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@ipse dixit I can't speak for everyone - but I'll do my best to explain my position regarding this range issue:
Historically the EPA numbers for an EV are aspirational in nature, and daily use is far less - therefore an EPA rating of 201 realistically would mean 160 miles daily driving range (since you typically only charge to 80-90% for battery longevity)
Cold weather is an additional 20-30% penalty so now your EPA 201 rated car which is really only 160 miles for daily use on a very cold day is really only 120 mile car - barely better than a Nissan leaf - it's fairly easy to come up with one day a week where you'll need 100 miles of driving range (2 hours of road driving at speed).
once you break the 200 mile barrier on the low end it's actually pretty easy to envision daily demands that come close to 150 miles necessary for daily use (in the SF Bay Area for example San Jose to SF, and then over to Oakland, and back to San Jose - could easily consume 150 miles or more…so now the car isn't that useful for a daily work load in most metropolitan areas
EV efficiency is also a proxy measurement for engineering aptitude - Porsche is supposedly a top top top best engineering group on the planet - given the relative inefficiency of their platform it does not shine a positive light on their engineering skills or their adaptation to this new world.
There are examples of existing EV's from multiple manufactures (not just Tesla) that are 20-40% more efficient that the Taycan - so it's not like it's an unrealistic expectation for Porsche/Taycan to be in the ball park of other EV's for it's relative efficiency - Taycan EV drive train is the LEAST efficient drive train on the market based on metrics
You can not blame the weight of Taycan - there are examples of heavier EV's (the Model X with worse aero dynamics) getting far better efficiency, and not just EPA numbers, but real world as well. So you have to conclude it's quite simply the EV drive train design from porsche that is simply consuming too many electrons - you can not explain it away by claiming it's a more luxurious and therefore heavier car
we also know the EV motor design itself is very efficient and there are examples of similar designs (ChevyBolt) that are efficient, - so the engineering question is -o where is all that power going, because again there are examples in production that are routinely dramatically more efficient - where is the power being "wasted" in Porsche's design?
Cost - quite simply other EV's are about $0.04/mile to drive, and the Taycan is going to be closer to $0.06-$0.09 mile a drive - it will simply cost more to drive this car over the life of ownership
Charging time - this cuts several ways - less efficient equals a longer overnight charging session (more cost)
while road tripping you are gaining fewer miles of driving range per-unit-time you are stopped at the charger
Porsche promised 300 miles driving range - the EPA numbers do not confirm that promise
you'll have stop more frequently and for longer charging sessions when road tripping the Taycan or take another more efficient vehicle. Again as a proxy/measure of industry standard expectations the Taycan's ability to be road tripped along with fast charging is negatively impacted by it's very very inefficient rating.
I expect better or at least equal from Porsche - they have missed expectations in this space.
The fact that its EPA-rated efficiency is the lowest of any EV yet rated/tested.
EPA-rated efficiency range is lower and EPA rated consumption is higher compared to other EVs. But these ratings don't say much about the efficiency of the drive train.
Several factors that can deviate EPA number from the drive train's efficiency:
- what compensation factor is used? Usually it's 70% of measured range but car makers may ask for different numbers.
- is the drive train tuned for sustained high power or good efficiency at low torque?
- how much additional content? electric sway bar control, luxury related accessories, HVAC with "luxury" specification
- does the car manufacturer provide realistic settings for the dyno? // why is Tesla's real world range so far from EPA range?
- does the car manufacturer implement some deep sleep mode for electronics to lower their consumption while on the dyno?
- wheel size
- eco tires?
- does the car manufacturer ask for higher tire pressure?
- what is the default setting for regen?
- EPA test cycle average speed is low, it doesn't say much about range at 75mph where it matters the most
- any tricks with the battery? Like offering 100% capacity when new and degrade it later over time as the vehicle ages?
- is there a bottom / top buffer in the battery? Bottom buffer is included in the results. Top buffer adds weight but it is not included in the results.
- weight of vehicle apart from battery cell energy density: different expectations for crash worthiness, weight of extra content
- EPA consumption might be adversely affected if the vehicle does additional activities while plugged into the charger, like preconditioning
- if it is AWD, is it permanent AWD or optimized RWD/FWD?
where is the power being "wasted" in Porsche's design?
for me this is perhaps the "key" issue - we know for example the Taycan is in fact the worse EV efficiency currently in production. What we don't know is why it's numbers are so low. Which means we can not have a rational conversation about what trade offs Porsche made which resulted in this level of efficiency.
1. We know it's not the weight - there are heavier EV's with better efficiencies
2. We know it's not the aero dynamics - Taycan has some of the best aero numbers on the market
3. We know it's not the EV motors (or can likely guess) - the EV motors "should" be very efficient given their similarity to other EV motors on the market which demonstrate greater efficiency
Not knowing why mean we can not have a rational conversation about what benefit we gain in exchange for the lower efficiency?
Is it Porsche's regen philosophy?
Is it the gear box?
Is it the cooling system design for repeatable performance?
Is it the 800 volt system for some reason?
Or is it just a death of a thousand cuts and there is no actual measurable benefit to the increased consumption and porsche brought the car "as is" to market "on time"
Is it something that can be "fixed" by driving style
Is it just a factor in the design that the EPA test unfairly emphasizes
Can it be improved with OTA updates, maybe they are just running the motors "wrong" and they could squeeze a 5% improvement with a software update
Is it the stereo?
Is it the car's screens?
Is it the HVAC system?
Is it the heated seats?
Is it the power steering system which porsche uses for that excellent road feel?
What are the trade offs for this lower efficiency? Or is it just pure waste because Porsche didn't have time to optimize the car?
Basically unless we know "why" the Taycan is less efficiency, we have no idea what we're gaining or losing for that level of inefficiency - it's certainly not the exhaust note
why is the Taycan so inefficient - and what design decisions did porsche commit to that makes it that way?
Why Porsche? Why is the Taycan taking 417 wh/mile on the EPA test when the Model S to achieve the same test only takes 300 wh/mile or 40% worse on the same test? 40%!!!!!
int he past I could explain away Porsche's less efficient ICE motors on "performance" - but it doesn't work that way in the EV world, it just quite simply un-necessary consumption
if I don't know why the Taycan is less efficient I can't defend it as having a rational trade off - it just appears to be "waste" rather than design....
let's say it's the gear box (hypothetically) that means would could have a conversation about the gear box and discuss/debate/argue as to if it's worth it to have that wonderful acceleration curve above legal speed limits, it also would mean their drive train isn't that inefficient, and simply removing the gear box in a future iteration would close some of the gap...that would be very very interesting to me.
but at the moment it appears they just suck at this - the Taycan is an out of hte park success in every dimension except two: price and expected efficiency - we know why it's priced the way it is, but we don't know why it's sooo inefficient - and that knaws at me.
Isn't that the cost for inefficiency when it comes to the Taycan?
it doesn't work that way in the EV world, there are only minor (fractional) penalties for carrying around a higher performance EV motor - there is much great $$$ cost (more copper and slight increase in weight for the EV motor) - but EV motors only use the power your request of them up to their performance limit - there is no "high performance" penalty if you aren't using "high performance" - there are only fractional differences between EV's of different performance levels - it's not like a turbo 4 vs. V8 where the V8 is just more costly even not being a "V8"…
Taycan's 40% short fall in efficiency can not be explained by greater performance - and Porsche to date certainly has not defended their efficiencies or provided for example a "that's the cost of doing business for a great EV" argument - rather they have taken a YMMV approach and produced multiple reports that show the can be slightly more efficiency depending on driving circumstances…
there is no reason for a Taycan @ 40 mph on a flat level road to consume dramatically more than a Model S/Bolt @ 40 mph on the same flat level road because of "performance" - you're not using the performance - the consumption should be very very close to the simple cost to move an object of that weight on those types of tires…
why is the Taycan 40% less efficient than a Tesla Model S? Performance isn't the answer - that's not the way it works, it's something else.
And an example for constant load from accessories:
From test results of multiple cars I calculated the average load of HVAC at 20F and 95F temperature.
On average (long drive) a PTC heater needs 4kW at 20F, heat pump averages at 2kW and A/C needs about 1kW to keep the cabin cool at 95F temperature.
The graph below shows the added consumption by the HVAC.
EPA city and highway test cycle average speed is about 18mph and 48mph respectively. Now let's say the electronics (not the HVAC but something that is always on) pull 1kW extra in the test. That will increase the EPA consumption by 56wh/mi*55%+21wh/mi*45% = 40Wh/mi. Add home charging efficiency (EPA includes this) > 40*1.12 = 45Wh/mi extra
it doesn't work that way in the EV world, there are only minor (fractional) penalties for carrying around a higher performance EV motor - there is much great $$$ cost (more copper and slight increase in weight for the EV motor) - but EV motors only use the power your request of them up to their performance limit - there is no "high performance" penalty if you aren't using "high performance" - there are only fractional differences between EV's of different performance levels - it's not like a turbo 4 vs. V8 where the V8 is just more costly even not being a "V8"…
Taycan's 40% short fall in efficiency can not be explained by greater performance - and Porsche to date certainly has not defended their efficiencies or provided for example a "that's the cost of doing business for a great EV" argument - rather they have taken a YMMV approach and produced multiple reports that show the can be slightly more efficiency depending on driving circumstances…
there is no reason for a Taycan @ 40 mph on a flat level road to consume dramatically more than a Model S/Bolt @ 40 mph on the same flat level road because of "performance" - you're not using the performance - the consumption should be very very close to the simple cost to move an object of that weight on those types of tires…
why is the Taycan 40% less efficient than a Tesla Model S? Performance isn't the answer - that's not the way it works, it's something else.
It is however partially the answer. Porsche says that in Range mode the cooling system is optimized for less consumption. That means in other modes cooling system is more active and expects some spirited driving.
Edit: one more thing Taycan is always in all wheel drive mode for performance. It switches to single motor mode occasionally only in Range mode.
01-15-2020, 03:52 PM
