How much HP to drive a PS pump?

When I switched to massive slicks on my race car it made the effort to saw the wheel too tiring to drive with it's de-powered rack. By the end of an enduro I can barely hit an apex.

So... I am putting PS back on but I am going to drive the pump with a 12v DC electric motor at a fixed RPM (say... 1750 since it is a common number) to keep the drain on the engine at a fixed load on the alternator.

My question - how do I size the electric motor? Is 1/4HP enough? 1/3?

I tried to find numbers for the mini's unit but I'm coming up dry.

EDIT: DOES ANYONE HAVE AN 92-93 MR2 ELECTRIC STEERING PUMP TO SELL?

I don't have answer, but I do have a question.

Why not adapt an electro-hydraulic system you can find in a junkyard, off of, say, an MR2? Weight?

MG Bryan wrote: I don't have answer, but I do have a question. Why not adapt an electro-hydraulic system you can find in a junkyard, off of, say, an MR2? Weight?

Because I didn't know they had them.... EDIT placed

So you're going to use engine HP to drive the alternator at a load so it can convert the electrons to the electric motor to run the PS pump?

Wouldn't cost less power just to run the PS pump on the engine?

(And as an aside, I have personally known 5 race cars with de-powered racks that went faster after putting the stock PS back on just out of sheer effort on the driver. One we drag raced before and after and had no change in ET/MPH. Just saying...)

Javelin wrote: So you're going to use engine HP to drive the alternator at a load so it can convert the electrons to the electric motor to run the PS pump?

When the engine is turning 7k rpms, the pump is at some linear function of that. If I drive the PS pump off an electric load I can use an RPM independent of engine RPM so the only loading (above the steady minumum to provide assist) on the system will come from the current draw of effort to drive fluid to the rack in hard cornering. It frees me from having to drag it down the straights at high RPM when I do not need it. I can also locate it on the firewall (or wherever I want) rather than hanging it off the front of the motor.

That makes sense. A lot of sense, actually.

Carry on then.

I got my info from an old thread linked to a Honda sight. A road race team running an Integra dyno tested thier car to find that the stock PS pump ate 8hp. Ran it with an electric pump (MR2 I think) and the extra drag only ate less than 1HP.

I run an MR2 pump and control it with a heavy duty voltage regulator. Pretty cool being able to adjust your steering boost with the twist of a knob.

In reply to Cone_Junky:

Is it only the 92-93 models?

What is the load I should be expecting to wire for? 15A? 50A? What is the regulator rated for?

What are the fittings? I'll need to plumb my own lines.

Chevy been using electric pumps too since around 04 ti think. My 05 Cobalt has one.

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The pump is countersunk in the l/f wheel well. The 100A voltage controller is the silver box mounted above it. Then you can see the pressure line running diagonally to the rack.

I have it on an 80A breaker, I think the stock breaker/fuse in the Toyota is 50A.

I haven't personally tested amperage draw, but during my research I did see a reference to it only pulling 15-20A at peak.

Not sure on the lines. I just took my stock high pressure hose and the MR2 pressure hose to shop and had them frankensteined together.

This would make a really awesome GRM article (HINT HINT) as a how-to. I'd love to replace the giant PS pump in the Javelin, and the one in the 944 will over-pressurize on the AX course.

dont honda k series have electric PS? and all ecotec cars?
maybe one of those would be easier to find in a JY than an mr2

Besides freeing up a couple of ponies, I really like how it minimized my p/s system. I literally got rid of 8-10 feet of p/s line and was able to have the pump, reservoir, and rack within a 2 foot radius of each other. I haven't spent a considerable time on track (other than auto-x), so I don't know if I'll need to plumb some sort of cooler in the system, but that will be painless.

I really lucked out by getting the pump, hoses, relay, and both p/s computers from a guy on CL for $35. Sold the two computers for $130 on eBay. My voltage regulator was $100 and the custom line was $70. So my net cost was only about $75 The controller wasn't necassary, it will run fine on 12V, but it feels overboosted. I heard 9V was the optimum voltage, although the adjustable regulator allows me to adjust for DD, auto-x, or road racing. I could even mount the potentiometer knob in the cockpit to adjust on the fly if I wanted.

Yep, this is a highly applicable bit of tech...

I'm curious about using an electric pump for hydroboost brakes, and the notion of being able to adjust boost is awesome.

I have run my mr2 PS setup on my civic for 3 years. No regulators or anything fancy. Works great steering 255 hoosiers , never a problem with heat or voltage. Just running a large fuse and a solnoid. Paid $100 for the pump. I copied a couple of SCCA guys running who operate in the same fashion - just a switch on the dash

I don't have an MR2 pump, but I do have one out of an XT6 I'd sell. $30??

Hocrest wrote: I don't have an MR2 pump, but I do have one out of an XT6 I'd sell. $30??

It is electric/hydraulic that connects to a rack or the shaft?

Some of the newer cars use a setup made to mount on the steering shaft and a manual rack. Got a pic?

In reply to Giant Purple Snorklewacker:

Essentially a booster inline in the steering shaft? Crazy...

grm tech article please!

Before you do all that, look into a bigger steering wheel. 2" is a LOT of additional leverage.

Giant Purple Snorklewacker wrote:

Hocrest wrote: I don't have an MR2 pump, but I do have one out of an XT6 I'd sell. $30??

It is electric/hydraulic that connects to a rack or the shaft? Some of the newer cars use a setup made to mount on the steering shaft and a manual rack. Got a pic?

It's an electric motor/hydraulic pump. On the XT6 it mounts on the steering wheel and has a HP supply and LP return line going to the rack just like the belt driven pumps on other soobs. They're down at my old house in Pottsville,, but I could have one in Pittston some time next week.

This is why I love this board. I would of never thought of this. I just removed the power steering pump to save weight and HP on my circle track racer, and just suffered with fighting the wheel. Now I'm gonna head to the wreckers looking for electric PS pumps.

I wonder if the electric PS pump would also handle hydroboost brake booster on top of the PS rack.

Taiden wrote: I wonder if the electric PS pump would also handle hydroboost brake booster on top of the PS rack.

Maybe I'm dense, but wouldn't you thereby be running brake fluid through your steering rack? (I shudder to think anyone would try the reverse situation)

Look at the S2000 as well and it seems some of the Civics have it as well.