PSCB Brakes

[Pozuelo]

Where did you get this graph ?

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[bsclywilly]

Where did you get this graph ?

MY22 Taycans with Sport Chrono can use the Porsche track precision app to log data at the track or on “free drives”. This is part of a log from my commute home.

 

[Pozuelo]

Envious, in a good way.

 

[Deleted member 6348]

PSCBs are worth it. You get bigger brakes which is helpful on a 2-2.5 ton EV — they are outstanding. The wheels stay clean as they’re practically dust free. They don’t rust after a rain or after you wash your car. Thanks to the blending of regen and physical braking, they’ll last a long time so replacement costs are more/less irrelevant for most owners. Oh, they also fill the big wheels in a way that a poster car does, ie look great.

If you’re concerned about weight and your trim can get them, you can option PCCBs, but the new pad compounds that Porsche uses for environmental concerns can generate a little more dust than people expect. They’re no longer the “dust free” option.

There are benefits to the lack of dust that are beyond cosmetic. When you wash the brake dust off of the wheels, where do you think that the metallic awful ends up? If you’re the type of person that cares about the environment, the truly dust free PSCBs deliver additional advantages.

I am not sure how threads like this always veer into Tesla’s approach. SPOILER: They are not the model. Tesla’s always felt under-braked to me. Tesla touts one-pedal and regenerative braking like the physical brakes don’t matter — heck, they’ve delivered cars missing brake pads. Shortly after I took delivery, I had a Tesla owner poke fun at my Taycan PSCBs “Why are they so big?”. Yeah, uh, I like to be able to stop. For enthusiast driving, you do need big brakes on top of regeneration. The numbers, data, and YouTube videos of Plaid track run offs support that.

To be clear, the iron rotors on the Taycan are outstanding — better than anything Tesla has ever fit to a car. The PSCBs are just the next step beyond that and deliver additional benefits.

 

[Skilly]

you are fundementally confused - just because porsche doesn't do regen by lifting off the accelerator does _NOT_ mean there is no regeneration.

Porsche offers regeneration _WITH THE BRAKE_ pedal - they only "add/blend" in friction braking _IF NECESSARY_ to achieve greater deceleration based on you pressing harder on the brake pedal - it is entirely possible and often the case the Taycan is brought to a FULL stop using NOTHING BUT regeneration with the brake pedal - they even have a display on the dash showing the regeneration (the green bar from about 7 o'clock to 12 o'clock is the level of regeneration you are doing - only when you are at max "green" and then press harder are the friction brakes brough into the equation.

your arguments will continue to make no sense until you understand how Porsche has blended regeneration into the brake pedal.

unless you're braking really really hard - nearly all deceleration on the Taycan is handled by regen and friction brakes are "added" when "necessary" to achieve higher rates of deceleration based on driver's input (how hard you're pressing the pedal) - Taycan has the highest level of regen available in a production automobile on the market today - which means unless you are running around panic braking all hte time - most/nearly-all deceleration is handled entirely via regeneration.

the choice of "one pedal" driving is a user interface/driver interface software "trick" - and to date nearly every EV has and uses regeneration - the question is how does the driver "invoke" it

in the case of TEsla it's invoked by lifting off the accelerator and the brake pedal is 100% friction brakes

in the case of Porsche there is very very light regen from accelerator "lift off" - and brake pedal is regen until you press hard enough to also 'blend/add' the friction brakes.

Porsche could if they wanted to change the Taycan's software to offer one-pedal driving - say 40% regen on lift off the accelerator, and then the rest of regen with the brake pedal blended (they already do this today in existing shipping Taycans) - the Taycan's FULL regen power on accelerator lift-off would be too much…

it's all software, it's all adjustable - it's all a user/driver interface design issue - the Taycan is fundementally a regen-first friction-brakes 2nd blended braking vehicle by design - there is no way to avoid regeneration - and as stated unless you are braking really really hard - you are actually very very rarely using the friction brakes on the Taycan EVER...

in t

yeah confused and in front of a keyboard. It wasn't a good combination. Apologies all around - I as I mentioned upstream, I was busy talking when I should have been listening.

These 'brakes' are so good at that simulation (almost .5g) that it never occured to me that the motors (mostly front it sounds like) was doing that rather than traditional brake friction.

 

[daveo4EV]

yeah confused and in front of a keyboard. It wasn't a good combination. Apologies all around - I as I mentioned upstream, I was busy talking when I should have been listening.

These 'brakes' are so good at that simulation (almost .5g) that it never occured to me that the motors (mostly front it sounds like) was doing that rather than traditional brake friction.

Taycan is amazing! Porsche's done a great job and this is only 1.0 - picture where we'll be in like 10 years with EV's and relentless incremental improvement

it's all good.

 

[wurzitup]

Taycan is amazing! Porsche's done a great job and this is only 1.0 - picture where we'll be in like 10 years with EV's and relentless incremental improvement

it's all good.

Hey Dave I think a little confusion on your part is you seem to be under the impression that ANY and ALL braking energy events up to 265kW are handled by the regeneration judging by some of your comments. This isn't how the system works........
The 265kW is the MAXIMUM amount of potential energy recovery the system is capable of harvesting. This is not synonymous with all of the energy recovered as the mechanical brakes are blended in well before this threshold. Think of it like under a panic stop, the motors may be recovering up to this amount.
Just because your regeneration meter is not maxed out does not mean that your mechanical brakes are not being utilized. Its not an all or none event. Its not as though a 400kW event is ALL 265kW and then the remaining 135kW made up by mechanical. Not all 3.8m/s2 braking events are done with regeneration- this is simply the MAXIMUM that the system is capable of harvesting. Mechanical brakes are blended in well before then.

 

[f1eng]

Mechanical brakes are blended in well before then.

Do you know why and at what level the friction brakes are blended in?

 

[wurzitup]

Do you know why and at what level the friction brakes are blended in?

I do not know the level at which- I'm not sure Porsche would even make this public. But my understanding from everything I've read and followed with the 919 and development of this braking system and its carryover to the Taycan it has to do with the consistency of the pedal feel and the transition of the braking application from motors to pad and rotors. The software and mecanics of integrating the two systems to provide consistent and reliable braking pressure I know was one of the biggest challenges of this car.

 

[f1eng]

I do not know the level at which- I'm not sure Porsche would even make this public. But my understanding from everything I've read and followed with the 919 and development of this braking system and its carryover to the Taycan it has to do with the consistency of the pedal feel and the transition of the braking application from motors to pad and rotors. The software and mecanics of integrating the two systems to provide consistent and reliable braking pressure I know was one of the biggest challenges of this car.

Certainly the brake pedal feel is good and equally certainly I know the 919 braking knowledge was used by the Taycan design team but I am pretty sure there is no need to blend the friction brakes in particularly early.

Even out PHEV Prius can be driven with almost no use of the friction brakes even though regen back torque isn’t much.

On the 919 the kinetic energy recuperation is on the front axle only (I am fairly sure) so there will be friction brakes on the rear all the time.
On the F1 cars 4WD is banned so we had to do all the kinetic energy recovery at the rear, which is an irritating limit given the front brakes do most of the work so we obviously have to use a “fly by wire” braking system to blend recuperation and friction at the rear whilst using only friction brakes at the front.

Most Taycans are 4WD and not constrained by racing rules so the recuperation can be balanced in software between front and rear and the friction brakes are actually not needed at all until the recuperation back torque is at a maximum - very much unlike the racing versions.

It was certainly my understanding that the Taycan friction brakes didn’t need to be used much - unlike the racing versions constrained by the rules.

 

[bsclywilly]

If it helps clarify further, here's a data trace from a longer driving event, about 17 mi over a mountain pass. @daveo4EV may appreciate this one as it's in his backyard - hwy 17 from Los Gatos to Santa Cruz. There's a few braking events around 0.3-0.4g but friction brakes not used once.

 

[wurzitup]

If it helps clarify further, here's a data trace from a longer driving event, about 17 mi over a mountain pass. @daveo4EV may appreciate this one as it's in his backyard - hwy 17 from Los Gatos to Santa Cruz. There's a few braking events around 0.3-0.4g but friction brakes not used once.

Psi on this data is brake pedal pressure, no? Or is it mechanical brake pedal system pressure? I would imagine the former?
Brake pedal pressure does not directly correlate to mechanical brake utilization, although the two are closely related?
What would be really interesting would be to see this graph with both with regeneration and mechanical braking graphed.
Really interesting data trace thanks for posting.

 

[bsclywilly]

Psi on this data is brake pedal pressure, no? Or is it mechanical brake pedal system pressure? I would imagine the former?
Brake pedal pressure does not directly correlate to mechanical brake utilization, although the two are closely related?
What would be really interesting would be to see this graph with both with regeneration and mechanical braking graphed.
Really interesting data trace thanks for posting.

Pressure at master cylinder.

 

[f1eng]

Psi on this data is brake pedal pressure, no?

PSI is lb per square inch so it is the hydraulic pressure in the brake system not the brake pedal showing that the friction brakes were not used at all.
This is pretty well what I would expect from how I believe the system works.

 

[wurzitup]

PSI is lb per square inch so it is the hydraulic pressure in the brake system not the brake pedal showing that the friction brakes were not used at all.
This is pretty well what I would expect from how I believe the system works.

I guess what I was clarifying was like you said system hydraulic pressure, and not pedal pressure. You could have a fair amount of pedal force without mechanical intervention, but system pressure would obviously correlate with mechanical braking. Agree?

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