Power Rack&Pinion Steering

[Brett Proctor]

This is a continuation of a discussion that was brought up on Peters build.

I did a search as Peter suggested on electric power steering pumps on ebay and most of the electric power steering pumps are bolted to the steering column so you would have to use their column for the pump to work. However the 2003-09 Mazda 3 has a remote, body mounted electric power steering pump that looks like it might work.

I'll check it out next time I go to the wrecking yard along with the rack and pinion out of a Mazda Miata.

Not saying this will be for everyone but those that have rack and pinion steering on their cars have given nothing but positive reviews for the modification and having an electric pump even the VW guys can use it with no HP loss

One thing I need to check is how many amps the pump pulls and the wiring for it(ok two things)

 

[Brett Proctor]

Well after doing some research I found a factory service manual free on line. Its over 100mb

I found out that this is a popular modification to do and the Toyota MR2 is the sought after pump for doing it.

Another thing I found out is that the rack and pinion on the Mazda 3 has the tie rod connections like that of the bug(on the back side not the front of the spindle). Whats this mean?? No major modifications need to be made to the rack and pinion to make it work on the bug. Just install mounts.

One problem about using the Mazda 3 pump is that it uses a sensor thats located in the steering column. Its called the steering angle sensor. From what I gather it sends a signal to the pump to tell it which direction the wheel is turning so you may have to use the steering column out of this car for the system to work properly

 

[CyCo]

This is a mod I'd love to do as well. There are some stupid hoops to do it legally down here in Oz, but it's something I think would improve the handling of the car. I know there are some that say we don't really need it, but looking at it one way, if it improves the handling of the car, isn't that making the car a little safer to drive too? Besides, who 'needs' a Nova/Eureka/Sterling' anyway? I don't 'need' the rack & peanut steering, but I'd like it!!

Mind, I'd be happy with a non powered R&W set up, once your up to maneuvering speeds, it's fairly easy to spin that wheel. Well, with a fair bit of elbow grease.

 

[Brett Proctor]

Went to the Pick a Part Yard today and all of the Mazda 3 electric steering pumps were gone so someone is using them for something.

Also checked the Miata R&P and it wont work because the tie rods connect in front of the spindle. so whats this mean?? when you turn right you'll go left and vice versa.

I did find something cool.
Check out my manual R&P post

 

[Brett Proctor]

More info on this (thought I had already posted this but maybe I didn't hit the submit button*hmmm*)

Looks like the system requires a 50 amp power source.
This is the MR2 pump

 

[Peter]

Another popular conversion, if you can find one over there, is the GM Corsa B (late) and C, Astra, etc, steering column which has electric driven assistance, as long as you get ALL the bits, such as the steering ECU and wiring, it is a easy fit..


The Mercedes/Porsche pump doesn't have any sensors, it's all done internally, somehow. with the pressure diverted by the pinion, I think it has a sleeve with holes in it which moves slightly on the shaft, opening left or right valves like a diversion valve. Electrical connections are only battery, earth and alternator signal..

The Mercedes A-Class, (bit rare over there I believe) rack with shorter ball joints on is spot on.



Having driven 'Fidel' without the EPS I can say it is a very heavy handful at low speeds but once on the move it's not too bad, just a sod parking.

I would say to anyone thinking of fitting R&P it isn't difficult, biggest job is welding the mount across the frame head.
My 1995 effort

Scorpions


My idea on the Mercedes theme


The Mercedes A-Class in a forward mounted rack so a RHD rack flipped would be needed

 

[Brett Proctor]

Well this is becoming more complicated than anticipated. Its still doable.

I guess with our suspension layout bump steer is a big issue and from what I've read it can be lessen but you'll never get rid of it.


Because of this I've decided to look for a center takeoff R&P unit. The tie rods are equal length and are longer than other R&P units so bump steer will be less noticeable.



The issue I'm having with these is they aren't that compact(small)

I've also found some have electric power steering but haven't researched the power requirements yet.



Bump steer
In a nut shell you want the tie rods to have the same arc travel as the control arm(trailing arm).
This can be done by changing the location of the pivot point and length of the tie rods. Of course with our layout you'll never get it right but you can get it closer than what it is.







Of course building a custom one off unit would not be that hard but I'm looking for a way that everyone can do this with minimum effort at an affordable price.

 

[Peter]

Hmmm, interesting, what is that centre one in the drawing off of? with a remote pump like the Mercedes/Porsche one it would fit as with the steering gear removed there is a fair bit of room over the frame head, just needs a chunky plate to suit welding on as above.

With the centre of the rack 2" above the frame head I had to reverse the ball joints to under the arms with anti-bump steer bushes to get a good angle on the tie rods but it works fine with minimum bump steer.

I think the Honda Civic one in the photo might fit as the main part with the pump would be just in front of the bulkhead along side the frame head and not over the beam, would need mounting further back than mine that's for sure.
(Done while Brett was posting).

 

[Brett Proctor]

One thing to remember also is those pictures are 2 dimensional and the tie rod pivot points are on a different plane than the pivot points of the trailing arms.

If you want power steering but don't want to hassle with putting in rack and pinion a cheaper way to go is to just install a power steering gear box and keep the existing steering parts.

Just another option

 

[Peter]

One thing to remember also is those pictures are 2 dimensional and the tie rod pivot points are on a different plane than the pivot points of the trailing arms.

If you want power steering but don't want to hassle with putting in rack and pinion a cheaper way to go is to just install a power steering gear box and keep the existing steering parts.

Just another option


View attachment 7342

If that is something like the VW one in size or even a tad bigger it could work. What is it off of?
Would still need the electric pump but as we have established there is a large selection from various makers out there.

Power requirements; The fuse for the EPS on the Mercedes is a 'jumbo' 40Amp, (constant running but only draws full power when turning, very little in a straight line).

 

[Brett Proctor]

I found electric power steering kits that go between the steering column and the steering box so you keep the steering box. Even easier to get power steering

 

[islandman]

Now I like the sound of that, where does it come from? Does it need speed sensor's etc..

edit: Just googled Electric Power Steering, found that one and many many more. I didn't realise that this had become such a big market. It looks like a very doable conversion using the existing column if you can find space for the motor to mount.

 

[Peter]

That looks good but I wonder what thpse thin wires are for, if it is for any sort of CAN bus/ECU then screwed.

 

[Brett Proctor]

That looks good but I wonder what thpse thin wires are for, if it is for any sort of CAN bus/ECU then screwed.

There are kits out there that give you everything so no worries.
There is more that comes with that unit. I just didn't post it all.

 

[Brett Proctor]

OK I think I discovered the closest thing to factory R&P for the bug.

Mounts are narrow enough to fit on the frame head and its narrow enough to fit between the shock mounts. I know it isn't a center take off for the tie rods. Sometimes you have to take what you get and make it work.

I'll post dimensions later

 

[Brett Proctor]

 

[Peter]

That is near enough the same as the Citroen C15 one Scorpion and I are using, overall needs to be 1100mm so 85mm (3.3") of each end and re thread will do it UNLESS they are right and left threaded, in which case it might be a problem getting a LH threaded die but they are about. Mounts look near the same only saddle instead of single bolt.

 

[Brett Proctor]

After researching steering geometry and learning more about it I'm at a cross road as to whether to do it or not. As you can see from my posts I've kept moving forward with it.

Steering geometry is going to change with installing the rack and pinion unit and I'm not sure if its for the good. Bump steer may be more of an issue I think when installing the R&P, plus the tie rods on the R&P will be at an angle for them to connect to the mount at the spindle. If you look at vehicles that come stock with R&P the rods are about at the same alignment as the unit itself not at an angle as they would have to be to connect to the VW spindle.

Another thing I've noticed is, in the stock configuration the pitman arm travels in an arc to turn the wheels. With the R&P it travels in a straight line and its not aimed at the connection point at spindle as it does in vehicles that come with R&P. What does this all mean?? I don't know but I'm just trying to eliminate any issues before they happen.

Yes I know alot of these conversions have been done but was it worth it.

OK here's a good thing(I think) with installing R&P

There maybe a safety outcome.
With the stock setup the steering shaft is aimed right at you so if you should ever get in a front impact accident you could get the steering shaft shoved into your chest



On the R&P the connection point is at an angle providing a deflection point, also the R&P I have has a small collapsible section to it providing more safety

 

[islandman]

I fitted R&P to my first Nova, I mounted to the R&P as low down as possible on the frame head so that when the car is on the ground the R&P arms are practically horizontal, thus removing some of the effects of bump steer.

I have driven quite a few miles with my set-up since I installed it about 20 years ago and I can't say I ever remember noticing bump steer whilst driving. I'm not saying there may not be some there, but its not enough that it has ever stuck in my mind. And yes you are quite right, having two offset UJ's as part of the column means it won't push the column into your chest if the worst occurs.

 

[Peter]

'Ats right David, I always had misgivings about the OEM steering in a shunt. Like most R&P converts I have a angled joint at the bottom of the column and in my case a sliding shaft in the Triumph column too.

As far as 'bump steer' goes I haven't noticed any, just nice smooth steering, in my photos the arms look as though they drop down but that is because there is no weight on the suspension, under normal load they are straight. My rack is 3cm above the frame head and 30cm forward of the cross member.
A slight back angle is desirable because as you say the track rod moves in an arc and fully out will be almost dead in line, starting out in line means the road would be forward of the rack at full stretch.
As you know, the amount is important for the Ackerman steering where the inboard wheel turns more than the outside wheel.