I have recently seen a hydraulic PAS pump mounted remotely instead of being powered by the engine. I’d like to start a discussion on the pros, cons and feasibility of this approach. There seem to be quite a few systems that have been fitted to production vehicles. One I have seen available secondhand for around £170 is from a Citroen Saxo, but I’m unsure how to assess its suitability. At least it only has two wires rather than anything more complex looking at speed sensors etc.
I’m keen on making my engine as efficient as possible by removing any unnecessary power drain such as the PAS pump when it is not needed. I believe the electric pump gets around this.
Cheers, Richard
Electric PAS pumps
Moderator: Board Moderators
-
- Senior Poster
- Posts: 3733
- Joined: Tue Apr 04, 2006 21:28
- Model: Elite
- Colour: Monaco White
- Year: 1974
- Location: Nottingham
Re: Electric PAS pumps
I used the Saxo pump on my track day Excel - worked perfectly. I'm not sure how much more efficient it would make your car as the alternator has to work harder - the pumps draw quite a bit of current.
Pete
Pete
-
- Moderator
- Posts: 2227
- Joined: Wed Feb 06, 2013 15:06
- Model: Elite S2.2 Automatic
- Colour: Essex Blue
- Year: 1981
- Location: Worcestershire
Re: Electric PAS pumps
Thanks Pete - good to know the Saxo pump works. I think it will use less energy as the pump will only cut in when needed rather than all the time - if I’m right! Anyway a lot less costly than an electric pas conversion and easier to fit.
Cheers, Richard
Edit: just found this article which explains the efficiencies that can be gained: https://pmmonline.co.uk/technical/elect ... explained/
Cheers, Richard
Edit: just found this article which explains the efficiencies that can be gained: https://pmmonline.co.uk/technical/elect ... explained/
- rbgosling
- Senior Poster
- Posts: 1723
- Joined: Sun Jul 04, 2010 22:55
- Model: Lotus Excel SE
- Colour: Midnight Blue
- Year: 1990
- Location: Rugby
Re: Electric PAS pumps
Also, I wouldn't go with full-electric PAS anyway, it would numb the steering feel. The fact that Lotus have stuck with hydraulic PAS for the Emira (with an electric pump - the Mercedes engine doesn't have anywhere to mount an engine-driven pump!) against any electric PAS they could have found tells you all you need to know.
"Farmer" Richard
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
- DavidOliver
- Senior Poster
- Posts: 694
- Joined: Fri Nov 07, 2014 11:18
- Model: Excel
- Colour: Calypso Red
- Year: 1985
- Location: Malaga Spain
Re: Electric PAS pumps
The steering when used needs an immediate response. I assume the electric pump would need to be working before the steering was activated.
Also when you use the steering generally you are not on full throttle to obtain maximum power.
And what is the total weight of an electric system compared to normal hydraulics, maybe more ?
Dave the cog
Also when you use the steering generally you are not on full throttle to obtain maximum power.
And what is the total weight of an electric system compared to normal hydraulics, maybe more ?
Dave the cog
- rbgosling
- Senior Poster
- Posts: 1723
- Joined: Sun Jul 04, 2010 22:55
- Model: Lotus Excel SE
- Colour: Midnight Blue
- Year: 1990
- Location: Rugby
Re: Electric PAS pumps
What David says it true, that the pump needs to be running prior to the steering input. However, an engine-driven pump is being driven at engine speed - when you are going flat out the pump is being driven far faster than it needs to be, so that is wasted energy. Equally, when you are parking your car the engine is slow yet the demand for PAS is high, so the pump is sized for that scenario and is pumping harder than necessary the rest of the time. An electric pump (well, at least this Saxo option that doesn't vary with car speed or anything) will pump at the same speed all the time, it'll still be wasteful but should be less wasteful.
Dunno whether it is bound to be heavier - yes, there is an electric motor to include in the package. But on the other hand the pump side may not need to be so massive, as its size can be optimised to the motor speed rather than having to work over the full range of engine speeds. My guess is it'll still be a bit heavier!
Dunno whether it is bound to be heavier - yes, there is an electric motor to include in the package. But on the other hand the pump side may not need to be so massive, as its size can be optimised to the motor speed rather than having to work over the full range of engine speeds. My guess is it'll still be a bit heavier!
"Farmer" Richard
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
-
- Senior Poster
- Posts: 3733
- Joined: Tue Apr 04, 2006 21:28
- Model: Elite
- Colour: Monaco White
- Year: 1974
- Location: Nottingham
Re: Electric PAS pumps
There are two types of this pump as well - one with an integral reservoir and one with a remote reservoir - the remote type makes installation slightly more flexible.
I'll see if I can find my pump and weigh it - perhaps someone can do the same with with a standard pump - then we can compare weights.
Pete
I'll see if I can find my pump and weigh it - perhaps someone can do the same with with a standard pump - then we can compare weights.
Pete
-
- Senior Poster
- Posts: 286
- Joined: Tue May 09, 2017 17:47
- Model: Excel SE (Now gone)
- Colour: White
- Year: 1988
- Location: Northamptonshire
Re: Electric PAS pumps
I don’t see how a saving of 0.3l/100km is equivalent to 3.75mpg. I think the author of that article needs to revisit that.
If the electric pump just keeps the system pressure topped up, the system should respond instantly. My MR2 has electrically-powered hydraulic power steering and is very responsive. The complications of measuring steering angle and road speed to vary the assistance under different conditions sound like something to avoid.
If the electric pump just keeps the system pressure topped up, the system should respond instantly. My MR2 has electrically-powered hydraulic power steering and is very responsive. The complications of measuring steering angle and road speed to vary the assistance under different conditions sound like something to avoid.
What car is that?
- rbgosling
- Senior Poster
- Posts: 1723
- Joined: Sun Jul 04, 2010 22:55
- Model: Lotus Excel SE
- Colour: Midnight Blue
- Year: 1990
- Location: Rugby
Re: Electric PAS pumps
Depends on what your starting point is! If your baseline fuel consumption is 4.9 l/100km (57.65 mpg) then an improvement to 4.6 l/100km gives 61.41 mpg, which is the improvement quoted. Sadly, our Lotus are doing about half this on their good days.
"Farmer" Richard
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
1990 Lotus Excel SE (Lilith)
2022 MG MG5 EV (not due to be a classic for quite a few years...)
2011 Nissan Leaf (Ragly - EV pioneer, must be due to be a classic one day)
- bash
- Senior Poster
- Posts: 2229
- Joined: Thu Nov 03, 2005 15:34
- Model: Se, V8
- Colour: white
- Year: 1986
- Location: Doncaster
- Contact:
Re: Electric PAS pumps
Im no electrical expert but I presume maximum current draw would only be when worked hard like parking ? and, could the voltage be varied to give less assistance on the move.
Bash
Bash
Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.