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iwcham1979

Lupo power steering conversion

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On 11/28/2019 at 2:24 PM, mk2 said:

@RAB, on a 3L or A2, does the steering assist vary with speed like on later Polos with their electrically pumped hydraulic system? Slowly, max assist, at speed, no assist....? 

Also, just as a matter of interest- what happens on the electrical system if the power fails? Does the system lock (like on BMWs and then they crash...)- does it use a worm gear? Is the torsion sensor (and control electronics) built into the column, meaning no external control is needed- the ECU only providing a vehicle speed signal?

I don't have a 3L with power steering but the A2 does have electro-hydraulic P/S which looks identical to the Polo P/S. Yes, it looks as if the 3L P/S is built into the column - the rack is the same as a 3L without P/S:

https://volkswagen.7zap.com/en/rdw/lupo++lupo+3l+tdi/lu/2004-441/4/419-419040/

The control unit (not ECU) is also attached to the steering column.

The 3L with P/S has it's own ECU, so that may supply a speed signal.

RAB

Edited by RAB

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Hey @iwcham1979, you might be able to use a standard lupo hydraulic steering rack with a polo pump...? The electric power steering column system looks like a complete self controlled system so you could try it?

@RAB, is the 3L quite heavy for parking? I haven't driven a post 1991 car without PAS... Old mk2 golfs are no fun unless you've just left the gym. That drawing looks like there's a worm gearbox on the steering column shaft. At least it looks like it, as the motor axis is perpendicular to the column. I imagine that if that motor stops dead, the steering must lock up (just like leccy windows).

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The Lupo hydraulic rack looks as if it might be compatible with a 3L but where to put the electric pump - there's not much space available, i.e. none. The electric conversion would probably be easier.

The non- P/S 3L steering is not heavy at all but I would imagine that if the motor fails, it would be!

RAB

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Yeah. BMW learnt a very big lesson there (as did the whole car industry). Was in all the auto news as well as general press. Some newish beemer was driving along der autobahn at about 160kph. Electric power steering motor stops. No steering- locks up solid. Autobahn curves slightly. Not enough time to react. Dead. Recall. Happened a few times apparently.

In any safety critical system, where control is required, there MUST be a redundant system. In cars there is never any redundant system (too expensive) with the exception of seat belts and air bags, dual circuit brakes and handbrake.

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Yes a worm/pinion arrangement is hardly ideal since obviously it only works in one direction - the pinion can't drive the worm. Maybe that explains the special ECU which would prevent starting if the mechanism shows any sign of failing, in much the same way that the system works with the clutch/clutch actuator.

RAB

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