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Ordered a new i3s - Debating the ACC - Opinions?

Posted: Wed Nov 24, 2021 7:41 am
by RicardoF1RST

As the title suggests, I haven't driven the i3 with ACC but what I do know is:

1) It's camera based (because radar weights more and would effect range much more than a camera)

2) ACC comes as part of the Driving Assist Plus pack, which for the i3s does not include auto park (because of the different bumpers on the 's')

3) I have driven cars with radar ACC


1) Can someone with an i3s that has ACC confirm if the ACC remains active if you take your hands off the steering wheel?

Because the standard i3 helps with the steering when in ACC to keep the car in lane, the steering wheel has sensors to make sure you are holding it. The steering assistance is part of the auto park I assume, hence its missing from the i3s ACC, but I am wondering if the steering wheel still has he sensors.

2) There are rumours that the system is now Radar based (2021-22 model) - I think that this is incorrect but can someone confirm it is camera only still?

3) There have been software improvements to the ACC for 2021, which makes throttle pedal transitions smoother, have people come across this?

4) I would like the ACC, but I'm not sure it's worth the money because of its inconsitencies plus I want to replace the steering wheel with one covered in Alcantara (hence the question above). My final reluctance is if the car randomly pics up phantoms and brakes suddenly / erratically - have people come across this?

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Wed Nov 24, 2021 8:32 am
by eNate
I switched from a 2017 to a 2021 and the ACC has been refined enough that it's notably better, though still not great. It works, and I use it often. The throttle operation is smoother, lane change indications "break" deceleration while passing a slower vehicle, and the camera has fewer disconnects.

However the systems distance estimation continues to be imperfect and I find little difference when adjusting the "follow behind distance."

It's definitely not radar based.

I don't know how BMW's steering wheel sensor works because we don't have that option in the US, but my understanding is it's part of the Traffic Jam Assist and only steers at low speeds when following another car, typically in stop-and-go traffic.

Vary rarely have I experienced a phantom braking event. These are more likely to occur in non ACC situations approaching a stop and the car slams on the brakes approaching the car stopped ahead (too quickly?). I've never had a "slam on the brakes" event under ACC, just modest braking. More often though, it just disconnects and gives me a moment to respond.

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Wed Nov 24, 2021 5:37 pm
by stumbledotcom
Another US driver seconding eNate’s thoughts. I’ve had a 2014, 2017, and 2021 all fitted with ACC. I use it frequently and consider it integral to the i3 experience. The ‘21 definitely is more refined. I can’t speak to the capacitive steering wheel operation of course. However Quidzel has developed a module that mimics the hands on signal to allow US owners to code their vehicles and enable Traffic Jam Assist. You might look into it if you replace your steering wheel.

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Thu Nov 25, 2021 2:49 pm
by RicardoF1RST
Many thanks for the replies. In the US is ACC a specific option? In the UK it comes as part of the pack that includes the collision system, I guess they all use software and the front camera. I assumed that the cars ability to steer for you used hardware included in the auto park system, but re-reading the UK specs on the i3 it looks like the auto park is a different option.

Decisions, decisions... :-)

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Thu Nov 25, 2021 3:43 pm
by stumbledotcom
Similar in the US. ACC was bundled in the Technology + Driving Assistant Package. Parking Assistant is a standalone option for the base model only. I believe I read the fender flairs that accommodate the wider wheels/tires on the i3s block the side sensors the system uses to locate open parallel parking spots.

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Fri Nov 26, 2021 1:25 am
by RicardoF1RST
Makes sense (fenders).

Last question, in the US do you guys that use the ACC a lot mainly get the most out of it in stop/go city traffic or do you use it on the interstate at 50-70mph? and if so, roughly what distance(s) does it hold to the vehicle ahead?

It appears to me that, being camera based and fitted to a car mainly intended for city commuting, that its intended for the stop/go nature of stationary queue's of traffic rather than the radar based "normal" ACC which monitors multiple targets on the freeway.

I can see myself, in the UK, mainly cruising along following lorries at 56mph.

I have had it confirmed that in the UK, with the ACC option (because it includes the traffic jam management) the steering wheel will have the capacitive sensor.

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Fri Nov 26, 2021 9:10 am
by eNate
I prefer ACC in flowing traffic or on open highways. In stop-and-go, it's a bit of a bear, even though it handles full braking to a stop and restarts. The camera (I believe) is just a little slow to pick up subtle movements and to judge distance precisely, and the smallest gap it leaves is larger than I would leave when I'm driving the car in traffic.

I don't know whether this behavior changes with TJA, which is a completely separate ACC operating mode if I were to retrofit it into my car. But I suspect it isn't. With only one camera / no stereo vision, the system needs relative motion to be able to estimate distance, unlike radar, which just "sees" motion and distance with a fairly precise degree of certainty.

Following distance? Guessing.... about 150+ feet? It feels "about right" at speed, but feels like it leaves too much room once down in the 40 MPH and below range.

Re: Ordered a new i3s - Debating the ACC - Opinions?

Posted: Fri Nov 26, 2021 1:52 pm
by RicardoF1RST
Perfect, many thanks for taking the time to advise. I am having a test drive in an i3s tomorrow, hopefully they will have one with ACC that I can try.