Can someone help me understand the speed limit settings under the Autopilot tab?

[Thebrits615]

Hello everyone,
I have watched videos on this and read forums but for some reason can’t wrap my head around the use for each of these settings and think I’m just confused.

Auto Pilot tab has two areas related to speed:

Set Speed: Speed Limit/Current Speed with the option to offset

Speed Limit Warning: Speed Limit Relative/Absolute with the option to offset.

So, if I am understanding correctly, the set speed limit/current speed with offset option allows me to select 5MPH or another amount above the speed limit and when I activate Autosteer (my car has no FSD or EAP) the car will do the speed limit + 5MPH.

The second speed limit options with relative and absolute are focused on when the car will give an excessive speed warning only?

Finally, is the car supposed to speed up and slow down as it goes through different speed signs? There are freeways near me that are 65 mph and go up to 75 mph and then drop down again to 50 mph. The car never changes its speed throughout all of these changes.

Thanks for helping me through my blonde moment!

 

[hugh_jassol]

So, if I am understanding correctly, the set speed limit/current speed with offset option allows me to select 5MPH or another amount above the speed limit and when I activate Autosteer (my car has no FSD or EAP) the car will do the speed limit + 5MPH.

Yes

The second speed limit options with relative and absolute are focused on when the car will give an excessive speed warning only?

yes

Finally, is the car supposed to speed up and slow down as it goes through different speed signs? There are freeways near me that are 65 mph and go up to 75 mph and then drop down again to 50 mph. The car never changes its speed throughout all of these changes.

This is 'sometimes' in my experience. Hopefully someone has a better grip on when it does and when it doesn't. On my commute there are situations where the limit is 65, then when I am on a transition ramp to a new freeway it's 55, then back up to 65 on the new freeway - it seems to handle that correctly. The owner's manual says:

When cruising at the speed limit, there may be situations where the cruising speed may not change when the speed limit changes.

 

[Fishstyx]

I have a new MYLR and the cruise speed setting doesn’t seem to work correctly. It seems buggy.

I have it set to a fixed 6mph over the speed limit bit when I engage cruise control it doesn’t honor that setting. Sometimes it does limit to the hard limit +5 on non highways (good) but not always. Yesterday I was on a 2 lane road and the speed limit of 30. I engaged AP and the car accelerated to 50mph. I expect the “Max Speed” value to always show what I set in AP menu (limit plus 5 or 6) but it fluctuates between that and a recent max actual driving speed. No apparent rhyme or reason. What’s going on?

 

[stopcrazypp]

I have a new MYLR and the cruise speed setting doesn’t seem to work correctly. It seems buggy.

I have it set to a fixed 6mph over the speed limit bit when I engage cruise control it doesn’t honor that setting. Sometimes it does limit to the hard limit +5 on non highways (good) but not always. Yesterday I was on a 2 lane road and the speed limit of 30. I engaged AP and the car accelerated to 50mph. I expect the “Max Speed” value to always show what I set in AP menu (limit plus 5 or 6) but it fluctuates between that and a recent max actual driving speed. No apparent rhyme or reason. What’s going on?

If it detects it is on a local road, it is limited to the detected speed limit +5. If it can't detect the limit it falls back to 45 mph max. See "Restricted Speed" section in the manual:
Model Y Owner's Manual | Tesla

As for the Set Speed setting, with the exception of scenarios mentioned above: If you set it to Speed Limit mode, when you were traveling slower than the detected speed limit at the time of activating TACC or AP, the set speed will be the speed limit + your offset. This is what the UI shows also. If instead you were going faster than the speed limit at the time of activating TACC or AP, the set speed will be your current speed. This seems to be what consistently happens for me, see if that makes more sense for you.

There are also other situations where it changes the set speed. When it goes to a split in the road and/or there is a curve, it may do a map based adjustment of the set speed. It mentions this in the manual:
"Traffic-Aware Cruise Control also adjusts the cruising speed when entering and exiting curves.
...
Due to limitations inherent in the onboard GPS (Global Positioning System), you may experience situations in which Model Y slows down, especially near exits or off-ramps where a curve is detected and/or you are navigating to a destination and not following the route."
Model Y Owner's Manual | Tesla

In my experience, once it goes past that section, it restores your most recent set speed.

 

[Fishstyx]

I’ve wondered what it would do approaching a sharp curve but I haven’t tested that yet. I’ve seen most of the scenarios you describe, but I’ve also experienced what I’d call flaky or unexpected behavior. The most specific example was on a 35 rural road (well marked) and the set speed jumped from 40 to 50 uncommanded even though it still indicated a 35 limit.

It definitely takes some getting used to. My opinion is that some of these modes are unnecessarily confusing or complex. If I set the cruise speed logic to limit +5, then it should do that regardless of the engagement speed unless I override it. It already forces limit +5 in many circumstances.

 

[stopcrazypp]

I’ve wondered what it would do approaching a sharp curve but I haven’t tested that yet. I’ve seen most of the scenarios you describe, but I’ve also experienced what I’d call flaky or unexpected behavior. The most specific example was on a 35 rural road (well marked) and the set speed jumped from 40 to 50 uncommanded even though it still indicated a 35 limit.

It definitely takes some getting used to. My opinion is that some of these modes are unnecessarily confusing or complex. If I set the cruise speed logic to limit +5, then it should do that regardless of the engagement speed unless I override it. It already forces limit +5 in many circumstances.

I think the logic is there because most people do not want the car to slow down from the current speed when they initially activate TACC or AP. That is why it only sets a set speed that is the same or higher than the current speed.

 

[Fishstyx]

I think the logic is there because most people do not want the car to slow down from the current speed when they initially activate TACC or AP. That is why it only sets a set speed that is the same or higher than the current speed.

But there’s a separate option for the “set current speed”. The function description states that the purpose of the setting is to fix the target cruise speed at a fixed mph or percentage offset from the speed limit. If it doesn’t actually do that it’s kind of pointless. Additionally, it doesn’t adjust up or down when the speed limit changes, which again, seems like the whole point. I had a Ford Lightning and its adaptive CC adjusts with changing speed limits.

 

[MidBaz]

It would be considerably more useful if EAP, on recognising a change in the speed limit, would increase or decrease the max speed accordingly (within the +8% parameter I have set). If I'm cruising along at 65mph in a 60 zone and enter a 30, the car displays the lower limit but I really want it to slow down to a max of 32mph. That doesn't feel like a strange request nor something the car should not be able to accommodate.

 

[Fishstyx]

It would be considerably more useful if EAP, on recognising a change in the speed limit, would increase or decrease the max speed accordingly (within the +8% parameter I have set). If I'm cruising along at 65mph in a 60 zone and enter a 30, the car displays the lower limit but I really want it to slow down to a max of 32mph. That doesn't feel like a strange request nor something the car should not be able to accommodate.

It will do this on roads where AP is limited to 5mph over the limit. These are usually 2 lane roads. On 4-lane or divided highway, where it lets you go as fast as you want on AP, it won’t slow down. It’s just strange that it doesn’t do this and makes one wonder why the setting exists at all.