EPAS, or E Power Steering

[hoveringuy]

So that said, any updates here?

Yeah, no PS sucks!

I'm about to start on version two of my EPAS swap which will use a much lighter assist motor. and hopefully it won't be so massively overboosted as before. I won't have any feedback on that for a month or two...

If you get an off-the-shelf kit the one from the Netherlands is more expensive but it's actually tuned to our chassis.

[hoveringuy]

The Ford Fiesta one won't fit without some hacking of the dash that I don't want to do. It's just the little junction box on top otherwise it would fit really well.



So, I ordered a Toyota Aygo unit from Ebay UK. The Aygo is a 2300lb car with skinny little tires and supposedly has a very minimal assist motor. I know it will fit.

[hoveringuy]

hexagone The Toyota Aygo EPAS actually works really well. It's much smaller than the Vue one, so besides weighing much less it rotates a bit more so that it doesn't hang down in front of the pedals. The level of assist is perfect. I can turn the gain up to 7 or 8 out of 10 and it's easy to maneuver in a parking lot, and turned down to 3 or 4 it's great for driving. Even at 3 or 4 it's perfectly comfortable in a parking lot.

It's hard to compare this to my hydraulic system because I had a purple tag rack and a well-tuned pressure regulator. My hydro system was just sublime, so anything compared to that would be like the girl you dated AFTER Heidi Klum.

I'll start with my complaints about the Vue EPAS. It was overboosted, steering was twitchy and the level of assist was to the point that it would occasionally get induced oscillations in the steering as it reacted to sympathetically to oscillations. Feeling was naturally really bad.

The Aygo is a European market compact that weighs about 2300 lbs. The size of the motor and the diameter of the gears is smaller so the unit has much less inertia to start with, so it's easier to turn the shaft. Assist and weight is perfect for cornering. It's not nervous or twitchy on the straight highway and tracks perfectly. Good on-center feel.

I still have the hydraulic rack installed presently with just the belt bypassing the pulley, but the only complaint is that the return to center force is weak. You need to turn into the corner, and you need to turn out consciously, whereas the hydro had the natural return to center force from the wheel caster. I need to swap my rack for a manual E85 Z4 rack which keeps the 3.0:1 ratio but doesn't have the hydraulics, I think that will help quite a bit.

I have yet to track the car so this is a first impression.

[Panici]

Lack of return-to-center would be a dealbreaker for me.
Have you tested how it behaves when you get the car sideways?

That's my main reason for keeping a power rack in my vehicles, as having to muscle a manual rack while in a slide could be disastrous.

[hoveringuy]

Lack of return-to-center would be a dealbreaker for me.
Have you tested how it behaves when you get the car sideways?

That's my main reason for keeping a power rack in my vehicles, as having to muscle a manual rack while in a slide could be disastrous.

Draining the PS fluid did help in regards to the return to center, not pushing a bunch of fluid around now. It's there now, but still not as strong as the hydro system. It does weight-up with G's.

There's no muscling with this right now, and the feel is definitely very direct and there is feedback. I drove it on an errand yesterday and it absolutely didn't feel like a science project. It was mostly transparent that it was electric.

I'm going to have some other people drive it to gather feedback, and I also need to do some hard driving.

I recognize that this will never feel as good as my Purple tag system, but I also gain the ability to dial-up assist for parking lots by making it speed sensitive, I'll lose about 7lbs (even more when I go with the Z4 manual rack..), gain 3-4hp, lose hot power steering fluid, a bunch of hoses and front-end accessories.

I removed the Vue one because it wasn't up to standard, I think this is.

[Victell]

...a well-tuned pressure regulator...

I have been wanting to tinker with this, but am not sure where to start. Any recommendations?

[hoveringuy]

I have been wanting to tinker with this, but am not sure where to start. Any recommendations?

The short version is that I had a Luk LF-30 pump off an E90 with a stock pressure of 130bar (N52 swap). It was ridiculously overboosted on the E30. The same pump is used on other cars where it has lower pressure. The Porsche Cayman, being a mid-engine car, only runs at 100bar if I recall correctly.

E30 stock is 110bar, so most of the DOHC swaps run pressure that's too high.

I swapped the entire pressure regulating bobbin (the big nut on the output of the pump) and my car is much happier at 100bar. There are some other cars that run the same pump at 90bar.

It was super-easy and life changing!

[Victell]

Right on. I heard there was an orifice on one of the hoses that controls pressure, good to know where it is. I was thinking of integrating a adjustable hydraulic pressure valve

[hoveringuy]

Right on. I heard there was an orifice on one of the hoses that controls pressure, good to know where it is. I was thinking of integrating a adjustable hydraulic pressure valve

Can't just use an orifice, it will reduce the pressure at a specific flow rate but not work at all flow rates

The pump pressure regulator is a finely engineered unit to have rated pressure at ALL flow rates

https://www.r3vlimited.com/board/filedata/fetch?id=10022242&d=1674234822

[Victell]

Aha! This is the direction I need. Thank you. And apologies for the threadjack!

[hoveringuy]

Evolution of my EPAS...

This is with the Vue unit 6 months ago. It used enough room that I could have charged it rent. Completely unacceptable.



The I went to the Toyota Aygo unit based on an an early column. MUCH better, but the early column geometry still had it about an inch lower than it needed to be.



Finaly, I integrated it into an airbag column and it sits up-tight and outta-sight!

[hoveringuy]

The mod to the airbag column is adding some brackets to capture the mounting points on the EPAS unit. The EPAS is adding torque to the column, so the torque reaction needs to be carried by the steering column. The U-joint is in almost exactly the same position, but maybe an inch closer to the pedals so the shaft is actually centered in the firewall a little bit better.

Overall, I can remove the EPAS column and swap in the regular column in a few minutes. My plan is to evaluate this at the track next season before going "all in" with a manual rack, plus I'll make a speed sensitive controller.

The weight is an additional 6lbs over the unmodified column, so I'd actually lose a little bit of weight from removing the PS pump, reservoir, fluid, lines and cooler, but that's not a reason to do it.

[e30davie]

This is some very good information, and thats some nice fab work to make it happen. Out of pure curiosity do you know how much electric current the system draws? what size fuse are you using?

[hoveringuy]

This is some very good information, and thats some nice fab work to make it happen. Out of pure curiosity do you know how much electric current the system draws? what size fuse are you using?

I'm running a 30amp fuse for now but it's on my "to do" list o measure actual current (shunt ammeter). Max draw would be if you had the wheel against a curb or something and really leaned into it, I'm guessing it's less than 10amps 90% of the time.

[e30davie]

Yer i would think you could spike it pretty high under some obscure condition. google suggests some cars have even higher than 30. 80A fusible links etc.

I was recently watching driftworks YouTube channel and they have Elec power steering in his crazy v8 e30 m3 race car, and found that the system they were using (some french car?) couldn't cope with the uber wide tyres and race conditions. Just physically wasn't strong enough at times and would give up and provide no assistance until reset, almost like an internal cut out. having no experience with Elec steering systems I was a bit surprised to see they had those issues (known issue with whatever system it was apparently, clio maybe?).