PSCB Brakes

[Jhenson29]

I will be at PECLA on wed. for a advanced driving courses

I almost scheduled a PECLA session on Tuesday! I ended up not and it’s a day apart; but still! So close!

Anyway, I think that all makes perfect sense.

If you’re taking requests, ask If there was ever any discussion about additional regen without recup over like a braking resistor or something. My guess is no because they likely need the pads regardless and these would then just be extra components for the sole purpose of further reducing pad use. But just curious.

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[Sidicks]

Haha you know I was actually going to say something like “I don’t Think I’ll keep the car that long” when I was writing my post

I wrote this a few pages back:

“Fair enough, but most people ordering new cars are not going to be needing new discs in the normal ownership period of these cars.”

 

[Taycan Turbo SD]

Get the surface coated brakes, and you won't regret it, in emergency stops they are simply amazing. Also the mirror look is cool.

 

[Sidicks]

Get the surface coated brakes, and you won't regret it, in emergency stops they are simply amazing. Also the mirror look is cool.

Same emergency stopping distance as the normal brakes, and if you want a mirror, there’s two or three on the inside of the car!

 

[daveo4EV]

I almost scheduled a PECLA session on Tuesday! I ended up not and it’s a day apart; but still! So close!

Anyway, I think that all makes perfect sense.

If you’re taking requests, ask If there was ever any discussion about additional regen without recup over like a braking resistor or something. My guess is no because they likely need the pads regardless and these would then just be extra components for the sole purpose of further reducing pad use. But just curious.

will ask

 

[wurzitup]

I will be at PECLA on wed. for a advanced driving courses - apparently they have some techs there that are fully brief'd on the intimate details of how Taycan does it's blended braking…I'll report back - they have agreed to meet with me at the 917 restaurant and answer my questions

but I've already learned one or two things over eMail:

TLDR Summary:



Gory details

• Taycan is mostly a "regen 1st" friction brakes "2nd" implementation
  [*]Porsche racing hybrids blend in friction brakes "sooner" to keep heat into the racing pads & rotors
  
  • testing showed regen was too effective and brakes/pads were being "over cooled" and falling outside of their optimal minimum temps - so it best to keep a "little" heat in them
  • this is not a factor in street driving
  • much much smaller batteries - used more for performance than range (augmenting the power of the ICE motor)
  • so very very different goals in optimizing power/regen/deceleration vs. an all BEV street car with limited range…
  [*][*][*][*][*][*]it is correct that Taycan doesn't always use it's max 265 kW regen capacity - rather there is a "target" max regen constantly being calculated based on available data from _ALL_ sensors
  
  • however mostly Taycan will go to this calculated "max" _FIRST_ then "add" friction brakes as necessary
  [*][*][*][*][*][*]the algorythm is slight more 919 hybrid like in sports & sports+ but stil mostly "regen" first friction "second"
  
  • this is mostly have the friction brakes "ready" and already engaged for minute pedal modulation and lowering the latency for the friction brakes to have effect on the rotors - sports/sports+ are not range sensitive driving modes
  • once you reach ABS it becomes much more complicated with ABS essentially disabling "regen"
  • once ABS is triggered the remainder of that braking "event" regen is no longer prioritized with friction carrying most of the load until the brake pedal is fully released
  [*][*][*][*][*][*]every press of the brake pedal is a "new" "event" - once you release the brake pedal fully the next "brake press" is a "new" event and new targets for max regen are calculated once you press on it again taking into account data from _ALL_ sensors at the beginning of the event
  [*]psi as reported by the precision track app _IS_ friction brakes essentially
  [*]Taycan is optimized for street driving and range - once you've decided to engage in deceleration it's best to recover as much kinectic energy as possible for the battery - any friction braking before you are at max regen is "wasted" energy that could've gone to the battery
  
  • this sort of "range 1st" optimization is not a goal in racing
  • pad/rotor wear and elongating service intervals was a goal for a street car
    • again when you're optimizing for maximum energy recovery and maximum service life the less you use the friction brakes the better for those two goals
  [*][*][*][*][*][*]it is possible but not common for Taycan to be blending regen & friction at the same before before reaching "max" regen - but again that goes against the max energy recovery goal
  
  • but that only happens once you're "close" to the max regen target value anyways - basically it's predictive - once you are approaching max regen and it's clear driver is requesting "more" deceleration Taycan will begin "ramping up brake PSI" to "blend" two deceleration forces…exact nature of this and when/how/why/under-what-circumstance is "secret sauce" for Porsche and why they are "better" than the other guys
  [*][*][*][*][*][*]coasting _IS_ more efficient than regen for range driving and hence no one pedal driving on Taycan - but once you've committed to deceleration (driver has touched the brake pedal) _ANY_ friction braking is wasted potential energy - friction brake heat does not charge the battery
  
  • recover as much energy as possible 1st (regen only) - then add friction (waste heat) if necessary.
  [*][*][*][*][*]

I'm looking forward to my lunch on wed. - I'll report back - fascinating stuff IMHO.

Dave this might provide you some insight into how this system works in preparation for your lunch. It's involved way more than I think you're aware of.
This is a quick 6 minute drive I just went on- onto the freeway, braking in traffic a bit, and off the freeway. 5 or 6 braking system pressure events (mechanical braking by your own acknowledgment) within 6 minutes, none of which were anywhere near threshold braking, and only one of which I believe maxed the regen.
I tried to tie video to it too so we could see the dash with speed and regen but it's kinda clunky unless your car is set up better.
You wanted data....... there's your data.

 

[f1eng]

Whatever

 

[bsclywilly]

Dave this might provide you some insight into how this system works in preparation for your lunch. It's involved way more than I think you're aware of.
This is a quick 6 minute drive I just went on- onto the freeway, braking in traffic a bit, and off the freeway. 5 or 6 braking system pressure events (mechanical braking by your own acknowledgment) within 6 minutes, none of which were anywhere near threshold braking, and only one of which I believe maxed the regen.
I tried to tie video to it too so we could see the dash with speed and regen but it's kinda clunky unless your car is set up better.
You wanted data....... there's your data.

That graph would mean a lot more if it also showed longitudinal acceleration since power is a function of v and a.

If you really want to reverse engineer the peak regen you can calculate the power just before the hydraulic system builds pressure by P=mass*accel*velocity.
You will find that the regen power varies alot before the friction brakes start building pressure. So you are right. You could also see the difference between a jab of the brakes, where the friction brakes are engaged immediately, or gradual application where regen is maximized. So many factors, as Dave’s post also pointed out.

*edit* It should also be pointed out that max regen of 265kW can only be achieved at speeds greater than 67mph, assuming they've designed it to peak at 0.38g deceleration. I think I saw that quoted that "up to 0.38g" can be attributed to regen. At lower speeds to reach that peak regen power the deceleration by motor only would have to be much higher. This would explain why it's hard or impossible to max out the regen meter on the dash at lower speeds (also assuming the regen meter scale is fixed at 265kW max).

 

[bsclywilly]

Btw is that app awesome or what?

 

[Archimedes]

Dave this might provide you some insight into how this system works in preparation for your lunch. It's involved way more than I think you're aware of.
This is a quick 6 minute drive I just went on- onto the freeway, braking in traffic a bit, and off the freeway. 5 or 6 braking system pressure events (mechanical braking by your own acknowledgment) within 6 minutes, none of which were anywhere near threshold braking, and only one of which I believe maxed the regen.
I tried to tie video to it too so we could see the dash with speed and regen but it's kinda clunky unless your car is set up better.
You wanted data....... there's your data.

Am I interpreting this graph correctly as follows? You did six full stops, and in four cases all of the braking was regen except for the very end of the stop, which was friction braking. In the other two, it was entirely regen.

Then you had three other braking events, all of which were very brief and the friction brakes engaged for a very short time.

 

[AV7]

PSCB brakes/rotors will last much longer than standard...

This is the Porsche recommendation:

For this reason and for the first time ever, Porsche is
prescribing a time-dependent replacement interval for the brake pads: they must be replaced every six years

 

[Archimedes]

This is the Porsche recommendation:

For this reason and for the first time ever, Porsche is
prescribing a time-dependent replacement interval for the brake pads: they must be replaced every six years

Meh, if the pads don’t need replacing then based on wear, there would be no reason to follow that, given the warranty on the vehicle will have expired.

 

[Jhenson29]

Meh, if the pads don’t need replacing then based on wear, there would be no reason to follow that, given the warranty on the vehicle will have expired.

Isn’t this typically a wear and non-warranty item anyway? Like tires?

 

[AV7]

Isn’t this typically a wear and non-warranty item anyway? Like tires?

Good point,

I should have included the full paragraph, according to this the pads will probably last alot longer

'Thanks to the Taycan’s high recuperation output of up to 265 kW,
approximately 90 percent of braking operations in everyday use are performed by the electric motors
alone, without activating the wheel brakes. For this reason and for the first time ever, Porsche is
prescribing a time-dependent replacement interval for the brake pads: they must be replaced every six years. '

 

[Archimedes]

Isn’t this typically a wear and non-warranty item anyway? Like tires?

If your rotors crapped out way early, you could claim warranty, assuming you did all the recommend maintenance. If the warranty is already gone, it’s a moot point.

That time based recommendation is simply Porsche wanting some service revenue IMO. If I still have the car when that time comes, I’ll do the pads based on wear levels.

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