[Juneau99803]

I have a 2019 230i with a stock motor and 8-speed automatic. How does one intentionally increase the engine compression-braking? When descending long steep roads in other cars, I downshift and let the engine drag provide the majority of the speed control. By choosing the appropriate gear, I only need to brush the brakes a few times on the steepest sections.

But with the fully computerized B-motor in the 230i, I can't find a combination of settings to achieve anything similar. I can downshift, and engine speed increases, but the drag does not (I suspect the valves are being held open specifically to decrease pumping losses). And after a couple of minutes, the computer upshifts again, anyway. I've tried different combinations of sport/comfort/eco and gear-lever/paddle shifting, and am unable to hit on a suitable combination.

[Shovelman]

Fortunately BMW compensates for the lack of a jake break by putting really good disc brakes on the car.

[celsdogg]

you might be outta luck.

Usually controlling speed in this way in a MT is because the throttle plate is closed and causing a vacuum behind the throttle. Turbos increase pressure (thus the reason we have vacuum pumps) but more pertinently, BMW keeps the throttle plate open and control engine speed with the valves (valvetronic). There is very little ability for the motor to control speed during deceleration. It still drags a little, but no where near what you need for a long steep downhill. I am not sure what the answer is to prevent overheating your brakes in those situations.

[Kernel Kurtz]

Originally Posted by Juneau99803

I have a 2019 230i with a stock motor and 8-speed automatic. How does one intentionally increase the engine compression-braking? When descending long steep roads in other cars, I downshift and let the engine drag provide the majority of the speed control. By choosing the appropriate gear, I only need to brush the brakes a few times on the steepest sections.

But with the fully computerized B-motor in the 230i, I can't find a combination of settings to achieve anything similar. I can downshift, and engine speed increases, but the drag does not (I suspect the valves are being held open specifically to decrease pumping losses). And after a couple of minutes, the computer upshifts again, anyway. I've tried different combinations of sport/comfort/eco and gear-lever/paddle shifting, and am unable to hit on a suitable combination.

At what RPM do you find you have no engine braking? You have ~7000 to play with, with a wide variety of response.

[Juneau99803]

"At what RPM do you find you have no engine braking? You have ~7000 to play with, with a wide variety of response."

I've paddle-shifted down until the engine is spinning about 5k, seen very minimal compression-braking, and then had the computer shift the transmission back up so the engine speed was back down to 1.5-2k.

[Kernel Kurtz]

Originally Posted by Juneau99803

"At what RPM do you find you have no engine braking? You have ~7000 to play with, with a wide variety of response."

I've paddle-shifted down until the engine is spinning about 5k, seen very minimal compression-braking, and then had the computer shift the transmission back up so the engine speed was back down to 1.5-2k.

OK, I have a B58 and have not noticed a lack of engine braking, but I'm only downshifting under braking into corners, not on long downhills. If you put the transmission in manual mode it should never shift by itself (but it still won't let you overrev).

[BlueberryPie]

Like Kernel Kurtz, I've got the B58 and am noticing plenty of engine braking (8 speed auto). My previous car was a Golf R (2.0T with dual clutch auto) and it felt like it had barely any engine braking compared to the M240i - could it be the difference in displacement making the difference? Or is it not that simple/unrelated?

[dradernh]

My car has what I consider to be fairly modest engine-braking qualities. That's not something that under any circumstances is going to slow my car by very much.

The extremes I've experienced were from the 60s and the early 70s, when high-compression four-stroke engines had remarkable engine-braking qualities, and the two-stroke engines had relatively none at all. Different driving techniques were required to make good time with those very different engines.

[harma24]

Are you guys all driving in Eco mode or something? I drive in Comfort or DSC Off, and in stop and go traffic, letting off the throttle is typically sufficient to maintain distance from the car in front of me. I drove up (and down) the Mount Washington Auto Road and had no issue with engine breaking once I caught up with traffic (I had fun when there was open road in front of me and had to use the brakes heavily in the corners). Putting the car in Eco mode drives me nuts because it disengages the transmission when you take your foot off the throttle and the car coasts.

[Juneau99803]

I ran another test on an easy-to-access hill.

In 'sport' mode, I pulled the shift lever left and downshifted until engine speed was in the 4-5k RPM range. The transmission did not switch back to 'drive', and there was modest engine braking. It wasn't as much as I would like, but it was better than nothing.

I expect to point it down a taller/steeper hill later this week.

[As an aside, I find that shift lever to be counter-intuitive. I'm regularly shifting into Reverse instead of putting it into Park. And upshifting when I mean to be downshifting. I've driven automatics before (but never owned one in +40 years), and Park has always been "all the way forward", and lower gears have always been found pulling the lever backwards. I'm sure the Germans have a reason for doing the lever the way they have, but I expect it's gonna take me some time to get used to it.]

[freakystyly]

6 cylinders will have greater engine braking than 4 cylinders due to having more cylinders. I've also noticed with my manual transmission, the sport/sport+ engine braking is greater than Eco/comfort settings. Makes me wonder if there is some programming behind that...
I know the alternator is on a clutch that engages under braking if told to do so, but is there anything else?

Can't speak of automatic transmissions unfortunately.

[SoftShoe]

Automatics in eco can coast without any mechanical drag from engine or alternator.

Engine drag in other modes feels much less than it was in my 1st gen is300 (Lexus) with a non-turbo inline six. However, on the long hill I drive each week engine drag in the 240 is normally enough to keep me from touching the brakes to avoid touching other traffic. And that’s at about 3200 rpm. It rarely feels enough to use for more performance oriented driving (so I more often use the brake).

Whatever the influence or intention (without knowledge, I assumed turbo or mpg) the overall off-throttle engine drag is simply less than what I’m used to.

[jzeiler4]

Originally Posted by freakystyly

.
I know the alternator is on a clutch that engages under braking if told to do so, but is there anything else?

There is no clutch on the alternator, that fact that the dash tells you regenerative braking is the alternator regulator commands full power (max volts of 14.5) and the injectors are shut off. That is all there is.