Radar cruise control-interestingly nice
Instructor
Joined: Jan 2003
Posts: 897
Likes: 56
From: IL
First experience with adaptive cruise control
Picked up up my 2017 RX 350 yesterday. Took it on a drive from NW SUBURBS OF Chicago to Milwaukee. Decided to try the cruise control. I was doing 65 and set the cruise. Apparently I was just at 3 car lengths from the car in front of me. I tried to move closer by lifting the cruise arm up to accelerate and nothing happened. I took my finger off the cruise arm. I then moved over a lane where there was no cars. The car started accelerating sharply by itself and was continuing to accelerate past 85 by itself when I finally it the brake. Is it possible the car remembered my attempt to accelerate with a car in front of me and then when there was no cars it implemented my acceleration request even after I had taken my finger off the cruise arm?
Driver
Joined: Oct 2017
Posts: 95
Likes: 14
From: NJ
When you lifted control arm to “accelerate“, you actually increased your set speed, potentially to over 100 miles an hour. That’s why your car accelerated when you changed lanes and there were no cars in front of you. You should really read the manual on how to use This feature before using it again otherwise it may be dangerous to you and others.
It may startle you next time and cause some delay in response. I’ve had my car for three months and I’ve been using dynamic cruise control for about 80 percent of my driving and what you’re describing is I think what happened.
also, setting three car lengths is pretty dangerous. You will see a lot of cars merging between you and the car in front of you. You can get closer by reducing the number of car length to 1 or just accelerating by using the gas pedal.
Once you figure out radar cruise control, will be hard to drive cars without it.
good luck!
It may startle you next time and cause some delay in response. I’ve had my car for three months and I’ve been using dynamic cruise control for about 80 percent of my driving and what you’re describing is I think what happened.
also, setting three car lengths is pretty dangerous. You will see a lot of cars merging between you and the car in front of you. You can get closer by reducing the number of car length to 1 or just accelerating by using the gas pedal.
Once you figure out radar cruise control, will be hard to drive cars without it.
good luck!
Advanced
Joined: Apr 2017
Posts: 701
Likes: 166
From: NSW
Picked up up my 2017 RX 350 yesterday. Took it on a drive from NW SUBURBS OF Chicago to Milwaukee. Decided to try the cruise control. I was doing 65 and set the cruise. Apparently I was just at 3 car lengths from the car in front of me. I tried to move closer by lifting the cruise arm up to accelerate and nothing happened. I took my finger off the cruise arm. I then moved over a lane where there was no cars. The car started accelerating sharply by itself and was continuing to accelerate past 85 by itself when I finally it the brake. Is it possible the car remembered my attempt to accelerate with a car in front of me and then when there was no cars it implemented my acceleration request even after I had taken my finger off the cruise arm?
Hope that all makes sense.
Driver School Candidate
Joined: Dec 2017
Posts: 1
Likes: 0
From: TX
Picked up up my 2017 RX 350 yesterday. Took it on a drive from NW SUBURBS OF Chicago to Milwaukee. Decided to try the cruise control. I was doing 65 and set the cruise. Apparently I was just at 3 car lengths from the car in front of me. I tried to move closer by lifting the cruise arm up to accelerate and nothing happened. I took my finger off the cruise arm. I then moved over a lane where there was no cars. The car started accelerating sharply by itself and was continuing to accelerate past 85 by itself when I finally it the brake. Is it possible the car remembered my attempt to accelerate with a car in front of me and then when there was no cars it implemented my acceleration request even after I had taken my finger off the cruise arm?
That said, I always select the "Driving Assist System Information" on the multi-information display. You'll find this on the instrument cluster as an icon with a car driving within two lanes (see below image). This will confirm that the cameras see definitive lane markings (indicated as two solid lanes) and also the speed the cruise control is set. This is helpful for two reasons. Sometimes the lane markings may not be detected (e.g. faded, dirty, weather, etc.). More helpful, it reminds me what speed the cruise is set, as the speed will adjust based on the selected car lengths (I always reduce to 1, which I think is still too much for Texas drivers). If I look down and the car is driving 65mph, I can glance down and see that the cruise is set at 70 and recognize that she has slowed down to keep distance.
Pit Crew
Joined: Oct 2017
Posts: 190
Likes: 55
From: WA
DRCC (Dynamic Radar Cruise Control) is really wonderful. However, the use of engine braking to quickly decelerate is quite annoying not to mention the rough down shifting of the transmission. If you have not experience this you can by doing the following: While in DRCC, quickly decrease set speed using the cruise control stalk down 10 MPH, i.e. if you are doing 70 MPH slow down to 60 MPH. Watch how the system reacts. In my case you will suddenly hear the transmission downshifts roughly, feeling a thud, and then the engine revving up to 4K RPM.
It seems this type of reaction by the engine is designed for the Hybrid where it uses engine braking to regenerate power. However, mine is not an hybrid but a regular RX350. I really would like Lexus to address this as it's very concerning with the rough downshifting and high revving of the engine.
There is also another instance where you can experience this engine braking for deceleration. While on DRCC, step on the accelerator to speed up at least an additional 10 MPH from the set speed. As soon as you reach the desired speed, let go of the accelerator and you will experience the same engine braking as stated above. And if the road is down slope, it's even worse.
It seems this type of reaction by the engine is designed for the Hybrid where it uses engine braking to regenerate power. However, mine is not an hybrid but a regular RX350. I really would like Lexus to address this as it's very concerning with the rough downshifting and high revving of the engine.
There is also another instance where you can experience this engine braking for deceleration. While on DRCC, step on the accelerator to speed up at least an additional 10 MPH from the set speed. As soon as you reach the desired speed, let go of the accelerator and you will experience the same engine braking as stated above. And if the road is down slope, it's even worse.
Advanced
Joined: Apr 2017
Posts: 701
Likes: 166
From: NSW
DRCC (Dynamic Radar Cruise Control) is really wonderful. However, the use of engine braking to quickly decelerate is quite annoying not to mention the rough down shifting of the transmission. If you have not experience this you can by doing the following: While in DRCC, quickly decrease set speed using the cruise control stalk down 10 MPH, i.e. if you are doing 70 MPH slow down to 60 MPH. Watch how the system reacts. In my case you will suddenly hear the transmission downshifts roughly, feeling a thud, and then the engine revving up to 4K RPM.
It seems this type of reaction by the engine is designed for the Hybrid where it uses engine braking to regenerate power. However, mine is not an hybrid but a regular RX350. I really would like Lexus to address this as it's very concerning with the rough downshifting and high revving of the engine.
There is also another instance where you can experience this engine braking for deceleration. While on DRCC, step on the accelerator to speed up at least an additional 10 MPH from the set speed. As soon as you reach the desired speed, let go of the accelerator and you will experience the same engine braking as stated above. And if the road is down slope, it's even worse.
It seems this type of reaction by the engine is designed for the Hybrid where it uses engine braking to regenerate power. However, mine is not an hybrid but a regular RX350. I really would like Lexus to address this as it's very concerning with the rough downshifting and high revving of the engine.
There is also another instance where you can experience this engine braking for deceleration. While on DRCC, step on the accelerator to speed up at least an additional 10 MPH from the set speed. As soon as you reach the desired speed, let go of the accelerator and you will experience the same engine braking as stated above. And if the road is down slope, it's even worse.
Pit Crew
Joined: Oct 2017
Posts: 190
Likes: 55
From: WA
I believe there are two reasons for this nuisance. One, like I mentioned has something to do with power regeneration and the other might have something to do using engine braking to quickly come down to the "new" set reduced speed. On my other Toyota, when I reduce speed, a conventional cruise control (Non-dynamic), it takes a little while to come down to the "newly" set reduced speed. And this is because the system doesn't do anything except to reduce engine rpm or power and letting the vehicle coast down to the new set reduced speed. In fact, the system will not even downshift the transmission but simply reduce engine rpm until the it meets the set speed and then pick it up from there. How long does this take? Well, it all depends how slow is the newly set reduced speed is from the previous setting. But it sure is a little longer than what the RX350 does, which is almost instantaneous by using engine braking and downshifting of the transmission, albeit sounding and feeling rough. Personally, I prefer that with DRCC, it just coast the engine down without downshifting the transmission for reducing set DRCC speed despite taking this a second or three longer than it takes.
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Lead Lap
Joined: Jan 2004
Posts: 3,595
Likes: 271
From: Kansas
It seems this type of reaction by the engine is designed for the Hybrid where it uses engine braking to regenerate power. However, mine is not an hybrid but a regular RX350. I really would like Lexus to address this as it's very concerning with the rough downshifting and high revving of the engine.
Sometimes I want DRCC to do the braking. Sometimes I don't. I use whichever technique is appropriate to the situation. I've been using DRCC for so many years that I almost always nail the new set speed I want the first time using the Cancel/Coast/Set method.
Intermediate
Joined: Apr 2017
Posts: 432
Likes: 114
From: NorCal
Let's say you have the cruise control set at 70 mph and you reach a downhill portion of the freeway, when the car reaches about 73/74 mph it will downshift into 5th gear and the rpms will jump to almost 4000, very annoying. Before that happens and you want to keep the same set speed you can gently use the brakes until you get close to the set speed and resume (push up) on cc lever. Or you can anticipate the speed increase, discontinue cc (pulling) and continue when you again reach about 70 mph by breaking or slowing down because the road is leveling.
I would prefer the cc did nothing until 70 mph was reached again and give the driver the option to slow down by braking or smoothly down shifting.
I would prefer the cc did nothing until 70 mph was reached again and give the driver the option to slow down by braking or smoothly down shifting.
Pit Crew
Joined: Oct 2017
Posts: 190
Likes: 55
From: WA
I just want to make sure we are focused on the issue on this thread, ". . . rough downshifting and high engine revving" Any car owner who had experience with dynamic or conventional cruise control (CC) fully understands Set/Coast/Cancel setting of the CC and fully understands that it will auto shift the transmission up or down as appropriate. However, the rough shifting and high engine revving is something not normal. Lexus probably thinks it is but it is not, hence this thread.
For me, to avoid this nuisance I just tap the brake to disengage CC if I want to slow down. But such action is just not practical if you want to pass a vehicle, where if you are on CC you should just step on the accelerator to gain speed, do the pass and should just let go of the accelerator and the CC will resume set speed. This is how most CC operates. But not with this 4RX. What it does as soon as you complete the pass and let go of the accelerator, it downshifts roughly and engine revs up for a few seconds and then resume set speed.
I know. I know. You're gonna tell me just to disengage the CC before making the pass, complete the pass and then resume speed and set the CC again. But that is not how normal CC works.
For me, to avoid this nuisance I just tap the brake to disengage CC if I want to slow down. But such action is just not practical if you want to pass a vehicle, where if you are on CC you should just step on the accelerator to gain speed, do the pass and should just let go of the accelerator and the CC will resume set speed. This is how most CC operates. But not with this 4RX. What it does as soon as you complete the pass and let go of the accelerator, it downshifts roughly and engine revs up for a few seconds and then resume set speed.
I know. I know. You're gonna tell me just to disengage the CC before making the pass, complete the pass and then resume speed and set the CC again. But that is not how normal CC works.
Instructor
Joined: Sep 2017
Posts: 992
Likes: 134
From: MN
I don't recall my 450 acting like you mentioned, with high rev but I will make an effort to play with it more, watching the tac in sport mode.
i do know on a hill road, the cc overshot several times creating hill in the demo I had before I got mine.
The only thing I had was someone shoot across my bow, changing several lanes right in front of me. Got beeps and warning. Don't recall much else. Not the same, but in the few hundred miles I have had the car, that was the first thing that was interesting.
The was described would be annoying as heck, for sure. Often times I set the cc, and still use the gas pedal. It sort of is my minimum speed I want to go. Many times I hit the gas to pass, in my vehicles and motorcycle with the cc set. The vehicle responds as expected every time.
Rough downshifting and high revs coasting to set speed doesn't sound good at all.
i do know on a hill road, the cc overshot several times creating hill in the demo I had before I got mine.
The only thing I had was someone shoot across my bow, changing several lanes right in front of me. Got beeps and warning. Don't recall much else. Not the same, but in the few hundred miles I have had the car, that was the first thing that was interesting.
The was described would be annoying as heck, for sure. Often times I set the cc, and still use the gas pedal. It sort of is my minimum speed I want to go. Many times I hit the gas to pass, in my vehicles and motorcycle with the cc set. The vehicle responds as expected every time.
Rough downshifting and high revs coasting to set speed doesn't sound good at all.
Lead Lap
Joined: Jan 2004
Posts: 3,595
Likes: 271
From: Kansas
If you are making a pass on a two lane / 2-way road, yes, of course, disengage the cruise control before passing. It matters less or not at all if you are driving on a 4-lane road where you don't need a burst of speed to pass.
Pit Crew
Joined: Oct 2017
Posts: 190
Likes: 55
From: WA
I'm not really sure what it takes to get my point across about the rough downshifting and high engine revving on the 4RX cruise control. I guess next time my headlights don't work I'll just have to bring with me a flashlight and forget about fixing the non-working headlights! Or in this case just use my right foot as the cruise control instead and pretend the built in DRCC is working perfectly.
I'm not sure why I'm being constantly told just "not to use the cruise control". I've been using CC for decades since the early 90's and this 4RX just doesn't feel normal at all, as discussed above.
If you are not having this abnormality on the CC, then maybe this thread is not for you and please don't tell me again just not to use it because that is not a fix.
I'm not sure why I'm being constantly told just "not to use the cruise control". I've been using CC for decades since the early 90's and this 4RX just doesn't feel normal at all, as discussed above.
If you are not having this abnormality on the CC, then maybe this thread is not for you and please don't tell me again just not to use it because that is not a fix.
Last edited by Jiggz858; Jan 1, 2018 at 09:04 PM.
Instructor
Joined: Sep 2017
Posts: 992
Likes: 134
From: MN
There are "Situations unsuitable for cruise control" sections in the Lexus RX owners manual.
If you are making a pass on a two lane / 2-way road, yes, of course, disengage the cruise control before passing. It matters less or not at all if you are driving on a 4-lane road where you don't need a burst of speed to pass.
If you are making a pass on a two lane / 2-way road, yes, of course, disengage the cruise control before passing. It matters less or not at all if you are driving on a 4-lane road where you don't need a burst of speed to pass.
Jiggz858, i get ya, for sure. i would not be happy with it like that.