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Old 05-09-2013, 04:45 PM   #1
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Default Electrons vs. molecules: Electric Power Steering Conversion

In a friggin' Miata, no less!


Gone are the mechanical pump, the belt, associated brackets, the reservoir and original plumbing...

I kept the cooler loop in place, measured and had some pressure and return lines made, and the electric pump works like a charm...

I swear the car feels faster, but that was not my original objective.

A local shop built me a 110 Amp alternator for about $80, and I bypassed the ECU and wired in a circuit for the charge warning light.
I also ran 35mm wires from the battery straight to the alternator, and from battery negative to the chassis. I left the original wiring in place, as well.

I get about a .2 - .4 Volt drop in full lock. That's really not bad, at all.

Didn't take any pics during the install, because I was working frantically to finish up in time. (I did the work at the Mazda service, so I had to button things up before they closed.
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Old 05-09-2013, 04:52 PM   #2
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Here's the pump:

It's from a Peugeot 106, I got a great deal for a brand new pump from the manufacturer.



I made the mount out of heavy duty gas line clamps (I mean, gas mains). The clamps have welded nuts on them. I ran 10 mm bolts through the chassis and double nutted them on the clamps, making them as sturdy as I could. I also ran 6 mm all thread down to the chassis from the clamping nuts to eliminate any twist.
Also, that 70 Amp relay in the foreground is for that pump. Power and ground lines run all the way back to the battery, per Joe's advice.


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Electrons vs. molecules: Electric Power Steering Conversion-20130508175818.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508175812.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508175859.jpg  

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Old 05-09-2013, 04:56 PM   #3
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New pressure and return lines, void left by the mechanical pump and stuff, and pump connections...




Attached Thumbnails
Electrons vs. molecules: Electric Power Steering Conversion-20130508175859.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508180142.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508180031.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508180014.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508175923.jpg  

Electrons vs. molecules: Electric Power Steering Conversion-20130508175913.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508175830.jpg  
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Old 05-09-2013, 05:01 PM   #4
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I also went with a 110 Amp alternator. This one is an "LS" setup as opposed to the "PD" Miata uses, so I ran a wire to the charge light on the dashboard from the Alt L terminal.

Second pic shows the 35mm wire I ran straight from the battery B+ terminal..


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Electrons vs. molecules: Electric Power Steering Conversion-20130508175923.jpg   Electrons vs. molecules: Electric Power Steering Conversion-20130508180142.jpg  

Last edited by Godless Commie; 05-09-2013 at 08:44 PM.
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Old 05-09-2013, 05:02 PM   #5
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And, I ended up with leftovers...

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Old 05-09-2013, 05:14 PM   #6
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Well done Hakan!
Interesting and well executed conversion. +1

I was working in Turkey recently, amazing country
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Old 05-09-2013, 05:22 PM   #7
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YES!!
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Old 05-09-2013, 05:25 PM   #8
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Looks quite good.

What did you ultimately decide upon in terms of a control system for the pump? Does it run continuously, or did you get it hooked up to the MS with an RPM or VSS-based control?
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Old 05-09-2013, 08:44 PM   #9
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Quote:
Originally Posted by Joe Perez View Post
Looks quite good.

What did you ultimately decide upon in terms of a control system for the pump? Does it run continuously, or did you get it hooked up to the MS with an RPM or VSS-based control?
The short answer is, the pump runs as long as the ignition is on for the time being.

The proper answer, however involves short-term torture testing the entire unit by letting it run continuously.

You may have noticed in the pics that I have removed the carbon canister to make room for the pump. I am using the B+ side of the solenoid feed to switch the relay for now.

I tried using the L terminal on the alt, so that the pump would only come on once the alt has started charging, but the relay causes too much of a voltage drop on that lead (14.2 Volts drops down to 6.7 to switch the relay on, and that causes the charge warning light to come on).

Now, the unit IS rated for continuous duty. It has an expected life of 11000 hours, per the manufacturer. But, I'm afraid the current drain created by the pump as soon as I turn the key on may prove too much in the winter.

I have a couple of solutions I am mulling over.

(Please keep in mind our business is not unlike a fire station, meaning, we get to work as soon as we are called. So, there is no regular "free time" I can set aside to devote to such hobby work. It may be a few days before I can get a chance to actually lay a hand on the car.)

One solution is sourcing a very low current drain relay or switching circuit, and daisy chaining it with the main relay. That way I can still use the alternator Light output to trigger the pump.

Or, I could use the MS output as a "-" trigger, and come up with some sort of a parameter for it. (like RPM>500).

I may install an override switch to turn it on without the engine running. It will make pushing the car easier in case I have engine trouble.

There is one important thing to mention:
The steering feels like an expensive BMW... I now realize the main shortcoming of the mechanical pump, that is, it spins faster with the rising engine revs, and actually makes the steering lighter at speed.

It is quite different with the electric setup. While there is perfect assistance at zero or very low speeds, the feel is just great at speed, since the pump runs at a constant speed. I never expected that benefit, and it was a pleasant surprise.

And, the engine feels "unburdened". Even at low speeds.
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Old 05-09-2013, 08:47 PM   #10
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That's really innovative, I like it.
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Old 05-09-2013, 09:35 PM   #11
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Quote:
Originally Posted by Godless Commie View Post
There is one important thing to mention:
The steering feels like an expensive BMW... I now realize the main shortcoming of the mechanical pump, that is, it spins faster with the rising engine revs, and actually makes the steering lighter at speed.
Interesting...
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Old 05-10-2013, 03:28 AM   #12
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Quote:
Originally Posted by Godless Commie View Post
Power and ground lines run all the way back to the battery,
Waste. The starter motor draws more current than your pump, and doesn't run at the same time as the pump. Why not get B+ from the starter motor, and get ground from the block just like the starter motor? You can also get it from the alternator, which now has a 110 A capacity.
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Old 05-10-2013, 03:36 AM   #13
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Quote:
Originally Posted by JasonC SBB View Post
Why not get B+ from the starter motor, and get ground from the block just like the starter motor?
I gave him the idea.

The underlying concept is to put the pump as far away (electrically) from the alternator as possible, thus reducing its effect on the rest of the electrical system, particularly when the load on the motor changes rapidly.

The pump may draw less power than the starter, but have you noticed how the starter tends to really **** with the coil dwell requirements and injector opening times when it's active?
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Old 05-10-2013, 09:31 AM   #14
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Quote:
Originally Posted by Joe Perez View Post
The pump may draw less power than the starter, but have you noticed how the starter tends to really **** with the coil dwell requirements and injector opening times when it's active?
I thought this was due to the relatively big voltage drop when you're spinning the motor, and don't have the alternator running? With the car actually running voltage through most of the system should be 14ish volts, and therefore not have wacky dwell and PW issues.
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Old 05-10-2013, 09:48 AM   #15
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I like this. And the pump packages much nicer than the MR2 pump I was looking at. I wonder if that pump came in any cars state side since we obviously dont get frenchie cars.

I do think though if you're gonna connect it to the MS you might as well vary the duty cycle by VSS.
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Old 05-10-2013, 11:30 AM   #16
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This is a great idea. They should sell something like this for the V8 swap kits from Flyin Miata.
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Old 05-10-2013, 11:34 AM   #17
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04+ Mazda 3's non-mazdaspeed have electric power steering pumps also. Possibly a good option us US Folk
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Old 05-10-2013, 11:44 AM   #18
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Quote:
Originally Posted by duffbuster243 View Post
04+ Mazda 3's non-mazdaspeed have electric power steering pumps also. Possibly a good option us US Folk
It was a pain in the *** to find it but dealer price is like $700something. Mazda motorsports has it for less, but not enough less that I wouldnt want to just buy a motorsports electric power steering setup from Australia.
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Old 05-10-2013, 11:48 AM   #19
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Quote:
Originally Posted by Joe Perez View Post
I gave him the idea.

The underlying concept is to put the pump as far away (electrically) from the alternator as possible, thus reducing its effect on the rest of the electrical system, particularly when the load on the motor changes rapidly.
This would make sense if talking about the AC component of the load - e.g. 500 Hz ripple current. Then the battery will act like a large capacitor. Like why I recommend a capacitor on the COPs. But load that changes from one second to the next - the alternator and its control system (bandwitdh) will handle it. The rise time of the PS motor current isn't very fast.

The alternator itself puts a 13% ripple current on the entire electrical system? If the alternator is putting out 50A DC, that current has a 6.5A AC component. With a typical battery and cabling, there will be about 0.1-0.15 Volts of AC ripple, at about 500 Hz at 3500 RPM on the electrical system.

The other problem with cabling the big load all the way to the battery is that there will be an error in the charging voltage setpoint at the battery, when the load is heavy, due to the voltage drops in the cabling between the alternator and the battery.
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Old 05-10-2013, 11:49 AM   #20
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Quote:
Originally Posted by JasonC SBB View Post
Did you know that the alternator itself puts a 13% ripple current on the entire electrical system? If the alternator is putting out 50A DC, that current has a 6.5A AC component. With a typical battery and cabling, there will be about 0.1-0.15 Volts of AC ripple, at about 500 Hz at 3500 RPM on the electrical system.
This is why its bad to disconnect the battery from a running car.
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