N00b TACC Questions

[DrWhoDey]

Hey all! I took delivery of my M3LR a week ago and got a chance yesterday to play around with TACC. Some of the behavior was unexpected, and I frankly don't know if it's due to my inexperience with the feature or if what I thought made sense to me isn't quite how the car is programmed. Figured I'd just ask y'all to try to recalibrate my expectations.

Here's what happened.

In my Autopilot settings, I believe I have things set to set my speed to the posted Speed Limit +7, and it appeared to work just fine.... I was in a 60 MPH zone (the car knew it) on a divided highway, two lanes in both directions, and was doing 63 when I engaged TACC. The car set itself to 67 and accelerated gently to that speed. It slowed when approaching slower traffic, resumed at 67 when it was safe to do so. Okay, that works.

I entered a section of highway where the speed limit dropped to 55 MPH. The car knew it, having seen the speed limit sign and displaying it on the screen. But the car did not slow. I had expected a deceleration to 62 MPH but instead it maintained 67. I gave it a few seconds to confirm it wasn't going to slow, then manually scrolled the set speed down to 62 using the right thumbwheel.... which of course meant now that I had manually selected my speed it was likely going to ignore the Speed Limit + 7 value in the Set Speed portion of the Autopilot settings screen.... which is what happened.

To get the car to drive Limit + 7, I had to disengage and reengage TACC.... but once set it would never update if/when the Speed Limit changed. Is that's what's SUPPOSED to happen and my expectations are too high, or am I doing something wrong here?

Additionally - and I'm more than willing to admit my own ignorance here - but while driving under TACC I *thought* I was able to command a lane change by using the turn signal. I know that FSD does that automatically and I suspect it will do it on command, but I honestly thought regular Autopilot included this feature. Same question as above - am I expecting something that's not part of the software or am I doing something wrong?

I've attached screencaps of my Autopilot settings.

I am on factory/delivery software version 2022.3.101.1, having just had the car added to the "Fleet" and not having had it long enough to be included in a standard OTA yet. The only OTA I've received was the upgrade from 2022.3.101 to 2022.3.101.1.

 

[brkaus]

There is no built in limit in a divided highway. So the car will not reduce its speed.

If you were on a two lane road where it’s limited to speed limit +5 it would have reduced.

 

[DrWhoDey]

There is no built in limit in a divided highway. So the car will not reduce its speed.

If you were on a two lane road where it’s limited to speed limit +5 it would have reduced.

That's odd. I mean, thanks for the info, but the car clearly knew the speed limit. When I engaged TACC initially it determined that 67 was the correct setting, having displayed 60 as the speed limit and complying with my +7 setting on the Autopilot settings screen.



If the car didn't know what the speed limit was, how did it determine to set my speed to 67?

 

[brkaus]

It does know. I think people complained when it first came out and it adjusted down. People wanted it more like cruise control.

I expect FSD will follow speed limits, but I’m not in the beta so I’m not sure.

 

[Supcom]

Holding down the gear stalk for a second or two will cause the car to readjust the set speed to whatever the current speed limit plus offset you have configured.

Auto speed adjustment requires FSD.

 

[S4WRXTTCS]

When discussing an issue on TMC it's important to distinguish whether it was TACC only or AP.

TACC only is when you pull down the stalk once and you get one confirmation chime. This is when the car is only controlling the speed.
AP is when you pull down the stalk twice in rapid succession and you get two confirmation chimes.

Basic AP (what you have) does not have Auto Lane Change capability, and it the lack of this capability frustrates a lot of owners as it would be really nice if it did.

I can't compare differences between what I have, and what you have as I have FSD. With my car it will adjust speed for a new speed AFTER it passes the sign which is too late. As a result of this deficiency I don't think the feature is all that useful. It's easy enough to use the scroll wheel to adjust the speed when you see the speed limit sign. Plus occasionally there are a lot of phantom speed limit changes where it thinks the speed limit is slower than what it really is.

All the FSD stuff needs more time in the oven, but you might want to subscribe to it in 6 months to try it out for a month or two.

 

[DrWhoDey]

Holding down the gear stalk for a second or two will cause the car to readjust the set speed to whatever the current speed limit plus offset you have configured.

Auto speed adjustment requires FSD.

Terrific! Thanks, that'll be the next thing I try when I'm back out relearning how this works.

 

[DrWhoDey]

When discussing an issue on TMC it's important to distinguish whether it was TACC only or AP.

TACC only is when you pull down the stalk once and you get one confirmation chime. This is when the car is only controlling the speed.
AP is when you pull down the stalk twice in rapid succession and you get two confirmation chimes.

Basic AP (what you have) does not have Auto Lane Change capability, and it the lack of this capability frustrates a lot of owners as it would be really nice if it did.

Got it. The double-pull into Autopilot was what I had engaged. Thanks for the clarification, I mistakenly used TACC and AP interchangeably. I figured out TACC on my own... single pull to set my cruise speed, right thumb wheel to adjust up/down, and the car automatically reducing speed for slower traffic ahead.

AP did that, plus added lane keeping functionality and had set my initial speed based on the configuration info on my setup pages.

The lack of lane changing is fine. I was uncertain if Basic AP included that or not and clearly did not know how to trigger it - but you can't trigger a function that the car doesn't have.

 

[Silicon Desert]

I expect FSD will follow speed limits, but I’m not in the beta so I’m not sure.

yes, it does for me... plus or minus whatever "offset" mph that I enter in the nav.