Porsche and the death of steering feel
Why Porsche reckons electric steering hasn't ruined the 911 and feel and feedback are safe in its hands...
And now there's a new cause celebre - electric steering and the supposed death of our cherished feel'n'feedback. When even the new 911, and Boxster not long after, adopted EPAS a watershed passed.
A 997 and a twisty British backroad - perfect!
Time to wheel out those clichés because, as ever, the 997's wheel offers the kind of texture, feel and feedback that we'll apparently not be getting again from a Porsche steering wheel. It's the gentle murmurs and shimmies that tease your palms as the 911's nose arcs through the twists and turns of a classic, flowing piece of British backroad that, for many of us, make the whole Porsche experience so enriching.
Sprenger (second left) and the Porsche team
Figuring words like 'nuggety' and 'feelsome' won't cut much mustard with the Porsche boffins I arrive at Silverstone armed with a bit of inside intel from a friendly engineer, and readiness to demonstrate quite how dangerous a little knowledge can be. I've also courted PHers for some questions, Actus_Reus, Ian_UK1, RemarkLima and Fioran0 among those chipping in with questions for the boffins.
And after a couple of hours on the twisty little handling circuit at the Porsche Experience Centre in a succession of 991s and new Boxsters I corner Porsche's General Manager Chassis Development Suspension, Steering and Hydraulic Systems (snappy!) Florian Sprenger and ask him "why have you ruined the 911's steering?" OK, I put it a little more tactfully than that but, regardless, I'm not entirely surprised to discover he's prepared for this.
Proving a point, via the medium of 911s
So the engineers like it. And so do the bean counters. But since when have we wanted them to dictate how our 911s drive?
This is just the start
But there's a bigger picture here. Start-stop is in its infancy but likely to expand into engine-off coasting and the need to be hybrid ready means you need power steering that works whether the engine is on or not. Put simply, EPAS is something we're all going to have to get used to, like it or not.
Having accepted that future Porsches are all going to have EPAS how are they going to make sure they still offer the feel and feedback we're used to?
Porsche EPAS system designed with ZF
And it's here I enter shaky ground - briefed with my questions I sound (a bit) like I know what I'm talking about. But much as one could learn how to ask 'which way is it to Starbucks?' in Mandarin in no time at all it's naff-all use if you don't understand the answer.
Porsche's steering uses 'bottom up' control
Top down versus bottom up
And the inertia? "The mass of inertia is higher because you have this huge electric motor that you have to accelerate and decelerate," says Sprenger. "But with our controller, since we are controlling a direct force we are able to compensate; other systems are just tuned to fixed graphs and you always have this much assistance [whatever the circumstances] but we leave the amount of assistance open and control it through our rack force controller." He goes on to say many rival EPAS systems are 'top down', ie, the assistance is calculated through the input torque from the steering wheel. Porsche goes the other way - "bottom up" in Sprenger's words - and uses the wealth of data available through the CAN from steering angle, yaw rate and other information coming through the stability control sensors to vary the assistance and, therefore, 'weight' at the wheel. Developed with ZF, the hardware and basic principles - referred to jokingly as EPAS 2.0 - is something Porsche claims a head start in. ZF will sell it to other manufacturers but, of course, installation, suspension geometry and programming will vary from brand to brand. Fundamentally though it's still a technology in its relative infancy and there's still room for it to develop further.
"Try it on a racetrack" they said ... rude not to
So there's the why and how. The final bit, the bit that matters to the likes of us, is that less definable 'feel' thing. And in Porsche's EPAS system it IS contrived.
Imagine you were to keep adding steering lock during a constant radius turn with a conventional HPAS or non-assisted system. The rack force increases with lateral G and slip angle but tails off as the tyre runs out of grip - that sickening lightening at the wheel that tells you you're understeering. On its own an EPAS system doesn't recognise this. It simply says 'steering angle x, speed y, assistance force z' and can't 'read' that loss of grip, unless you tell it to. Which Porsche says it does, through that 'bottom up' system and a contrived reduction in rack force to simulate - yes, simulate - the sense of feedback at the wheel.
Artificial or not, on-limit feel is still there
Artificially enhanced
So 'feedback' is filtered out and 'feel' is artificially created. But does it matter? Sprenger and his colleagues say no. With a roll of the eyes they point to similar outcry at the introduction of power steering on the 964. "The steering should be in the background and it should be comfortable and let you focus on the main task," says Sprenger. "We found a way to transmit things like road texture, understeer and oversteer these are the critical things the driver wants to feel. What I would recommend is be open-minded, drive it on the track, just be honest - did you miss anything? Did the steering hold you back? I'm pretty confident you would say no."
And pushing a 991 hard around Silverstone's National circuit he's right. It doesn't hold you back. You can sense that limit. The steering is well weighted, instinctive and pin sharp.
997's steering still the last word in feel
What is so wrong with electrically assisted hydraulic power steering, like in a Mini? Could that not be the solution to maintain feel and allow the steering to work with the engine off?
"Another new component which you need to get used to is the electronic steering ... It's not really letting u feel the road so i guess that some "old school" drivers like me won't completely trust it and push to the limit as with a "normal" steering."
Just my 0.5 cents ...
""Another new component which you need to get used to is the electronic steering ... It's not really letting u feel the road so i guess that some "old school" drivers like me won't completely trust it and push to the limit as with a "normal" steering.""
If the system really does not give you a feel of the road at all times, I wonder if this will mean that sometimes (very rarely I presume but sometimes?) you will not know (such as when driving on a blind tightening radius bend in the wet) what the wheels and subsequently the car is doing, and unless the electronic systems can cut in, in such quick time, maybe you lose control of the car?
I always thought that any electronic system (no matter how good) be it Haldex 4wd, or any of Bosch or ZF's systems, still needed some time to sort things out before doing their thing- braking a wheel, applying slip control, now apparently applying power to the steering. Sometimes the real event happening in real time going to your hands and mind gives quicker warning and reaction time. I wonder if the Porsche guys know that, I am sure they must. b
Put it frankly, after one day of driving hard the 991 I had quite enough ... even the sound system of the exhaust felt artificial and annoying after a while (and actually it is, sadly). On the contrary I have NEVER enough of driving around with my "veterans".
This is progress, but not progress for the press on driver. Believe me, I love my TVR for the rawness and I love my Boxster for the steering feel, and how it feels when hooked up on the right road. If that feel goes there is not much left, apart from a car you can point and squirt.
I tried the 991 at Silverstone, and really it did not light my fire. A very very good car and capable, but did it excite....A bit, but on the road you would only be having fun at warp speed.....
So in summary, a good article, which basically says lets just get used to the new steering and mothball a 996 so our children can understand what steering feel used to be all about.
Progress ah!
Ian
Though it actually answers mine, namely why do most epas systems give you no confidence or feel in wet/damp conditions?
Going by what the "boffins" say here they'd have to run a seperate software program to "simulate" it, & obviously that can't happen as wet weather creates infinitely varied levels of grip which you need to "feel".
Epas has its place in the modern world but not on true performance cars.
Even vauxhall have engineered a true hpas system for their vxr Astra, that Porsche hasn't speeds volumes about the modern company it has become.
Bonkers
They are hardly going to say "Yes, we were made to do it. We don't like it either. But there you go." even if this is probably the truth.
But I certainly get the wheel weighting up nicely with cornering force, and I certainly get that lightness on understeer. What I'd say about it is that it does make the car very chuckable and placeable. You can put it exactly where you want on the road or track, and it never feels like it's fighting you, and you can still feel the car's balance.*
* Providing the car's geometry is spot on
http://www.youtube.com/watch?v=Gk-6s-ZhlYs
But I certainly get the wheel weighting up nicely with cornering force, and I certainly get that lightness on understeer. What I'd say about it is that it does make the car very chuckable and placeable. You can put it exactly where you want on the road or track, and it never feels like it's fighting you, and you can still feel the car's balance.
http://www.youtube.com/watch?v=Gk-6s-ZhlYs
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