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Old 10-28-2015, 12:43 AM   #28 (permalink)
oil pan 4
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Quote:
Originally Posted by OilFilter View Post
It probably would be relatively easy to directly couple an electric motor to the stock PS pump and spin it at idle speed. No question that would be enough power. And it would sure make the plumbing easy! Might be able to find a motor with a longer duty cycle than that other pump I was looking at.
The largest motor that I could find and would fit is 3/4hp that weighs about 33lb. and cost $400 for a decent one or you can buy a cheap $150 motor every few weeks as they burn up.
It might have a very long duty cycle if it were not in a 200'F environment.
I already know it takes about 200 watts to spin the power steering pump over at close to idle speed at no load (not trying to turn the steering wheel) just letting all the fluid bypass.
Note pump speed may be slightly higher than crank speed, in at least some vehicles the power steering pumps appears to be slightly over driven. So pump speed may be closer to 1000rpm.
If it takes 1000psi to drive 2.5gpm through a steering box that is about 1.5hp when turning the wheel.
Not a problem for a 12v DC motor at room temperature or start up, in those conditions you could run a motor like that at 200% load for a minute or 2 with no ill effect. But start with the motor at 200'F warmed from heat coming off the engine, I would expect that motor to be scorching hot after maybe 30 seconds of use and if it has a thermal over load it will trip.
This is why I am going to use a hydraulic power unit slung down low and forward, maybe even just behind the bumper (not next to the scorching hot engine) and only weighs about 20lb.

This mod is fairly common to do in electric vehicles, but the motor driving the power steering pump isn't sitting near 900'F exhaust manifolds.
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