[rkptl]

HI,

I'm new to BMW's and probably this is normal, but I just drove a 328i and felt the car slowing down automatically at lower speeds.

I took my foot off the gas pedal and as the car eventually slowed down to 15-20 mph range, it felt like it was braking automatically, and there was a smooth but noticeable jerk (as if the brakes were being applied). This was my first BMW test drive and im not sure if its something that BMW's have.

I've mostly driven a mustang, but ive never experienced something like this.

Is this normal?

BTW it was the new 2012 model (4cyl)

Thanks

[WKMG]

Was it an 8 speed automatic? Could just have been the transmission down shifting.

[340driver]

As part of the Efficient Dynamics tech doesn't it hook up the alternator to charge the battery when you take your foot off the gas / step on the brake?

Could it be that?

[BMWinGE]

I've noticed something to this effect with my car but always thought it was the auto downshifting

[Frogman]

The "jerking" is the AT downshifting; quite normal, but I'm pretty sure it's also the effect of the regenerative breaking kicking in. You can see it on the MPG gauge when the indicator turns blue on the left.

I feel a lot more "engine" braking when that happens.

When I want to coast without slowing down too much, I actually give the car a very tiny bit of throttle to keep the regeneration from kicking in. Let off the throttle completely and you can really feel it slowing down faster.

[Elk]

It is an inelegant characteristic of the AT. It can even be readily felt when braking, not just coasting.

[rkptl]

Thanks for the replies..

Is there a way this "effect" can be reduced if not completely eliminated by some setting? Or is this just one of the things you need to get used to?

[Elk]

Unfortunately, it is what it is.

[Micleg]

Sounds like engine braking like on an MT car?! That's what I have been lacking on my Saab AT gearbox that just kept increasing the speed downhill. Perhaps I will enjoy this But it doesn't seems that subtle on your descriptions

[bimmerjph]

Originally Posted by 340driver

As part of the Efficient Dynamics tech doesn't it hook up the alternator to charge the battery when you take your foot off the gas / step on the brake?

Could it be that?

+1 I think that is a lot of it.

[Frogman]

Originally Posted by Micleg

Sounds like engine braking like on an MT car?! That's what I have been lacking on my Saab AT gearbox that just kept increasing the speed downhill. Perhaps I will enjoy this But it doesn't seems that subtle on your descriptions

I think we're talking about 2 different behaviors.

One is the feeling you get when the trans downshifts while you are braking. You can definitely feel it as a driver, but to me, it's not jarring, just different.

The second is the extra braking you get by the efficient dynamics adding electrical generation load while decelerating.

I too was worried about how much "engine" braking a modern AT would actually provide give me (I miss my MT there), but was pleasantly surprised with how much braking the ED and 8AT gives.

For me, going down long moderately sloped hills with the foot off the throttle actually slows the car down too much and I have to supply a tiny bit of throttle to stop the ED and maintain speed. Speeding up too much downhill and then letting off the throttle, you can really feel the ED kick in and slow the car. It doesn't feel the same as a MT, but it's the same effect.

[RPM90]

Originally Posted by Elk

It is an inelegant characteristic of the AT. It can even be readily felt when braking, not just coasting.

This is likely due to the ZF's very low mph/rpm lock out.
I believe lock out occurs at something between 20-25mph.
Under lock out the trans is "locked" to the flywheel.
So even thought the driver is not on throttle, the car will naturally slow due to tire friction drag and engine braking, as there no throttle applied.
The "jerking" is simply the trans downshifting as it should.

OP:
In the Mustang, was it manual trans?
If so, then even with the 3, if you are in neutral with no throttle than it too will coast longer and slow less.
If it AT, then it's older tech AT with it's higher mph/rpm lock out and thus longer coasting. It's just not as connected to the engine/flywheel as it is with the new ZF AT.

[RPM90]

Originally Posted by rkptl

Thanks for the replies..

Is there a way this "effect" can be reduced if not completely eliminated by some setting? Or is this just one of the things you need to get used to?

Get a manual trans.

I don't have my 335i AT yet so I don't know if this is possible, but try going to full manual mode where you select the gears and not the trans computer. When you let off the throttle, don't downshift. Let it sit in a higher gear for the given speed. It should slow less as it's in a higher gear.
Much like a manual where you can coast to near stop in 4th or 5th until the engine rpm drops to around 1000rpm.

Anyone with the AT/Sport AT comment on whether you can do this in full manual mode? Can you let it coast in higher gear with no throttle without the trans downshifting itself?

[RPM90]

Originally Posted by bimmerjph

+1 I think that is a lot of it.

Don't you have to be on the brakes for the ED to activate?
OP said he was off the throttle but not on the brakes, at least I think that's why he described.

[Frogman]

Originally Posted by RPM90

Don't you have to be on the brakes for the ED to activate?
OP said he was off the throttle but not on the brakes, at least I think that's why he described.

On my 328i (non-sports 8AT), ED engages off throttle and without the brakes; the blue indicator lights on the MPG gauge.

I don't know of any other indicators/tells for ED engaging/disengaging. Anyone know differently?

[FotiosF90M5]

In full manual sport plus the only way the computer will take over shifting is if your putting it in extreme conditions. It will not up shift or downshift unless you tell it too. If past redline it will keep bouncing off rev limiter. It can certainly handle 5th gear at very low tpms. I believe in even regular mode you can coast very low. You have quite a bit of control with this amazingly flexible zf tranny.

[FotiosF90M5]

[QUOTE=RPM90]

Originally Posted by rkptl

Thanks for the replies..


Anyone with the AT/Sport AT comment on whether you can do this in full manual mode? Can you let it coast in higher gear with no throttle without the trans downshifting itself?

In full manual sport plus the only way the computer will take over shifting is if your putting it in extreme conditions. It will not up shift or downshift unless you tell it too. If past redline it will keep bouncing off rev limiter. It can certainly handle 5th gear at very low tpms. I believe in even regular mode you can coast very low. You have quite a bit of control with this amazingly flexible zf tranny.

[Raspartan]

I've experienced a jerk at walking speeds when the regenerative braking kicks in. It's happened to me once so far but I saw the blue bar in the dash at exactly that moment. Downshifting isn't nearly as intrusive.

[bimmerjph]

Originally Posted by RPM90

Don't you have to be on the brakes for the ED to activate?
OP said he was off the throttle but not on the brakes, at least I think that's why he described.

http://www.bmw.com/com/en/insights/t...eneration.html

[The X Men]

Its a German car thing, most German downshifts while coasting to a certain extent.

[Elk]

Originally Posted by The X Men

Its a German car thing, most German downshifts while coasting to a certain extent.

All ATs do. This just happens to be an AT where one can easily feel each shift and the engine braking changes with each.

[RPM90]

[QUOTE=fotios335i;12252760]

Originally Posted by RPM90

In full manual sport plus the only way the computer will take over shifting is if your putting it in extreme conditions. It will not up shift or downshift unless you tell it too. If past redline it will keep bouncing off rev limiter. It can certainly handle 5th gear at very low tpms. I believe in even regular mode you can coast very low. You have quite a bit of control with this amazingly flexible zf tranny.

Nice.