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Old 02-19-2008, 11:00 AM   #1 (permalink)
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Converting power steering to electric power steering

So I was reading about the new Ford Fiesta the other day and saw that it (as well as many other new cars, and especially hybrids, it just clicked now for some reason) uses electric power steering. So, there is no load on the engine from the power steering, minus the electric load, and thats only under set conditions. What a great idea. So, I thought to myself, how can I do that with my car? Get a motor and pulley, or couple them directly. Relocate the PS pump off the engine. Setup a circuit to kick in the electric motor when your under say 20 mph, and/or when you are actually turning the wheels. Doesn't sound too hard, does it?

However, my question is, how much power does it take to spin that pump? Is it even worth the time of doing any of this work if it only sucks .25 hp? Probably not. Would it be better to just try to get a manual rack for the car? Possibly, but you loose the niceness of power steering. Wikipedia seems to think that you'll see a 3% gain from going to electric power steering. Thats roughly 1 - 1.5 mpg in either of my cars.

Thoughts?

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Old 02-19-2008, 11:06 AM   #2 (permalink)
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Can you disconnect the power steering now and see what kind of FE improvement you get before you go to the trouble? Then it would give you an idea if it is something worth the gain.
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Old 02-19-2008, 11:23 AM   #3 (permalink)
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I think your car uses the same rack as a toyota Corrola, and that does not have power steering,and all of them that I have driven were easy to steer, but it's one of those things that they can check off the list of frills that a new car has.
my civic is extreamly easy to steer, using only my little finger I can pull the wheel all the way sround at a dead stop.
the lack of power steering also frees up alot of space under the hood
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Old 02-19-2008, 11:33 AM   #4 (permalink)
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I was just reading an interesting writeup at Honda-Tech related to putting MR2 electric PS pumps into hondas... its apparently worth a few horsepower, and reportedly worth a few MPG...

I want to take my belt off and see sometime soon.

http://www.honda-tech.com/zerothread/2222562
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Old 02-19-2008, 11:56 AM   #5 (permalink)
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I know I can get a manual rack for the car, but its kind of a pain. If I was going to do this on the Paseo I'd probably just get a manual rack. However, you also need to change out the steering column since they are different lengths. If I was going to do this with the Matrix I would want to keep the power steering for the wife since thats what she drives.

The Honda link was interesting, but obviously not focused on fuel effeciency. I don't think my power steering is sucking up anywhere near 5 horsepower, let alone 8.5. Those numbers must be at peak rpms. I didn't read all the replies to the original message, but it sounds like he is still running the pump all the time since he just has it on a switch. I'd definitly want some sort of circuit to turn it off when not needed.

I wonder how an all electric rack from a Prius would fit into a Matrix...
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Old 02-19-2008, 12:19 PM   #6 (permalink)
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Since you're removing a component from the serpentine belt, you would have to find a new belt that would fit the new pulley configuration once you've done it. How hard is it to find these custom length belts since they obviously aren't factory spec length. That's my only concern with removing the power steering from my Camry, that I won't be able to find a belt that will fit the new pulley setup. If I knew there was a supplier that could provide these special length belts, I would have already done it.
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Old 02-19-2008, 12:55 PM   #7 (permalink)
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Quote:
Originally Posted by Daox View Post

The Honda link was interesting, but obviously not focused on fuel effeciency. I don't think my power steering is sucking up anywhere near 5 horsepower, let alone 8.5. Those numbers must be at peak rpms. I didn't read all the replies to the original message, but it sounds like he is still running the pump all the time since he just has it on a switch. I'd definitly want some sort of circuit to turn it off when not needed.
There's some important info in there though....

Quote:
There are two thick wires in one connector - one red and one black. You must remember that the pump draws a lot of current (allow for 60 amps), so you need heavy duty wiring. All the parts are commonly available from most automotive electrical suppliers. We used 8 gauge wires with an 80 amp circuit breaker. We mounted the Circuit Breaker beside the shifter so it is within easy reach of the driver so if he wishes, he can turn it on and off, but for a street car you would probably need to also use a high power relay to switch the Steering pump motor on after the engine is started. I don’t want to get too carried away as my electronics knowledge is very basic…
The pump draws 15A with no steering input, and 30-50A when turning the wheel quickly.
Sounds like it stays on to keep the system pressurized... 50A is about 1hp of energy... not sure how that translates to engine power, but that's a lot of freaking energy going into power steering....
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Old 02-19-2008, 01:52 PM   #8 (permalink)
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Quote:
Originally Posted by Daox View Post
The Honda link was interesting, but obviously not focused on fuel effeciency. I don't think my power steering is sucking up anywhere near 5 horsepower, let alone 8.5.
You would be surprised to see how much power it takes to spin the PS pump at 2000 to 3000 rpm. Its especially noticible on small displacement engines. My 1.8 BMW picked up 3mpg by going to manual steering and the power gain allowed me to go to a taller differential without giving up acceleration.
A simple solution I'm working on for a heavier FWD Volvo 850 is to replace the PS pump pulley with a clutch pulley from an AC compressor with a switch in the dash. Turn it on when I need it (slow speed city driving and parking) and off the rest of the time. Its just an idea at this point but to me it seems like a cheaper simpler solution.
Electric PS load can overpower your existing alternator. Most EPS systems have a built and capacitor to absorb the load spikes as well as speed and agle sensors to give the appropriate amount of assist.
Quote:
Originally Posted by NoCO2 View Post
Since you're removing a component from the serpentine belt. However, how hard is it to find a belt that will fit the new pulley configuration once you've done it? That's my only concern with removing the power steering from my Camry is that I won't be able to find a belt that will fit the new pulley setup.
Use a piece of wire to measure the length of the new belt routing and take that number to any auto parts store. Serpentine belts are available in 1/2" increments. Usually the last 3 digits of the part number represent the length. So XXXXXX375 would be a 37.5" belt. The same is true for V belts. You also have to make you to get the correct width and number of ridges. The hard part is finding an employee that can do more than just look up parts in the computer.
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Old 02-20-2008, 07:32 AM   #9 (permalink)
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In my car (3000 lb. Volvo, rear drive) I simply removed the belt. It's a bit heavy to steer at parking speeds but I'm OK with that. My front tires are at 52 psi; I'm sure that at 35-40 psi it would be tougher to steer.

I asked for comments before trying it. Suggestions were to get a manual rack (more of a project than I wanted) and also to 'loop' the p/s hoses. That is, the two hoses from rack to the pump, just connect them together and leave the pump out of the system. I'm sure that would make it easier but I didn't do it.

I did swap in synthetic fluid first because there will be less fluid circulation and after the belt delete the fluid might stay there a long time. The car uses ATF for the p/s system so I used Mobil 1 ATF. Suck out reservoir with turkey baster and replace. Three times, running system to mix fluid in between.
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Old 02-20-2008, 08:44 AM   #10 (permalink)
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I've noodled around with the idea of looping my hoses (with a 'breather' added) or just replacing the rack with a manual one (saves 35lbs) but in the end I need to consider my wife driving the car once in a while, so I'll probably just remove the belt... even at a stand still, its not all that hard to turn when the engine is off, so I'm not worried.

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