Regenerative brake

[whitex]

jfc, how many times can you miss the fucking point completely. I'm done with this forum.

Oh come on! Why done with the forum? It is possible that you are the only one correct while the rest of the people are wrong, but how likely is it? Even if, why not educate others with convincing points, factual data? Most on this forum appreciate factual data (though please don't disclose anything you cannot under your NDA with Rivian).

I think what most are saying here is that one pedal driving will at best be as efficient as coasting, however any deviation from absolutely perfect accelerator operation will lower energy efficiency. As far as I can see, there is physically no way that one pedal driving can be more efficient on energy usage than two pedal driving (I am excluding the energy driver has to use move their foot between pedals). If you have evidence to the contrary, please provide it.

Nobody is trying to convince you your preference of using one pedal driving is wrong. Everyone has their own preferences. I drive in a less than energy optimal way, both because I turn regen on, and because I like quick accelerations and fast speeds. That is MY preference, I paid extra to get the additional power, but I was not kidding myself thinking it will be more efficient that way. YOUR preference is to drive with one-pedal-driving, I think everyone here accepts that (has anyone here tried to convince you that it is not more fun or convenient for you to use one pedal driving?).

Perhaps if you don't have the will power or resources to do the experiment yourself, reach out to someone at your employer(Rivian) to do the experiments and produce an informative video on the topic. If not someone at your work, maybe one of the YouTubers who cover topics like this, like EngineeringExplained? Better yet, hookup the youtuber with Rivian engineers who could help the youtuber by providing a vehicle, maybe access to a test track, and ability turn on an unofficial coasting mode in a Rivian, so they can do the experiments to measure efficiency? I'm thinking an objective video from EngineeringExplained on "Is one pedal EV driving most efficient" would get some views. Of course, if the conclusions are it's not the most efficient, that might not work in your employer's favor, and perhaps they don't want to spend the resources to develop a properly tuned two pedal driving, as it really does take more work.

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[F1Ruaraidh]

No.

The only point is and was that regeneration is NEVER as efficient as coasting, however it is achieved since regeneration is less than 100% efficient. Simple.

If a person is capable of controlling the throttle to not draw power or instigate regeneration in a one-pedal driving car they would equal the efficiency of coasting. I suspect they are few and far between. Anyway you don't do it for long as you do still slow down just more slowlyt.

You surely can understand this??

It has sweet FA to do with a preference for one pedal driving. I suspect the bloke did not realise the Taycan uses regenerative rather than friction brakes.

It isn't that big a deal but enthusiasts of one-pedal driving using bollox to claim it is more efficient gets on my wick.

Yes of course I understand it, it's about ease of control. As simple as that.

Stop thinking like a physicist and think like a dynamicist.

And yes it's absolutely about preference and ease of control so if you ignore that point, you miss the whole argument entirely. Just like Porsche did.

Providing you don't hunt around in speed and control regen cleanly, then it makes no absolutely no difference to efficiency. I'm quite capable of doing that thanks.

Allowing one mode where the throttle neutral point is deeper than zero before regen is engaged is not hard, nor is it any less efficient than regenning on the fake brake pedal first section of travel, it's just easier and more intuitive. The Porsche auto setting is as irritating and overly complex as the charging timers and profiles mess. Overthought system which definitely does result in the speed hunting they're trying to avoid (as it continually tries to force a larger gap in front of the car) but which I've never experienced in 6 years of EV driving any other car. Woeful so it creates the problem they say they're trying to avoid by design.

The only reason for Porsche avoiding OPD was because an old grey haired board member didn't want brake lights lighting without the brake pedal being pressed by the driver (which they must do above a legally mandated decel level by law during regen). They didn't want that.

That's it. That's the whole "technical" reasoning. The efficiency thing is just a post hoc justification they came out with much later after everyone citicised the poor brake pedal feel resulting from their overly complicated "engineering" (see brake light idiocy) design giving regen based on intial dead pedal travel. Resulting in poor brake pedal feel and no OPD. Worst of both worlds and a much more complicated design. I worked with that system with Bosch. Complex is the word especially from a FuSa pov.

But this is a Porsche - the most driver centric car there is - so there should be at least an one mode with an OPD option to keep experienced EV drivers happy rather than trying to emulate an ICE car in all its modes to keep its EV learner drivers and ICE drivers happy. Absolutely not every mode but at least one option in normal or range.

And it's clearly having no effect on efficiency as even when driven like Miss Daisy, the Turbo S has laughably bad efficiency.

Ho Hum. Every car has its irritations and this is a big one for me on the Taycan after the hopeless (<200 miles) range. But I bought it eyes open knowing it was a great car but a woeful EV. That's why I still have the ancient old Model S which is a great EV but flaky car.

But there really is no actual engineering justification given good driving.

PS Since you like the F1 card I spent 10 years leading the development of KERs and ERS at Mercedes so don't need lectures on how things work.

 

[F1Ruaraidh]

jfc, how many times can you miss the fucking point completely. I'm done with this forum.

oh I wouldn't go that far. People always find things to disagree about of forums and this has been very civil.

Main thing to be thankful for here is that, on any other forum, this thread would be littered with "break pedal" and "breaking".

cheers all.

 

[f1eng]

Yes of course I understand it, it's about ease of control. As simple as that.

Stop thinking like a physicist and think like a dynamicist.

And yes it's absolutely about preference and ease of control so if you ignore that point, you miss the whole argument entirely. Just like Porsche did.

Providing you don't hunt around in speed and control regen cleanly, then it makes no absolutely no difference to efficiency. I'm quite capable of doing that thanks.

Allowing one mode where the throttle neutral point is deeper than zero before regen is engaged is not hard, nor is it any less efficient than regenning on the fake brake pedal first section of travel, it's just easier and more intuitive. The Porsche auto setting is as irritating and overly complex as the charging timers and profiles mess. Overthought system which definitely does result in the speed hunting they're trying to avoid (as it continually tries to force a larger gap in front of the car) but which I've never experienced in 6 years of EV driving any other car. Woeful so it creates the problem they say they're trying to avoid by design.

The only reason for Porsche avoiding OPD was because an old grey haired board member didn't want brake lights lighting without the brake pedal being pressed by the driver (which they must do above a legally mandated decel level by law during regen). They didn't want that.

That's it. That's the whole "technical" reasoning. The efficiency thing is just a post hoc justification they came out with much later after everyone citicised the poor brake pedal feel resulting from their overly complicated "engineering" (see brake light idiocy) design giving regen based on intial dead pedal travel. Resulting in poor brake pedal feel and no OPD. Worst of both worlds and a much more complicated design. I worked with that system with Bosch. Complex is the word especially from a FuSa pov.

But this is a Porsche - the most driver centric car there is - so there should be at least an one mode with an OPD option to keep experienced EV drivers happy rather than trying to emulate an ICE car in all its modes to keep its EV learner drivers and ICE drivers happy. Absolutely not every mode but at least one option in normal or range.

And it's clearly having no effect on efficiency as even when driven like Miss Daisy, the Turbo S has laughably bad efficiency.

Ho Hum. Every car has its irritations and this is a big one for me on the Taycan after the hopeless (<200 miles) range. But I bought it eyes open knowing it was a great car but a woeful EV. That's why I still have the ancient old Model S which is a great EV but flaky car.

But there really is no actual engineering justification given good driving.

PS Since you like the F1 card I spent 10 years leading the development of KERs and ERS at Mercedes so don't need lectures on how things work.

Literally the only point I have made in this whole discussion is that 1 pedal driving is not fundamentally more efficient than 2 pedal driving as long as the brake pedal is regenerative.
Is this wrong?

I like my car as it is. You clearly don't, but preference was never my point.

If you wish to talk preference I would have no objection to Porsche adding a one-pedal mode as long as it is additional and doesn't replace any of the current modes. I would not use it myself.

I suspect the Porsche poor efficiency is due to the duty cycle they chose being nowhere near needed for typical road car use.

On a change of subject what do you think of the loss of the MGU-H for 2026 F1 engine rules?

 

[F1Ruaraidh]

Literally the only point I have made in this whole discussion is that 1 pedal driving is not fundamentally more efficient than 2 pedal driving as long as the brake pedal is regenerative.
Is this wrong?

I like my car as it is. You clearly don't, but preference was never my point.

If you wish to talk preference I would have no objection to Porsche adding a one-pedal mode as long as it is additional and doesn't replace any of the current modes. I would not use it myself.

I suspect the Porsche poor efficiency is due to the duty cycle they chose being nowhere near needed for typical road car use.

On a change of subject what do you think of the loss of the MGU-H for 2026 F1 engine rules?

There we agree. It's about preference that's all.

I just feel a Porsche - above all things a drivers car - should cater to all drivers, not impose some daft "brand value" for an area they've never operated in before.

Definitely all about personal preference, not engineering.

Agree on duty cycle entirely.

2026 again was a political, not engineering decision. Was at Applied when we did the consulting report on H removal for FOM way back in 2018. It was clearly going to have a very big effect and they've gone along with some of our recommendations though not all. To adequately balance H removal, it really needed a 350kW K at the front too a la FE as well as at the rear. It's not got that so pace will suffer as a result. What we have now is a big 2009 KERS.

The art will be in deploying PTH as antilag among other things.

The arguments around H in F1 have sadly been asinine (Porsche didn't want H despite developing one for Endurance and then, having got that rule change didn't enter anyway - give me strength) and was not helped by arguments about noise which was actually more a case not wanting to properly mike the tracks for sound rather than only having mikes on the cameras. H does reduce sound but also does so much more than that but we don't hear about it as too many commentators are ex-drivers..

Meanwhile H generates power of a family car the whole length of the straight, gives laundering mode, qually mode, anti lag, boost control and a host of other features that are now lost or will have to be replaced.

Did talk about some of this stuff on an F1TV slot with Scarbs last year

Ho hum. The art, as ever in F1, will be making the best of the reg changes before everyone else especially given the big staff changes at companies on the engine side.

25 will be fun and 26 even more so. Great stuff. I'm having a powertrain break for the first time in 30 years and doing active suspension instead. Always a school day.

 

[f1eng]

Meanwhile H generates power of a family car the whole length of the straight, gives laundering mode, qually mode, anti lag, boost control and a host of other features that are now lost or will have to be replaced/lost.

Ho hum. The art, as ever in F1, will be making the best of the reg changes before everyone else especially given the big staff changes at companies on the engine side.

25 will be fun and 26 even more so. Great stuff. I'm having a powertrain break for the first time in 30 years and doing active suspension instead. Always a school day.

I had a chat with it with Pat Symmonds at Ross's 70th do and he said it was mainly Porsche and Renault who were against and, of course, only 4wd makes sense for maximum braking recovery and some teams don't want that either.

Ironically afaik the only road car with MGU-H is the new Porsche 911 GTS. I was told it was too expensive to mass produce for production cars because of the rpm and heat resistance needed.
I was interested because it was the only way of charging the battery over a long period, and as you will know the braking period is very short.

I developed active suspension entirely to control the aero platform and it was a big gain almost 40 years ago. Still no longer permitted in F1 I thought?

 

[F1Ruaraidh]

AMGs have H on all 45s for a long while now and Audi have had eboosters since 2016. It's pretty commoditised tech now with multiple Tier ones active in that space.

No active not allowed in F1 but happening widely in high end road cars now.

 

[f1eng]

AMGs have H on all 45s for a long while now

Excellent, I had not realised!
They probably work really well then lag-wise.

 

[tigerbalm]

The only point is and was that regeneration is NEVER as efficient as coasting, however it is achieved since regeneration is less than 100% efficient. Simple.

Wait ... are you saying that my perpetual motion machine isn't efficient ?

 

[tigerbalm]

I like my car as it is. You clearly don't, but preference was never my point.

Agreed.

We've had a few EV's as our second car: Peugeot 206, Fiat 500EV, etc. One criteria for all of them is that coasting is possible in them and one-pedal driving is not enforced (and preferable is not the default mode).

 

[F1Ruaraidh]

Agreed.

We've had a few EV's as our second car: Peugeot 206, Fiat 500EV, etc. One criteria for all of them is that coasting is possible in them and one-pedal driving is not enforced (and preferable is not the default mode).

Yep exact opposite this end.

Probably because I've had EVs as my primary car for 6 years and the Taycan is a second car

If there was a OPD option on the Taycan, even if it had to be selected every drive, I'd be quite happy.

 

[Scandinavian]

Yep exact opposite this end.

Probably because I've had EVs as my primary car for 6 years and the Taycan is a second car

If there was a OPD option on the Taycan, even if it had to be selected every drive, I'd be quite happy.

I am quite happy with the way the Porsche is designed and implemented.

But I can also see that it will be desirable to have the options to engage no recuperation, little , medium and strong, as well as adaptive like the auto setting.

I live at 550 m above sea level and often go down to the coast. Driving down for about 15 km, I can have a higher SoC down there as when I started! Consumption can be indicated as negative in the town at the coast. With the Taycan I can either dab the brakes most of the time to slowdown to speed limit 50 km/h or engage the ACC speed settings. It will the recuperate energy nicely.

Our BMW i4 has brake recuperation blended as the Taycan, but it also has a few extra settings.
’I can engage strong brake recup and it is then a OPD car called B (brake?) setting.
Or I can engage D drive mode and then choose level of recuperation. None =coasting, light = lift off, medium slightly stronger and then strong = OPD. Or I can set it to adaptive. At that setting it will coast, but if there is slower traffic ahead it will slow down as with ACC. And it works really well, if you want it.

It is quite useful to easily switch between town driving in start stop and long motorway stints.

I guess my brake lights turn on and off more frequently with the strong recuperation setting, but it feels great.

And the car is only rear wheel drive so not as powerful recuperation as if it had been as a 4WD.

To me this is a great implementation by BMW and you can then set the preference as you like.

But of course this would be Software, which is not a Porsche speciality.

In the cooler part of the year the recuperation going down to sea level helps heating up the battery ata low penalty in consumption. Of course climbing back up takes a lot of energy, but my average has been surprisingly good

 

[f1eng]

Of course one pedal driving with lift off regeneration and friction brakes is the cheapest and both mechanically and electrically the easiest to implement, so was the early solution naturally enough.

 

[Jhenson29]

And it's clearly having no effect on efficiency as even when driven like Miss Daisy, the Turbo S has laughably bad efficiency.

You can’t take one difference between two systems with many differences and draw conclusions on its utility by comparing the systems as a whole.

 

[F1Ruaraidh]

You can’t take one difference between two systems with many differences and draw conclusions on its utility by comparing the systems as a whole.

Obviously.

I should have put a winky face after it to show it was a joke. Clearly the Miss Daisy comment was insufficient....

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