Electric torque vectoring a reason to be cheerful
Concerned about the tidal wave of electric performance cars? Well, it's definitely not all bad news...
I spent a full day this week behind the wheel of the Porsche Taycan 4S, although I can't tell you a great deal about the car. That's partly because I've signed an official-looking piece of paper agreeing not to until early next week, but also because I only drove it on snow covered roads in Finnish Lapland and on sheet ice at Porsche's experience centre up there in the Arctic Circle. You learn so little about a car on snow and ice that I couldn't shed a great deal of light on the entry-level Taycan even if I was allowed to.
But I can tell you about its trick torque vectoring capability. Like the Turbo and Turbo S, the 4S has pair of electric motors - one on each axle. On its prow it uses the same motor as the more expensive models, while at the rear you'll find a smaller one. That explains why, when the Turbo develops 680hp and the Turbo S 761hp, the 4S makes do with a frankly laughable 571hp (or 530hp if you don't specify Performance Battery Plus).
The active limited slip differential (PTV+) that is standard kit on range-topping Taycans is available optionally on the £83,367 base model. You'll need that in the back of your 4S if you want it to vector torque to the fullness of Porsche's capabilities, but even without it the Taycan will pull off stunts beyond the limit of adhesion that no conventional combustion engine machine with four-wheel drive could ever manage.
'Electric torque vectoring is faster to react and more precise than combustion engine torque vectoring,' says Taycan engineer, Christian Wolfsried. 'It's maybe ten times faster. But the big advantage is there's no physical connection between the front and rear axles. That means we can make the Taycan's front axle slip [or over-rotate] without the rear axle slipping. You can't do that on a conventional car with hang-on four-wheel drive; it's not physically possible.'
The significance of that? It means the Taycan can be chucked to a 90-degree angle in a corner and if the driver stands on the accelerator pedal hard enough, it'll be pulled back into line. The torque vectoring system will cut drive to the rear end and spin the front motor up as forcefully as possible, dragging the car straight. Try the same in a Panamera, for instance, and the rear axle will have to slip in order to make the front over-rotate, meaning the car probably won't exit the corner pointing in the right direction.
So with electric torque vectoring, you can save much bigger slides than with the conventional kind. Wolfsried ably demonstrated this point by taking me for a pre-dinner dash through the pitch black woods in a Taycan Turbo S with studded tyres. On the little wriggly road that ducked and weaved between the pines, he flung the car to hilarious angles of drift and brought it back into line using that unusual torque vectoring capability.
Of course, a Panamera with its interconnected axles and intelligent four-wheel drive system can send the fullness of its power to either end, whereas a car with two disconnected power units, such as the Taycan, can only ever distribute so much to a given axle. But there's no torque curve to worry about on the Taycan and you'd never need more than one motor's worth of shove to make the car dance balletically.
When an electric car has one motor for each wheel, it can be made to do really extraordinary things. I once watched an Audi RS3 kitted out with four Formula E motors perform donuts on the spot without travelling an inch in any direction. It was effectively spinning like a tank, its tracks pulling in opposite directions. I've also driven the Rimac Concept One as well as the company's Pikes Peak racer, both of which used one motor per wheel. The hillclimb car weighed around 1500kg and the Concept One significantly more than that, but with Rimac's All-Wheel Torque Vectoring activated, both were as agile as cars weighing not much more than a tonne. They also had an amazingly positive way of getting from the apex of a corner to the exit, as though they were being yanked through on a wire. I haven't felt anything remotely like it in a car with a combustion engine.
Electric torque vectoring is exactly what gives me hope - even if only a glimmer of it - that the forthcoming generation of electric sports cars might actually be interesting to drive, rather than just unsettlingly fast. Of course, rescuing 90-degree drifts on an ice driving course, or spinning on the spot, is all well and good. It's up to car manufacturers to find a way to harness this amazing technology to make cars fun on the road in a way that won't get you arrested. It surely isn't beyond them. I don't know if an electric sports car with very clever torque vectoring will ever be as rewarding to drive as one with a howling petrol engine and a manual transmission, but I can't wait to find out.
The reason you don't see any "series" hybrids (as they are properly known) in production is that they are the "worst of all worlds"
1) Cost. You need pretty much all the parts of the electric vehicle, and pretty much all the parts of the ICE powered one. Yes, you can get away with a smaller overall battery, but you still need a battery (because the generator cannot respond fast enough, and because you want to be able to regen, and an ICE generator does not make petrol if you drive it backwards!). So al lyou save is a little bit of battery size (which these days is increasingly cheap) but you need all the same support systems (battery cooling, battery management etc etc). The result is a VERY expensive car
2) Complexity. All hybrids are horendosuly complex things compared to a basic battery electric vehicle. Trying to package and optimise all those dissperate systems is difficult, takes a long time (expensive to develop) and leads to a myriad of failure cases.
3) Reliability. It's simple, for any given component reliability level, the more components you have, the more you are likely to fail overall. Like the space shuttle, that had a 99.999% reliability, wow, but unfortunately it had 100,000 or more components, meaning on any given flight, you could still expect 100 things to stop working!! Hybrids are a reliability knightmare
4) Efficency. It might not be intuitive, but in the real world, a series hybrid is not actually very efficient, because of the numerous energy conversion stages between the energy store and the wheels. Only under certain specific cases does the overall efficiency actually exceed that of a conventional ICE powertrain, and those cases do not make up the majority of useage cases. This is why hybrids also include a "direct drive" mode, where the engine (ICE) can mechanically drive the wheels, so energy flow is flywheel -> gearbox -> wheels, and not flywheel -> generator (AC) ->inverter (DC) ->inverter (AC)->motor->driveshaft->wheels! Something like a BMW i3 with the series hybrid capability (Range Extender), despite being a relaitvely light car, with a small (600cc) enigne, only returns around 45mpg in ReX mode! Which is comparatively terrible (especially as it does the equivalent of ~200 mpg in BeV mode...)
And as for mass/weight, a pure series hybrid is no lighter than a BeV for the same performance, because yes, you downsize the battery, saving perhaps as much as 400kg, but an engine, fuel system, cooling system, generator and inverter, exhaust system, intake system adds that right back in again and then some!
By comparison, to get more range from an BeV, all you do is add more battery, and as that battery is intrinsically a modular architecture, that's not actually that expensive, as you've already done all the work to develop those parts. With battery costs per kWh falling dramatically, there is simply no reason not to go full BeV, and that is exactly what we are seeing.
It just means the driver can do stupid things and the car will sort itself out.
As an aside there is a theory that electric cars are simpler, thus will be mroe reliable/cost less to maintain. I wonder if that holds true for this sort of system.
BEVs are on their way and we'll soon all be forced to buy one, but lets not fool ourselves.
Way back i the late 1990's and early 2000's when i worked at Prodive we developed the Active Torque Dynamics system used on the WRC cars, and we tried to make a road version available for passenger cars. The problem was, that whilst top flight rally and racing drivers can adapt to the car doing the torque distribution, normal drivers really struggled.
Firstly, what a normal driver does when the cars goes sideways is lifts off, unlike a motorsports driver, who knows / learns to keep some positive torque applied. And you can't move torque around if their isn't any to move
Secondly, what a normal driver does is instinctively turn the handwheel into the slide, to try to get the car to go where they want it too. However, due to a lack of experience and skill, they generally input far too big an input, which often results in a huge fishtalling moment as they try to then catch up with the car as it veers wildly down the road.
With full Torque Vectoring, what you must do is accelerate (apply positive torque) to maintain/regain stability, and to ensure you minimise the steering input, because the steering is being done by the torque vectoring an NOT by the direction the front wheels are pointing! Watch any WRC video, and see how the cars drift perfectly round the turns, yet the front wheels are pretty much inline with the cars centre line at all times!
If you lift off, bang on a load of steering then the vectoring electronics thinks "hey this driver really wants to turn" and simply spits the car off the road in the direction the driver has steered!!
One advantage of BeVs in terms of torque vectoring is the fact that they have equal torque ability in both quandrants, ie they can apply as much negative torque as positive torque, unlike an ICE, where the negative torque is only that furnished by friction and enigne pumping losses (typically only around 10% of peak positive torque). That means the Torque Vectoring system can now control vehicle attitude during decceleration rather than only under positive acceleration. This makes is MUCH more useful on a road car in the real world, with cars driven by Colin Smith rather than Coliin Mcrae ;-)
The advantage of a system that can provide a large positive stability is that the fundamental chassis settings can actually now be tuned towards more oversteer, ie to make the car feel more agile, and yet still have the safety net there to jump in an restore stability should the driver overcook things. In most cases, it is the rear axle lateral performance and rear tyre slip that dominates the feel of the car at the critical turn in point, ie when the driver first asks the car to start to change direction, as this is cruical for driver confidence, ie the car turns when they ask it too.
The real game changer is still yet to come, which is when the systems already know which way the road goes (camera's + mapping + peer2peer coms) and can pre-adapt the chassis to suit ;-)
https://twitter.com/TheDanProsser/status/106271741...
Perfect for those tricky turn arounds in the preschool mum-mele after dropping off Tarquin and Tiffany!
Way back i the late 1990's and early 2000's when i worked at Prodive we developed the Active Torque Dynamics system used on the WRC cars, and we tried to make a road version available for passenger cars. The problem was, that whilst top flight rally and racing drivers can adapt to the car doing the torque distribution, normal drivers really struggled.
Firstly, what a normal driver does when the cars goes sideways is lifts off, unlike a motorsports driver, who knows / learns to keep some positive torque applied. And you can't move torque around if their isn't any to move
Secondly, what a normal driver does is instinctively turn the handwheel into the slide, to try to get the car to go where they want it too. However, due to a lack of experience and skill, they generally input far too big an input, which often results in a huge fishtalling moment as they try to then catch up with the car as it veers wildly down the road.
With full Torque Vectoring, what you must do is accelerate (apply positive torque) to maintain/regain stability, and to ensure you minimise the steering input, because the steering is being done by the torque vectoring an NOT by the direction the front wheels are pointing! Watch any WRC video, and see how the cars drift perfectly round the turns, yet the front wheels are pretty much inline with the cars centre line at all times!
If you lift off, bang on a load of steering then the vectoring electronics thinks "hey this driver really wants to turn" and simply spits the car off the road in the direction the driver has steered!!
One advantage of BeVs in terms of torque vectoring is the fact that they have equal torque ability in both quandrants, ie they can apply as much negative torque as positive torque, unlike an ICE, where the negative torque is only that furnished by friction and enigne pumping losses (typically only around 10% of peak positive torque). That means the Torque Vectoring system can now control vehicle attitude during decceleration rather than only under positive acceleration. This makes is MUCH more useful on a road car in the real world, with cars driven by Colin Smith rather than Coliin Mcrae ;-)
The advantage of a system that can provide a large positive stability is that the fundamental chassis settings can actually now be tuned towards more oversteer, ie to make the car feel more agile, and yet still have the safety net there to jump in an restore stability should the driver overcook things. In most cases, it is the rear axle lateral performance and rear tyre slip that dominates the feel of the car at the critical turn in point, ie when the driver first asks the car to start to change direction, as this is cruical for driver confidence, ie the car turns when they ask it too.
The real game changer is still yet to come, which is when the systems already know which way the road goes (camera's + mapping + peer2peer coms) and can pre-adapt the chassis to suit ;-)
Will they be able to apply negative torque to one wheel and positive to the other to rotate the car?
Gassing Station | General Gassing | Top of Page | What's New | My Stuff