Mach-E Brake Pressure Data for Each Drive Mode

[phidauex]

OK, @breeves002 and I just did an FDRS session to look at the brake pressure. In FDRS there are separate parameters for each wheel's brake pressure. I can confirm the input pressure from the pedal and the output pressure to the wheels are different as I suspected because the HCU decides what it's going to output. In terms of one-pedal, it does not apply brakes at all until just after you come to a stop (slight delay). So you might feel like you roll for a half sec before the brakes grab. Probably more noticeable stopping on a hill. Brake pressure in the wheels is released as you press the accelerator pedal after a stop.

So no brake blending is happening in one-pedal.

Awesome, thanks for the quick confirmation with the additional datapoints! How do the individual brake pressures respond to the input pressure? I had sort of assumed that they would generally match unless the car was actively overriding something (ABS, traction control, collision avoidance, etc), but sounds like I'm off there.

I took a look through my CarScanner PIDs and I don't see any of the individual wheel points, though I think FORScan has them, I'll see if I can dig deeper.

I don't believe this is confirmed. It would honestly surprise me because that's a decent amount of engineering work and possible tooling for only 1 year of use. I think it may be more expensive than leaving it in for a few years. Also it is still in the service manual for the 2022 model year.

If they did get rid of the pawl, it would just use the parking brake to hold the car when you put it in park.

You could be right, I think it was in that Sandy Munro interview that they said they would eliminate the pawl, but that could mean a lot of different things (even just leaving it there and just not using it).

@phidauex , sorry if I didn't understand this correct, what was your SOC? If you can regen 91kW. I have noticed in my previous EV's regen was weak at high state of charge.
I usually charge to 90% and have a lot of brake dust while I drive mostly conservative.

SOC for this run was probably mid 60% or so, not low, not high. I don't spend much time above 90% but I've noticed as much as 100kW of regen in a number of cases. At 90% displayed you are around 85% real SOC, so there shouldn't be a limitation to regen at that point. I think some others have confirmed that they are getting regen at 100% displayed SOC, though I don't know what the maximum regen power is at that SOC.

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[phidauex]

Can someone ELI5 what these findings mean to the average MME user?

Not much, just drive the car. Many people have asked about whether 1PD is more efficient than other modes, or how often the car blends friction brakes with regeneration braking, and this attempts to answer that question, that in 1PD mode, without firmly pressing the brake pedal, the car will not use the friction brakes until after you are at a complete stop. This is basically "good news" because it means the car is doing a good job of regenerating energy, and not wasting much energy to friction.

 

[breeves002]

Awesome, thanks for the quick confirmation with the additional datapoints! How do the individual brake pressures respond to the input pressure? I had sort of assumed that they would generally match unless the car was actively overriding something (ABS, traction control, collision avoidance, etc), but sounds like I'm off there.

I took a look through my CarScanner PIDs and I don't see any of the individual wheel points, though I think FORScan has them, I'll see if I can dig deeper.



You could be right, I think it was in that Sandy Munro interview that they said they would eliminate the pawl, but that could mean a lot of different things (even just leaving it there and just not using it).

Yeah all pressures were almost equal. It also is evident you really don't have any control over actual brake pressure. It kind of does what it wants.

Yeah I know she did talk about that but it wasn't like a "yes for 2022 it is gone".

 

[JamieGeek]

Not much, just drive the car. Many people have asked about whether 1PD is more efficient than other modes, or how often the car blends friction brakes with regeneration braking, and this attempts to answer that question, that in 1PD mode, without firmly pressing the brake pedal, the car will not use the friction brakes until after you are at a complete stop. This is basically "good news" because it means the car is doing a good job of regenerating energy, and not wasting much energy to friction.

This is only one piece of that puzzle as people who think 1-P isn't efficient argue that you can't coast in 1-P and thus speeding up after "coasting" (e.g. taking your foot off the accelerator) consumes more energy than simply "coasting" w/o 1-P....

Yes they completely ignore the fact that you can find the coast point in the pedal movement and coast without regen.

 

[Trick.Mach-E]

I can see there is some skepticism so I’ll do a sharpie test this week. That said, I really don’t see much brake dust at all, and my brakes seem to have a light rust film on them most of the time, so it might be driving style or the traffic situation that people are in that would be causing more brake usage.

Your post was a very interesting read and I too asked myself where is the brake dust coming from???

This is what the inside of my wheel looked like at 6200 miles. Lots of excuses for why I never really got the inside clean but clearly I saw a lot of brake dust on the front wheels after 6200 miles...

All cleaned for before a very long road trip to TX...

After a 3200 mostly highway trip to TX and back...

Around town I use 1PD on the highway I usually turn it off and I can say with good certainty that on the I-10 to TX and back I didn't have to use the brakes all that much.

 

[RetiredDP]

[QUOTE="Mach-Lee, post: 280530,
- I don't think it can hold the car still using the motors alone?

One of the Ford engineers stated that when the car stops, the parking pawl engages...so at zero speed, the motors aren't being used...just the parking pawl. This engineer said that the parking pawl could be eliminated on the 2022 models, along with the 2nd coolant pump...which may give the 2021's a cooling advantage.

 

[Mach-Lee]

One of the Ford engineers stated that when the car stops, the parking pawl engages...so at zero speed, the motors aren't being used...just the parking pawl. This engineer said that the parking pawl could be eliminated on the 2022 models, along with the 2nd coolant pump...which may give the 2021's a cooling advantage.

We've confirmed that it holds the car stopped with brake pressure. Parking pawl only engages in park.

Donna (chief engineer) did not say those things would be eliminated in '22 vehicles, only that they may consider removing them in the future. It was a tentative/informal statement, not factual. People have assigned way too much weight to the statements she made in that video, no changes were announced officially. Wiring for the park pawl solenoid and second coolant pump is present in the '22 service manual, so I'm virtually 100% certain '22 vehicles will still have them.

 

[timbop]

We've confirmed that it holds the car stopped with brake pressure. Parking pawl only engages in park.

Donna (chief engineer) did not say those things would be eliminated in '22 vehicles, only that they may consider removing them in the future. It was a tentative/informal statement, not factual. People have assigned way too much weight to the statements she made in that video, no changes were announced officially. Wiring for the park pawl solenoid and second coolant pump is present in the '22 service manual, so I'm virtually 100% certain '22 vehicles will still have them.

That's my take also - she was basically blowing him off rather than arguing with him about it.

 

[rgreene]

I’m also curious to see what things look like for non-1PD driving. When I’m engaged the brake coach will tell you how efficiently you reclaimed energy. Is a 100% score from the brake coach the same as if you were using 1PD? What about in unbridled where there is a light 1PD always on?

 

[Lord Polymath]

Newbie without a MME questions:
I get the implication that if you lightly press the brake pedal, the car might not even use friction brakes. Is that true?
In 1P mode you can let off the pedal a certain amount and the car will coast without any regen?

 

[phidauex]

Newbie without a MME questions:
I get the implication that if you lightly press the brake pedal, the car might not even use friction brakes. Is that true?
In 1P mode you can let off the pedal a certain amount and the car will coast without any regen?

In 1PD, a light application of the brake pedal may not trigger the friction brakes (at least, it doesn't show an increase in input pressure). As for coasting, it depends on how you describe it. True coasting where the motors are off but free-spinning - no. But if you hold the pedal steady and back off a little bit the power will drop to something very close to zero, but the motors are still engaged (inverters are switching), you are just hanging out around the zero crossing point with very little current flowing either direction.

 

[timbop]

Newbie without a MME questions:
I get the implication that if you lightly press the brake pedal, the car might not even use friction brakes. Is that true?
In 1P mode you can let off the pedal a certain amount and the car will coast without any regen?

Think of 1PD as a manual transmission with the clutch out. As you let up on the accelerator a little, the "engine" slows the car down a little but then keeps that speed. If you take your foot off the accelerator, the "engine" slows you down to a stop (without stalling of course). The analogy is imperfect as the car doesn't stall and it is not herky-jerky than a stickshift

 

[phidauex]

Ok, a few updates from a quick test run this afternoon.

First, the sharpie test. I put a sharpie stripe on my rotor, and then did two 1PD runs up to ~60mph, and then let off the pedal completely and let the car slow me to a complete stop. One in Engage, and a 2nd in Unbridled. I came to a complete stop each time, and I did not touch the brake pedal.

The sharpie mark stayed intact through both runs. However, after doing a friction brake test the mark disappeared almost completely (as expected). After driving 10 miles home after the test, the mark is still just barely visible, it seemed my friction test was the main thing scrubbing it off.

Before:

After 2 runs:

From what @Mach-Lee said from the FDRS tests, I was listening closely and I could hear the friction brake come on after coming to a stop (but it didn’t rub my mark off because the vehicle was already stopped). I did NOT hear the parking pawl, but I did hear it when switching to P after the tests.

In another run, I was going about 50mph, and slowed down by applying the brake pedal. I gradually increased the pressure on the pedal until the friction brakes came on. Interestingly, as I approached 100kW of regen, that is when the brakes engaged. I was waiting for it, but I could definitely hear and feel the brakes coming in - it does not feel the same as regen. It also coincided with the brake pressure PID increasing.

See the below screenshot - the top line got a bit cut off, but it is the Brake Light Switch, so that tells you when I started depressing the brake pedal. You can see regen power increasing on the Power line, and as regen gets to 100kW and my acceleration drops to -0.2g, the friction brakes come in, pressure goes up, and my acceleration drops to nearly -0.5g. This was not a panic stop, just a firm slow-down.

From all this, I’m still standing by my original claim that 1PD does not use the friction brakes, unless you are already stopped (as confirmed by @Mach-Lee and @breeves002), or unless traction control, collision avoidance, or some other system is taking over (still needs some testing).

I’m still not completely sure when the brake pressure PID will increase - it clearly doesn’t show the “already stopped” brake application, but on this driving test it seemed to be correlated to my rate of slowing and the sound and feel of friction brakes being applied. I’ll keep playing with it.

 

[SnBGC]

Ok, a few updates from a quick test run this afternoon.

First, the sharpie test. I put a sharpie stripe on my rotor, and then did two 1PD runs up to ~60mph, and then let off the pedal completely and let the car slow me to a complete stop. One in Engage, and a 2nd in Unbridled. I came to a complete stop each time, and I did not touch the brake pedal.

The sharpie mark stayed intact through both runs. However, after doing a friction brake test the mark disappeared almost completely (as expected). After driving 10 miles home after the test, the mark is still just barely visible, it seemed my friction test was the main thing scrubbing it off.

Before:

After 2 runs:

From what @Mach-Lee said from the FDRS tests, I was listening closely and I could hear the friction brake come on after coming to a stop (but it didn’t rub my mark off because the vehicle was already stopped). I did NOT hear the parking pawl, but I did hear it when switching to P after the tests.

In another run, I was going about 50mph, and slowed down by applying the brake pedal. I gradually increased the pressure on the pedal until the friction brakes came on. Interestingly, as I approached 100kW of regen, that is when the brakes engaged. I was waiting for it, but I could definitely hear and feel the brakes coming in - it does not feel the same as regen. It also coincided with the brake pressure PID increasing.

See the below screenshot - the top line got a bit cut off, but it is the Brake Light Switch, so that tells you when I started depressing the brake pedal. You can see regen power increasing on the Power line, and as regen gets to 100kW and my acceleration drops to -0.2g, the friction brakes come in, pressure goes up, and my acceleration drops to nearly -0.5g. This was not a panic stop, just a firm slow-down.

From all this, I’m still standing by my original claim that 1PD does not use the friction brakes, unless you are already stopped (as confirmed by @Mach-Lee and @breeves002), or unless traction control, collision avoidance, or some other system is taking over (still needs some testing).

I’m still not completely sure when the brake pressure PID will increase - it clearly doesn’t show the “already stopped” brake application, but on this driving test it seemed to be correlated to my rate of slowing and the sound and feel of friction brakes being applied. I’ll keep playing with it.

In 1PD, is there measurable energy harvesting all the way to zero mph?

 

[RMoore]

Fascinating thread. I continue to be impressed by what I would call the “engineering” skills (for lack of a better phrase) of folks here and their willingness to roll up their sleeves and probe the inner workings of the MME to educate us. So here’s perhaps a dumb question but I don’t think I’ve seen it addressed: what happens if you depress the accelerator pedal and the brake pedal at the same time? Does it depend on how much pressure you put on the brake pedal? This is something one can do in an ICE vehicle (simultaneously brake and rev the engine) both with manual transmission (heel and toe shifting) and I think even with automatics, but was wondering what would happen with the MME.

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