Advanced Driving Hub

Imsensible wrote:Having driven vehicles with EPS, HPS and no PS, all I can say is that despite what some may say, in my experience, modern EPS is a pale imitation of the other methods, no matter how sensitive the driver. I can feel the vibrations in modern cars, but it's like wearing a thick layer of cushioning on your hands... it isn't anything like non assisted steering. The 'weight' tends to be wrong as well, generally too light around the centre. It doesn't have to be that way.

Is it simply that manufacturers have implemented it badly, or that electronic v hydraulic can never have the same feel?

Alasdair

With enough time and money, just about anything is possible. No doubt SD will be along to explain the intricate details. But they are both poor facsimilies of unassisted steering. Why we worry about the fuel savings due to EPS, when modern cars weigh so much just boggles the mind... but that's another topic.

Because the weight of a car has next to no effect on fuel consumption on the flat. You've only got rolling resistance (Which is about 0.01 times the vehicle weight) and aerodynamic resistance (A function of forward speed squared) to deal with above and beyond the various frictional bits to do with gearboxes, wheel bearings etc.

Needing a chunk of power to permanently drive a hydraulic pump and thus wasting fuel all the time is inferior to running an electric motor as and when the steering is turned.

You can't have unassisted steering these days. In the quest for stability, much larger castor angles are being used. When you turn the wheel, you're lifting the front end of the car upwards (can't be asked to do a diagram). The heavier the car and the greater the castor angle, the harder it is to lift that weight. There's a maximum force at the wheel, but you'd need to use the power muscles to turn it and any real chance for lovely, lovely feedback is lost.

Outside of very lightweight cars, you are not going to get unassisted steering

StressedDave wrote:Needing a chunk of power to permanently drive a hydraulic pump and thus wasting fuel all the time is inferior to running an electric motor as and when the steering is turned.

We have a car that has an electric pump driving the hydraulic system which seems like a nice compromise. I suppose it'll be heavier than an EPS system, though, plus more complicated.

Plus you still have a hydraulic fluid with the complexities that it brings with it. while most manufacturers don't require it, did you ever on your accord replace the fluid inside a hydraulic power steering? The difference between old and new is mind-boggling.

Imsensible wrote:But they are both poor facsimilies of unassisted steering.

Try dry steering a car when it's turned off so you have no assist. Yes, there are also quicker ratios because of the power steering but no matter how you slice it - it's bloody heavy. The extra effort is just as feedback-robbing as the lack of effort required to turn a heavily assisted wheel.

If you have a custom-molded wheel and you take some castor out of the car, you might be able to enjoy more feedback, but that's quite an investment for a road car and it's not something that can be mass produced.

Gareth wrote:

StressedDave wrote:Needing a chunk of power to permanently drive a hydraulic pump and thus wasting fuel all the time is inferior to running an electric motor as and when the steering is turned.

We have a car that has an electric pump driving the hydraulic system which seems like a nice compromise. I suppose it'll be heavier than an EPS system, though, plus more complicated.

That's just to make the engine bay fitout easier. The pump is still running all the time - no accumulators in the system to store hydraulic pressure.

StressedDave wrote:That's just to make the engine bay fitout easier. The pump is still running all the time - no accumulators in the system to store hydraulic pressure.

I had the impression, probably mistaken, that the power steering assistance was reduced to zero above a certain speed, (~35 mph?), and concluded that this was done by the pump being turned off or down.

Want that purity of feel?
Go classic. 'Cos I'm old I can remember Classic Minis, Imps, Spitfires.
All of which I had and all were driven flat out.
Flat out that would probably be a problem today.
It's all gone wrong.

Astraist wrote:Plus you still have a hydraulic fluid with the complexities that it brings with it. while most manufacturers don't require it, did you ever on your accord replace the fluid inside a hydraulic power steering? The difference between old and new is mind-boggling.

Imsensible wrote:But they are both poor facsimilies of unassisted steering.

Try dry steering a car when it's turned off so you have no assist. Yes, there are also quicker ratios because of the power steering but no matter how you slice it - it's bloody heavy. The extra effort is just as feedback-robbing as the lack of effort required to turn a heavily assisted wheel.

If you have a custom-molded wheel and you take some castor out of the car, you might be able to enjoy more feedback, but that's quite an investment for a road car and it's not something that can be mass produced.

Thanks for the advice, but I have owned two cars with no power steering, several with hydraulic and several with electric power steering. I am more than happy to trade a bit of extra effort to feel what is going on at the wheel.

StressedDave wrote:Because the weight of a car has next to no effect on fuel consumption on the flat. You've only got rolling resistance (Which is about 0.01 times the vehicle weight) and aerodynamic resistance (A function of forward speed squared) to deal with above and beyond the various frictional bits to do with gearboxes, wheel bearings etc.

Needing a chunk of power to permanently drive a hydraulic pump and thus wasting fuel all the time is inferior to running an electric motor as and when the steering is turned.

You can't have unassisted steering these days. In the quest for stability, much larger castor angles are being used. When you turn the wheel, you're lifting the front end of the car upwards (can't be asked to do a diagram). The heavier the car and the greater the castor angle, the harder it is to lift that weight. There's a maximum force at the wheel, but you'd need to use the power muscles to turn it and any real chance for lovely, lovely feedback is lost.

Outside of very lightweight cars, you are not going to get unassisted steering

If you never have to move off from a standstill, brake or go up and down hills, you make a good point about weight having no effect on fuel consumption. Unfortunately, I don't live in the Netherlands and I do have to start and stop. Not to mention the effects of weight on handling and wear and tear on brakes and tyres etc. And at higher speeds, power steering isn't necessary anyway.