Electric Power Steering Pump - 1967 Barracuda

[DNasty777]

Just for anyone who runs across this. The Volvo pump I'm using is a problem, not enough flow. I hooked a flow meter up to it and it runs just under 1 GPM in it's limp mode, so it's just fine for around town driving, but no good for racing / autocrossing. It looks like you need at least 2 to 2.5 GPM for the borgeson box, and I suspect more for the OEM box. The OEM specs are something like 2.7 GPM for the factory pumps at idle.

You can program an arduino to spoof the CANbus messaging for the Volvo pump to get it out of limp mode. You could even add a potentiometer input to the arduino to get variable pump speed or hook up a VSS input to have it do that automatically. That's assuming the Volvo can put out 2.7gpm when its out of limp mode.

 

[hal9000]

Yep, that I can do. But unless I can find proof that the pump can flow at least 2 GPM, it won't mater. If anybody has some idea where to look for that (and the documented CAN messages for the pump speed) I'm all ears! I can knock out a little board and firmware to run it all. In the cars that I have driven in the past with this pump, they seem to idle down and spin up as soon as you get after it on the steering wheel, so a steering angle sensor would seem the way to go. I don't think they instrument the load on the steering shaft.

EPAS has a kit for this it looks like, I asked if they sold just the controller and if it would work with other pumps and they said it was all custom for there pump (which looks more or less like the volvo one) but is also listed to flow 5 GPM!

 

[hal9000]

Ok, doing a little more research, in the years since I did this lots of people have published the CAN bus info to run the pump, so that's great, but now we have to figure out how much the Volvo pump will flow. I know it's supposed to be running 70 or 80% in limp mode, and that limp mode measures out right under 1GPM for me on my inline digital flow meter. A lot of others have done work with other OEM EPAS systems. I'll put some links here for people in case they want to dig around and learn more.

This one has a note about Volvo pump speeds, and it does seem to verify the ~75% speed, with this known, we should not be looking at Volvo pumps for high performance steering for Mopars. Volvo Electric power steering conversion (Full write up)

Some general great discussion on the mater and a link to some source code. Volvo and Other Electric PS Pump Controller

Someone who offers code and a product to control the pumps: GitHub - NMSTEC/Volvo_EPS_FREE

A great end to end video and write up, with links to there source and a great google doc with more general info in it.

For myself, I will probably just put the Van pump I have on my Barracuda in the short term as I don't have the energy to deal with another EPAS setup right now and I don't think the Volvo can really be made to work becuse of its low max flow. To do EPAS right, you really need a steering angle sensor to ramp the pump up quick IMO. So one has to add that, or more easily add a VSS signal, but then, you pump is super loud when going slow...

EDIT: I found a reasonable flow table here! https://www.nmstec.ca/2023/05/01/which-ehpas-pump-is-right-for-me/ some info copied below in case it ever goes down.

Volvo pump: 1200psi 1.91 GPM

 

[DNasty777]

Excellent job on the research. Have you thought about switching to a manual box and running the inline motor EPAS units, like whats found in the prius? I think the steering box style is the problem with flow, the hydraulic steering racks probably take way less flow.

 

[hal9000]

Excellent job on the research. Have you thought about switching to a manual box and running the inline motor EPAS units, like whats found in the prius? I think the steering box style is the problem with flow, the hydraulic steering racks probably take way less flow.

That's not a half bad idea, but I don't think there is enough room to easily fit it all in there. I agree, the racks take a less flow (and use more pressure typically) from some basic research. The hydraulic assist circuit area is also much smaller on the all the racks I've seen so it would take more pressure less flow for the same amount of power.