Hydraulic Steering?
Discussion
Not Porsche, but an interesting view of why BMW steering isn't as 'good' as it used to be-
https://blog.caranddriver.com/steer-me-feel-me-exp...
TL:DR Core customers prefer isolated steering.
You might as well ask why Porsche still don't do an affordable 911 that is a real sports car as opposed to the GT it has turned into. I've been doing some research into 911s recently and it seems people have been bemoaning the loss of the raw feeeling of the car since it went water cooled. At the same time it is acknowledged that it has also become a technically much better car.
https://blog.caranddriver.com/steer-me-feel-me-exp...
TL:DR Core customers prefer isolated steering.
You might as well ask why Porsche still don't do an affordable 911 that is a real sports car as opposed to the GT it has turned into. I've been doing some research into 911s recently and it seems people have been bemoaning the loss of the raw feeeling of the car since it went water cooled. At the same time it is acknowledged that it has also become a technically much better car.
Fuel economy/emissions. With a hydraulic system the pump is constantly driven, wasting fuel. It's also wasting power, so EPAS is much more suitable for sports cars. 
It's the same reason many alternators are now fitted with a clutch so they're only driven when necessary.
I don't know why people want the return of hydraulic systems - everyone used to complain about them! Anyway, with modern suspension geometry and big wheels/tyres a car would be almost undriveable without some sort of power steering.
What I DO want is a manual handbrake. Can't stand these electric things.
It's the same reason many alternators are now fitted with a clutch so they're only driven when necessary.
I don't know why people want the return of hydraulic systems - everyone used to complain about them! Anyway, with modern suspension geometry and big wheels/tyres a car would be almost undriveable without some sort of power steering.
What I DO want is a manual handbrake. Can't stand these electric things.
rockin said:
Fuel economy/emissions. With a hydraulic system the pump is constantly driven, wasting fuel. It's also wasting power, so EPAS is much more suitable for sports cars.
EPAS still draws power from the engine to provide the electrical assitance though; proper sports cars have unassisted steering. 
Dr Interceptor said:
...and it can be integrated easily with driver aids.
^ This bit, with bells on.Wasn't there something on here recently about the Jag XJ, and how it'd only be getting whichever alphabetti spaghetti once it'd gone to EPAS from hydraulic? Might have been semi-autonomy, can't remember.
kambites said:
EPAS still draws power from the engine to provide the electrical assitance though; proper sports cars have unassisted steering.
There is no reason why EPAS couldn't be better than hydraulic, but most people don't want much feedback and designing it to be adjustable is expensive for the few who do want to feel what is happening. Wider, low profile tyres don't help either, but they go with the heavier, safer, gadget filled, more powerful and faster cars customers demand.
Toltec said:
There is no reason why EPAS couldn't be better than hydraulic, but most people don't want much feedback and designing it to be adjustable is expensive for the few who do want to feel what is happening. Wider, low profile tyres don't help either, but they go with the heavier, safer, gadget filled, more powerful and faster cars customers demand.
EPAS can be tuned to equal the feel and weIght of HPAS, but OEMs insist on giving the stupid light lifeless feel.
Having driven a car with a system tuned by an actual steering engineer it actually feels very good.
HPAS is being completly ruled out from the major OEM players as the constant hunt for less and less co2 from the engine driving the hyd pump, as well as the environmental impact from disposing of hydraulic fluid at end of life.
The size of pump needed these days with large cross section tyres would be rather large and destroy any hope of acceptable emissions, Also the race for auto driving from the OEMs would also rule any HPAS featuring.
Best bet get a car without any or put up with it, it’s here to stay :-)
Interesting, from the experience I've had with all 3, I've found unassisted is a bit of a ball ache until you learn to drive around it, I found cars with EPAS just too disconnected and light, the sweet spot for me was on the 00's cars with PAS, the E46, E60, Focus, Ka/Fiesta and cars of the like. I've never driven any new hot hatch, although I've driven the 340i which suffers from horrid steering, it's so artificial, light and disconnected that it isn't that enjoyable in the corners for me.
Icehanger said:
This with bells on!
EPAS can be tuned to equal the feel and weIght of HPAS, but OEMs insist on giving the stupid light lifeless feel.
Having driven a car with a system tuned by an actual steering engineer it actually feels very good.
Weight maybe, at some fixed points, but EPAS can never have the natural, progressive feel of a hydraulic rack, purely because of the physics. I don't doubt that it can get close, but to a keen driver I don't think it can cut it.EPAS can be tuned to equal the feel and weIght of HPAS, but OEMs insist on giving the stupid light lifeless feel.
Having driven a car with a system tuned by an actual steering engineer it actually feels very good.
Willy Nilly said:
I can't see how electric steering can make a jot of difference to steering feel
Er, it can, and it does!With hydraulic steering, there is a small hydraulic ram mounted concentrically to the rack bar, and as the rack moves left / right it moves with it.
Connected to the (rotating) steering column is an OPEN SPOOL (and that bit's important) proportional valve. When you apply torque to the handwheel, the rotary valve, which has a small torsion bar in it it) deflects, and opens up the ports to the cylinder, allowing oil pressure to be applied to one side of the ram. The more torque you put in, the more pressure is applied. The clever bit is two fold. When the rack moves, the torque falls, meaning the torsion bar twist automatically reduces, and so assistance pressure tails off, unless you keep moving the handwheel as the rack actually moves. But because it is an open spool valve, no system pressure is built up when you are not applying torque to the handwheel, hence the rack ism broadly speaking, pretty free to move, with just a small amount of damping from having to pump the hydraulic fluid out of the ram.
EPAS is very different. A large electric motor is geared directly to the rack, with a reasonably high gear ratio. That means as the rack moves, even a tiny amount, the motor must rotate. So what you say, well, the motors rotating inertia is referenced to the rack via the gear ratio, so that inertia appears to be large, meaning there is a large damping force resisting free movement of the rack. Early systems, with big motors and low power struggled to control their own inertia, leading to flat, lifeless steering feel. Later EPAS systems, with much more power and much smarter control electronics can now negate their own inertia (by applying electric power to spin up the motor at the same speed the rack is moving, so the motor doesn't act as a damper to free movement
Worth noting that the other reason for near universal EPAS is that it makes the engine FEAD simpler, is cheaper, removes a service requirement and a failure mode (no fluid to leak with EPAS), makes the car quicker to build on the line (system doesn't have to be filled, bled and with the pump on the engine and the rack on the body HPAS is a real pita come stuff up time on the line), and allows different tunings between models and modes with the same hardware spec.
DoubleD said:
What is there to like or dislike about a handbrake?
Electric systems,- No "just on" position
- No control over release. Often slow to release.
- Brake switch in a different position in every car
- Some switches push to apply brake, some switches pull to apply brake
- Some cars have a hold function, some don't. Many different hold systems
- Some cars have automatic hill hold, some don't. Rarely does hill hold manage to spot a hill.
- Can't release brakes without battery connected
- Can't release brakes with a flat battery.
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