RWD Power/Weight vs Accel Anomoly

[Avantgarde]

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 goes down with speed and higher HP trumps. 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 speed 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 profile even though they 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 slightly 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 somewhere around 110 miles of speed it will have fully closed the 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 the even with the same 0-60 times, the speeds at which heavier car 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!

If this is difficult to conceptualize, here is another way to think: PB and PB+ started the race at the same time, at 11.5 seconds, PB is travelling at 99 mph, PB+ at that point travelling at 102 mph but is physically behind PB, while approaching & making up the distance it lost in the first meters of the race. It will take another ~2 seconds for PB+ to physically catch (and pass) the PB. Actually as I think about this as a RWD PB+ owner who also tested a RWD PB I totally feel this. I did think 0-30 (slow) to 30-60 (fast) anomaly people are talking about was a lot more pronounced in the PB+ than PB. Data proves why. I still prefer the PB+ as higher speed elasticity is more important for my driving habits.

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[whan]

Hmm I think that may be some of it, although I'd still argue more of it is a combination of just Porsche choosing to publish the same numbers, and Porsche electronically limiting torque provided at launch

One thing to note is that the PB+ produces 263ft-lb of torque while the PB produces 254ft-lb per the spec sheet. That's a 3.5% increase in torque. The PB+ weighs 4742lb vs 4566lb for PB, which is 3.8% difference in weight. Because EVs (in theory) deliver peak torque at 0RPM, and HP linearly rises with RPM as a function of that peak torque until it hits peak HP, the PB+ should be producing 3.5% more power at low speeds for a given RPM. This should balance out the weight difference at low speed

Thus, in theory, the PB+ should be just as quick at low speeds (say 0-30mph) and faster thereafter per the HP increase (17% more peak and constant HP). It does appear actually in that table that Fish Fingers posted that the PB+ does a 13.5 quarter vs PB 13.7, so there have been some porsche documents that do show the PB+ being faster

Regarding 0-60, I strongly believe that Porsche artificially limits peak torque provided at 0 and low RPM in both the PB+ and PB RWD cars. Why? Because otherwise the Taycan RWD should in general be a much faster car 0-60 than it is. Looking at a Polestar 2 Dual Motor, this makes 487ft-lb of torque at the motor and weighs 4650lbs. But wait, it's geared at an 8.6:1 ratio, so to the wheels it makes 4188ft-lb of torque. The Taycan PBP+ makes 263ft-lb, but because it has a two speed gearbox, has a 15:1 1st gear ratio, and actually produces 3945ft-lb of torque to the wheels. Given the comparable weights and theoretical torque at wheels, and the fact that the Polestar makes less peak power at 408hp, the Taycan should be just as fast as the polestar in 0-60. But it's not, with the Taycan RWD only doing a 5.1 vs Polestar 4.6

The only conclusion IMO is that Porsche doesn't allow for peak torque at 0rpm, both for the PB+ and PB. This explains why reviewers like RBR on youtube notice that launch speeds feel sluggish, but higher speed power is strong. It's possible that Porsche is doing this because the RWD only has a rear driven axle to prevent traction loss, but I think they are gimping it even more than that, since almost no reviewers have been able to lose traction of the rear wheels on launch. The car should be able to launch much harder even with just RWD with the amount of torque it has and should be able to do a pretty big burnout on an uncontrolled launch. I think they are trying to get people to step up to the 4S. If the Taycan RWD did a 4.5 0-60 as it should based on specs, and the 4S did 3.8, I think a lot more people would take the RWD

Back to the question of PB+ vs PB, Porsche may be playing around and limiting the PB+ torque artificially even more so that 0-60 is the same as the PB.

 

[f1eng]

Regarding 0-60, I strongly believe that Porsche artificially limits peak torque provided at 0 and low RPM in both the PB+ and PB RWD cars. Why? Because otherwise the Taycan RWD should in general be a much faster car 0-60 than it is.

Don't forget traction.
a 4WD has better traction than a 2WD and initial launch acceleration is probably traction limited, yes electronically but not to artificially reduce the car's performance but to set optimum tyre over-rotation.
Porsche presumably quote the acceleration times with standard tyres and a significant proportion of the initial acceleration of the more expensive models will be the wider tyres.

It is pretty well sure the road tests of the 4S all show better 0-60 times than official figures since most test cars have 21" wheels not standard 19"
The rear tyres are 11% wider and the fronts 17% wider.
This will make a bigger difference to initial acceleration than motor parameters as long as the car is powerful enough to break traction on the smaller tyre.

 

[Pozuelo]

Don't forget traction.
a 4WD has better traction than a 2WD and initial launch acceleration is probably traction limited, yes electronically but not to artificially reduce the car's performance but to set optimum tyre over-rotation.
Porsche presumably quote the acceleration times with standard tyres and a significant proportion of the initial acceleration of the more expensive models will be the wider tyres.

It is pretty well sure the road tests of the 4S all show better 0-60 times than official figures since most test cars have 21" wheels not standard 19"
The rear tyres are 11% wider and the fronts 17% wider.
This will make a bigger difference to initial acceleration than motor parameters as long as the car is powerful enough to break traction on the smaller tyre.

Agree 100%.

 

[Avantgarde]

Hmm I think that may be some of it, although I'd still argue more of it is a combination of just Porsche choosing to publish the same numbers, and Porsche electronically limiting torque provided at launch

One thing to note is that the PB+ produces 263ft-lb of torque while the PB produces 254ft-lb per the spec sheet. That's a 3.5% increase in torque. The PB+ weighs 4742lb vs 4566lb for PB, which is 3.8% difference in weight. Because EVs (in theory) deliver peak torque at 0RPM, and HP linearly rises with RPM as a function of that peak torque until it hits peak HP, the PB+ should be producing 3.5% more power at low speeds for a given RPM. This should balance out the weight difference at low speed

Thus, in theory, the PB+ should be just as quick at low speeds (say 0-30mph) and faster thereafter per the HP increase (17% more peak and constant HP). It does appear actually in that table that Fish Fingers posted that the PB+ does a 13.5 quarter vs PB 13.7, so there have been some porsche documents that do show the PB+ being faster

Regarding 0-60, I strongly believe that Porsche artificially limits peak torque provided at 0 and low RPM in both the PB+ and PB RWD cars. Why? Because otherwise the Taycan RWD should in general be a much faster car 0-60 than it is. Looking at a Polestar 2 Dual Motor, this makes 487ft-lb of torque at the motor and weighs 4650lbs. But wait, it's geared at an 8.6:1 ratio, so to the wheels it makes 4188ft-lb of torque. The Taycan PBP+ makes 263ft-lb, but because it has a two speed gearbox, has a 15:1 1st gear ratio, and actually produces 3945ft-lb of torque to the wheels. Given the comparable weights and theoretical torque at wheels, and the fact that the Polestar makes less peak power at 408hp, the Taycan should be just as fast as the polestar in 0-60. But it's not, with the Taycan RWD only doing a 5.1 vs Polestar 4.6

The only conclusion IMO is that Porsche doesn't allow for peak torque at 0rpm, both for the PB+ and PB. This explains why reviewers like RBR on youtube notice that launch speeds feel sluggish, but higher speed power is strong. It's possible that Porsche is doing this because the RWD only has a rear driven axle to prevent traction loss, but I think they are gimping it even more than that, since almost no reviewers have been able to lose traction of the rear wheels on launch. The car should be able to launch much harder even with just RWD with the amount of torque it has and should be able to do a pretty big burnout on an uncontrolled launch. I think they are trying to get people to step up to the 4S. If the Taycan RWD did a 4.5 0-60 as it should based on specs, and the 4S did 3.8, I think a lot more people would take the RWD

Back to the question of PB+ vs PB, Porsche may be playing around and limiting the PB+ torque artificially even more so that 0-60 is the same as the PB.

I do see inconsistency in official 1/4 mile times. It is either quoted at 13.7 for both PB+ and PB or slightly faster at 13.5 sec for PB+. But even if you go with the latter, the difference is 0.2 sec compared to 0-99 difference of 0.5 sec. That would only happen if PB is losing some ground in the very first meters of the race. It is possible Porsche is more aggressively software-limiting top wheel torque for RWD vehicles at the very first seconds of a kick-off. But this may not be due to optical considerations only. There may be technical reasons as they may want to avoid repeated (albeit momentary) traction loss on every take off on RWD vehicles, which could cause excessively uneven tire wear (which will unavoidably happen to some extent in RWD versions) or put pressure on other drive train elements. So even if they are applying a constant torque limit (say a 250nm limit for the very first 1 second of the race) for both PB and PB+ that would create the impact i mentioned above, meaning PB will gain slight ground initially and PB+ will catchup after, and all the other times will make sense. What would not make sense to me is Porsche playing with official figures in an un-even fashion (eg engineer 0-60 times and 1/4 mile time but not the 0-99mph, or publish a slightly higher torque figure for PB+ but then actually limit it back) We all know Porsche is conservative with tech data, but I'd expect that conservatism to apply evenly across the board between PB and PB+.

 

[whan]

Don't forget traction.
a 4WD has better traction than a 2WD and initial launch acceleration is probably traction limited, yes electronically but not to artificially reduce the car's performance but to set optimum tyre over-rotation.
Porsche presumably quote the acceleration times with standard tyres and a significant proportion of the initial acceleration of the more expensive models will be the wider tyres.

It is pretty well sure the road tests of the 4S all show better 0-60 times than official figures since most test cars have 21" wheels not standard 19"
The rear tyres are 11% wider and the fronts 17% wider.
This will make a bigger difference to initial acceleration than motor parameters as long as the car is powerful enough to break traction on the smaller tyre.

I agree that traction is a part of it, but I still believe that the RWD should be able to pull out better 0-60 times with the power and torque it has. For example, a Dodge Challenger Scat Pack with 485hp can pull a 4.2-4.3 0-60, weighs 4,250lbs, and has 275 rears, which is the same as the 19 inch Taycan rear tire, and smaller than the 285s on the 20s and 305s on the 21s. The Taycan being a heavier vehicle and slightly rear biased weight distribution should be even less traction limited than the Scat pack. Porsche is indeed cutting torque at launch to prevent wheelspin, but likely overly aggressively as reviews have shown 0 wheelspin. In reality they're limiting torque to a sub-optimal level, as other RWD cars achieve faster launches with some limited amount of wheelspin.

This serves two purposes IMO: the first is to make the car more manageable and safe, and the second is to provide differentiation between the RWD and 4S. It's fairly common for manufacturers to software limit cars to preserve model lineup integrity. In Porsche's lineup, both the 2022 Macan S and GTS seem to have the same 2.9L V6TT yet the GTS makes significantly more power (118hp) due to just a tune. Apparently confirmed as well here on Rennlist https://www.macanforum.com/threads/engine-question-s-vs-gts.183678/page-2. I'd assume the same story with the Panamera 4 and 4S

 

[jasperp]

So the conclusions are:
1) You should take the PB+ for additional range. Not for additional performance.
2) Porsche is reducing the RWD performance in the software for marketing reasons.

 

[whan]

I do see inconsistency in official 1/4 mile times. It is either quoted at 13.7 for both PB+ and PB or slightly faster at 13.5 sec for PB+. But even if you go with the latter, the difference is 0.2 sec compared to 0-99 difference of 0.5 sec. That would only happen if PB is losing some ground in the very first meters of the race. It is possible Porsche is more aggressively software-limiting top wheel torque for RWD vehicles at the very first seconds of a kick-off. But this may not be due to optical considerations only. There may be technical reasons as they may want to avoid repeated (albeit momentary) traction loss on every take off on RWD vehicles, which could cause excessively uneven tire wear (which will unavoidably happen to some extent in RWD versions) or put pressure on other drive train elements. So even if they are applying a constant torque limit (say a 250nm limit for the very first 1 second of the race) for both PB and PB+ that would create the impact i mentioned above, meaning PB will gain slight ground initially and PB+ will catchup after, and all the other times will make sense. What would not make sense to me is Porsche playing with official figures in an un-even fashion (eg engineer 0-60 times and 1/4 mile time but not the 0-99mph, or publish a slightly higher torque figure for PB+ but then actually limit it back) We all know Porsche is conservative with tech data, but I'd expect that conservatism to apply evenly across the board between PB and PB+.

I do agree that what you're proposing with the limit being the same between PB and PB+ in the first second or two could very well be happening to end up with the same 0-60 times and helps explains the only 0.2 sec difference in 1/4 vs 0.5 in 0-99. That said, I do think Porsche is fudging around with the numbers a bit. The fact that there is an inconsistency between published documents in the quarter mile, with some showing 13.7 for both, and 13.5 for PB+ in others means that I think Porsche is aware of trying to maintain a perception that the PB+ and PB are similar in accel stats.

The software limitation in my mind is still just to maintain lineup integrity - I doubt they're worried about traction loss, tire wear or stress on other components and more about maintaining model lineup perception. It wouldn't make sense for a performance brand like Porsche to be worried about wheelspin/tire wear or have an ultra fragile drivetrain that couldn't handle it. Many other cars in Porsche's lineup allow aggressive launches with wheelspin, and stuff like the 911 Turbo S launched 50 times back to back without breakage - Porsche is almost famous for drivetrain durability.

Again, we do know that Porsche does care about making sure the higher trims are significantly better, both in real performance, and on paper than lower ones. I even wonder if the 1/4 mile time for the PB+ is even more conservative than usual. C&D did a 12.9s with a 0.3s rollout, so without rollout it'd be 13.2. That 13.2 vs the published PB of 13.7 would be equivalent to the 0.5 second difference 0-99 in published figures

 

[whan]

So the conclusions are:
1) You should take the PB+ for additional range. Not for additional performance.
2) Porsche is reducing the RWD performance in the software for marketing reasons.

2, yes at least it seems to be the case, unless Porsche discloses some technical reason why the RWD is too fragile to handle full torque on launch.

1, you should take the PB+ for additional performance as well. We know for sure at least it's faster above 50mph (first page has Porsche figures with 49-74mph faster by 0.3), and probably above 30mph as well. Pretty much it'll be faster anytime you're already moving at more than within city speeds. Only time it might be slower is 0-30, but this assumes that porsches 0-6] for both cars are accurate

 

[Avantgarde]

2, yes at least it seems to be the case, unless Porsche discloses some technical reason why the RWD is too fragile to handle full torque on launch.

1, you should take the PB+ for additional performance as well. We know for sure at least it's faster above 50mph (first page has Porsche figures with 49-74mph faster by 0.3), and probably above 30mph as well. Pretty much it'll be faster anytime you're already moving at more than within city speeds. Only time it might be slower is 0-30, but this assumes that porsches 0-6] for both cars are accurate

Driving both PB and PB+ I do think there is a noticeable performance difference 30mph and up. So it is range + performance. Also I think there is a battery longevity point to be made. With a larger battery you have more flexibility keeping it in the safe SOC window (30%-80%). Honestly I think price/value wise PBP is one of the cheapest options on the list all things considered. My build had a 3.2K premium paint and almost 7-8K for Mission E wheels and the mandatory PSCB upgrade that come with. I think those are insanely expensive options but I had to live with them to get the only brand new vehicle that I could find with PBP and 2+1 seats (both were musts for me) in dealers around me.

 

[f1eng]

I agree that traction is a part of it, but I still believe that the RWD should be able to pull out better 0-60 times with the power and torque it has. For example, a Dodge Challenger Scat Pack with 485hp can pull a 4.2-4.3 0-60, weighs 4,250lbs, and has 275 rears, which is the same as the 19 inch Taycan rear tire, and smaller than the 285s on the 20s and 305s on the 21s. The Taycan being a heavier vehicle and slightly rear biased weight distribution should be even less traction limited than the Scat pack. Porsche is indeed cutting torque at launch to prevent wheelspin, but likely overly aggressively as reviews have shown 0 wheelspin. In reality they're limiting torque to a sub-optimal level, as other RWD cars achieve faster launches with some limited amount of wheelspin.

This serves two purposes IMO: the first is to make the car more manageable and safe, and the second is to provide differentiation between the RWD and 4S. It's fairly common for manufacturers to software limit cars to preserve model lineup integrity. In Porsche's lineup, both the 2022 Macan S and GTS seem to have the same 2.9L V6TT yet the GTS makes significantly more power (118hp) due to just a tune. Apparently confirmed as well here on Rennlist https://www.macanforum.com/threads/engine-question-s-vs-gts.183678/page-2. I'd assume the same story with the Panamera 4 and 4S

The Dodge Challenger has no dealers here so we don't get any info about it. Also standing start acceleration isn't a parameter considered very important either because we don't have many multi-lane straight roads with frequent traffic lights so a "drag race" has never been a thing here.

In terms of wheelspin, apart from a burnout to get the tyre into a good temperature window wheelspin reduces acceleration. I only know this from work optimising the start of Formula 1 cars but I am sure it applies to all tyres, once the overspeed exceeds around 10% iirc the thrust starts to go down and acceleration gets worse.
Zero over-rotation gives zero thrust so we try to keep the over-rotation near optimum for best start.
Electronic control was banned a few years ago so the driver has to do a lot of practice

 

[Fish Fingers]

Driving both PB and PB+ I do think there is a noticeable performance difference 30mph and up. So it is range + performance. Also I think there is a battery longevity point to be made. With a larger battery you have more flexibility keeping it in the safe SOC window (30%-80%). Honestly I think price/value wise PBP is one of the cheapest options on the list all things considered. My build had a 3.2K premium paint and almost 7-8K for Mission E wheels and the mandatory PSCB upgrade that come with. I think those are insanely expensive options but I had to live with them to get the only brand new vehicle that I could find with PBP and 2+1 seats (both were musts for me) in dealers around me.

The real world driving difference is notable. I have just looked at the stats which show the 80-120kmh figures as follows:

RWD = 3.0s
RWD PB+ = 2.7s
4S (either battery) = 2.3s

If correct this would make 'overtaking' for the RWD PB in between the RWD and 4S.

That said, the RWD will be the lightest and may corner and handle better and be the purists choice.

Ideally someone would do a track test on two similarly specced RWD with each battery.

 

[f1eng]

The real world driving difference is notable. I have just looked at the stats which show the 80-120kmh figures as follows:

RWD = 3.0s
RWD PB+ = 2.7s
4S (either battery) = 2.3s

If correct this would make 'overtaking' for the RWD PB in between the RWD and 4S.

That said, the RWD will be the lightest and may corner and handle better and be the purists choice.

Ideally someone would do a track test on two similarly specced RWD with each battery.

The only concern I have with the RWD is braking regen which can (obviously) only happen on the rear wheels whereas weight transfer is onto the front so not sure the amount of energy recuperation will be available on it compared to the 4WD versions.

Personally I feel 4WD isn't worth the extra weight in IC engined cars here in the UK but really think it is better for an EV if only to optimally use potential regeneration efficiencies.

 

[jasperp]

The only concern I have with the RWD is braking regen which can (obviously) only happen on the rear wheels whereas weight transfer is onto the front so not sure the amount of energy recuperation will be available on it compared to the 4WD versions.

It sounds like a problem in theory. But in practice it does not seem a problem to only do regen on the rear wheels.
When I brake with my RWD in normal traffic, I do not feel it brakes with the rear wheels. It brakes like any other car.
The screen displays the recuperation energy. You can see when it passed the maximum level of recuperation. After that point it needs to do friction braking.
In normal traffic, you almost never pass the maximum. +90% of the braking is pure recuperation. In fact sometimes I look at it while braking to keep the power level low and spread over time to recupurate the maximum amount of energy.

So It looks like that in practice, in most cases, braking with the rear wheels works fine.

 

[whitex]

It sounds like a problem in theory. But in practice it does not seem a problem to only do regen on the rear wheels.
When I brake with my RWD in normal traffic, I do not feel it brakes with the rear wheels. It brakes like any other car.
The screen displays the recuperation energy. You can see when it passed the maximum level of recuperation. After that point it needs to do friction braking.
In normal traffic, you almost never pass the maximum. +90% of the braking is pure recuperation. In fact sometimes I look at it while braking to keep the power level low and spread over time to recupurate the maximum amount of energy.

So It looks like that in practice, in most cases, braking with the rear wheels works fine.

I can confirm that for regular commuting driving rear only regen can work very well. My first Tesla Model S was RWD and Tesla doesn't have blended braking, only the one-pedal-driving regen. I still managed to do most of my driving without touching the brake pedal. When I switched to AWD, regen felt almost the same for every day driving. The only time I noticed the difference was when the roads were slippery, there RWD regen could actually be dangerous on the curves, so when really bad I would turn off regen to avoid oversteer. Also note, Tesla regen is much weaker than Taycan (~60KW vs. up to 260KW).

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