Electric Power steering (EPS)

[richbaker78]

I dont know if this has been done before but I thought it would be useful to do a sort of blog of my power steering set up as is develops:

EPS is becoming more and more common in modern cars and is fitted to Vauxhal Corsas, MGFs, Fiat Puntos and probably loads of other cars I dont know about.

The units are basically an electric motor which provides the assistance at the column rather than at the rack as a conventional system would.

EDIT: EPS systems do not require engine power to operate. Thus, a vehicle equipped with EPS may achieve an estimated improvement in fuel economy of 3% compared to the same vehicle with conventional HPS. As an added benefit, more of the engine's power is transmitted to its intended location


For us Modders this is great as it means the whole unit can effectively be transplanted into pretty much anything. Im not the first to do this - its a common midification in older non PAs cars, grasstrackers and rallycars.....and I should give credit to Ricola who has used it in his Phantom and provided me with assistance / ideas.

Choosing a column: There are numerous sources of columns as mentioned before, but the column of choice seems to be from a corsa B, or corsa C - i dont really know why!. The going rate seems to be £100-200 for one of these depending on your luck and ebay skills and the for that you should get a column & motor, a link bar with two UJs on and most important the steering control unit (a small box of electrickery).
this is what the coluymn should look like:



Wheel choice: there are a number of options - but i think if you want to retain your original wheel you will make life hard for yourself - plus a massive wheel will no longer be required if your conversion is succesful. For the corsa c a steering wheel boss can be used to convert to MOMO for about £25 on ebay. Corsa B has a much wide choice available....once you have a boss...the world of wheel choice is your oyster.

other important bits: The corsa rack requires a speed signal which when fitted to a corsa varies the assistance given to the steering related to your speed...however when you dont have a corsa attached to your column anymore you will require a small plug in unit which replaces the signal. There are a few of these availble and there are regular traders on ebay selling these - prices range from £40-£100 depending on how you wish to adjust it. i will be having a manual adjuster fitted to my dashboard. NOTE: if you go for a non corsa rack then you might find it hard to buy one of these for eg a fiat rack.

the rest of the steering system If you steering system is not in tip top condition - ie pretty much slack free...EPS will be a bad idea as it will accentuate the sloppiness already presnt in your system. Because my old steering box was worn out and slack I ditched it and have converted to use a Bedford rascal steering rack - thats covered in another thread on this forum. Just because thats what I have done does not mean you cannot do this with the original steering box set up...but as already mentioned the steering really must be in tip top condition.

so thats the background....heres the start of proper work:

First job was to sort out mounting the steering column. This is a time consuming job and you have to get it right or your wheel will be off centre and column all wonky. The column is heavy - but leave the motor on it for positioning purposes.

I removed all the original mounting gubbins on the van - there are 2x 10mm bolts on the front panel - i reused these mounting points and drilled 2 pieces of 20mm box cut to an approximate length (basically where they met the back of the dash).

Then I made a frame for the corsa rack - again out of 20mm box - this picks up the 4 existing points on the rack. I unplugged an removved the ecu during this work to make sure it didnt get fried or damaged. The frame is essentially two parallel bars with brackets to pick up the rack mounts. If you have a tilting mechanism as I do then its important to make sure the UJ is not overstretched causing tight spots. ONce youve tacked the frame together test the steering action in all positions of adjustment. you can see the frame in the pic below:



ONce this is good its time to fit the column to the van - initially this will be just precariously dangled and takc welded with whatever spare steel you have to hand. I used some plastic pipe to support the bottom of the clumn as this could be trimmed to length to give me the wheel height, I thne used ratched straps to adjust the location of the column in all directions. I then sat in the driving seat and checked it all felt right and that i had enough clearance for my fet / knees on the pedals etc......once your happy tack weld it into place......

this pic is looking in from above the dash - obviously at this point we are only concerned with positioning - this will all be remade later properly and strong!



it should look something like this....



with that done then check again that its all lined up how you want it etc and if your using a steering box, that it all lines up with the rubber connecting donut thing! with that done, then start working out how you are going to make your frame to support this all properly. For this part I will use 15mm thin wall tubing cos its less industrial and more easily bent by my knees when i crash!!

thats all so far....updates will follow.

[ricola]

Good summary Rich

The main reason for using the corsa column is that it is not heavily integrated into the car's electrical system (CAN) like most others.

Another big consideration is column switchgear. I managed to adapt the column to take the original stalks in the phantom, but you will either have to work out the corsa wiring or one popular modification is welding the top end of your original column on to the corsa column and keep all your existing wiring, this is easier to do on a height adjustable column.
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http://www.ricola.co.uk

[richbaker78]

cheers Rich,

a couple more hours in the barn have been spent re-inforcing what has been mocked into place above.

I once had parcel shelves in my van and found em very useful for putting stuff on and for my GF to put her feet up on whilst we were driving....unfortunatly the ones I had were sh*te and fell apart so I thought i would tie in their re-design with making a strong framework to support the column.

First job was to provide some vertical support so I could remove the pice of drainpip holding up the column. getting the angles was a pain...but its in now.....rememebr to check clearance on the pedals etc. you will also notice i have opted to bolt these onto the kickboard - this is so I can remove the whole column and frame assembly should I encounter problems in future and have to replace it with another.....


next up i made a long bar with a matched radias to the dashboard on the end (for looks really) -this will form the front edge of the under dash parcel shelf and will be further re-inforced. THe end is bolted to the steering column subframe for the same reason as above:


the pipe supporting the column can now be removed and the colum supports its own weight.....Its worth peridically throughout checking the alignment to ensure things havent got out of line. I can also test the tilt mechanism now - all is good

[hege]

I'm interested in something a bit more powerful than the corsa unit? are there any available that are as easy to install as the one in the corsa?
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T3 Race Taxi

[richbaker78]

i honestly have no idea im afraid....why do you need something more powerful? THe alternative is of course hydraulics but then your into more difficulties fitting it and finding a rack of appropriate size - it has been done thought I believe.

[ricola]

If anything I'd want one less powerful. These have been installed in big engined cobra replicas with no problem, do you want to fit one in a truck or something?! Remember the corsa has the whole engine over the steering axle so far heavier duty than any VW application...
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http://www.ricola.co.uk

[hege]

Two BMW's run corsa units, and other one just began using slick tyres instead of street tyres and burnt the engine. Both have reported that the motor runs extremely hot when driving on the race track.

I'm thinking of options for our race project, it's a T3 transporter, so factory hydraulic PS is an option. But it weighs, needs a cooler and isn't as efficient as the corsa one.
I know the corsa unit probably is more than enough for the street, but sadly it isn't suitable for our use.
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T3 Race Taxi

[sven]

Oh, what a nice setup! I have to this on my van.

I rented a Fiat Panda when I went to Italy recently, they have a "city"-button. When on, the EPS is powered. When off, the EPS is off. It was a uge difference when using the EPS in cities, but it was also VERY nice to get rid of it on the highway.

[richbaker78]

hege - i would have thought the reason for the heating issue would be due to the fact that the BMW engine is located at the front - ie more wieght over the wheels than in the standard application (corsa) rather than the amount of use they are getting. As ricola points out the wieght you will have in the t3 will be a lot less (especially if its a lightweight race project)

The corsa rack does unfortunatly have a bit of a reputation for some unreliability problems regardless of the application....but i figured that since they are readily available in scrapyards and on Ebay for not Huge amounts of money then i could replace mine very easily (just two bolts) still not much use in the mddle of a race though!!

I have read that you can get electric steering pumps rather than engine driven ones? perhaps this would be an option (not sure it would save much weight though) - last month the Practical Performance car magazine track day Rolls Royce was fitted with one due to space restrictions in the engine bay when they were fitting a turbo....i can find out more if required as i still have the magazine somewhere!

[hege]

Thanks for the reply's, sorry that I haven't had the time to reply. The last days have been spent trying to find a PS rack for a T3 and I found one, and we also have one for spare in my project car.

So our system will consist of a Subaru PS pump, Subaru wrx sti cooler and the stock T3 steering rack. We will also use a 2:1 steering quickner. It's a unit with gears inside that you mount between the steering wheel and the steering rack to make the steering two times faster.

This route probably isn't the cheapest one, but it doesn't take much effort to bolt on a stock item instead of another stock item.

Our car will be heavier than the BMW's that have had corsa EPS (even in the front), but the higher caster angle they are running might also contribute to the loads the EPS has to fight against. We are planning to run the car up to 6 hours a day on race tracks, so we don't want to risk it. The heating could also be countered by cooling the system, but that would take too much of our time to test it. I would be 100% comfortable running one on the street though, after seeing what they can put up with on the track.
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T3 Race Taxi

[ricola]

[sven]