Interest in an Electric Power Steering Pump

[Mike B.]

I've seen a few of you have questions about the removal of the pulley driven power steering pump to free up the associated parasitic losses.

The removal of the stock setup means capping the lines and running the steering rack manually.

I am looking into importing some Mercedes A-class electric power steering pumps to replace the stock setup and keep power steering.



These are compact units with an integrated reservoir and are mounted vertically (on it's side in the picture). They provide enough pressure for the rack and only take 20 amps to run.

Any interest in a package with the pump, associated lines and wiring harness?

I don't have a price yet, but I am just determining interest.

[hoveringuy]

Yes, I'd like to see that. Switching to the M54 meanst that I couldn't re-use my old M50 PS pump. I've had no power steering for the last 2 weeks.

I have a new pump on the way but that alone was $150. Meanwhile, I've gotten used to it.

Is the electric motor demand actuated? Does it only run when you are demanding a lot of pressure from it? That would make it worth it for the loss of parasitic drag.

[george graves]

Interesting. I would assume there would be some kind of pressure accumulator in a stock electric PS pump system?

How does the pump know when to turn on? Turn off? Run a tiny bit? Run full on?

Or does it run full time and is only under load when the rack needs assistance?

[Mike B.]

All good questions, and at this time I don't have an answer. Let me do some checking...

[hoveringuy]

It may have a small accumulator and a pressure switch.

If it doesn't, it could either run full-time

OR

it wouldn't be too tough to create a small motor control circuit... here I go again ... that runs the pump at 100% below 10mph and then ramps down to to 0% by 30mph. It wouldn't jerk on and off that way and you would only have the boost you need. Of course, you steel motor guys would need slightly more boost:grin:

With no PS right now I only have an issue parking and below 10mph. At any kind of driving speed I don't miss it at all.
Another question... if the pump is turned off will the hydraulic fluid in the system tend to hydro-ock the steeringn in one postion??

[Mike B.]

From what I understand, with the pump turned off, the rack operates manually.

From an A-Class website -

Power Steering pump Failure/Defects .
Breakdown of power steering pumps, yes there have been a few, and a new replacement from MB is expensive The type of breakdown falls mainly in to two categories,
One the pump continues to run even with the engine switched off, this is a real problem because if you don't hear the pump running then your battery will be flat in next to no time. ( in view of the fact that the pump is wired to only run when the alternator is producing power, I.e. engine running, indicates to me that the pump has a short circuit which is causing the pump circuits to remain live and therefore the pump to run continuously ) even with this defect the pump works normally when driving
The only way the pump can be stopped is to pull the large 60 amp fuse in position Number 47, replacing it when you intend driving.
so at least you will be able to get the vehicle home and pick up a spare part.
Feed back from one owner with this problem has confirmed that this is an electrical fault on the pump's complex electrical system, in his case after trying second hand pumps without success he fitted a new pump and has had no problem since.

. The second of the defects is where the pump failed to run at all, check the 60amp fuse position 59 main fuse layout. Fuses are best tested with a meter which ensures they are sound if a reading is achieved. Test that power is being delivered to the pump via the blue wire which comes from the alternator. On my car with the pump working normally I get a reading of approx 12.5 volts on tick-over , with the ignition on but engine off I get a reading of approx 1.3 volts
If no power is received at the power-steering junction box n/s/front blue wire then check the connection onto the alternator, is is vital that possible defects on the alternator be discounted before considering the problem to be the PSP the pump does not run with ignition only ON, the alternator must be producing power in the blue wire. i.e. engine running .
At present I have no more information on either defect I will add it if and when any becomes available.
Even in the case of the failed pump the car can be driven with caution, But be aware that the steering will be very when compared to the normal situation, to overcome this in the short term extra pressure in the front tyres will help.

[george graves]

create a small motor control circuit... here I go again ... that runs the pump at 100% below 10mph and then ramps down to to 0% by 30mph.

What would be really cool is to read the front ABS sensors, looking for a difference in wheel speed, and then vary the pump based on that - then have a dial, that you could control the amount of assist.

:D

[Mike B.]

I sense a new project... :)

[PiercedE30]

Only bad thing about the pump is the price. I believe it is like 500 bucks for it.

[Mike B.]

I can get better pricing than that...

But yes, this isn't going to be one of those "electric power steering pump for $100" deals. I expect this to be interesting to those folks involved in racing that are looking for every last bit out of their engines.

The pricing will be fair, but reflect the cost of the componants involved.

[325Projectz]

check into mini's electric power steering pumps... it might be an expensive setup.

those pumps are always running but variable speed. the wires that run to those pump are big, but i don't know about the amps that it'll draw. then they have coolers on them because they get so hot.

http://www.realoem.com/bmw/showparts.do?model=RE33&mospid=48021&btnr=32_1265&hg=32&fg=15

[dude8383]

quite interesting. i will keep a close eye on this!

[Mike B.]

I've looked at the Mini pumps. The pump draws around 60 amps and has a remote reservoir. I was looking for something with an integrated reservoir and less amp draw. People have also used pumps from Toyota MR2's.

The Mercedes pump (or a motorsport version of it) is being used currently by Porsche and BMW race teams. I have it on good authority that the motorsport version is minimally different performance wise than the stock MB pump. The motorsport version is $2000 while the stock pump is much less.

[PiercedE30]

Yea, the mini pump isn't the greatest. I looked at it a while back when comparing it and the MB pump. I took a good look at it when I was assisting in a 6-sp clutch change on a MiniS. I wouldn't want to use it unless it was given to me.

[m3_eater]

it wouldn't be too tough to create a small motor control circuit... here I go again ... that runs the pump at 100% below 10mph and then ramps down to to 0% by 30mph. It wouldn't jerk on and off that way and you would only have the boost you need. Of course, you steel motor guys would need slightly more boost:grin:

You've just described the steering on an Acura NSX. Might want to take a look at a wiring schematic for one (I think it's all 1994+ cars)