Electric hydraulic high pressure pump for DS...
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  1. #1
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    Default Electric hydraulic high pressure pump for DS...

    Seeing that the modern Cits use an electric high pressure pump, what would be required to run one on the DS?
    First I tried to look up the pressure it puts out, the link below has the Regulator cut out of 175bar, thats nearly 2500psi! So is that what the pump needs to put out!?
    http://www.mycitroen.dk/library/ds/red/hydraulics/Chas'%20Hydraulic%20Course.pdf
    I have been told that a c5 pump will not be enough as it runs at a lower pressure.

    So what sort of flow vs pressure output would one need?

    Cheers,

    Harley

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    The pump in a C5 does far less than that in LHM models. In a C5 it only provides suspension pressure. Once the car has adjusted to its load at the opening of doors or unless the driver changes a height setting, the pump is fairly dormant.

    In an LHM (or most LHS) car you've got to deal with the constant and demaning changing pressure requirements of steering and brakes too.
    Craig K
    2009 C5 HDi Exclusive

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    The laws of conservation of energy suggest you'd have to put at least as much energy into the driving alternator as is needed for the pump. This suggests that direct drive might be the way to go...
    JohnW

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    Quote Originally Posted by JohnW View Post
    The laws of conservation of energy suggest you'd have to put at least as much energy into the driving alternator as is needed for the pump. This suggests that direct drive might be the way to go...
    Yes, I realise this may be the case and would like to get some figure so that the amps required to run the pump can be calculated.
    The main reason I am looking into this is that with a modern engine transplant I am looking at there may be no other option bit electric pump...

    Harley

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  5. #5
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    Quote Originally Posted by Harley View Post
    Yes, I realise this may be the case and would like to get some figure so that the amps required to run the pump can be calculated.
    The main reason I am looking into this is that with a modern engine transplant I am looking at there may be no other option bit electric pump...

    Harley

    Sent via the future...
    A quick and dirty estimate would be 30-40 amps on a Maxifuse or a PAL fuse. With that and the Honda injection (even modern systems are surprisingly power hungry), I wouldn't guess any lower than 120 amps at the alternator. It's not so much the pump running, it's the pump spiking on startup. A C5 owners manual won't give you the actual motor spec, but it will give you the size of the fuse used to protect the circuit.

    Another fly in the ointment: doesn't the C5 pump run on a fluid that's as incompatible with LHM rubber parts as LHS2 is? I guess you could separate the systems like the C5 does and run a more modern C5-like system for the suspension, brakes and steering off of one of the smaller CX pumps.

    Or, you could go with manual steering and "Jesus" brakes from an early ID.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Just want to clarify that I have/had no intention of using a c5 pump, i realise it is not powerful enough, just used it as an example.
    I want to find out what sort of pressure the Ds pump runs at, which I guess is the figures stated in the link above.
    I work with a company who builds custom DC high pressure hydraulic systems, no doubt they will be able to supply me a pump compatible with LHM I just need a ball park to start them off.

    Cheers,

    Harley

    Sent via the future...

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    If you really want to know what it's drawing, try clamp meter on a C5 and see what it reads.

    The C5 pump runs LDS, which is not quite the same as LHM, but is certainly not brake fluid. People have incorrectly run C5s on LHM for many months and not had problems. Brake fluid is a different matter.

    In pre-X7 C5s, the LDS reservoir is shared by the engine-driven steering pump and the suspension pump, which operates infrequently. It has a soft start circuit from memory, but whether the motor is rated for possibly continuous operation is another question you need to consider. You might find it instructive to look at the electro-hydraulic steering pump used in C4, Picasso and C5 X7 as that is clearly designed to operate regularly enough to meet the needs of the steering system. I've no idea what pressure the steering pump produces though. In an X7 C5, you have a vacuum booster running the brakes on Dot 4, an electro-hydraulic package for the steering and the suspension pump using LDS.

    You could adapt a CX shaft drive pump (5 or 7 pistons) rather than a D style pulley pump. A single piston pump is deemed adequate for an ID/CX with manual steering, so that another way of looking at the problem.

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    Think there's a need to consider efficiency and power loss of the electrical route. An alternator is around 60-65% efficiency then if you account for the pump motor's electrical efficiency (80-90%) and the energy losses in the cable from running such a high current pump, the impeller will be getting only about 50% of the mechanical energy input that the present DS pump does. So I reckon the electrical route will roughly double the parasitic mechanical power load of the hydraulic pump on the engine, which won't help fuel consumption. But maybe there's a more modern alternator/rectifier combination that would be more efficient so as to compensate the effect.

    Any idea how many horsepower the pump uses? Must use a fair bit when raising the suspension from flat and during lots of steering action, but otherwise very little. Maybe a modern mechanical hydraulic pump will have a higher mechanical efficiency than one designed in the 1950s.

    Cheers

    Marc
    Cheers, Marc.

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    Ds pumps run between 1750 and 2250 psi in a perfect world.

    Via the aussiefrogs App

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    Default Electric hydraulic high pressure pump for DS...

    Recently a fellow was giving away parts for CX's in Qld via the Queensland Citroen Car club. Some he put on ebay. He did two conversions with CX's. A rotary and a 2.2 litre 4, both Mazda engines. He used aircraft hydraulic pumps. One mechanical, one electric and listed them for sale about a month ago. I missed out on the freebies and have spare pumps already. He has since used the engines in other cars & used the modified CX's as land fill
    Last edited by Jinandfonic; 12th April 2014 at 08:02 PM.
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    Quote Originally Posted by daffyduck View Post
    Ds pumps run between 1750 and 2250 psi in a perfect world.

    Via the aussiefrogs App
    A correctly set steel regulator has a cut-in pressure of 2150 psi and a cut out pressure of 2450psi - not the figures quoted above. Those figures are for the older Al bodied pressure regulators and hopefully they have all been junked and replaced by the steel units. Being a positive displacement pump (volumetric) the volume of fluid delivered is speed based (RPM) and is the same at 0 psi as well as at the regulator's cutout value. Per 600 engine RPM the 7 piston pumps delivers in the area of 840cc of fluid per minute. Not sure of the actual power requirements in the car - on my test bench a 1hp electric motor will drive the pump just fine with little trouble. Keep in mind that the pump is running at camshaft speed - not motor speed.

    Steve

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    Now go make me a sandwich Hotrodelectric's Avatar
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    An AC or a DC motor, Steve? That''s an important distinction in terms of start up, continuous run, and power consumption. I get the idea, and I've been thinking about it as well. My thoughts tended towards one of those stop/start style starter motors. Although it isn't continuous run (no starter motor can be, severe overheating would occur in a matter of minutes), it might cover the cycle times as necessary. The problem there is battery use and life- a starter cranking continuously, even if cycled would destroy a battery in short order. On the plus side, there is probably more than 1hp in that motor, and cranking rather faster than camshaft speed the hydraulic "on" times would theoretically be shorter.

    A high-output (150A+) alternator would probably ease the battery life problem, since all electrical systems run on the alternator once the car is started. You could even run a second battery strictly for the motor as a capacitor to ease system spiking.

    Switching the system on and off would be almost too easy.
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    Quote Originally Posted by Hotrodelectric View Post
    An AC or a DC motor, Steve? That''s an important distinction in terms of start up, continuous run, and power consumption. I get the idea, and I've been thinking about it as well. My thoughts tended towards one of those stop/start style starter motors. Although it isn't continuous run (no starter motor can be, severe overheating would occur in a matter of minutes), it might cover the cycle times as necessary. The problem there is battery use and life- a starter cranking continuously, even if cycled would destroy a battery in short order. On the plus side, there is probably more than 1hp in that motor, and cranking rather faster than camshaft speed the hydraulic "on" times would theoretically be shorter.

    A high-output (150A+) alternator would probably ease the battery life problem, since all electrical systems run on the alternator once the car is started. You could even run a second battery strictly for the motor as a capacitor to ease system spiking.

    Switching the system on and off would be almost too easy.

    220 AC - though do keep in mind that when the pump is in its by-pass mode the current draw is going to be almost zero.

    Steve

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    Quote Originally Posted by Citroenfan View Post
    220 AC - though do keep in mind that when the pump is in its by-pass mode the current draw is going to be almost zero.

    Steve
    Yah, that's where the rub is. 220VAC, 1hp I'm going to venture is running 15-20 or so amps after the spike you get on startup. 12VDC is going to be severely limited in pressing 2300psi of hydraulic oil. I haven't crunched numbers, but I bet it will be one hell of a lot higher amperage draw. Ergo, thoughts along the line of a starter motor, which can regularly run at 200A without problem. The question here is getting enough power to it on a regular, reliable basis. We all know the pump runs far and away more frequently than any starter we ever knew, even the stop/start tech ones.

    Harley, have you yet talked to your mates at the hydraulics company?
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    Could you reduce the load spike by starting the pump, on zero load ,utilizing a by pass then gradually close the by pass to introduce the load once the pump was running ,a larger than normal battery could be used to accommodate the power draw when the car was in lift mode ,then the alternator would replace the lost charge when driving ,not so good for short trips though ,a larger or second accumulator could be fitted to smooth out high usage periods, lots to think about .

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    Hi Hotrod,

    I have not spoken to the hydraulic guys yet.
    But I now have enough info to provide them with what I require, I hope... It is still mostly witchcraft to me ;-)
    Thanks for all the replies guys it's very helpful!

    Cheers,

    Sent via the future...

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    Quote Originally Posted by Harley View Post
    Hi Hotrod,

    I have not spoken to the hydraulic guys yet.
    But I now have enough info to provide them with what I require, I hope... It is still mostly witchcraft to me ;-)
    Thanks for all the replies guys it's very helpful!

    Cheers,

    Sent via the future...
    The real problem is the volume of fluid the 5 (CX style) or 7 piston pumps output and what the cars need. As someone else pointed out the C5 only uses fluid for the suspension - which, under normal driving conditions, uses little fluid volume once at ride height. It is not the pressure required so much as the volume of fluid at that pressure that soaks up energy.

    Steve

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    FWIW, after working on the C5 yesterday and having the suspension in low, it took about 90 seconds for it to lift to high position..
    Craig K
    2009 C5 HDi Exclusive

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