If I have one complaint about the race car it’s that the steering wheel is fairly brutal on the driver. With aero and 9″ slicks going through a Manual rack there’s a ton of feedback. Too much feedback. And because of how heavy it is even with the Manual rack (again, 9″ slicks), I haven’t even wanted to run a depowered PS rack.
Of course, power steering would fix this, but it’s heavy, often messy when they boil over, and saps power from the engine. I already don’t have nearly enough power, so that’s out.
However, I found out recently about a GM electric steering column that’s been seeing heavy use in Rally and other offroad racing disciplines, along with a company that sells a controller that spoofs the CanBus signal, and allows you to adjust the amount of steering assist. I’ve been toying with the idea for a while now, but an autox buddy had one installed in his Ecotec powered Lotus 7 clone and frigging loves it. With some direct experience and some research in the bag, the time came to start building.
So here’s the plan:
-Snag a steering column & controller
-Fabricate mounts and an intermediate “adapter” to go between the end of the GM rack and the input of the Miata’s intermediate shaft. I want to keep it as bolt-in as possible in case something breaks and I need to swap stock parts in.
-De-Power and refurb the PS rack I’ve had sitting on the shelf for ages now waiting for its moment to shine. With the power steering, adding in the faster rack would be good. I’m going to pair this with a smaller steering wheel to lower the distance my hands will need to travel on the wheel for a given angle of input.
-Add steering rack travel limiters to prevent the 15x10s rubbing on the sway-bar in paddock / grid / during big spins.
The steering column in question is out of the Saturn Vue & Chevy Equinox, and is a little over 3″ shorter than the stock NA steering column. I went to the local Pull A Part and snagged one out of the yard, along with the full wiring harness. The nice thing about this column is that they’re built for far heavier cars than what I’m putting it into, so it should be plenty. This system has seen extensive use in the offroad racing community, and I’ve seen them installed in things between ride-on lawnmowers and Unimogs. It appears to be insanely versatile.
To get everything lined up in the right place took a lot of careful measurement. It doesn’t need to be micron-perfect, but within 1/8″ or so is the goal.
The mounts are within an inch or so of where the Miata’s mounts are, so I’ll be able to use the stock upper mounts points (using a modified stock column mount), and will need to re-engineer the lower mounts. The plan is to weld brackets onto a stock upper column mount, and cut the lower mounts off of a sacrificial stock column.
Overall, the GM column is about 3″ shorter than the stock Miata column. This is a good thing as it will allow me to get the steering wheel in a stock location without having to modify the intermediate shaft that runs between the column and rack.
After disassembling the sacrificial stock Miata steering column, I discovered, much to my amazement, that the lower section (where it bolts to the intermediate shaft) is 3/4″ diameter. And just about every aftermarket steering component out there is 3/4″. Due to that size being ubiquitous, EPowerSteering.com sells a 16mm spline to 3/4″ shaft adapter. I’ll use that and a section of the stock steering column to build a small adapter that will spline / bolt onto the bottom of the GM column, and spline / bolt into the stock intermediate shaft.
I took the parts to a buddy’s shop where we cut the stock steering column down to length, and TIG welded the parts together. It could have been MIGed, but with the threads and fine splines, I wanted to avoid spatter at all costs.
After it was welded, I drilled and tapped through the adapter and spline stub to run a bolt to serve as a failsafe in the event the weld breaks, as that weld essentially is a single-point-of-failure in the steering system.
With the column setup complete, it was time to start fabbing the mounts in the car.