[Bingdon]

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Hi All,

I picked up my car over the weekend and noticed that when I roll up to a stop sign or light my car seems to downshift at the last second before I stop. It's a little jerky but nothing a passenger may really notice unless I'm pointing it out. This is even in the comfort mode. Car is an automatic.

Is this normal?

[Ehodzic6]

Happens in my 2013 all the time.

[Bingdon]

Maybe it is somewithing with the programming and the way it is supposed to be for all I know. I just wanted to confirm there isn't something wrong. Like I said, it's not super jerky and almost feels kind of natural is if you were in a manual - it just kind of catches me off guard.

[timmahh]

Are you on an incline by chance when this is happening, or is it all the time? It sounds like it's assisting with slowing the car down, but one would think it's not going be that noticeable unless you're in sport mode or something and it's programmed to be more aggressive. You don't have the transmission in sport do you?

[Bingdon]

No - I just have it in comfort mode for now since I am in the break-in period. It would be happening all the time on a flat surface. If i let go of the gas and roll real slow to the stop sign - there is a subtle downshift.

[timmahh]

Originally Posted by Bingdon

No - I just have it in comfort mode for now since I am in the break-in period. It would be happening all the time on a flat surface. If i let go of the gas and roll real slow to the stop sign - there is a subtle downshift.

I think the '15 loaner I have right now (20 miles on it) does the same; seems normal - and makes sense. If it didn't downshift itself when you let off the gas and you needed to accelerate quickly for some reason, there would be a delay while it shifts. In 'pre-downshifting' the car is putting itself in the optimum gear for the current engine/vehicle speed. /shrug.

[tturedraider]

Originally Posted by Bingdon

Hi All,

I picked up my car over the weekend and noticed that when I roll up to a stop sign or light my car seems to downshift at the last second before I stop. It's a little jerky but nothing a passenger may really notice unless I'm pointing it out. This is even in the comfort mode. Car is an automatic.

Is this normal?

Normal BMW automatic transmission operation. Unlike most other manufacturers BMW automatics downshift so you're already in the proper gear to accelerate on command. They've done this for years. It's frequently a little disconcerting for new BMW owners.

[Rautha]

also as its downshifting, its using engine braking to slow the car down and spinning the alternator to charge up the battery rather then just burning up that kinetic energy into heat at the brakes.

Normal behavior.

In Sport / Sport + the downshifts on decel will occur sooner.

as stated above also makes sure car is in the right gear to re-accelerate if need be.

This was one of the behaviors of this autobox that convinced me to cross over to the dark side (manual --> auto). Well...that and the fact that you can't get the MTX in the wagon in the US!

[smithf80]

Originally Posted by tturedraider

Normal BMW automatic transmission operation. Unlike most other manufacturers BMW automatics downshift so you're already in the proper gear to accelerate on command. They've done this for years.

Beat me to it, all BMW's do this.

[carzaddict]

give the car some time to learn your driving style, it might get better

[KneeDragr]

I realize this is how it is supposed to operate, but from my understanding of cars motors, its not particularly healthy to use the motor to slow the car. Basically engine braking is much tougher on a motor than accelerating is. Its one reason why you see race cars blow motors more frequently in braking zones then when accelerating. Im surprised the torque converter does not soften this out.

[....,,,,..,,..]

Originally Posted by carzaddict

give the car some time to learn your driving style, it might get better

+1

Let it learn how you drive the gearbox setup will learn how you drive, throttle response etc.

Rather than rolling to a stop use the brakes a bit more.

[ft1330]

Originally Posted by KneeDragr

I realize this is how it is supposed to operate, but from my understanding of cars motors, its not particularly healthy to use the motor to slow the car. Basically engine braking is much tougher on a motor than accelerating is. Its one reason why you see race cars blow motors more frequently in braking zones then when accelerating. Im surprised the torque converter does not soften this out.

Never heard that one before. It's used a lot in manual driving. I think the reason they blow up their engines is if they downshift wrong and cause an RPM overrun. Not the engine itself causes that.

[Thumper333]

Originally Posted by Rautha

also as its downshifting, its using engine braking to slow the car down and spinning the alternator to charge up the battery rather then just burning up that kinetic energy into heat at the brakes.

In addition, in a DI car (I know for a fact this is true on VW/Audi, I assume BMW DI are the same) when engine braking the injectors turn off completely, spraying no fuel. That equals boosted fuel mileage. If you let it idle while slowing, the engine has to burn fuel to stay running.

Plus yes, having the engine ready for power if needed. If you need to get out of the way of something fast it's dangerous to have to downshift manually or wait for the car. Even with fast shifting DCT and sport autos.

Originally Posted by KneeDragr

I realize this is how it is supposed to operate, but from my understanding of cars motors, its not particularly healthy to use the motor to slow the car. Basically engine braking is much tougher on a motor than accelerating is. Its one reason why you see race cars blow motors more frequently in braking zones then when accelerating. Im surprised the torque converter does not soften this out.

Um, no.

If a race car blows a motor in a braking zone it's cause they missed their shift and went to 2nd instead of 4th. LMAO

Big rig's use engine braking all the time, and those motors go hundreds of thousands of miles and need to be dependable. If it's good enough for a 30,000 lb semi, I think our 2 ton sports cars can manage.

That said, my 328d doesn't jerk or is even NOTICEABLE when it downshifts while braking. I often have to look and see if it is in fact doing it. LOL

[KneeDragr]

Originally Posted by Thumper333

Um, no.

If a race car blows a motor in a braking zone it's cause they missed their shift and went to 2nd instead of 4th. LMAO

Big rig's use engine braking all the time, and those motors go hundreds of thousands of miles and need to be dependable. If it's good enough for a 30,000 lb semi, I think our 2 ton sports cars can manage.

Engines were designed to push pistons forward, when you use the engine to brake you are using the car to pull the pistons in the opposite direction, in effect putting a drag on the combustion forces. The pistons want to move up and down in response to the firing of the engine, they dont want to be pulled against by the engine and transmission to slow the car.

Even the crankshafts and transmission gears were designed to push power one direction, so sufficient force in the opposite direction over a long period of time is bad for them.

The reason truckers do it, is because in general their brakes wear out a lot faster than their clutch and motors do, so it tends to keep them out of the shop longer. But it does reduce engine and transmission life.

And no, there are not high level race drivers who consistently put the car into the wrong gear like you suggest.