P mode vs Park mode

[Mario Veras]

What’s the difference between putting the Model 3 in P versus Park mode? I’ve seen some YouTubers talk about that it makes no difference, so why is there a logo displayed on the screen if it makes no difference?
I can’t seem to find this in the manual.

 

[launchd]

Yet, Tesla has ZERO documentation of this in their manuals. Zero reference to an emergency brake. Just that you can either engage the parking brake by putting it in park OR pressing and holding. Same definition and description. Weird that a company would go to all this trouble for this feature, and then completely avoid telling users about it in any way or form.

Really? I would think that anyone who can read English would read this from the Tesla manual and assume that pressing and holding the Park button on the drive stalk is engaging your emergency brake.

You say there is proof- where is there proof that the calipers apply more clamping on the rotor when a long press occurs? A singular Model X not rolling after a complicated path of multiple parking brake actuations is not proof.=

Bringing your car to a stop by pressing on your brake pedal, putting your car into park, releasing your brake pedal, realizing that your car is rolling, pressing your brake pedal again to stop it and engaging your emergency brake to successfully hold your car in place is not a "complicated path of multiple parking brake actuations" it is actually a very common series of events that can occur in ANY CAR.

 

[gearchruncher]

Really? I would think that anyone who can read English would read this from the Tesla manual and assume that pressing and holding the Park button on the drive stalk is engaging your emergency brake.

So pressing and holding PARK engages your EMERGENCY BRAKES, not your PARKING BRAKES? Tesla doesn't even tell you that pressing and holding engages brakes- it tells you it brings the car to a stop. For all you know, it uses regen. But for sure, Tesla never once refers to emergency brakes in the manual.

But nowhere in there does it say "this applies the brakes harder than if you were to put the car into park while stopped." And nowhere does it say that this works the same way if you are stopped (hint, it does not).

Ironically, you might want your emergency brakes while under motion to use LESS friction than parking brakes. You don't want them to lock up while slowing down.

Bringing your car to a stop by pressing on your brake pedal, putting your car into park, releasing your brake pedal, realizing that your car is rolling, pressing your brake pedal again to stop it and engaging your emergency brake to successfully hold your car in place is not a "complicated path of multiple parking brake actuations" it is actually a very common series of events that can occur in ANY CAR.

I didn't say it was abnormal. I said it was not PROOF that the clamping force you get in PARK mode is different than the clamping force you get in PARK+BRAKE. This is far from a scientific test.

Scientific test would be actually measuring the breakout force required to spin a wheel in the two proposed states for the caliper, and entering that mode in a controlled way. Unfortunately, the brakes can resist thousands of foot pounds of torque at the hub, so this is hard to do.

 

[android04]

I just wanted to comment on the scenario where the Model X attached to a boat and trailer on a boat ramp started rolling backwards while in Park. How much did it roll? Because when you put the Tesla in Park there is a slight delay before it actually clamps down the EPB. This slight delay may have been enough for the driver to thing that Park didn't work. It is also possible that the EPB was applied and clamped down normally, but there was still a delay and it wouldn't clamp down as hard as when one was pressing on the brake pedal. The reason Parking Brake worked right away is that there is no delay and it clamps down and holds whatever pressure you're applying to the brake pads through via the brake pedal. It's easier for the EPB to hold whatever pressure is currently being applied by the hydraulic brakes than to apply the pressure itself once the hydraulic pressure is relieved.

The best way to test for the differences is to stop on a step hill and test out both Park and Parking Brake.

 

[Gauss Guzzler]

Dude, the manual literally references "brakes" for "emergency situations". Why you gotta keep insisting that every documented fact is wrong just because you "feel" like it's wrong. Get a voltmeter if you're so confused. Or just read.

And no, it does not use regen. Everyone knows that. Just stop fabricating ridiculous theories about the way you think cars work. Maybe your neighbor has a voltmeter? It'd be worth asking because it will save you a lot of trouble making up crazy stuff.

 

[gearchruncher]

Dude, the manual literally references "brakes" for "emergency situations". Why you gotta keep insisting that every documented fact is wrong just because you "feel" like it's wrong. Get a voltmeter if you're so confused. Or just read.

Except it literally does not. It says if you brakes aren't working, press and hold and the car will stop. It does not tell you how it will achieve this.

Plus you are SO SURE that emergency braking, if it exists, would be MORE friction than parking brakes? Why? Wouldn't that lock up the rear axle?

Like I said, I'll grab a voltmeter once you tell me what voltages you think I'll see. All I'm asking you to do is type in numbers into a forum, while I have to go take apart a car and wiring harness and make a video.

 

[Gauss Guzzler]

The emergency brake likely uses a different voltage and might even ramp up over time. I don't know, why does it matter? Who said anything about it having more or less voltage than Park or the Parking Brake? I explained everything anyone would ever want to know here. But you seem really obsessed with voltages and special relativity rather than just accepting the user manual and CAN message data. Maybe you should check one of your calipers with a voltmeter?

 

[DownshiftDre]

Haha You guys are still debating conceptually and Im trying to get empirical data still in my garage with my deaf ears. If this keeps going, I may just have to take my rear wheel off, take measurements and put you both to shame for not following through with your hypothesis with data lol. Step it up, stop using keyboards and lets get some much needed truth.

I did the test again, but this time from Neutral. Using my uncalibrated ears.

Neutral then Push P Once: Normal whir/whine noise and then brake pedal moves and pumps. Display shows P.

Neutral then Hold P: Normal whir/whine noise and then brake pedal moves and pumps with an additional clunk/clank/clamp by the pedal. Display shows P then the “PARK” symbol comes on right at that last clunk/clank/clamp.

Somebody repeat and tell me if they hear that difference? Is it the sound of trying again or is it some kind of final clamp?

 

[gearchruncher]

Neutral then Push P Once: Normal whir/whine noise and then brake pedal moves and pumps. Display shows P.

Neutral then Hold P: Normal whir/whine noise and then brake pedal moves and pumps with an additional clunk/clank/clamp by the pedal. Display shows P then the “PARK” symbol comes on right at that last clunk/clank/clamp.

I've done this exact thing in my car multiple times, and I can't hear any difference. The only time it sounds different is if I go into park first, then parking brake. I did this years ago, and again last night. I posted about this in post #15 of this thread.

 

[gearchruncher]

The emergency brake likely uses a different voltage and might even ramp up over time. I don't know, why does it matter? Who said anything about it having more or less voltage than Park or the Parking Brake? I explained everything anyone would ever want to know here. But you seem really obsessed with voltages and special relativity rather than just accepting the user manual and CAN message data. Maybe you should check one of your calipers with a voltmeter?

Man, you'd make a great politician with your gaslighting!

The emergency brake likely uses a different voltage and might even ramp up over time. I don't know, why does it matter? Who said anything about it having more or less voltage than Park or the Parking Brake?

Umm, you did. You were literally the first person in this thread to say the voltage was different. This was your first post in this thread, which is the one you linked to:

Park, Parking Brake, and Emergency Brake are different modes of activating the electric override on the rear calipers. The "Parking Brake" option uses a much higher voltage for better clamping at the expense of increased noise and wear. The "Emergency Brake" option is only active while continuously holding the button in at speed, it becomes regular "Park" below 5mph. There is no relationship between this and the hydraulic braking system - by design.

And then every single post since, you comment on voltage.
But now, it's "Likely it's voltage" and "who said anything about it having more or less voltage?"
But yeah, I'm the one obsessed with voltages and without data.

You say the user manual makes this all clear, indicating that the "emergency brakes" work differently than the "parking brake." You also said:

I told you the exact voltages and cited the data,

Since I can't find anywhere where you showed the exact quote from the user manual, nor where you posted the EXACT voltages, all I am asking is that you spend 30 seconds re-posting both of these so that I can go measure my car and see if it lines up with your data and behavior as described in the manual. This should be a trivial exercise for you if your opinion is backed up by data.

 

[DownshiftDre]

In God we trust, all others bring data.

 

[Gauss Guzzler]

Pay attention @gearchruncher. I referenced “Park” and “Parking Brake” along with JWardell’s data. Then you got all spun up about the “Emergency Brake” which is the function that only operates over 5mph and I simply stated that it might use a different voltage profile.

 

[gearchruncher]

I went and did what I promised.

I'll get a video later, but the simple answer is that any time the parking brake is running, the voltage is 13.88.
No difference no matter how I engaged it- "Park", "Park than hold", just Hold, just use the touchscreen. Always 13.88
So much for voltage being the difference that could clearly be seen on a voltmeter.

Also, I manually drove the motor with a power supply. The motor won't move until about 6V. At that point it takes about 30 seconds to engage it's so slow. So much for:

For example, a nearly dead 12V battery might be at 9V resting and sag to 6V under load all the way back at the parking brake, so a motor designed for 4.5V max would make sense.

So what's next to test?

 

[gearchruncher]

Then you got all spun up about the “Emergency Brake” which is the function that only operates over 5mph and I simply stated that it might use a different voltage profile.

The "emergency brake" function that isn't documented in Tesla's manuals at all, and that Jwardell never evaluated? One that is just theorized due to the "press the button when moving if your brakes have failed?"

You really need to go back and read what you posted, we can all see it: Search results

But I've got data now. Voltage is always the same, and is the bus voltage. What do you want to see next?

 

[Gauss Guzzler]

Yes, all 3 functions are described in the manual and indicated on the screen as well. Pro tip: to read more about the "emergency brake" function, look for the words "emergency" and "brake" in the manual.

I don't know why you're all spun up about the emergency brake. That's not the topic of this thread and we don't have any voltage data. Rightfully, no one has speculated about the voltage of the emergency brake function - except you, of course.

So now, thanks to you, we have more data. You're stating that the two parking modes deliver 12.2V/16V. So that would indicate that it just runs the motor as fast as possible until something triggers it to cut the power. It could be a timer but the most logical trigger would be a stall current threshold. This actually makes a lot of sense because as you noted, current is a direct indicator of torque whereas voltage involves more unknowns (temperature, connector wear, etc.). Plus it makes for a simpler motor controller that doesn't need to do high frequency modulation.

Cool! So now we're one step deeper into the nerd hole. This didn't do anything to resolve your doubt about the park functions being different of course, we still have the owner's manual, on-screen indicators, trailer towing stories, CAN bus data, and logical theory all suggesting that the functions are different. But now we know that it's likely current limited rather than voltage limited - and that makes perfect sense. So now that you have your meter out, have a look at the current - it should be well within the limits of a standard 10A meter.

 

[gearchruncher]

So as an FYI to this thread, I'm done with @Gauss Guzzler - They're being intellectually dishonest and anyone that looks at their posts in this thread can see it. First stating that it's absolutely voltage that is the difference, that voltage and current are always proportional, that this is about the emergency brake not parking brake, refusing to quote anything specific but giving vague statements to read the manual, saying that any cheap voltmeter can do this, saying they already posted numbers that they didn't... Then when the data goes against them, they act like they never brought it up and it's someone else being irrational, and they have always been right. For instance:

I don't know why you're all spun up about the emergency brake. That's not the topic of this thread and we don't have any voltage data. Rightfully, no one has speculated about the voltage of the emergency brake function - except you, of course.

Meanwhile, the very first post in this thread:

Park, Parking Brake, and Emergency Brake are different modes of activating the electric override on the rear calipers. The "Parking Brake" option uses a much higher voltage for better clamping at the expense of increased noise and wear. The "Emergency Brake" option is only active while continuously holding the button in at speed, it becomes regular "Park" below 5mph.

And then a follow up post was:

Who said anything about it having more or less voltage than Park or the Parking Brake?

Yeah... That's not an honest or consistent argument.

To be clear here- I'm the only one that went and got data, in exactly the way requested. It didn't show what was stated to be true, which is that the "parking brake option uses a much higher voltage for better clamping". Now the goalposts have moved, and it's about current, not voltage, even though "current and voltage are *always* proportional", and thus there was no need to ever measure current, the very first thing I pointed out would be needed. I mean "And FYI, current in a motor is based on voltage," right? Why do we need to measure current AND voltage suddenly?

Second, it's not a "12V" motor. It nominally runs on much lower voltages to ensure that even in the case of a very low 12V battery that it can still safely deliver the full parking brake current. For example, a nearly dead 12V battery might be at 9V resting and sag to 6V under load all the way back at the parking brake, so a motor designed for 4.5V max would make sense.

Who cares? It's not relevant to this topic. I know you're trying to get all pedantic with me because current is what technically produces torque but again, no one cares and neither does the system - it adjusts the *voltage*. Because current is always proportional to voltage.

But now we know that it's likely current limited rather than voltage limited - and that makes perfect sense.

Weird how fast physics changes in the face of data.

No simple voltmeter or current meter will be useful here, which I pointed out very early. The whole parking brake activation cycle is only 1-2 seconds, and voltmeters average over half second type timeframes. If there is a current control phase, it's going to only be a few hundred milliseconds, which no simple voltmeter can identify. This requires an oscilloscope with a current clamp.

I'll keep going because this is an interesting question that keeps coming up in the community, and I am willing to get the data and accept the data if it shows my hypothesis is wrong.

So, here's my data collection plan for the community to review:
1) Collect current vs time data when going into park from neutral
2) Collect current vs time data when going into parking brake (press and hold) from neutral
3) Collect current vs time data when going into parking brake (via touchscreen) from neutral.

If there is a difference in the stall current amount or duration between #1 and #2 or #3, then there is a difference. If there isn't, then there's not.

 

[Gauss Guzzler]

I see how this can be confusing out of context (not my bolding):

Park, Parking Brake, and Emergency Brake are different modes of activating the electric override on the rear calipers. The "Parking Brake" option uses a much higher voltage

But I merely meant that the Parking brake was higher than Park, not both Park and Emergency. We hadn't been talking about Emergency voltages so I didn't consider that you'd get all wrapped up in that. I do expect that the Parking brake would be more aggressive than the Emergency brake but I don't have any data so I don't make any claims.

I said it was voltage controlled because there is supporting data suggesting that. You now claim to have supporting data which both refutes that and also makes logical sense, so I believe you. That's not a moving of the goalpost or a changing of the physics. The principal issue still remains - that you think all the evidence is wrong about the brake offering multiple force levels.

Thanks for digging deeper and I agree this is interesting. I expect that the voltages JWardell found are raw ADC readings at the current shunt so you may find similar ratios. BTW a regular voltmeter will do 250us captures and I can't imagine why Tesla would want to use trigger logic anywhere near that fast.

 

[gearchruncher]

expect that the voltages JWardell found are raw ADC readings at the current shunt so you may find similar ratios.

I've already disproven this. I have access to the CAN bus (I have a CANServer made by Jwardell and have done development on the CANDash android app)- and the CAN bus label only changes when the requested state changes. But it reads non-zero when there is 0 voltage/current on the motor. Heck, it reads non-zero when the motor is disconnected and no current is possible. It's some sort of estimated state, not any kind of real time reading. Given the parking brake refuses to engage a third time (if you press and hold it only goes once), my guess is this is just a counter. But we're all here acting like it's some sort of proof that the clamping force is different.

There is zero voltage/current on the motor when it's not moving. So look at Jwardell's own CAN data and you can tell that it's not any kind of realtime reading because it doesn't return to zero within a few seconds.

BTW a regular voltmeter will do 250us captures and I can't imagine why Tesla would want to use trigger logic anywhere near that fast.

No "Regular" voltmeter updates at 4,000Hz. Point me to one that does. Even if it did, your eye couldn't see it, and no LCD is that fast. Just how the heck do you think someone can use a voltmeter to repeatably measure and see the stall current phase of something that only lasts 200ms?

 

[freed0m]

So, if I park my Model 3 on a steep hill, do I press the P "once" or "hold"?
Asking for a friend.

 

[gearchruncher]

So, if I park my Model 3 on a steep hill, do I press the P "once" or "hold"?
Asking for a friend.

Given the ambiguity in the manual, best option is to zip tie the P button down every time you get out of the car.

 

[mtmra70]

I've done this exact thing in my car multiple times, and I can't hear any difference. The only time it sounds different is if I go into park first, then parking brake. I did this years ago, and again last night. I posted about this in post #15 of this thread.

Same for me.

So, if I park my Model 3 on a steep hill, do I press the P "once" or "hold"?
Asking for a friend.

Turn your wheel all the way to the right...haha