Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
I've always wanted to know the mechanics behind what gives EPS that distinctive feel. I've searched but unable to see why EPS feels so much different to hydraulic, considering both do the same exact task of providing power assistance to steer the vehicle.
Why can't HPS feel like EPS and vice verse? How does EPS filter out surface imperfections? Driving over water causes no swerving to the wheel with EPS, whereas steering will pull to the side with HPS.
Also I know it's got nothing to do with over assistance - as I've used over boosted HPS and they feel nothing like EPS systems.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
Reputation: 2305
Quote:
Originally Posted by yowps3
I've always wanted to know the mechanics behind what gives EPS that distinctive feel. I've searched but unable to see why EPS feels so much different to hydraulic, considering both do the same exact task of providing power assistance to steer the vehicle.
Why can't HPS feel like EPS and vice verse? How does EPS filter out surface imperfections? Driving over water causes no swerving to the wheel with EPS, whereas steering will pull to the side with HPS.
Also I know it's got nothing to do with over assistance - as I've used over boosted HPS and they feel nothing like EPS systems.
EPS = fewer moving parts than conventional(HPS). The action is direct with EPS. And yes, until recently, most EPS-equipped cars were overboosted. Easier to build an overboosted EPS system than an overboosted conventional.
HPS has more links-in-the-chain, so to speak. More slop, latency. There is a minute delay between your steering commands and turning of the front tires. But what gives it more or less "weight" has more to do with alignment angles.
Amount of road feel/feedback is directly proportional to amount of steering assist, be it hydraulic or electric. Sufficient alignment angles(Caster, etc) count also, but that's for another thread.
Last edited by TheGrandK-Man; 08-02-2017 at 07:54 AM..
To me HPS gives a lot better connection/feeling to the car & road and I find hard to buy the new BMW's with EPS (done to please the less demanding "fashion/name tag" drivers) when older HPS are much better.
HPS offers a physical/mechanical connection through the oil pressure built up when steering.
EPS is disconnected due to lack of mechanical/physical connection, unless they find a way to better improve feedback in the magnetic field forces created during steering. Software right now tries to copy the HPS feedback and up to a measure it does (algorithm of increasing resistance with speed, etc). One of my new Audi does it decent, but it is no match for the older BMW.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
Reputation: 2305
Quote:
Originally Posted by 28079
To me HPS gives a lot better connection/feeling to the car & road and I find hard to buy the new BMW's with EPS (done to please the less demanding "fashion/name tag" drivers) when older HPS are much better.
HPS offers a physical/mechanical connection through the oil pressure built up when steering.
EPS is disconnected due to lack of mechanical/physical connection, unless they find a way to better improve feedback in the magnetic field forces created during steering. Software right now tries to copy the HPS feedback and up to a measure it does (algorithm of increasing resistance with speed, etc). One of my new Audi does it decent, but it is no match for the older BMW.
Most EPS is still motor-driven - that is, an electric motor on the steering column. So there is a physical connection between you and the wheels, but it's how much boost is built in that determines presence/lack of feel.
My F150 has EPS on it and I'm not a fan. A hydraulic system has a complete steering system complete with steering box. The steering wheel is attached to the steering system. With an EPS, the steering wheel does not have any connection at all to the steering. It does not have a steering column that goes thru the firewall. There is a "box" in the dash that the steering wheel goes to. It's called a potentiometer. It sends signal to the ECM and it sends power, one way or the other, to the electric motor that is moving the wheels left or right. With a hydraulic system, you can remove the battery and steer the vehicle. Take the battery out of my F150 and the wheels will not turn left or right- there is NO steering. EPS gives zero feedback from the road. Hydraulic in most cases does a great job at road feel. Most often, the hydraulic system only work at slow speeds and pretty much does nothing at hiway speeds allowing the driver to get the road feel.
My personal opinion, the demands on the electrical system in our cars is at a critical stage. The car makers have been for a number of decades pushing for a 42 Volt system. Problem is it can kill you. There's enough amperage and voltage that should you come in between the poles of the electricity, most likely you won't be shocked, you'll be killed. Maybe with some of the hybrid technology they're learning how to make it a much better and safer system but until then, it's in your best interest to maintain the battery on a new car or expect issues. I've also noticed that in many of the new cars, the battery is buried and the average Joe has no access to it. The wifes 2017 Escape, you can't even see the battery. To get to it, you either have to remove the cowl or remove the entire intake system. GM is still burying some of theirs under the air filter box. The demands on your battery has never been higher.
Most EPS is still motor-driven - that is, an electric motor on the steering column. So there is a physical connection between you and the wheels, but it's how much boost is built in that determines presence/lack of feel.
by the very definition of an electrical motor (rotor spinning inside stator due to electro-magnetic force) there is no touching, physical (as in mechanical forces) connection.
Hence the disconnect or lack of mechanical feeling in the steering.
I would not purchase a "performance car" with electrical steering.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
Reputation: 2305
Quote:
Originally Posted by 28079
by the very definition of an electrical motor (rotor spinning inside stator due to electro-magnetic force) there is no touching, physical (as in mechanical forces) connection.
Hence the disconnect or lack of mechanical feeling in the steering.
I would not purchase a "performance car" with electrical steering.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
Reputation: 2305
Folks: Read up on wheel offset and 'scrub radius'. Both have at least as much to do with road feel as does power steering assist. I'll give you this Easter Egg: One type of scrub radius increases road feel, the other reduces it. Look the rest up.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
