Electric Power Steering Conversion

[uk525td]

been thinking about this, after removing the parasitic drain from the viscous fan i am toying with the idea of electric power steering..reading about figures varying from 1-3mpg being bounced around

various systems are available, without major headaches of replacing racks/ball steering systems i came to the conclusion its easier to fit an electric motor to the current pump.
So i read some more and found all in one electric pumps for cheap on ebay, some of which with speed sensitive feeds. ideally on demand would be better but that would require lots of fancy sensors.
in theory if its speed sensitive all parasitic losses shoudl disappear under normal driving conditions, when moving i have found the e34 not too bad to steer without any power assist.

Anyone got any thoughts about the conversion using a 3 wire pump (power plus speed input), plan being to remove current pump and fit the pump to the stock pipework, and obviosuly run a short accesory belt (if at all possible)

edit
jsut looked at space and it would be easier to mount an all in one assembly in the right hand side engine bay near the steering box with short lines
is hte cooler really necessary in the stock system? wouldnt be too hard to impliment however the lines are all on the wrong side of hte car
the belt run looks clear between the alternator and crank pulley just missing an intermediate pulley

this sort of thing

http://cgi.ebay.co.uk/ASTRA-G-MK4-EL...item19b9e2acbc

item number 110492822716

reading up it has been mentioned that the electric pumps draw about 10-15 amp at low load and as much as 50-60 at maximum load so thats 120w-720w electrical....
obviously that figure is greater after the engine has generated it via the generator etc, but still can only be equal or less to that of the mechanical pump, and only used at low speeds...

[93FIM5]

Ive looked into doing this and using the Porsche 911 GT3 RSR pump or even possibly the first generation MINI pump (They had issues with bursting into flames, so yea) but I worry mainly about the added noise (the Porsche unit is pretty noisy from what Ive listened too), plus I need to eliminate my self leveling suspension. Another option is the pump off of a Mercedes A class I believe, I'll see if I cant dig up some of my links and research later. Also I would make sure you have plenty of generator capacity before making too many things electric but this is certainly on my list of things to do.

[uk525td]

yes i have the 140 amp alternator
i also would have had the huge battery out of my diesel fitted if some thieving scum hadnt of stolen it from my friends garden :S
at the moment the electric fan barely cuts in im not too concerned about overloading the charging system, i dont have ac, and mostly i control cabin temperature by openign nad closing windows so all im really running is engine electronics and stereo, of course, lights at night etc.

yes, saw the a class item mentioned in my investigation too, i guess my primary concern is current draw and how the pump activates, ie just feeding it a pulsed signal would be a great from the vehicle speed line.

[ross1]

I don't see the P/S pump being accountable for even 1 mpg. It's a tiny little bugger that doesn't work much unless you are turning.
You could slow it down with different pulleys. For that matter you could slow all the accessories down with a pulley change.

[uk525td]

yes true, underdriving would be a suitable solution and adequate. I found it hard to assess the actual losses from a ps pump but reading around suggested a 1-3mpg figure, more of a noticable effect on smaller engines.
trouble with underdrive pulleys is hte cost probably twice that i can buy what i am lookig at for.

the way i see it if hte pump is completely disabled at 20+mph there is no loss from power steering, and as my average speed is over 20mph according to obc its free power and economy, no matter how small.

let your car idle and turn the wheel full lock, you can hear the engine load up. so power steering can have an impact on engine power/fuel consumption.
Hell i never though a viscous fan could have much effect but i can genuinely say it is different after removal.

pretty serious tech doc, mainly about friction on piston components, but has an estimated breakdown on what power is used where
http://www1.eere.energy.gov/vehicles..._17_fenske.pdf

essentialy they are saying alternator, power steering and engine fan all use 0.5% of the energy produced by an internal combustion nergy
doesnt sound a lot BUT!!!!! we only see 9.5% of the energy produced by combustion at the wheels so that 0.5% per accesory is quite a hit, obviously the plan isnt to free up that 0.5 as some of it will be consumed by generating hte power to turn the electric motor

[93FIM5]

Since we are talking about efficiency http://www.motorauthority.com/blog/1...ics-technology

[moroza]

My concern would be that the maximum draw on the alternator would be at idle, which is when it's least capable of providing it.

Why not just replace the PS pump pulley with an electrically-activated clutch, like the AC compressor?

[M Quick]

Have in mind that the car has 13.8-14.4v when running and not 12v (noted your calculations and they seem to be calculated with 12v in mind and not 14v) So the highest draw would be around 850W (at 60A) and minimum around 150W.

Great idea however, if you get it too work, with speed sense that would be awesome!
I would love to have an electric steering pump that makes the steering a little harder when going really fast so that you feel more "stability" and ofcourse make it as smooth as possible when going real slow.

[moroza]

I would love to have an electric steering pump that makes the steering a little harder when going really fast so that you feel more "stability" and ofcourse make it as smooth as possible when going real slow.

Remove the word "electric" and you've described Servotronic.

[M Quick]

Remove the word "electric" and you've described Servotronic.

Yeah, but i would like it to be electric Because i don't have servotronic on mine.

All US cars have this feature already, right?

[moroza]

I'm not aware of any E34 with Servotronic, though E32's have it. A Servotronic gearbox without the electronics hooked up functions on low-boost all the time, which makes for very nice-feeling, heavy steering.

[uk525td]

moroza, the way i see it yes there will be maximum draw at idle, ie when most likely to be using hte most of the power steering. However the battery is the primary source for power surely? so 10-15 seconds of heavy draw on the battery once in a while, when parking etc which is then topped up by the alternator. not sure how much power a starter motor uses but itll be probbaly in the region of 3 times more for a few seconds when starting. And maximum draw is only if you are using full capabilities of hte power steering, ie lock to lock at idle not moving. A very rare situation. Sure the alternator has to work for a bit topping the battery back up, but once it has your back into a lossless system once more
i did investigate servotronic, and looked at the e39 systems but htey appear to use a full rack.

as for the clutch arrangement, yes that would also work pretty well, but that would require a lot more fabrication than i have access to the facilities for.

as for my math, yes i was working on 12v, so hte figures i calculated are smaller, was all ball park figures to be honest

also there is the scanrio when the car is idling (maintanence or sat in traffic etc) where there is no need for the ps pump to be running, granted its power consumption will be lower when there is no demand but it is still unneceessary.
Without building some complex sterring wheel positioning system it would be great to rig a cut out for the pump, the only way i can think of doing that easily is by using the hand brake switch. Ie handbrake on pump off always.

Got to remember too, the stock system intergrates a ps line cooler, that is suggesting that there is heat generated in the stock system and therefore more wasted energy. Also there is the possibility modern electri pumps are more efficient (the pump side not motor) than the mechanical item we curently have, after all the mechanical pump is designed for continuous running at variable rotational speeds, electric is designed (i assume) for specific speed ranges. The mechanical item has to pump enough oil at pressure at idle to make steering possible, at speeds above idle it is still pumping jsut a lot more...also unnecessary. I assume it does have some sort of internal bypass however..

[shiremux]

ill dig the topic out, any new info on the conversions?
MY steering is pretty harsh and the pump is screaming sometimes, buying used working pump is almost impossible there so im thinking of switching to electric power steering from Opel/Vauxhall Astra G.
Has anyone done it similiar way? Im little worried about steering feel with high speeds but from what i've heard there is no ECU that stops the flow in Astra G pump when the speed gets higher etc and the steering is still ok..
Anyway, i'd gladly hear your opinions!

[ross1]

ill dig the topic out, any new info on the conversions?
MY steering is pretty harsh and the pump is screaming sometimes, buying used working pump is almost impossible there so im thinking of switching to electric power steering from Opel/Vauxhall Astra G.
Has anyone done it similiar way? Im little worried about steering feel with high speeds but from what i've heard there is no ECU that stops the flow in Astra G pump when the speed gets higher etc and the steering is still ok..
Anyway, i'd gladly hear your opinions!

Okay, you asked for it. Dumb idea. Do you really think with a bunch of ill fitting junkyard crap you can re-engineer the steering system of this(very well regarded for handling) car? For some kind of improvement no less? Don't try to re-invent the wheel.
Replace your bad pump and call it a day, they can't that hard to find. I'm sure Andy has several and would be willing to ship

[shiremux]

dont get me wrong, im not trying to re-invent the wheel, just trying to make my life easier and get better steering with less work. Why not get some of the new technology into old car, im not one of those that has to have 100% original car and orders only original stuff. Don't know Andy but im sure shipping to Poland willl cost twice as much as used pump there

[ross1]

Here is one of Andy's parts FS threads;https://www.bimmerforums.com/forum/s...k-black-manual
If he doesn't have it I might even have one. Shipping to Poland isn't so expensive as to make you re-engineer the car. Hope this helps

[m60power]

I'm not aware of any E34 with Servotronic, though E32's have it. A Servotronic gearbox without the electronics hooked up functions on low-boost all the time, which makes for very nice-feeling, heavy steering.

I think e34 M5's have servotronic? Yup, both my e32s have it. It feels weird how overboosted the steering is at parking lot speeds; I should probably unplug it, then the power steering lines would probably last a reasonable amount of time haha