Introducing Colin - a Mini-ature WRX

Pete. (l33t FS) said:

#amidoingitright

Neon wheels acquired from a salvage yard in Warren MI that actually had what they said they had

yes.  yes you are.

Let's back up a bit.

Pete. (l33t FS) said:

Stop right there.  You see that dowel pin/rivet looking thing at the top of the input?

Okay, let's continue.

New problem... okay, two new problems.  First new problem is that the pinion shaft is actually two piece, and the outer section can slide freely up and down.  Will need to break out the welder to deal with that, although I may disassemble the thing first to make sure it goes together in the right spot.

It turns out this is a major problem.  Not only can the outer piece slide up and down, but it can also rotate, and this clued me in as to what was actually going on and how I had majorly berkeleyed up.

More later, McMuffins are required.  Going to explain this and then go back to soothing, soothing wiring

So.  How power steering works.

It is a neat negative feedback loop. There is a vertical spool valve in the quill that directs pump pressure to the return line or to either side of a piston mounted in the middle of the rack.  Rotating the spool valve inside its housing one way or the other will direct flow to the appropriate side of the ram.  The housing is connected to the outside of the input shaft and the spool valve is connected via a torsion spring directly to the input shaft.  Steering force twists the spring, rotating the spool valve in the housing. More twist means more assist, which untwists the spring, and it all feels very progressive and natural.

That rivet, or dowel, connects the torsion spring to the shaft.

This means that the two shafts must be precisely aligned with each other, or the power assist will be biased one way or the other.  As in, the steering can actually ram itself all the way to one side with no steering input, which is a failure mode that can happen when the torsion spring gets bent.

So, yesterday, since I was able to get some proper sized steel tube from the metal supermarket (no 3/4" ID steering shafts in the Batcave), instead of modding the fuel tank, I made the steering shaft and set about fixing the rack.

The steering shaft came out very nice.  The rack...

I pulled the input assembly off of the rack, removed the whole quill assembly, and then one snapring and pulled the spool valves housing off.  Now I was looking at this.

No obvious things things to see.  So, I moved things back and forth against their stops and eyeballed the center position, tacked it into place, and not trusting just some welds on top I drilled a 10.5/64ths hole so I could tap it 5mm-.8 to take a hardened bolt I found, which would be installed with green Loctite before cutting the ends flush.

Then this happened.

My right wrist has been gimping for a while so I was trying to tap left handed, and I ended up breaking the tap off.

Arg.

Was able to remove the tap, decided I could deal with that part on the car after Snap-On replaced the tap on Tuesday, so I went to reassemble the rack so it could go back in the car so I could put the steering shaft in so I could finish firewall mods.

Step one, put housing and circlip on.

I had welded the two pieces together too low to get the circlip in.  And found out AFTER drilling the through hole.

Disgusted, I threw everything into the car and went home.  Time to buy another rack.

One each: MS GPIO kit, one collection of additionals components, one high side driver control box.  Not pictured: Assembly instructions.

I knew this going in.  And I knew that the Mshift firmware has been abandoned since 2015ish.  However, there are two major reasons why this PITA is necessary:

The Microsquirt based trans controller does not support the 4EAT.

The Microsquirt based trans controller does not have a gear indicator.

Saw  this for sale today and thought of your build.........Facebook