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5 Posts
Discussion Starter · #1 · (Edited)
Long story short, here's a log of my lataest useless endeavour.

I wanted to see what would be required to build an ACD pump from "scratch"-without using any of the parts from an OEM pump.
It is possible, for less than 300EUR, with a few downsides, which could be fixed if given more effort.
Volvo EPS pumps have been used in DIY projects and had been already figured out, so I started from there. Idea was based around making pressure in a continuous-flow loop, by adding an arbitrary restriction somewhere, then by controlling flow, it controls pressure before the restrictor.

Here's the plan:
Font Rectangle Parallel Handwriting Slope

Scientific instrument Gas Cylinder Machine Nickel

I built the controller from an Olimex ESP32-EVB devboard, as I had a case and connectors designed for other purposes. (It's not pretty on the inside)

Wood Slope Flooring Landscape Electrical wiring

The ACD ECU checks for a specific behavior of the solenoid, so my initial plan of replacing it with an equivalent 3.7Ohm resistance failed.
I had to compromise and keep my broken-neck solenoid in line, as I didn't want to figure this one out.
At idle the solenoid receives an average of 50mA. Specifications say 50-1000mA can be commanded, so I mapped that range to a 0-100% request.

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Wood Circuit component Cable Wire Auto part

ACD ECU sends a 200hz control signal, with an initial duty cycle of 50%, but the "high" part of the duty cycle is composed of another 18kHz PWM signal, with varying amplitudes apparently.
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The simple way to measure something in this case was to add a ~400Hz 1st order RC LPF, with an included 1/6 voltage divider to keep my ADC happy.
Simulation of what I'm measuring after this is applied:
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5 Posts
Discussion Starter · #2 ·
Part 2:

Just a few ATF leaks later, bam, it's mounted. Not the prettiest sight. There is a remote-reservoir version of the pump which MAY fit in the OEM location. These are bulletproof and made for always-on operation, but they don't mind switching on/off if done properly.
I also used completely inappropriate hoses and clamps for the job:
Fluid Automotive lighting Liquid Gas Auto part
Automotive tire Motor vehicle Gas Automotive wheel system Machine

I didn't try to find the matching connectors for the oil pressure sensor and/or solenoid, as this is not gonna stay this way.
Currently I am faking the OEM pressure signal, incrementing when pump relay is ON, slowly lowering pressure when it's OFF. This might not be necessary, but I did it anyway in hopes of keeping the ACD ECU happy.
Car Speedometer Vehicle Trip computer Motor vehicle

Yay no more error!

Pump sounds funny, like a second electric turbo in the trunk.

This is not a permanent solution. I just did it to see 1. what's required to trick the ACD ECU and 2. actually build a close-enough equivalent.

1. Big pump, extra current draw, must be wired to battery 12V with AWG8 wires - not a problem if you have relocated the battery to the trunk.
2. Slow to start - i managed to have the pump start "instantly", but it's still almost 1s of delay until ACD line pressure rises over 3bar. - funnily enough, the OEM ACD system also takes a while to build pressure. It only triggers the pump on ACD valve request AND if the pressure is under a threshold. It does not keep the accumulator under pressure for instant clutch locks.
3. Small pressure control range. Flow restrictor + pump speed ends up giving a 6bar adjustemnt range over canbus. Currently I have it set at between 3(min pump speed) and 9 bar(max pump speed).

Possible improvements:
1. Figure out faster start or
2. Add bypass valve to restrictor and keep pump always running at minimum speed and
3. Tune duty cycle tables and pressure range to actually get it on target.

Fun stuff:
1. Could build A LOT more pressure if done properly, pump is 1000psi rated...
2. Can override factory control for FULL LOCK MODE
3. I used an OEM-like button to toggle modes: OFF,ON with Auto pump start, ON-Pump always primed at min speed, ON-FULL Lock
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This is as far as I want to go with this implementation, as there's several calibration issues which I feel are just too much hassle and many unknowns. The more I got done, the stupider the whole thing looked.

Next up: I'll probably be using the EPS pump to build pressure in the OEM accumulator + manifold, and keep the factory proportional control.

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30 Posts
Nicely done! The project is stupid, but hopefully it gets us going in a direction for when parts are no longer available. Great research and progress in my humble opinion, even if it doesn't seem like much.

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5 Posts
Discussion Starter · #5 ·
Here's phase 2:
Hybrid version using the OEM solenoid, body, sensor and accumulator.
Had an aluminum AN6 bung welded to the input valve in the OEM block. This will make it impossible to go back to the stock pump setup.
not the prettiest job, but it works.

Minimum DN10 20bar hose between eps pump pressure port and welded bung. Same DN10 from valvebody return(thinner pipe) to eps pump reservoir. OEM pump low pressure supply(thick pipe) is not used anymore.
Routed hoses through the factory 2hose grommet.

OEM pressure sensor and solenoid must be connected to the car harness as from factory.
Motor supply is used to trigger the EPS pump. This is done through my external controller, as the pump is wired to battery 12v using thick wires. You don't want to repeatedly connect and disconnect the main pump supply because it contains huge caps.

For "safety" and because I used standard hose clamps for now, I'm running the pump with soft start and at minimum speed(controlled over canbus). Still builds pressure(>16bar) in 4-5s.

As the pump is massively overpowered for the purpose, no more worries about the puny motor burning out.
One could run several accumulators, or just crank up the pump speed to build accumulator pressure in 1-2s. The ACD ECU stops the pump as soon as max pressure is reached.
It might be possible to use the Volvo pump in failsafe mode, with canbus disconnected and the ignition wire connected directly to the pump motor wires. No more custom controller needed, but one should have proper hydraulic crimping before attempting this. The volvo pump starts at ~70% speed in failsafe mode, with a 2.5-3 second delay.

Another maybe nicer pump option would be from a mini, mounted in the bumper, using the OEM reservoir. But that's for another time.


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