Electric Power Steering
04-16-2010, 10:41 AM
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Electric Power Steering
More and more new cars are coming out with 'electric power steering' and this has been discussed before as a retrofit possibility for a 928. My understanding is that most implementations are actually an electronic PS pump used with a conventional steering rack ... the concept being you can pressurize fluid more efficiently with an electric motor than an engine-driven belt.
So what I'm curious about ...
1. Is the rack indeed completely unchanged?
2. Belt-driven pumps incorporate a so-called "speed-sensitive" characteristic that in some fashion reduces output pressure as engine speed increases.
Does an electric pump have this same functionality, and how is it controlled? Is there an electronic circuit that tracks engine speed, or possibly other inputs (vehicle speed, etc.) and tells the pump how much pressure to bleed off?
3. If you put a 100-bar rated electronic pump in a 928 and connected it up, would the steering feel different and if so, why?
So what I'm curious about ...
1. Is the rack indeed completely unchanged?
2. Belt-driven pumps incorporate a so-called "speed-sensitive" characteristic that in some fashion reduces output pressure as engine speed increases.
Does an electric pump have this same functionality, and how is it controlled? Is there an electronic circuit that tracks engine speed, or possibly other inputs (vehicle speed, etc.) and tells the pump how much pressure to bleed off?
3. If you put a 100-bar rated electronic pump in a 928 and connected it up, would the steering feel different and if so, why?
