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No automatic braking with Cruise Control ?

 
Old 06-02-2019, 09:43 AM
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No automatic braking with Cruise Control ?

I am a bit surprised to find that when using cruise control and going down a hill, the car does not brake to keep the selected speed. The car just speeds up due to gravity. I presume all of your RDXs act similarly?

My 2011 BMW 335i did apply the brakes to maintain the selected speed.
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Old 06-02-2019, 10:18 AM
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The RDX does not apply the brakes.

https://acurazine.com/forums/third-g...ontrol-972694/
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Old 06-02-2019, 03:12 PM
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Oddly enough, Acura does not do everything a BMW does. Who’d have thunk it?

My 2008 535 did apply the brakes to maintain cruse control speed.


Otoh, you can’t get torque-vectoring AWD on a comparable BMW at all.
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Old 06-02-2019, 03:57 PM
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My 2011 and 2015 Hyundai Genesis’ both braked to keep the preset speed!
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Old 06-02-2019, 04:53 PM
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If there is anything that really needs automatic braking on cruise control, it was that cruise ship in Venice.
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Old 06-02-2019, 09:36 PM
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I guess I am the odd one on this as I don't want the cruise to apply brakes on down hills. Why? Well, gas mileage for one reason. I have noted on this car and my previous Honda CR-V's that in hilly regions I did better on gas by driving the car myself than by letting R2 drive it. To accomplish this I let the car speed up on its own (within reason) on the down hill and then give it just enough throttle on the uphill to keep the speed from dropping too much. Cruise controls tend to chop the speed on the downhills only to gas it hard (wasting fuel) on the uphill trying to maintain a set speed. I see 3 to 4 MPG difference between cruise and "me" driving the car in hilly regions (like i have in Kentucky where I live). On the flatland of Indiana or Ohio the cruise does fine on mileage as you don't get all the variations in speed due to altitude changes.

I won't judge a complete car on the merits of one function. I see the vehicle as a total package. Like would I trade my wonderfully performing RDX for a Kia over the operation of a cruise control? Nah! But you might.....
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Old 06-03-2019, 02:23 AM
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Originally Posted by Madd Dog View Post
Oddly enough, Acura does not do everything a BMW does. Who’d have thunk it?

My 2008 535 did apply the brakes to maintain cruse control speed.


Otoh, you can’t get torque-vectoring AWD on a comparable BMW at all.
Does the X3 M40i have it?
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Old 06-03-2019, 03:13 AM
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Originally Posted by Madd Dog View Post
If there is anything that really needs automatic braking on cruise control, it was that cruise ship in Venice.
IKR?

At first, I also thought it was in Venice, LA, lol....
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Old 06-03-2019, 03:16 AM
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Now doesn't it downshift and engine brake to loose excessive speed?


Suppose you're going down a tall mountain with cruise set at 50 mph, will it speed up to 100 mph just because of gravity?
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Old 06-03-2019, 08:45 AM
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I go down a steep grade fairly frequently, so I put the Transmission in Sequential Mode and use the Paddle Shifter to "Engine Brake" the speed. It works very effectively.
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Old 06-03-2019, 08:55 AM
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Originally Posted by Madd Dog View Post
Oddly enough, Acura does not do everything a BMW does. Who’d have thunk it?

My 2008 535 did apply the brakes to maintain cruse control speed.


Otoh, you can’t get torque-vectoring AWD on a comparable BMW at all.
Did your 535i apply the brakes, or did it simply downshift the transmission?
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Old 06-03-2019, 09:12 AM
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Honda used to have Grade Logic Control to hold a lower gear to maintain your speed up or down a hill. I don't think Honda/Acura has that anymore? Might have to do it manually by tapping the paddles a few times on downhill runs to maintain your speed. I had a few MDX loaners with the 9AT and the vehicle would speed up when I hit the paddles to downshift to slow down. I would have to hit the paddles 4-5 times before I would get the braking I needed before hitting a curve. Not sure if the 10AT does the same downshift/acceleration quirk and/or the 2.0T may not have enough engine braking on a 2 ton vehicle to make a difference unless you drop 4-5 gears?
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Old 06-03-2019, 09:15 AM
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Originally Posted by Midnight Mystery View Post
Now doesn't it downshift and engine brake to loose excessive speed?


Suppose you're going down a tall mountain with cruise set at 50 mph, will it speed up to 100 mph just because of gravity?
Wind resistance will probably slow you before then. I drive a couple different cars for work, and down most grades wind resistance keeps them at 80 or below.
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Old 06-03-2019, 09:26 AM
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Originally Posted by Alias1431 View Post
Does the X3 M40i have it?
I think only upper levels have it. It is called Dynamic Performance Control. The lower level cars, like the 3s, mumble around it and use slightly different wording, like ‘intelligent’ and ‘Performance Control’, but it seems to be brake vectoring not torque vectoring.

The X6 has it. The brochures are vague.

I would not trust a salesman to know or say whether a particular car has torque or brake vectoring. I would want to see it in official BMW print. Maybe a monroney sticker?
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Old 06-03-2019, 10:42 AM
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If we didnt have this post than we would have the "had to get new brakes at 9k miles" post like what you get on the other manufacturer forums. The systems tend to just ride the brakes causing them to need to be replaced frequently.

Rather have it our way tbh. I hated driving my c43 out of the mountains in cruise control.
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Old 06-03-2019, 07:00 PM
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Doesn't the ZF-9 and 10AT differ so much (and use newer designs?) That is likely the cause of losing grade logic...
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Old 06-03-2019, 07:04 PM
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Originally Posted by horseshoez View Post
Did your 535i apply the brakes, or did it simply downshift the transmission?
Both.

I did European delivery, and went from unlimited into a much lower limit. I hit the stalk about 6 or 7 times at -5 each time, and them brakes worked. In day to day driving, the cruise control speed never varied by more than 2 or 3 mph, up or down a hill, regardless of how steep it was.

Last edited by Madd Dog; 06-03-2019 at 07:07 PM.
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Old 06-04-2019, 09:10 AM
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Originally Posted by mrgold35 View Post
Honda used to have Grade Logic Control to hold a lower gear to maintain your speed up or down a hill. I don't think Honda/Acura has that anymore?
Originally Posted by Midnight Mystery View Post
Doesn't the ZF-9 and 10AT differ so much (and use newer designs?) That is likely the cause of losing grade logic...
All of the automatic transmissions and DCT's currently used by Honda including the Honda 6AT, ZF 9HP, Honda 10AT, 7-speed DCT, and 8-speed DCT use Grade Logic Control.

This can be verified by reading the powertrain press releases or viewing the transmission description of operation in the service information (subscription required).

Here's the powertrain press release for the 2019 RDX:

"Sequential SportShift 10-Speed Automatic Transmission with Paddle Shifters
  • Electronic shift-by-wire gear selector
  • Sequential SportShift automatic transmission allows semi-manual operation
  • Steering wheel-mounted paddle shifters
  • Cooperative control between Drive-by-Wire throttle and transmission
  • Advanced shift-hold control limits upshifts during spirited driving
  • Grade Logic Control reduces gear "hunting" on various road gradients"
https://hondanews.com/acura-automobi...kit-powertrain

Honda's CVT's don't have or need Grade Logic Control since there are no "gears to hunt between". Most of them, however, have Honda's G-Design shift logic which is intended to emulate the feel of a stepped automatic transmission while negating some of the benefits of a continuously variable transmission in order to make the powertrain feel more "natural".
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Old 06-05-2019, 12:08 PM
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Originally Posted by mrgold35 View Post
Honda used to have Grade Logic Control to hold a lower gear to maintain your speed up or down a hill. I don't think Honda/Acura has that anymore? Might have to do it manually by tapping the paddles a few times on downhill runs to maintain your speed. I had a few MDX loaners with the 9AT and the vehicle would speed up when I hit the paddles to downshift to slow down. I would have to hit the paddles 4-5 times before I would get the braking I needed before hitting a curve. Not sure if the 10AT does the same downshift/acceleration quirk and/or the 2.0T may not have enough engine braking on a 2 ton vehicle to make a difference unless you drop 4-5 gears?
^^ This. Tiny engines in big heavy vehicles are not very useful for engine braking.
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Old 06-05-2019, 02:31 PM
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Originally Posted by samiam_68 View Post
^^ This. Tiny engines in big heavy vehicles are not very useful for engine braking.
Compared to the 340 in my 1970 Challenger, even modern I6 and V6 engines don't provide much useful engine braking. In the Challenger I could actually chirp the rear tires when downshifting.
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