Electro-hydraulic Power Steering

[F3kka]

I'm thinking of swapping my power steering pump out for an electric pump. Not a complete electric system but instead run my hydraulic system with an electric pump. It seems that a few non micras (106/saxo/MR2 for example) have had this system installed as standard so won't cost the earth. I've built an engine on a every little helps approach so I'm also adopting it here for all those loses!
My question is tho how does the pump know when to pump? Sounds stupid I know but would I need to install something to measure angular displacement or torque wired to a relay rather than a direct ignition feed to the pump. This I guess is where it gets difficult as presumably my micra won't have anything like that fitted?! And don't really want to start cutting and shutting other racks to fit.
I think @Jordan27 has done something similar before?! (apologies for the tag if you haven't!) But I can't find much info about it here.

PS don't turn this into a debate on pro's and con's of power steering!!

 

[F3kka]

Or does it just work off the shuttle in the rack as the standard pump would, which will be countinously pumping anyhow

 

[frank]

here,s the pump and chamber from a pug iirc, and i think the motor was in coast mode when the ign was on, then would kick in fully if you turned the steering

 

[F3kka]

I see, I thought it would do something like that. Excuse the potentially simple questions; how does the motor go into coast mode?
If it’s wired to the ignition (via a relay) is the pump smart enough (maybe by pressure) to realise there is no demand so goes into coast mode or do i need an external driver? Aforementioned torque/angular displacement sensor or ECU
Does the standard one not just continuously pump to the return of the reservoir until the demand arises? Surely if I wire the electric one in this way it should all be good? (I don’t think I know enough about how the standard power steering system works)
This may be me over thinking it massively but if I get a feed from the ECU to the motor, which is only live after a predetermined rpm (which i think you can do with Emerald) this would save my battery from being flattened from the pump when it’s just on ignition and not running or tickover say?

 

[frank]

i think you would burn the motor out if you zigzagged for long enough without it coasting, so they would either run a constant 5v ish, or else pwm control
i checked on a french car about 15 yrs ago and the motor was spinning slowly, i did,nt try moving the steering tho

 

[SuperUno]

It's quite a common mod in rallying, IIRC people just wire in a BIG feed (40A+) via a relay and the motor supplies pressure as needed. I have thought about this to reduce power loses, but they are quite heavy IIRC.

 

[GeorgeG]

Does using the 106/saxo pump improve the steering feel?
Steering wheel weight etc?

 

[Jordan27]

Yes I do have the Saxo power steering pump in my rally car.
If there's no steering input then there's just a pressure relief valve I guess because it's constantly pumping.
It's just the case of connecting it to the power steering rack and supplying power!

Corsa steering is another alternative, although that is electric and adjustable.

@GeorgeG I can't really compare sorry, I drive my road car with power steering and the rally car with power steering, but the LSD makes the steering much heavier and different anyway

I do recommend it though, when I was in juniors it shaved quite a few seconds off every stage time with my skinny arms


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[GeorgeG]

@Jordan27 I remember seeing your micra on your blog with the pug p/s
I was also sure that the gripper would make any comparison impossible in a nice way
I keep a close eye on your progress on the blog and on the british road rally site.
I am in the process of doing something similar
Keep the blog updated

 

[Jordan27]

@Jordan27 I remember seeing your micra on your blog with the pug p/s
I was also sure that the gripper would make any comparison impossible in a nice way
I keep a close eye on your progress on the blog and on the british road rally site.
I am in the process of doing something similar
Keep the blog updated

I did have it on my junior car without a diff, but I wasn't driving my road car every day then because I didn't own a road car or a license haha!

You planning to do road rallying?


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[GeorgeG]

@Jordan27 ohhh yes living in North Wales and not doing road rallies is just wrong lol

On the p/s topic just bare in mind that the saxo vts/ 106 gti are slightly different (Saxo gives a lighter feeling).

 

[F3kka]

So I've done some more research into this and I'm in agreement with @SuperUno their size and hence weight of these pumps don't make it worthwhile imo. Plus the fact i have a tiny alternator and battery means it'll sap all my electrical power! So I'm sticking with a standard mechanical pump and the tiny amount of parasitic losses that go with it!

 

[Jordan27]

So I've done some more research into this and I'm in agreement with @SuperUno their size and hence weight of these pumps don't make it worthwhile imo. Plus the fact i have a tiny alternator and battery means it'll sap all my electrical power! So I'm sticking with a standard mechanical pump and the tiny amount of parasitic losses that go with it!

Wise choice I think, the pump is heavy I only had one on my car because it came without power steering in the first place and it was a 1.0 at the time so every hp counted haha


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