Taycan efficiency vs VW ID7 … can it be true?

[Grim]

Have just been browsing through Apple News+ and came upon a Car review of an ID7 …

Not that interesting in itself but it quoted a range of 384 miles from its 77kWh battery which seemed a lot for a car that weighs 2,172kg per the article. This is equivalent of 5 miles per kWh! Initially I thought they had misquoted the numbers but the same info can be found on the VW website …

https://www.volkswagen.co.uk/en/electric-and-hybrid/electric-cars/id7.html

Any idea how this could be possible when a RWD Taycan with a 71kWh usable battery can only officially manage 276 miles or 3.9 miles per kWh with a lower Cd of 0.22 (compared to ID7’s 0.23), smaller front surface area as well as 5% lower weight (2,050kg)?

We know from experience that those quoted Porsche efficiency stats are very hard to hit (I’ve managed around 2.5 miles per kWh since August in a CT 4S and around a third of my driving is on a stretch of road with 60mph average speed cameras and it is a bit colder in Scotland so I have had the heater on and do pre-condition ahead of some fast DC charging) unless you are driving in nose to tail traffic at 40mph.

So are VW figures real or total pie in the sky? Am I comparing apples and oranges in terms of the bases used for ranges being quoted? A Tesla Model 3 claims to deliver up to 5.5 miles per kWh but it does weigh 400kgs less than the ID7 … and it’s not like Tesla hasn’t come under criticism for its quoted ranges either.

How far from a miss-selling scandal are we as far as advertised ranges for electric cars are concerned? Or have the manufacturers caveated things enough to get away with it?

A lot of questions, I know and mostly rhetorical - more food for thought than anything else.

 

[W1NGE]

Have just been browsing through Apple News+ and came upon a Car review of an ID7 …

Not that interesting in itself but it quoted a range of 384 miles from its 77kWh battery which seemed a lot for a car that weighs 2,172kg per the article. This is equivalent of 5 miles per kWh! Initially I thought they had misquoted the numbers but the same info can be found on the VW website …

https://www.volkswagen.co.uk/en/electric-and-hybrid/electric-cars/id7.html

Any idea how this could be possible when a RWD Taycan with a 71kWh usable battery can only officially manage 276 miles or 3.9 miles per kWh with a lower Cd of 0.22 (compared to ID7’s 0.23), smaller front surface area as well as 5% lower weight (2,050kg)?

We know from experience that those quoted Porsche efficiency stats are very hard to hit (I’ve managed around 2.5 miles per kWh since August in a CT 4S and around a third of my driving is on a stretch of road with 60mph average speed cameras and it is a bit colder in Scotland so I have had the heater on and do pre-condition ahead of some fast DC charging) unless you are driving in nose to tail traffic at 40mph.

So are VW figures real or total pie in the sky? Am I comparing apples and oranges in terms of the bases used for ranges being quoted? A Tesla Model 3 claims to deliver up to 5.5 miles per kWh but it does weigh 400kgs less than the ID7 … and it’s not like Tesla hasn’t come under criticism for its quoted ranges either.

How far from a miss-selling scandal are we as far as advertised ranges for electric cars are concerned? Or have the manufacturers caveated things enough to get away with it?

A lot of questions, I know and mostly rhetorical - more food for thought than anything else.

These will be WLTP (lab based numbers) which are as much use as a chocolate teapot and generally unobtainable in the real world.

Id 7 may have a single motor and or be much lower powered and so I would expect tis efficiency to be greater than the Taycan. May also have smaller wheels with better aero. These items and others can enhance range.

 

[Grim]

Didn’t think about wheels but its single motor was the reason I compared it to the RWD Taycan.

 

[ben1]

I can't speak about the ID.7, but it is clear that the Taycan drivetrains is very inefficient.
The Cw value is low, so we cannot blame bad aerodynamics.
Somehow the motor and invertor are not well engineered. Maybe it is the stupid 2-spead gearbox ?
Hopefully Porsche improves this for the new Macan and Cayman.

 

[f1eng]

I can't speak about the ID.7, but it is clear that the Taycan drivetrains is very inefficient.
The Cw value is low, so we cannot blame bad aerodynamics.
Somehow the motor and invertor are not well engineered. Maybe it is the stupid 2-spead gearbox ?
Hopefully Porsche improves this for the new Macan and Cayman.

The motors are, I believe, based on the racing design from the hybrid Le Mans 919 and for that high duty cycle keeping it cool enough under heavy usage was needed.
Producing super efficient motors with high short term power may well be a better choice for a road car where specs and "fuel consumption" are more important than maximum performance but there we are.
No idea about the inverter.
The 2 speed gearbox isn't stupid.

 

[Grim]

I guess trade offs have to be made.

Is there any loss of efficiency by using a gearbox - presumably very small losses due to additional friction vs being directly coupled?

 

[f1eng]

I guess trade offs have to be made.

Is there any loss of efficiency by using a gearbox - presumably very small losses due to additional friction vs being directly coupled?

No EV is directly coupled, the motor runs at far too high a speed for that to be feasible, so every EV has reduction gears between motor and differential.
It is unlikely the losses are different between the 2 ratios in the Taycan.
An electric motor has a much bigger power band than any IC engine, and works from zero rpm so needs neither a clutch nor a multi ratio gearbox but 1 ratio is a compromise and, obviously much cheaper to make. It is probably fine for most road car use too but for good performance on the autobahn it is good to have a higher ratio, most EVs run out of "puff" at high speed which in most countries won't be noticed.
In the end I think the Porsche design is less efficient than others because they majored on high performance. In retrospect it probably wasn't necessary because with road cars almost nobody ever goes anywhere near performance limits and most people will be more interested in range than keeping good performance in heavy usage simply because range is the buzz word for EVs and few people actually use their sports car performance hard.

 

[Jhenson29]

I can get up to 3.8mi/kwh in the summer. 3.5-3.6 fairly easily. This is looking at actual range and consumption, not just whatever mi/kwh the PCM spits out, which is as high as 4.1 for me.

As @f1eng point out, other EVs have gearboxes. The difference in the Taycan is a 2 speed gearbox on the rear and clutches.

There are electric motors that could be direct coupled. They typically have much higher pole counts and a larger diameter.

e.g.
https://www.celeramotion.com/zettle...pers/direct-drive-motors-frameless-resolvers/

But these aren’t used in any production cars that I’m aware of

 

[andb]

As seen on this test, the ID7 isn't that efficient compared to M3 or BYD.

 

[_Brian_]

Didn’t think about wheels but its single motor was the reason I compared it to the RWD Taycan.

Difference in wheel sizes between the cars can have a significant impact to KWH consumption. The Taycan has wider tires with a bigger 'footprint' on the pavement creating a larger 'rolling resistance'

 

[Jhenson29]

Difference in wheel sizes between the cars can have a significant impact to KWH consumption. The Taycan has wider tires with a bigger 'footprint' on the pavement creating a larger 'rolling resistance'

Differences in tires too. IIRC, @daveo4EV had a post about a large range drop switching from all seasons to summer tires. I think I’ve also read on here that all season tires aren’t as available in the UK and they mostly use summer tires. Someone else can confirm or correct that.

I run all seasons on my Macan and Taycan. Summer/winter on the 911.

 

[Bognar67]

No EV is directly coupled, the motor runs at far too high a speed for that to be feasible, so every EV has reduction gears between motor and differential.
It is unlikely the losses are different between the 2 ratios in the Taycan.
An electric motor has a much bigger power band than any IC engine, and works from zero rpm so needs neither a clutch nor a multi ratio gearbox but 1 ratio is a compromise and, obviously much cheaper to make. It is probably fine for most road car use too but for good performance on the autobahn it is good to have a higher ratio, most EVs run out of "puff" at high speed which in most countries won't be noticed.
In the end I think the Porsche design is less efficient than others because they majored on high performance. In retrospect it probably wasn't necessary because with road cars almost nobody ever goes anywhere near performance limits and most people will be more interested in range than keeping good performance in heavy usage simply because range is the buzz word for EVs and few people actually use their sports car performance hard.

I really enjoy the advantage of a 2-speed gearbox above of 110km/h when for example my TM3P starts to loose the acceleration dynamics. Taycan keeps up nicely and progressively, able to reproducing ICE style acceleration curve up to the high ends. For me it is key for a sports car being electric or not.
Traveling frequently to/via Germany + our local real (ticketing) speed limit is 150km/h so please do not touch it. Accelerating from 130km/h with a Taycan is still a joy, while 1-speed cars become degressive.
Yes, Taycan is using more energy for the same distance as VW, but honestly 911 is also uses more energy than an ICE VW.
This is a compromise we need to take for the special dynamics of a sports car independently ICE or electric.
For a sports car efficiency is not on the 1st priority, we need to understand it.

Finally comparing Taycan with ID7 is more or less useless in any aspect.
Actually I have never seen comparison between 911 vs Touareg on economy or anything else, although I understand that, Taycan is a Sport limousine not a 2-door sports car like 911.

 

[Jhenson29]

I really enjoy the advantage of a 2-speed gearbox above of 110km/h

I think the advantages are below, not above. 1st is the extra gear. Not 2nd. Anything in 2nd gear is how it would be as a single speed gearbox.

 

[Grim]

I think the advantages are below, not above. 1st is the extra gear. Not 2nd. Anything in 2nd gear is how it would be as a single speed gearbox.

Surely depends how the ratios are chosen? If the higher gear is the same ratio as on any other EV then the advantage would be largely restricted to lower speeds. If on the other hand the fact that the Taycan already has a lower gear means the 2nd gear is more optimised to higher speeds then surely there is a benefit there too vs a “compromise” gear that has to do it all?

 

[f1eng]

I think the advantages are below, not above. 1st is the extra gear. Not 2nd. Anything in 2nd gear is how it would be as a single speed gearbox.

I thought it was a bit of both, a split the difference design with low gear being a bit lower than average and the 2nd a bit longer so giving benefit at both low and high speeds.
The front motor is a similar compromise to everybody else’s.