C5 hydroelectric pump in electric DS?

Andy N

Andy N

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Does anyone have any idea how Electrogenic in the UK was able to adapt a C5 pump to power the steering, brakes and suspension in their electric DS conversion?

I've sent them several emails and finally received one that said they weren't offering the converted units for sale, despite mentioning they might. Other EV conversions mostly use a separate DC motor to drive the 7 piston hydraulic pump which is simple and I spoke with Krzsystof from EV Garage in Poland who runs a 24v 500W motor at idle at all times when the ignition is on and so the regulator still works 'mechanically',cutting in and out with a motor speed about 1000rpm. He said the amp draw when free spinning is quite low. I will probably do this, however I like the idea of a more quiet system and not have this constant noise at idle.

I still have questions about how much pressure and volume delivery a C5 pump could output. In my C5 it only pressurises the suspension and is very slow to rise. Steering takes alot especially when parking and I can't see how the low pressure/output pump plus the compatibility of mineral LHM and synthetic LDS fluid and seals, etc. could cut it.

If you haven't seen the YT clip about the EV conversion, it's here:

The suspension does seem to rise ok and no mention of running out of steering but they do say something about the ride being stiffer, which to me doesn't make sense. The source of pressure shouldn't affect ride unless they are using LDS and viscosity changes damping rates but then would have to change all the seals in the LHM system would they? I would guess you could run two C5 pumps in parallel with LHM but would mineral oil wreck a C5 pump?
 
From the French C5 (1st series Hydractive 3+) documentation:

The 12.5 V electric pump has 5 axial pistons of 6.35mm diameter.
The motor maintains 2350 +- 150 rpm.
Output is 0.7 l/min at 2300 rpm.
The relief valve setting is 180 bars.

Other documents I have state that the belt driven earlier system could output 4 cc per revolution. The accumulator relief was set at 165 - 175 bars.
 
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Thanks for those numbers, I wonder how the 0.7L/min of the C5 pump compares to 4cc per revolution of the old pump? The calculation is probably obvious but I’m feeling lazy today 😅
 
It depends on how fast your old engine is turning, but the electric pump will be less at normal engine speeds. The C5 doesn't run the brakes.

The belt driven pump will be causing a heavy relief spill, as the wide variability of its output has to be allowed for.

It would be nice to know the accumulator rate the DS needs for its functions. I only have pressure values. The accumulator is running the functions.
 
The DS pump outputs 2.8cc per revolution. Acording to manual 814 with the engine at 600rpm the pump output is 840cc/min so the pump must be running at about half engine speed. Regulator cutout pressure is max 175bar but the pump will happily generate far more than that.

Actual flow through the system depends on a lot of variables but the steering is the biggest user.
 
So if the C5 pump regulator cutout is 180 bar, that’s probably ok? I didn’t think about how the regulator works initially. I thought the pump was sending pressure through the priority valve to the various functions and then once that is done the accumulator pressurises and cuts off. If the C5 pump can do it with perhaps more accumulators?? It’s a D Special and doesn’t look like it has a brake accumulator.
 
the steering will be your fall down. you would need to convert the car to a later electric power steering. I doubt that weeny little pump is going to run a DS powered rack. You would need to retrofit a modern poogoe electric power steering rack.
 
The C5 pump has an anti-pulsing accumulator built-in. Hydractive 3+ has further valved spheres on each axle which can block flow - see note at the bottom.

c5 pump.png
 
That C5 pump was not intended to run all the time. It has a small accumulator in the back of the case but it only ever operates the suspension in a C5/C6. I wouldn't think it's really up to the required duty cycle in the long-term if you want to use it for more, but you might be OK if it can pump up the original accumulator. You might compare it more to an ID without power steering and a single piston engine pump that is enough for the suspension and brakes. You could possibly add a single piston pump from an early CX or ID (these will have a roller) to add pressure and run off a cam on a driveshaft??? There are electric steering pumps in C4, C5, DS5 etc. and some Pugs you could possibly adapt.
 
You'd definitly need more of an acumulator, maybe plumb in a ds brake acumulator if the pump has built in pressure monitoring.

The pump also doesn't have to run all the time
 
I fitted an electric power steering unit for the VW Kombi I converted and it works really well with speed sensing variable assistance. It uses the original rack but the column is replaced with a motor built in. If I used a similar system I would have to replace the hydraulic rack as well perhaps with a non-powered ID rack? Or as some have suggested adapting a full system from a newer vehicle with electric steering. It may sound ironic that I do in fact want to keep the hydraulic steering if possible.

The motor I’m using is a Netgain Hyper 9. I’ve already completed two Hyper conversions, a T2 VW Kombi and a 1959 Porsche 356a. The DS is next.

It’s a December 1974 D Special that has been off the road since 1992 and most of the engine bay components are out or not there at all. But it has good bones as they say and some of the metalwork when I take trim off is like it left the factory last week. The 50 something thousand miles may be all it has done….or 150,000 but I doubt any more.

There’s a bit of welding needed around the lower rear window c-pillar boot area but otherwise it’s a good base for a conversion and I thought the one least likely to offend anyone. Just another way of putting a DS back on the road to be used after languishing in sheds for the last 34 years. And like all my conversions is totally reversible if anyone feels the need in future. I’ll keep the engine most probably, could make a good coffee table base.
1715059845766.jpeg
 
The smaller Cits and Peugeots use electric power steering. The system is driven by the usual pulse modulation, with input from the steering wheel, vehicle speed, and ESP.
elec rack.png
 
I really like the DS hydraulic steering especially with the light centering and that characteristic sound the steering makes, which again is weird considering I'm removing the piston engine sound and am trying to work out if I can also remove the rat tat of the hydraulic pump and regulator. One of the things I love about the Hyper 9 motors is they aren't especially quiet and mated to the original transmission there is plenty of mechanical noise. I imagine too an electric rack from a modern PSA vehicle is going to need quite alot of modification to adapt to tie rods, steering column, mounts, etc. But it's a possibility and I won't rule it out entirely just yet!
 
can you run the hydraulic pump with the electric motor ? I guess the problem is the motor only turns when the car is moving. so you don't have any hydraulic power for parking and startup.
 
I have not seen a conversion up close ... but why would an electric motor need the original gearbox ? ..... of course the brakes are attached, but surely most of the oily bits will be redundant with instant torque available. Would you only use say two gears ?
 
fritzelhund said:
I have not seen a conversion up close ... but why would an electric motor need the original gearbox ? ..... of course the brakes are attached, but surely most of the oily bits will be redundant with instant torque available. Would you only use say two gears ?
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In the DS case, as you mention, the brakes being mounted on the gearbox.

But most other conversions can get away without a gearbox, however, donor EV motor 'stacks' (motor/inverter) from OEM vehicles generally have a reduction gear box (usually about 2:1) attached to the electric motor. The Hyper 9 is an aftermarket electric motor without a reduction gearbox.
 
DoubleChevron said:
can you run the hydraulic pump with the electric motor ? I guess the problem is the motor only turns when the car is moving. so you don't have any hydraulic power for parking and startup.
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Yeah this was something I had considered except Netgain has stopped making the dual shaft Hyper 9’s so you can no longer operate accessories off the motor. Also it wouldn’t work with parking when the pump needs to be spun at a good speed to maintain pressure for steering. Also the motor goes up to 8000rpm so even if there was a 2:1 reduction it would still spin the pump perhaps faster than designed!?
 
keepsmiling said:
Will the Hyper 9 motor, while attached to the gearbox, clear the cross member?
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I asked the same question. With the right spacing between the bell housing to motor adapter plate it’s supposedly straightforward and to clear the cross member. I guess I’ll just have to see.
 
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