Miata Electric Power Steering Conversion

K-Miata just introduced a kit where they take a stock Miata column and cut and weld an electric power steering motor into it. It even has an adjustable switch that you mount on the dashboard, so you can vary assist on the fly. Pretty interesting option for if you want to do some crazy swap and have power steering, this way you don't have to worry about pump clearance and having custom lines made and routed. Also, in my case, my Rotrex-blown BP has the charge piping routed right over the reservoir, and to even check the fluid, I have to remove charge piping (the instructions have you cut the top off the handle just to even fit the piping). 

Link: https://kmiata.com/products/electric-power-steering-kit

Thats quite neat, but wonder how it feels vs depowered rack?

In reply to Professor_Brap :

According to the website:

the steering feel of this EPS system is tunable to each user’s preference. Just mount the supplied adjustment knob on your dash and turn one way for lighter steering and the other way for a heavier feel.

Agreed w/Professor_Brap; how's the feel? My (admittedly limited) experience with electric power steering has led me to believe that if I were doing a crazy pump-delete/alternative setup, that I'd be better off using a remote electric pump (I think R53 Mini and Mercedes A-class are "popular" donors, for tiny values of popular) to drive a conventional rack.

OTOH, one hopes that electric assist has been improving and will continue to improve. I can't imagine that it's actually technically impossible for electric assist to be as good, I just expect it's been limited so far by developments in how it senses input, applies boost, and stuff like powerful enough motors that don't "cog" from pole to pole... Just theorizing, of course.

The adjustable assist seems like a nice feature. At worst, you could turn up the assist for parking, and turn it down (or off) for when you're moving and need feel. Unless of course the motor's draggy enough that when you turn it off you're now fighting a depowered rack *and* a motor and gearbox...

In reply to Ian F :

That addresses the amount of assist, but my (again, caveats all over the place about my limited experience) worry is that there's something about the manner in which electric assist works that makes the feeling really uncommunicative. My Mini has a "sport" mode, and I swear the effort gets higher, but it's just as numb. The first thought I had when trying sport mode was that I could now feel the too-tight bushings on the steering column that the boost was masking. I don't suspect that's what I was actually feeling, but that's what the steering felt like; no sense of the noise/vibes/nuance coming from the tires, just X amount of resistance.

Mazda put the EPAS motor on the rack in the ND because they claim it gave better feel than the on-column solutions they used on their other cars. And no, an ND rack won't fit an NA/NB - too wide and you'd have crazy bumpsteer. The ND also runs a LOT of caster.

On this thing, I'd want to be able to feed it a VSS signal so you could have all the assist at parking speeds and taper it off at speed.

About feel - Mazda's chassis guru told me "don't confuse weight for feel". He's right - even if there's no weight, you're still getting the information.

The electric steering in my Focus RS is pretty nice.  Nice and firm, very responsive and communicates quite well.

The one in our Pacifica is just slightly firm and dead, much like old style power steering systems on appliances have been for decades.

The power steering system on my former 944 Turbo was responsive and felt quite nice (I don't understand manual conversions on these cars, the ratio is terrible or you risk having a depowered rack lock up if you do it wrong).

As with everything, its all about how it and the suspension are tuned.

I want to put an electric column from a Cobalt, etc. on my 924 because for autocross, its just too stiff and it could allow me to add a Quaiffe steering gear to a MK1 Golf rack and install it in the car.  Unlike most aftermarket conversions like the one above, I'd tie the adjustment into vehicle speed with some sort of base boost setting and adjustment.

In reply to Ransom :

It's hard to say without trying it.  What feels good to some may feel like crap to others.  The steering in my R53 doesn't feel numb at all.  And that is comparing it to the pure R&P steering in my Spitfire and GT6 or my previous Mini.  The steering in my minivan feels numb, but I've gotten used to it and have learned to deal with it. Likewise the even more vague recirculating ball P/S in my trucks and full-size vans I've owned. The steering feel of a Volvo 1800 is pretty damn bad to me, but other owners say it great.  It's also a recric-ball, but un-powered. There is a kit for the 1800 sold by a company in the Netherlands that is almost the same as this one (although about $500 more expensive). 

The only person who can answer your question is you, and you won't know until you try it.

The EPS in my AP1 S2k is the bomb.  I'd like to convert my 240sx, but there's not enough room to put the electric rack where I want it without raising the engine more than I want.  The class rules for the 240sx don't allow changing the steering rack, and I've heard the same thing about the rack mounted units not having the feel.  

I'm not saying its for every Miata, or a perfect solution, but, like I said, it's a nice option for if the stock hydraulic system won't work for you and you have to have (or want) power steering. The adjust-on-the-fly would be kind of handy if you had a co-driver at an autocross who preferred or required a different amount of assist.

How much resistance do you feel when these boxes are free wheeling without any power to them ?

And is it the same electric box for rack and pinion as it would be for old style steering ?

K-Miata is doing some neat projects. The fact that I can K-swap a Miata and still have AC and power steering is amazing. 

I haven't experienced it myself, but a friend did this to his NA Miata and documented it here: https://preparedmiata.wordpress.com/2017/09/27/electric-power-steering-conversion-p1/

Anyone know how much the pump, reservoir and all the lines weigh? Because they say this sytem weighs only 12 pounds. Curious if it's a weight savings, a draw or heavier?

I'd estimate a draw or heaver. There aren't that many lines and the pump isn't all that heavy.

Keep in mind that if you put this on a BP-powered Miata and you want to keep AC, you'll have to come up with one of the tensioner setups that were used on factory cars that had AC and no PS. They are NLA and there are no aftermarket options as far as I know, but I may be out of date there. If you don't have AC, then no worries. It's an interesting option for engine swaps that don't easily give you a way to run a hydraulic PS pump, but I'm not sure it would make sense on a BP.

My question, if I were considering this, is what the signal from the adjustment dial looks like. I'm guessing simple resistance, so you feed it xV and yV comes down the signal. I'd want to figure out how to feed it a speed related signal as noted earlier. That has the potential to make a depowered rack quite driveable.

Saw this on the V8 Miata forum. Could be on the wish list for the Molvo if Mrs NOHOME decides that my excuse for building upper body muscle is not going to fly.

Plenty familiar with he Saturn Vue parts being used in Hot Rods, so thanks Katya4me for the Miata specific DIY link!

Pete

Keith Tanner said:

 

My question, if I were considering this, is what the signal from the adjustment dial looks like. I'm guessing simple resistance, so you feed it xV and yV comes down the signal. I'd want to figure out how to feed it a speed related signal as noted earlier. That has the potential to make a depowered rack quite driveable.

Some discussion of that here:  Miata EPS on MT.net

Looks like it should be possible to feed it a VSS signal and make it speed sensitive.

Keith Tanner said:

Keep in mind that if you put this on a BP-powered Miata and you want to keep AC, you'll have to come up with one of the tensioner setups that were used on factory cars that had AC and no PS. They are NLA and there are no aftermarket options as far as I know, but I may be out of date there.

I don't know any details, but I've seen this linked:

https://www.kainjection.com/product-page/oem-style-p-s-delete-bracket-kit

Thanks. I know we looked at doing one but didn't think there would be a market in that price range. But if you need one you need one and there aren't a lot of options! I thought I'd heard of a Kia application that could be repurposed but that's just a dim spark from the synapses.

Keith Tanner said:

Thanks. I know we looked at doing one but didn't think there would be a market in that price range. But if you need one you need one and there aren't a lot of options! I thought I'd heard of a Kia application that could be repurposed but that's just a dim spark from the synapses.

There was a Kia part, but I think it's also NLA at this point.

I'm eventually considering it for my Rotrex-supercharged BP Miata, depending on reviews. The charge piping from the blower to the intercooler is literally sitting on top of the power steering reservoir. The instruction for the blower install requires you to even slice the handle off the reservoir cap just to clear it. And during the autocrossing on 225-width tires and the heat from the air exiting the blower, it cooked the power steering fluid over at least once.