# Figured out how autopilot speed is calculated



## Brian3 (May 11, 2017)

When I enable autopilot the car usually increases speed to something higher than the speed limit.

When driving 65 in a 70 zone, the car would accelerate to 81 when I activated AP. That seemed very odd to me, but today I figured out what's going on.

You all probably already know this.

I had set a speed warning chime. I set it to +11 mph. After a while I fell out of love with the warning chime and disabled it... But it still remembers having been set to +11 mph.

That is why the car chooses to accelerate to 81 when I'm in a 70 zone.

To fix this I had to enable the warning chime again so that I could change the value. I set it to +5 mph, then disabled it again.

Now in a 70 zone the car will only accelerate to 75.

I'm happy to have figured that out. I was always hard pressed to explain why the car lurched forward while activating AP.

I also happen to know that if you first activate adaptive cruise control (one flip up or down on the stalk) that cruise will commence at your current speed. That's nice. If you then activate AP, it will stay set at your current speed.


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## Frully (Aug 30, 2018)

Edited for clarity:

The limit you set in your warning is your speed assist offset. They happen to use that same speed as a chime or not. You don't need the chime set to change your relative offset for speed assist.

https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf
Page 93


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## Love (Sep 13, 2017)

Brian3 said:


> When I enable autopilot the car usually increases speed to something higher than the speed limit.
> 
> When driving 65 in a 70 zone, the car would accelerate to 81 when I activated AP. That seemed very odd to me, but today I figured out what's going on.
> 
> ...


I just want to reply out of respect for the poll vote option "I disagree with the claim." Love it for some reason. 😂😍😃


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## garsh (Apr 4, 2016)

Frully said:


> The limit you set in your warning is your speed assist offset. They happen to use that same speed as a chime or not. You don't need the chime set to change your relative offset for speed assist.


I agree with Frully. @Brian3, I think you were a little confused about what you were configuring.

"Speed Limit" is not a subsection under "Speed Limit Warning". But the arrangement is a bit confusing.


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## Brian3 (May 11, 2017)

Fair enough, but I am unable to change the offset unless I first enable the speed limit warning.


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## garsh (Apr 4, 2016)

Oh yeah, you are correct sir.
I didn't remember that being the case earlier.
Strange. It shouldn't be performing double-duty as the autopilot speed offset then.



Brian3 said:


> Fair enough, but I am unable to change the offset unless I first enable the speed limit warning.
> 
> View attachment 29285


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## eXntrc (Jan 14, 2019)

Brian3 said:


> When driving 65 in a 70 zone, the car would accelerate to 81 when I activated AP.


Okay, I really want to understand how this works because it seems the maps in my area are quite outdated and many of the speed limits are wrong. However, no matter what I set for "Speed Limit Relative" I can't get it to do more than 5 MPH over the speed limit on city streets. Are you only talking about on the highway?

These seem to be two hard-set rules for me that cannot be superseded:


*City Streets:* Never exceed speed limit (according to the map software) by more than 5 MPH.
*Highway:* Never exceed 90 MPH.

Are those true for everyone else as well?


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## garsh (Apr 4, 2016)

eXntrc said:


> These seem to be two hard-set rules for me that cannot be superseded:
> 
> 
> *City Streets:* Never exceed speed limit (according to the map software) by more than 5 MPH.
> ...


That is exactly correct.


__ https://twitter.com/i/web/status/1096628590374879233


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## eXntrc (Jan 14, 2019)

Okay. So I guess what @Brian3 was saying was when he was on the freeway. That makes sense now, thanks.


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