RWD Power/Weight vs Accel Anomoly

[whitex]

Oh, you don't have to be in England to not have any interest in drag racing from stoplights, I know I don't, It is a good way to get unwanted attention, can be dangerous, etc. About the only time I step on it from a traffic light is when I'm on my MC and that is as much about self-preservation as anything else.

The primary reason I accelerate from the lights is to get away from the crowd who like to drive like a heard of cows, with a couple of people driving side by side 5-10 under the speed limit, and the herd on their bumpers. Sometimes I catch the previous green wave like that, but primarily I just prefer to not be boxed in on all sides when I drive. I do it on a highways too, accelerate until I'm in a clear, then slow down so I don't end up in the herd in front of me.

P.S. In Arizona (USA) there is a two-second delay between when your light turns red and the opposite direction turns green. You wouldn't believe how many Arizona drivers are time-challenged and zoom through a red light. Stepping on it when your light turns green is a good way to get t-boned.

Sounds like you guys need a few well placed red-light-cams. People learn quick after a few tickets. Of course, it's important that the government doesn't try to turn it into a profit center, like they did in a few places where once people stopped running red lights, they started decreasing the time from yellow to red down to as low as half a second in Chicago IIRC.

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[Gwaihir]

I don’t think PWR is the primary factor for EV performance. The larger battery capacity allows more electrons to flow out in a given period of time, creating more power. PWR is secondary to this part of the equation.

With that said, I also think there are some software shenanigans for the base models, as I expressed in a thread about launching the CT4.

It’s also worth noting that the larger battery is also generating a higher voltage so all is then delivering power at a lower current, hence less losses.

 

[Ambroos]

I wonder how much of the power reduction is to stop the rear wheels from losing traction. I think the Taycan 4 is being even more artificially limited than the RWD.

I also have a feeling they're leaving room for a Taycan S at some point, RWD but with the full power potential unlocked. (Wouldn't it be fun if they offered that upgrade as a Function On Demand...)

 

[Taytayshayshay]

I wonder how much of the power reduction is to stop the rear wheels from losing traction. I think the Taycan 4 is being even more artificially limited than the RWD.

I also have a feeling they're leaving room for a Taycan S at some point, RWD but with the full power potential unlocked. (Wouldn't it be fun if they offered that upgrade as a Function On Demand...)

I doubt it would come from Porsche, but I wonder how long before a tuner figures out how to do it, without bricking the car. Not sure how the code is written obviously, but it seems more invasive than the traditional ECU tuner flashes in ICE cars.

 

[Fish Fingers]

I wonder how much of the power reduction is to stop the rear wheels from losing traction. I think the Taycan 4 is being even more artificially limited than the RWD.

That would actually make sense.

It is the very first few feet off the line that feels sluggish in my RWD - as others have also commented on.

Once it's away, it's fine.

But I do still get some wheelspin in the wet from a standing start.

I had just assumed it was getting that much weight moving from a standing start that slowed it off the line.

 

[f1eng]

I wonder how much of the power reduction is to stop the rear wheels from losing traction. I think the Taycan 4 is being even more artificially limited than the RWD.

I also have a feeling they're leaving room for a Taycan S at some point, RWD but with the full power potential unlocked. (Wouldn't it be fun if they offered that upgrade as a Function On Demand...)

I have an older Ferrari with no driver aids. It is 2WD, of course, and nominaaly 380 bhp iirc. It is on Pirelli P Zero tyres and is traction limited all the way through first gear if I break traction from standstill.
Almost all cars have some sort of traction or stability control electronics these days, and quite a few even still have some control even when this is nominally switched "off".
My guess is that the RWD Taycan will be grip limited on initial traction, so any limit set in the electronics will be to limit overspeed of the rear tyres to a few percent.
Almost certainly the best way to improve the launch time on the RWD will be wider rear tyres.

 

[whitex]

I also have a feeling they're leaving room for a Taycan S at some point, RWD but with the full power potential unlocked. (Wouldn't it be fun if they offered that upgrade as a Function On Demand...)

If they learn from other manufacturers, they will never offer it via FOD. Tesla had experimented with that and sadly it was a PR disaster every time. In couple instances they sold larger batteries which you could unlock over the air, and in another instance another the initial Model 3's all came with performance drivetrain but software limited for those who purchased lowered trims. The public outcry of "I own the damned hardware, how dare they limit my battery or performance, it costs them nothing to unlock it" was enough for Tesla to stop offering this. I remember reading about a Tesla owners club even picketing a service center once. Tesla stopped selling software limited batteries and redesigned the Model 3 drivetrain with less capable wires which could not handle the high loads of a performance spec, so that people would stop complaining.

There was an example in the media recently where a person bought an Audi, but didn't pay for tri-zone climate control. The car came with all the hardware for tri-zone climate control, including a physical "sync" button (instead of a blank) on the dash which, when pressed, popped up a message saying tri-zone feature is not purchased. Oh the public complaining that spawned, and a bunch of internet "news" stories on how horrible Audi is. 5.9K comments on this on redit alone!



That's what Audi gets for giving customers free hardware and an ability to upgrade functionality instantly at a later time for a cheaper price than a retrofit would cost. The added revenue from a power upgrade for a Taycan RWD would not offset the bad press, headlines like "Porsche cripples cars so they can gouge owners for a fix over the air after delivery", etc. That's why we can't have nice things - entitled people.

 

[whitex]

I doubt it would come from Porsche, but I wonder how long before a tuner figures out how to do it, without bricking the car. Not sure how the code is written obviously, but it seems more invasive than the traditional ECU tuner flashes in ICE cars.

That depends on the level of security Porsche and their suppliers apply to their designs. I work with car manufacturers, and you can absolutely design cars which would be extremely difficult to hack, but that costs extra resources (design, test, maintenance, more complicated field service, etc). Different manufacturers place different value on these things, however if there is potential lost revenue stream, they are willing to spend more to secure the designs. Teslas used to be more "tunable" than they are now, and they are getting even more secured as time goes by. I suspect Porsche today is still hackable. Of course one problem is, if you push the battery or motors beyond their spec, you may end up with a dead car. I would not be surprised if the RWD came with a lower rated pyro fuse inside the battery, which would blow if you hacked the computer to tell the motors to draw more power. That would render the HV battery dead. Even Tesla did that for a bit. I had one of my Model S max power upgraded by Tesla. That upgrade included software plus a higher rated pyro fuse (which required the battery to be drained, removed, opened up, and pyro-fuse to be replaced - a multi-hour job).

 

[jasperp]

Quite a few reviewers have noted that there's not an initial shove in the RWD you get from EVs, but that it builds pretty quickly afterwards, or even once on the move for passing power.

I can confirm that. My tesla has similar 0-100 km/u timing. And has the same feeling of acceleration. Except for the first half a second. The Taycan does not give a very aggressive first push.
Especially because they introduced this silly 'press your two pedals to enable full motor power'-feature. Launch control is really the most idiotic feature you can design in an EV. That should be done in software. Maybe they should make that a FoD feature.

 

[W1NGE]

It’s also worth noting that the larger battery is also generating a higher voltage so all is then delivering power at a lower current, hence less losses.

Voltage differential is not that much - is it material, not sure?

 

[Jrkennedy37]

I would not be surprised if the RWD came with a lower rated pyro fuse inside the battery, which would blow if you hacked the computer to tell the motors to draw more power. That would render the HV battery dead. Even Tesla did that for a bit. I had one of my Model S max power upgraded by Tesla. That upgrade included software plus a higher rated pyro fuse (which required the battery to be drained, removed, opened up, and pyro-fuse to be replaced - a multi-hour job).

Super interesting. The fuses for the Taycan are housed in their own module - not sure if the part number for this module varies by trim level. Can report back on part # once my CT4 fuse module is replaced over the next couple weeks ?.

 

[whitex]

Super interesting. The fuses for the Taycan are housed in their own module - not sure if the part number for this module varies by trim level. Can report back on part # once my CT4 fuse module is replaced over the next couple weeks ?.

Yea, but is that module inside the battery (together with the cell modules)? It would seem odd to have the fuse outside of the battery. In a crash, the battery could short out before the fuse, which could be disastrous, even deadly.

 

[Jrkennedy37]

Yea, but is that module inside the battery (together with the cell modules)? It would seem odd to have the fuse outside of the battery. In a crash, the battery could short out before the fuse, which could be disastrous, even deadly.

Not sure. They said the wires between the module and HV battery also are being replaced.

 

[whitex]

Not sure. They said the wires between the module and HV battery also are being replaced.

Ok, I looked it up some more. There is a HV fuse inside the battery (800A) on the 2nd level where the three battery modules 18-20 reside. There are are 2 additional fuses, 350A each, between the battery and the front and rear contactors (1 each). Those fuse ratings are for a 2020 Turbo S. Others trims may be different.

 

[Avantgarde]

Interesting post.
According to Porsche the power to weight ratio is higher with the PB+ (attached 1).
And the RWD standard battery v PB+ stats are also an anomoly and discussed here previously.

According to those they both have the same 0-60 and similar 1/4 mile, yet the PB+ has faster mid range (attached 2 & 3).
Suggesting they launch the same, then the PB+ pulls away.....then loses it at the end.

?

Doesn't make sense apart from either software settings or false stats.

I've been thinking about this quite a bit (the 0-60, 1/4 mile and 0-99 anomaly you raise between PB and PB+)and I found the answer! and it is not an anomaly at all! Mind you it is not an intuitive one at first sight so listen to this carefully please: 1- We all know higher powered but heavier PB+ will increasingly have more benefit as speed builds up. This is by the simple fact that the at lower speeds horsepower is almost entirely fighting against the weight, as speed builds up wheel and air friction go up exponentially so the engine is now fighting a mix of weight and friction. Since friction is constant between PB and PB+ the importance of weight difference goes down with speed and higher HP trumps the less powerful engine. 2- Data supports this directional relationship, for the 0-124 mph run PB+ is 1.1 seconds faster than PB, the difference falls to 0.5 for the 0-99 mph run and finally falls to zero seconds for the 0-60 mph run. But what does that tell you? If you were to extrapolate the same logic you'd see PB is faster than PB+ 0 to 30 mph ! Porsche does not reveal this data but it has to be the case. 0-30 mph PB will be faster and 30-60 mph PB+ would be faster and things would even out at 60 mph. Now lets hold this thought as it will be relevant 3- When you look at the 1/4 mile time you automatically assume that 1/4 mile test is equivalent to something like a 0-110 mph test (based in interpolation between 0-99 and 0-124 times) except IT IS NOT! it is a DISTANCE time not TIME TO A SPECIFIC MPH, and when two vehicles have different acceleration curves, things turn funky in a distance race! 4- So looking at the same 13.7 sec 1/4 mile times you automatically assume PB and PB+ would have the same speed when they hit the 1/4 mile, but they won't! In reality based on the acceleration profiles we discussed, even though they will hit the distance mark at the same time PB+ will carry a higher speed at that point. BUT HOW? 5- We established that 0-30 PB will have to be faster which means when they start a standing race at second 2 or so, PB will have travelled farther. between 30-60 mph PB+ will close the SPEED GAP (careful though not the distance GAP yet) and by 5.1 seconds, both vehicles will be travelling at the same speed although at that point PB will still maintain the initial DISTANCE GAP it gained in the first 0-30. This is normal because during the first 5.1 seconds of the race PB+ never travelled at a faster speed than the PB. Starting from 60 mph PB+ will start closing the distance GAP as it will build speed quicker than the PB and somewhere around 110 miles of speed it will have fully closed the DISTANCE GAP but at that moment PB+ will be travelling at a higher speed than PB (well it has to, as that is the only way to close the GAP!) 6- Bottom line it is perfectly normal for PB+ to have faster 0-99 mph time but still hit 1/4 mile at around the same time with PB. This dynamic will be true in almost all cases where you compare a heavier vehicle with more power with a lighter vehicle with less power with a matching 0-60 time. Even though they have the same 0-60 time Lighter vehicle's speed curve will be more logaritmic (steep first with sharp decline in speed) vs the heavier car. Which means even with the same 0-60 times, the speeds at which heavier car physically catches the lighter car will be at a point higher than 60 mph. YES! I was so excited to discover this, hope it makes sense to you!

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