Volvo S40 Electric Power Steering Swap

[DPDISXR4Ti]

We touched on this topic in a different thread, but I thought it might be a good idea to have a new thread dedicated to just the Volvo pump which seems to be semi-commonly used. The beauty of this approach is that no re-engineering of steering racks/columns are needed. It's basically just a replacement for the belt-driven pump so all you need to do is re-plumb your hydraulic lines and make sure you're delivering enough amperage for the electric pump.

I'm going to start off by just linking in other forum threads / project pages that discuss what's involved. Here's a simple one that lists what's needed.
https://www.camaro5.com/forums/showthread.php?t=579691

Here's a thread where a guy mentions, among other things, a possible way to do manual settings rather than hacking the software to do it via CAN bus. https://www.therangerstation.com/forums ... on.183274/

[andyofcolumbusmerkur]

So if you install an electric pump found in a Volvo (but made by Ford) it will be in limp mode and run at 70-80% of it's maximum capacity correct? And that pump will pull between 55-63 amps. Unless you have some type of CANBUS setup to control it. So why not just limit the input with a resistor? Or install it so it can be turned on and off. Only problem I see is if I "depower" the steering rack I can't have hydro assist. And if I leave the rack fully functioning it would be hard to steer when the assist is not present. I don't see how "road feel" would factor into this. The rack wouldn't know the difference between fluid pressurized via a mechanical pump or an electric pump. I can see how "way to much assist" would not be desirable.

[my8950]

And that pump will pull between 55-63 amps. Unless you have some type of CANBUS setup to control it. So why not just limit the input with a resistor?

The resistor needed to drop 50-60amps is going to be pretty huge I'd have to guess...

[my8950]

Here's a thread where a guy mentions, among other things, a possible way to do manual settings rather than hacking the software to do it via CAN bus. https://www.therangerstation.com/forums ... on.183274/

Do we have to be registered to see the information on Rangerstation? I can see the initial post, but then steps 1, 2 and 3 show nothing.
Edit, disregard, as I'm reading more closely, its a place holder for the guy to finish writing...Blah, sorry...

[DPDISXR4Ti]

So if you install an electric pump found in a Volvo (but made by Ford) it will be in limp mode and run at 70-80% of it's maximum capacity correct? And that pump will pull between 55-63 amps.

I had the same initial thought. But from the little I've read on this, there is some sort of input based on steering pressure which means it's not pulling anywhere near ~50 amps if you're not yanking on the steering wheel.

[thesameguy]

My understanding is the Volvo pump is made by TRW and is found in a few other places as well. IIRC it normally gets input on vehicle speed and steering rate, which allows it to speed up and slow down proactively. Without these inputs, the pump runs reactively trying to maintain a fixed failsafe pressure. From what I have read, the problem with this failsafe reactive mode is that the pump can fall behind with sudden aggressive steering. I'd really want to not deal with that.

There are plenty of solutions for writing CAN messages to a bus, so IMO the mission here would be to read an analog signal and then write out a corresponding CAN message. I know it can be done... I just don't know how.

[andyofcolumbusmerkur]

Sounds pretty hard. So you'd have to have something like a raspberry up and running to control the pump? That Hoovie dude said the steering feels fantastic with the eps kit installed. But that was an old school rack and pinion with no power assist before the prius style electric assist was added. Not so sure how that would make a rack and pinion style setup feel. I like the Volvo hydro pump idea better. And using parts from the junkyard. What about simply using a blower motor resistor or even multiple resistors in a series?

[my8950]

Filter the signals for steering input, and then mimic that.
From what quick and dirty reading I've done, it would need a VSS input to vary the steering assist, so you'd need to know the messages for speed sensor and the pump. I need to find someone with one of the supplied vehicles to listen to the bus and see what happens when speed increases and decreases, steering left or right.

[thesameguy]

I don't think it would matter left or right - it's just two rate signals... Like miles per hour and degrees per second or whatever. This is something Arduino or some other $10 microcontroller can do. It's just a matter of the right sensor and the right message.

[thesameguy]

The big problem I've had reading these threads on EHPS is that most people are retrofitting them into '60s boats and stuff. Cars people probably aren't going to autocross or HPDE in. Whenever someone says "it seems okay" I assume "it seems okay in a parking lot" and they don't know what it's like going 60mph in a parking lot through a bunch of cones.

Anyway, something else worth mentioning:

Another approach for control here could be bypassing the "modern car friendly" controller and interfacing the BLDC motor directly. It's obviously a very high draw, but overlooking that truly minor difficulty, you could "invent" a control scheme yourself. AFAIK, the only thing the inbuilt controller does is take some CAN signals and then control the BLDC pump motor with PWM.

I'm fairly certain an approach here is to bypass the controller the pump comes with and interface with the DC motor directly... basically roll your own controller. I think rudimentary control would be pretty easy - turn a VSS signal into a PWM DC supply, ramping up to other inputs if necessary.

A guy on ls1tech posted a bunch of info on using Arduino to control PWM fan controllers, and helped me with a customized version of it. I'd envision something similar here... use a VSS signal, Arduino, and a BLDC PWM controller. All you would need is math or a table correlating VSS to PWM, like 10mph = 90% duty cycle, 40mph = 10%, etc.

Maybe another approach could be something like a "track mode" switch to take the pump out of failsafe mode and make sure it's always available.

Just thoughts. I do know a guy who I am 100% confident could build this, but it's his job and I'm sure it's a $5k project. Maybe there's a kickstarter in here somewhere.

[andyofcolumbusmerkur]

Still sounds really complicated. I mean the stock setup (with a mechanical pump) didn't need all these inputs and variables etc. I can see why the motor assist (Prius) would need that but the Volvo style?

[thesameguy]

The point of these systems is to save fuel (and thus horsepower) providing boost only when necessary. Old-school engine-driven hydraulics work backwards in that they generally need to provide the most boost when engine speed is lowest and the least boost when engine speed is highest. Since most driving isn't done at idle, the result is 5-10 wasted horsepower all the time. Literally horsepower disappeared running a pump that isn't doing anything.

By knowing engine speed and/or road speed and/or steering angle the pump uses power only when it needs it, freeing up horsepower and thus improving fuel economy.

Where the assist comes from is immaterial. An electric motor (EPAS) is the more direct, efficient solution since it provides force directly to the steering. Hydraulic (EHPS) is less efficient because a motor is pumping hydraulic fluid which then acts on the steering. But EPAS is isolating while EHPS has a more traditional feel.

Most people just don't care how numb their cars are, and most manufacturers don't waste time implementing something few people cares about. But some people do care, and manufacturers of those cars take steps accordingly. Some cars like the S2000 and RX8 seek to address this by placing the motor on the rack so it behaves more like traditional steering but these are obviously not good for retrofit solutions. BMW, Porsche, Mazda, and I'm sure all the hypercar makers build complicated control systems. Those are also not good for retrofits for obvious reasons. That leaves the easy solutions as the ones that drive the worst.

So this thread is about adapting a specific EHPS system (the Volvo/TRW system) to the XR's existing hydraulic system. Marrying some new, horsepower-freeing technology to a legacy power steering system. My hope would be to maximize that power savings AND reduce the XR's silly overboosted Ford feel at the same time.

Writing CAN messages to a CAN bus is NOT complicated. It's a few dollars in parts. I just don't know the messages to write, and I don't know how to robustly design a circuit to do it. They teach this stuff in high school these days!

[andyofcolumbusmerkur]

From what I see on Corral.net people seem to like the s40 electric pump with a sn95 type steering rack, just wired up sans controller, for normal driving. But the pump couldn't keep up with autocross demands. So if you could make the canbus stuff work (even just a little) and get the pump up to full pressure that would be pretty neat. Or possibly bypass the electronics and power the pump directly but using a potentiometer to raise or lower voltage? First step would be to find the pump from ( 2004 - 2013 Volvo C70 / C30 / S40 / V50 ) this according to western motorsports.


https://www.wmsracing.com/wmsweb/volvo- ... tails.html

[thesameguy]

Step 1 is finding an S40 and throwing a CAN analyzer on it and trying to trap the relevant messages. Or, maybe an FSM for the car that goes into detail here. My only experiences with CAN-enabled cars are Saabs, Jaguars, and Jeeps and *none* of those FSMs delve into the CAN at all, so I don't have a high expectation Volvo does, but hope springs external.

Then, in my head, it's Arduino, a CAN shield, and some logic to turn a VSS pulse into a CAN message.

[my8950]

Step 1 is finding an S40 and throwing a CAN analyzer on it and trying to trap the relevant messages. Or, maybe an FSM for the car that goes into detail here. My only experiences with CAN-enabled cars are Saabs, Jaguars, and Jeeps and *none* of those FSMs delve into the CAN at all, so I don't have a high expectation Volvo does, but hope springs external.

Then, in my head, it's Arduino, a CAN shield, and some logic to turn a VSS pulse into a CAN message.

CAN db's are not published in manuals, or anywhere else really. Even working for OEM's, they're quite difficult to get your hands on.