Electric PAS conversion Part 1

[mjheathcote]

My Mercedes A class electric-hydraulic pump arrived today

A buy-it-now from a nice low mileage car being broken in the channel Islands, only £29.95.

Its a nice compact unit, only requiring +ve, -ve, and ignition.



An initial trial fit looks good, very good infact where the expansion bottle used to be. Plenty of scope to bracket off the bulkhead using existing horn blanking plates without drilling any holes.



Just think, without the mechanical PAS pump easy access to the battery, or maybe easy access to a mechanical or electric water pump....



I'm not the first to swop abelt drivenPAS for an electric one. Those carrying engine swops, kit cars, seeking more BHP etc.

Long term for me is for a future a/c compressor...

Mike

[pcoleman]

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looks like it's always been there! without wishing to advertise my lack of grey matter how do you integrate the electric pump into the steering rack assy and do away with the old pump etc :?

[mjheathcote]

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pcoleman wrote:

looks like it's always been there! without wishing to advertise my lack of grey matter how do you integrate the electric pump into the steering rack assy and do away with the old pump etc :?

Thats easy, both original hoses just connect to the new electric PAS pump the same way. The high pressure hose screws in with an hydraulic fitting, the low pressure hose pushes onto a hose tail, just like the original pump.

I have custom hoses anyway with the original PAS pump due to the tubular exhaust manifolds. So I will just re-route them to the electric PAS pump. Will have to most likely shorten them, and change the existing high pressure fitting to match the new electric PAS pump.

[stagmuffin]

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mike im interested in how you comunicate with the pump,have you got a plan and how do you compensate for speed changes ie motorway or town driving.

steve....................

[mjheathcote]

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stagmuffin wrote:

mike im interested in how you comunicate with the pump,have you got a plan and how do you compensate for speed changes ie motorway or town driving.

steve....................

The original belt driven pump does not compensate for speed changes, likewise this pump does not compensate, as no speed sensor inputs, just +, -, and ignition.

Saying that there is a load of circuitry beneath the cover that must do something, maybe speed sense with voltage rise of alternator, I don't know.

What I do know is that when it has been done with other vehicles... 'it just works'!

Likewise the saxo/106 electric PAS pump is also popular to replace the belt driven pump, and that also has no external speed sensor...

[V Mad]

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I think that there is a bit of confusion. You are not replacing the stag hydraulic control system (built into the rack) you are just replacing the mechanically powered pump with an electrically powered pump, is that correct?

In that case there will be no change in the operation or feel of the steering.

[mjheathcote]

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V Mad wrote:

I think that there is a bit of confusion. You are not replacing the stag hydraulic control system (built into the rack) you are just replacing the mechanically powered pump with an electrically powered pump, is that correct?

In that case there will be no change in the operation or feel of the steering.

Correct

[cosmicwheels]

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Wouldyou be able to switch it off when cruising[ in the car that is]? john

[mjheathcote]

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cosmicwheels wrote:

Wouldyou be able to switch it off when cruising[ in the car that is]? john

To switch it off all you need is a switch in circuit with the ignition feed to the pump.

Can't see why you would want too though, plus not good if you have to carry out an emergency maneuver with heavy steering.

Could be beneficial to have the power steering without the engine running however...pushing the car around the garage for example...or heaven forbid, being towed!!

[stagmuffin]

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mjheathcote wrote:

stagmuffin wrote:

mike im interested in how you comunicate with the pump,have you got a plan and how do you compensate for speed changes ie motorway or town driving.

steve....................

The original belt driven pump does not compensate for speed changes, likewise this pump does not compensate, as no speed sensor inputs, just +, -, and ignition.

Saying that there is a load of circuitry beneath the cover that must do something, maybe speed sense with voltage rise of alternator, I don't know.

What I do know is that when it has been done with other vehicles... 'it just works'!

Likewise the saxo/106 electric PAS pump is also popular to replace the belt driven pump, and that also has no external speed sensor...

mike,
i was under the impression from a previous post you made,that you were considering voltage control to the pump in order to control fluid output volume and therefore efectively asisting or desisting acording to driving demands,this is what i was interested in .or maybe i got it wrong.

i plan to work on this area on my project stag in the future because of an engine change.

thanks( a not confused) steve

[V Mad]

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I wonder how this would be assessed on an MOT test, since steering is a safety critical part? An MOTfailure could mean a lot of messing around putting it back to standard. Is it really worth it?

my 2p

[stagmuffin]

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i dont see that this installation would have any bearing on the test with regard to design?.they are mot testers not design engineers the examiner will be looking for function and wear in moving parts that affect the ability of the vehicle to change direction safely or could fail as a result of wear or as a result of obvious poor fitment.but not how it is engineered to do so, that is not their remit.if the vehicle can perform direction change manouvres safely without evidence of poor workmanship or of failing defective parts then i assume it will pass this section of the test.i stand to be corrected.

steve..................

[mjheathcote]

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stagmuffin wrote:

mjheathcote wrote:

stagmuffin wrote:

mike im interested in how you comunicate with the pump,have you got a plan and how do you compensate for speed changes ie motorway or town driving.

steve....................

The original belt driven pump does not compensate for speed changes, likewise this pump does not compensate, as no speed sensor inputs, just +, -, and ignition.

Saying that there is a load of circuitry beneath the cover that must do something, maybe speed sense with voltage rise of alternator, I don't know.

What I do know is that when it has been done with other vehicles... 'it just works'!

Likewise the saxo/106 electric PAS pump is also popular to replace the belt driven pump, and that also has no external speed sensor...

mike,
i was under the impression from a previous post you made,that you were considering voltage control to the pump in order to control fluid output volume and therefore efectively asisting or desisting acording to driving demands,this is what i was interested in .or maybe i got it wrong.

i plan to work on this area on my project stag in the future because of an engine change.

thanks ( a not confused) steve

No you are not wrong, that option is possible using a Toyota MR2 electric PAS pump.

In the end I decided on the simpler Mercedes A class pump mainly because its the perfect size to fit where the overflow bottle used to be.

[Stagdad]

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V Mad wrote:

I wonder how this would be assessed on an MOT test, since steering is a safety critical part? An MOTfailure could mean a lot of messing around putting it back to standard. Is it really worth it?

my 2p

Chris ,they didn't give my rear transplant much off a going over and that has got to be safety critical (I did though).

Cheers Steve

[Andy Rundell]

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V Mad wrote:

I wonder how this would be assessed on an MOT test, since steering is a safety critical part? An MOTfailure could mean a lot of messing around putting it back to standard. Is it really worth it?

my 2p

They are looking for leaks and excessive wear - if these aspects are ok it won't fail on that particular area

............Andy