Retrofits

Depowering a 2015 STi Steering Rack [Part 4]

Preparing a Steering Rack for Electrification

I originally planned to use a BRZ rack for this retrofit as it doesn’t have any of the hydraulic lines to deal with and as basically a manual rack. I somehow stumbled upon a thread on Nasioc where someone else tried to use the BRZ rack in their Forester only to find out that it won’t work.


Previous Posts

The reason is that the BRZ is connected to the rear of the knuckle which is the reverse of AWD Subaru’s. So if we put this on a GD setup, our steering would be reversed. Not good.

I found this VA STi rack on eBay for relatively cheap. I’ve seen clearly bent VA STi racks listed for ~$500. A leaking rack is fine since we are depowering it, and a bent one may be fine for the right price, but I haven’t seen a good price until recently.

This rack came with tie rod ends, but we don’t need those since we already have the SuperPro Roll Center Kit installed.

We can start by pulling the hydraulic lines off. There are four M12x1.0 fittings along with an M14x1.5 and M16x1.5 fitting. I ordered plugs from BelMetric.com, however, you can cut the fittings off of the lines and seal them with epoxy or RTV.

At this point, I would recommend taking the boots off and removing the inner tie rod ends. But that’s not what I did as I was eager to get to the pinion within the control valve housing.

We can remove the rack guide which sets tension on the rack gear.

Next, we can pull the control valve housing out.

I don’t know what these are, I assume that they are relief valves or something, but we probably don’t need them anymore. I used a Torx T-70 to remove the caps. It doesn’t really fit but it works.

Unlike with the GD racks, the VA STi pinion pops right out without special tools.

Here we have the pinion and the spool valve. We don’t need the spool valve anymore so we can toss that.

The spool valve is held in place by a snap ring.

With the boots off, the inner clamps are one-time use, we can look at the inner tie rods. The lock washer needs to be bent back before we can attempt to break the inner tie rod loose. My adjustable wrench wouldn’t fit so I ordered a 30mm wrench from Amazon.

While we wait on the 30mm wrench to arrive, we can reassemble the rack. This will keep the rack gear from spinning as we try to remove the inner tie rods.

I did try to remove this end cap; it turned about a half turn and then stopped. This indentation was keeping it from turning. I eventually drilled it out to be able to remove the cap.

Once the 30mm wrench arrived we can knock off the inner tie rod ends.

And with some channel locks we can remove the end cap after drilling out the indentation.

And now we can pop out the rack gear.

Now we can remove the piston to prevent pressure from building up in the rack housing. In retrospect, I probably would just remove the teflon seal and leave the piston as a potential internal stop.

There is a c-clip holding the piston in, however, I didn’t see it until I removed the piston. Cutting a few slots in the piston and hitting a vise grip with a hammer made quick work of the piston.

Next, we need to weld up the pinion and the input shaft. They are connected internally via a torsion bar which allows the fluids to flow to their proper destinations. If they aren’t welded together then there will a delay in the steering response. Pardon my welds, I am still learning.

At this point, we can lube up the rack with grease and start the reassembly process. I’m using Redline CV-2.

Be sure to repack the bearing just above the pinion gear with grease.

And we can reinstall the end cap and the control valve housing. I think eventually, I will get the Moore Sport solid rack bushings, but for now, I just want to make sure this setup will work.

At this point we need to do some test fitting and figure out what I need to cut and/or fabricated. Leaving the inner tie rod ends off will make that process easier.


Update on BRZ P/S Motor Progress

I found another p/s controller on eBay with part of the harnesses intact. We don’t have the full run of the wiring but this is enough to figure out if this setup will even work.

For now, I am going to stick the controller into the radio slot. It might live there forever as eventually, I would like to go to a hidden/minimalist stereo setup. I only use my phone for music and I just need a permanent Bluetooth receiver, an eq/amp, and a volume knob. I have a few parts sourced, but that is a project for another day.

As for the controller, we only needed to run power to the battery, a ground, and one to an ignition on source. The two CANBUS wires (b&w) can remain unconnected. And the other two harnesses are from the power steering motor.

With everything connected the power steering works with the key on/engine off! I’ve only turned the wheel back and forth while the car is parked in the garage. But it seems to have way more assist than I was expecting. From what I’ve read, this is the bare minimum assist you can get without giving it some form of CANBUS input.

I can’t take it for a drive yet as I need to clean up the wiring and figure out a bypass for the p/s hydraulics. I honestly wasn’t expecting this to work so soon.

Cheers!


References

Nasioc Thread – Redneck DIY: De-powering your steering rack

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