Converting power steering to electric power steering

[Peter7307]

Changing from a purely (engine driven pump) hydraulic to an electric driven pump will reduce the power demand by around 80% according to Reimpell , Stoll and Betzler in The Automotive Chassis , p286 in Edition 2.

Power requirements are around 80 amps at full demand , like parking lots for instance , but reduce to the 15 / 20 amps range for suburban driving.
Operating pressures are around 120 bar (1800 psi approx)

Many automotive suppliers (ZF , SKF etc) supply these as complete sub assemblies to car builders so perhaps this may be a good place to begin your search.

Good luck , Pete.

[dremd]

Several years ago at SEMA http://www.semashow.com/ I saw someone selling Electric powersteerig kits for Street rods (main claim was cleaning up engine bay) If I recall they were using a rack from a Saturn Ion (definitely a saturn, not 100% on which car it was) It may be worth a look. I MAY still have my old show directories if nobody can dig up info on this. (if cheap I'd do the swap on the TDI)

On a side note:
A friend of mine removed his powersteering on his supra (turbo outlet hit the pump); he was involved in an accident and permanently injured his wrist. To this day he would tell you that the powersteering would not have protected his wrist, but I disagree (for more info check out the rock crawler guys without powersteering, they break thumbs, wrist frequently). All just to keep in mind, don't want to scare anyone out of pulling out the pump, but just that they be aware of the potential consequences.

[dremd]

Just read the Honda Tech article, tat is pretty sweet, I doubt it would be as efficient as direct EPS, but it would be super easy, work on any car and likely cheaper (all good things on this board).

[extragoode]

I know I'm a little late to this, but I was thinking about this the other day and was wondering if one could simply change the size of the pulleys on the hydraulic power steering pump. I'm not familiar with them to know whether they work on speed or force, but I assume either halving or doubling the circumferance of the pulley would halve the power and therefore halve the load on the engine. I personally have a 4000 lb truck and it is not the easiest to steer while eocing even at speed(30mph), so I don't want to get rid of power steering completely, but I also don't need it's entire capacity.

[dremd]

Originally Posted by extragoode

I know I'm a little late to this, but I was thinking about this the other day and was wondering if one could simply change the size of the pulleys on the hydraulic power steering pump. I'm not familiar with them to know whether they work on speed or force, but I assume either halving or doubling the circumferance of the pulley would halve the power and therefore halve the load on the engine. I personally have a 4000 lb truck and it is not the easiest to steer while eocing even at speed(30mph), so I don't want to get rid of power steering completely, but I also don't need it's entire capacity.

Mmm Interesting thought.
Another idea may be to cut some off of the springs in the spool valve.
You cut a few coils off of the Rx7 spool valve (rack) when using the factory pump on swapped LsX Motors. Makes a HUGE difference in effort/ feedback, Unsure how much difference it would make on engine load. (Only seen it done on 300+++ Hp cars so load is basically invisible.

[extragoode]

I'm not sure I follow you entirely, but it sounds like that would increase your turning radius by decreasing the maximum angle the wheels are allowed to rotate, which wouldn't matter in a race car, but would be devistating in a parking lot.

[cfg83]

NoCO2 -

Originally Posted by NoCO2

Since you're removing a component from the serpentine belt, you would have to find a new belt that would fit the new pulley configuration once you've done it. How hard is it to find these custom length belts since they obviously aren't factory spec length. That's my only concern with removing the power steering from my Camry, that I won't be able to find a belt that will fit the new pulley setup. If I knew there was a supplier that could provide these special length belts, I would have already done it.

I keep thinking that you could get a broken version of your PS pump from a junkyard, gut it, and turn it into the "extra pulley" you need to make your belt work. That doesn't get you (all of) the extra weight savings of removing the PS pump, but it insures that you would be able to use your stock belt.

Otherwise yes, you'd have to go on a quest for the "perfect belt".

CarloSW2

[dremd]

Originally Posted by extragoode

I'm not sure I follow you entirely, but it sounds like that would increase your turning radius by decreasing the maximum angle the wheels are allowed to rotate, which wouldn't matter in a race car, but would be devistating in a parking lot.

Sorry, I didn't make it clear. This mod does not affect steering radius, just steering effort/ feedback.
What I am talking about (spool valve) is essentially a pressure regulator linked to the steering shaft. Harder you turn, the higher the line pressure goes.(also reulates left - Right). By cutting the springs down you are decreasing the line pressure. The decrease in line pressure reduces the "boost" to the steering. I'm "guessing" that by reducing the line pressure you MAY reduce energy consumption.

[extragoode]

Originally Posted by dremd

Sorry, I didn't make it clear. This mod does not affect steering radius, just steering effort/ feedback.
What I am talking about (spool valve) is essentially a pressure regulator linked to the steering shaft. Harder you turn, the higher the line pressure goes.(also reulates left - Right). By cutting the springs down you are decreasing the line pressure. The decrease in line pressure reduces the "boost" to the steering. I'm "guessing" that by reducing the line pressure you MAY reduce energy consumption.

I'm on track now, but I don't like the sound of cutting anything. Sounds very permenant. I'd be okay with it if it was proven to work, but I'd want any mod I was just guessing at be reversable.

[s2man]

Originally Posted by extragoode

I'd want any mod I was just guessing at be reversable.

It's reversible, just put some stock springs back in. When I was designing coal-mining equipment, it was standard proceedure (ie, in the catalog) to change springs or drill out an orifice to change the characteristics of spool valves.

I've peeked at my p/s pump before, but was unsure if I could rebelt the engine to delete it. Last week, when I was removing my a/c and installing the new belt, I gave it a thorough inspection. I determined I will be able to eliminate the p/s pump and still use the belt tensioner . I'll be doing that soon. If I like it, I'll loop the hoses and toss the pump.

There is no manual rack available for the Cavalier. But the guys in the race forums delete the pump all the time.