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Electric power steering




Oh, sure, sure.

The 02 is not a car that does need a power steering. It's easy enough to drive and, if it's not wheeled like a monster truck, does not need too much effort to steer.

Some things I did to my car are not done because of their effect but because of the making. I like changing and improving things and, if possible, realizing my own ideas. How to fix this, how to connect that, how to combine those... The way is the target! Some of them are invisible, for example the sunroof drive, but whenever I'm driving and it's not raining, I enjoy the comfort.

The other aspect is... We all get older. Don't we? Let's imagine: when we are 70+ or 80+ years, we may think about choosing the 02 for an afternoon drive to a coffee with friends or choosing the modern car because it's more comfortable and the 02 gets forgotten in the garage or is for sale. Horrible.

And the third: many years ago, I used to know somebody who has lost his right arm in WW2. To be able to drive, his car was modified to his special demands and today I wanted to find out how to modify an 02 for certain special demands. I think it can't be excluded that even a handicapped person wants to drive an old 02, so let's make this possible for him or her.

Ok, here's a short description of the project.

This is a power steering unit taken from a 2001 Renault Twingo:


I had to buy this lower part of the Renault spindle extra because the delivered spindle wasn't massive enough to be connected to the BMW shaft:


The black part is scrapped, the silver part is fixed to the lower BMW spindle by a sleeve I let lathed.

The installation into the car was quite easy. All the Renault stuff from the power unit upwards was removed and the yellow/gold pipe was shortened to about 20mm. The black BMW pipe was shortened, too, and slotted. After removing the paint inside the BMW pipe could be pushed over the Renault pipe. Fixed with a strong clamp taken from a child's scooter- finished. In the lower area I added a kind of torque support to the left bolt of the heater box. Now the steering column can't be dragged downwards while deboarding.

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The blue part in the background is the support, behind it the heater box, to the left the remaining BMW spindle and above the upper blower hose. The later added sleeve is located inside the black pipe flange in the firewall- invisible from the engine bay (no pic).

The upper crossover was some more difficult because the Renault shaft has got a kind of oval O-profile. The crossover could be done between ignition lock and top bearing, what is easier, but the slots in the sleeve for the lock are much wider than the BMW slots. This would mean much more clearance even if the wheel is locked and it would be quicker to knock out what I didn't want. Here's an overview:


02 lock with switch, Renault shaft and 02 shaft. The 02 shaft was routed or milled to this oval profile, too, and connected to the Renault unit by this oval sleeve inside the lock sleeve. The measurements had to be some exact because there's not so much space between lock housing and steering unit.

Now let's come to the electric part. It's enourmous. There are seven wires coming out of the Renault steering control unit: 30 (power), 31 (ground) and 15 (switched power). No problem. The next two are for diagnosis -not needed- no problem.

Then there's a wire for the engine signal. The SCU requires a negative square signal. This doesn't need to be the exact RPM, but only to tell the SCU if the engine is running or not. Since I don't have a TDC sensor or something similar on my engine, I bought an adjustable aftermarket simulator unit made for Opel Corsa from Portugal. Unfortunately this unit delivers a positive signal, so I had to reverse it into negative by a small transistor circuit with a base resistor. In the meantime, these units are available for Renault SCUs, too.

The last one is the speed signal. This signal is parallel delivered by the Opel simulator unit but it is always fix- if adjustable or not, there's no dependance on the real speed. This means that the power steering is in order while driving with 80mph on the highway and the 02 gets swammy like a 59 Cadillac Eldorado. No way.

So I bought a VDO speedo cable sensor:


Just a little bigger than a thumb. A male thumb. It delivers a square signal with the correct polarity and six beeps per turn. Basing on the fact that the SCU in the Renault switches off the steering at 70kmh and the 02 has W 0,91, I calculated that now in the 02 it switches off at about 58kmh. That's ok.

Well, the steering unit was ready to be installed, crossovers made, all signals provided- but no space for the SCU near the steering column. It is still a bit bigger than a 318i ECU. So I located it under the passenger seat with a kind of aluminium basket. This meant to prolong 15 wires to 2,5 metres- an entire afternoon job with solding, shrink hose and so on. Gosh:

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Ground is everywhere, and power I already ran under the rear seat for the Pioneer steamer. The costs: 70 or 75€ shipped for the steering, 25€ for the spindle, 35€ for the simulator and 44€ for the speed sensor. Not too expensive I think.

All in all, this upgrade is not done in a lunchbreak. Especially the wiring action was much more effort than expected, but: maybe we get older...

With improvized wiring and not taped yet, but already working:


Feel free to ask for more pictures, if interested! Thanks for watching!

Edited by Henning

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Excuse the dumb question: does this just provide additional torque to the existing steering box or does it replace the steering box?

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Hi Simeon,

there's no question that's too dumb to be asked. In the last picture you can see a brass colored tin surrounded by the blower hose. That's an electric motor what supports the steering force. So yes, it provides additional torque, depending on the car's speed. The original 02 steering box remains on its place on the front axle's subframe. In the engine bay there's absolutely nothing to be seen of the upgrade and if the underdash panels are installed, the entire system is completely invisible.





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