Olasek

I have 2016 IS350 (no dynamic cruise control) and I am having impression the car would brake to maintain set speed while under cruise control and when going downhill. Never before saw a cruise control that would protect your speed 'from above' by applying brakes. I wonder if my observation is correct and this is really what happens - the car may in fact apply brakes under some conditions to keep speed in check. The manual is surprisingly mute on the subject.

Rudiculous

iTrader: (15)

I could be wrong, but I thought it was only engine braking to maintain speed not disc braking

Matroushi

I believe it's only engine braking too.

Olasek

For engine braking I would have to see it downshift - it did not do that, at least not to the extent that would arrest speed build-up on steeper downhill.

Machine13

The transmission could also temporarily suspend the overdrive function in a downhill situation when the speed is increasing beyond the set cruise speed, which would increase the drag on the engine causing it to slow faster. This could almost appear to the driver as a downshift, because the RPM's could jump up a bit when overdrive is suspended. Overdrive is also turned off completely when in Sport or Sport + mode, I believe. Try comparing your downhill speed in normal mode as well as Sport mode to see what if overdrive is the difference.

Olasek

Nope, this isn't true, not in my Sport mode (I have no Sport+). BTW, in my 8-spd transmission both 7 and 8-th gears are overdrive.

AZMacaroni

Most vehicles now have this to keep your speed in check. Doesn't have anything to do with collision sensors, just manufacturer CYA to avoid accidents. Most people have no idea how to properly slow a vehicle down from a high rate of speed so technology isn't letting speed get out of hand.

Olasek

So please explain this technology, how it works and whether it in fact applies brakes.

AZMacaroni

You set your cruise control for 1 of 2 reasons:
1. You know if you go faster than that you are getting a ticket
or
2. That is as fast as you are comfortable going under the circumstances

To keep you at the speed you set it at the vehicle computers will normally do what above posters have mentioned. Either it will engine brake (most common) or the transmission will temporarily suspend OD to increase engine drag and quickly reduce the speed. No matter how its done, know that it is something you will see on almost all new and future vehicles to protect manufacturers from those drivers who will ultimately blame them if the vehicle gets away from the driver and there is an accident.

Olasek

You guys were right - it uses engine braking only. I finally tested it well in the mountains - to maintain set speed it would downshift even quite aggressively if necessary.

BTW, I love the 'snow' mode, I have RWD only and had to navigate through some partially ice covered roads - the snow mode was a big help.

anthonys2r

iTrader: (1)

I've had this on my 96 camry. Cruise control is so that it'll maintain the exact speed you set. If you're on a hill, it'll automatically push the throttle.

Olasek

I had many cruise controls in my life, I never had a car that would downshift to protect the speed from exceeding the set speed, pushing the throttle all they were able to do.

350Alex

Yeah, I've definitely seen mine downshift before to keep the speed. I usually disable cruise and let the car speed up, to get better gas mileage, as conditions permit. My 2007 BMW 335i had dynamic cruise control, I think they called it (Adaptive radar was actually an option back then, my car didn't have it), but with the dynamic cruise, it was able to actually apply brakes to slow the car down, unlike my IS.

snabbledab

yes it is only engine breaking