweepers instead of the green outside and blue inside display on the power delivery display below 78mph, I noticed two and even three blue discharge on the inside rear wheel, sometime two and three blue discharge on both rear wheels at the same time, and occasionally two and three blue/green action of the rear motors ABOVE 78 mph. In fact at 85 in a couple of places I noticed that the drive train almost felt as if it put itself into sport mode by itself. It didn't but it was very lively to say the least. I then put it in sport mode and continued the experience. Well it was even more enhanced. This car moves very smartly! Now I can't say for sure if that was active torque vectoring with added thrust or not, but I was not deep into the throttle, had plenty of reserves remaining and was able to accelerate with ease. The handling was amazing and felt very glued to the ground at all times. There is no question in my mind that what I measured a long time ago on the dyno is accurate. This is putting down very efficiently more than 400 fl/lbs of torque to the wheels at all times. What an awesome ride. By the way I am getting the new Michelin Sport AS 3+ tires on Thursday.

getakey

I just don't see how it can do torque vectoring with the E-motors disengaged.

RLX-Sport Hybrid

Try it yourself and see if it duplicates the experience. It was repeatable over and over again for me. Maybe we all have it wrong and they don't disengage at 78mph?

getakey

I'll try it when I can. Not very many places around here that I can go 80+

Edit:
Ok I did not see this in that previous article. I don't follow it completely. Would like to see a diagram

Decoupling the motors from their wheels, though, would eliminate the SH-AWD's system from performing torque-vectoring—and that would change the RLX's
cornering behavior dramatically. The solution is to remove the motors' ability to assist or regen (and thus slow their rotational speeds) but not remove
their ability to remove torque from one side and add it to the other

pgeorg

^^
I said the same thing......I don't think any of us understands this....

RLX-Sport Hybrid

One correction to my statement. What I meant was in a traditional turn where we would expect to see green discharge or energy recapture and slowing of the "inside" wheel and blue "discharge" or added thrust to the outside wheel, at speeds above 78 mph it displayed different behaviors. I saw combinations of two and three blue discharge bars or added thrust to the various wheels. Like I said it was repeatable over and over again. It is fun to have discovered something new with 51,000 miles on the car.

getakey

Did you see similar to my observation where at higher speeds the inside wheel gets boost and outside wheel is braked which is opposite to the torque vector expectation?

RLX-Sport Hybrid

I think I understand your question. What I saw was something different than what we all see below 78mph. Above 78 mph it was a completely unique experience. More blue discharge or added thrust, at least on the power delivery display and very little blue green combinations as we see all the time below 78mph. The car was moving for sure and the thrust was prodigious and I was not deep into the gas at all.

getakey

OK, so above 78 was different
My question is more basic - at ~60+, I see a marked difference in the way the power versus braking is applied. Below 60, power to outside wheel and brake to inside. Above 60, I see the opposite.

RLX-Sport Hybrid

In short yes you are right. It seems to be programmed to produce different experiences at various speeds and throttle applications. Just a unique engineering package.

getakey

In simple terms, it seems that at low to modest speeds the car can be pushed around the corner. However, at higher speeds it is programmed to correct for an oversteer tendency.
To be clear, my observations are in the MDX Hybrid, not the RLX, so the behavior could be different.

RLX-Sport Hybrid

My comments were/are for the RLX-SH. I have not and will not push the MDX-SH in the same way under any circumstances. I apologize for not picking up on that important detail. Regarding the MDX-SH it is clearly programmed for smoothness and is way less finicky and lively than the RLX-SH. Sorry for the confusion my friend.

getakey

no issues - looking forward to your comparisons between the two

George Knighton

Please forgive me, I'm going to push back a little bit.

I believe that the rear motors will act to preserve a neutral attitude, not really correct for oversteer. If you're smooth and controlled, the car will not force you to understeer.

In my experience, in a 10/10 exercise on a skid pad, the car allows for mild oversteer unless the driver behaves in a way that indicates that the car needs to intervene.

If you lift suddenly, or if you jerk the wheel too quickly, the car's going to intervene and try to straighten itself.

We need to be really careful when we're experimenting with things like "how do the rear motors behave at extremely high speed."

Forcing the car to intervene to straighten itself could be the very last thing you want to have happening in an extreme performance scenario.

pgeorg

^^
So what you are trying to say George is, never drive the SH (or MDX SH) at 9/10 or 10/10

George Knighton

I'm a little glad to hear that.

I've wondered a few times whether all KC2 are programmed the same and, if they are, whether people need to be indoctrinated to how they behave.

:-)

George Knighton

Let's just say I would probably ask to see your FIA license with photo ID. :-)

RLX-Sport Hybrid

Agreed about driving near the limits. For the record I was not doing that at all. Not even close.

getakey

No - not anything like correcting an driver over steer. These are sweeping turns on an Interstate Freeway at 65+ mph. I'm barely turning the wheel. The car puts power to the inside rear wheel for a good portion of the turn, not a quick correction. Sometimes it also brakes outside wheel. I monitored it on my 130 mile trip today and it was very consistent behavior. Under 60 mph, the expected torque vectoring occurs.
I also sped up to 85mph and applied brakes. The rear Regen brake did not come on until speed reduced below 80 mph. Similar on a very long downhill, I was going 80+ and let off gas. Car gradually slowed, but Rear Regen did not come on until below 80.
Went through a few very gradual curves above 80 mph. No light up of rear power or brake, but the curves were very gradual.

RLX-Sport Hybrid

It is very clear to me that the hybrid system in the MDX-SH is programmed differently than the RLX-SH. The behavior is clearly unique.