Hey guys, looking for some honest feedback from anyone running an aftermarket electric power steering (EPS) kit on an S30. I have a 1976 280Z that I’m trying to figure out a solution for, which I used to daily drive, but I stopped once I put on quick-steer knuckles and wider track tires. The manual steering with these mods is just too heavy and lacks the precision and fine adjustment I'd like for the track. My goal is to add a US-available EPS kit so I can comfortably daily the car again, while still using it for 50% track and autocross duty. I’ve been looking at the main options available here in the US, but I can't decide which route to go:

Option 1: Manual Dial / Potentiometer (Z Power Steering)

• This appears to use a knob under the dash to manually set a fixed level of assist.

• My worry here is the highway drive. S30s already get naturally light in the front end at speed. If I leave the manual dial turned up enough for local driving, is the highway cruise going to feel twitchy and annoying? Am I going to get completely annoyed having to constantly fiddle with a knob between street driving and autocross runs?

Option 2: Automatic / GPS Speed-Sensitive (SilverMine Motors)

• This appears to use a GPS antenna to automatically give max assist at a standstill and taper it down assist at highway speeds.

• My big concern here is track reliability and lag. When you slam on the brakes right before a tight autocross hairpin, does the GPS signal lag keep the steering heavy, or does it suddenly surge and go super light mid-corner?

• I am also specifically looking for feedback from anyone with personal experience regarding the motor they use. There's a rumor floating around online that the SilverMine setup is actually using a cheap, under-powered electric steering motor designed for ATVs rather than a true automotive passenger car core. Is there any truth to that, or is it a solid automotive unit capable of handling track abuse?

Newer Options:

• If anyone knows of any newer, more modern US-based EPS options on the market that I should look at instead, please let me know.

If you are running any of these setups on a track or daily driver, what has your personal experience been? With my steering geometry, should I go manual dial or GPS auto-adjust? Appreciate any insights or warnings!

---

Here's a thread on the Silver mine version...

Thanks! Based on my research over the past week, a GPS-based variable assist system seems most suitable. Static systems (like resistor-variable setups) tend to draw more complaints, often causing high-speed twitchiness or a lack of assistance at low speeds. It looks like Silvermine Motors may be the best solution for my needs that's currently available.

Just adding some other forum posts I found that were helpful:

https://forums.hybridz.org/topic/140867-electric-power-steering-manual-vs-gps-for-280z-autocrossdaily-quick-steer-wide-tires/
https://forums.hybridz.org/topic/125428-electric-power-steering-100-1500/page/4/#comments
https://forums.hybridz.org/topic/127702-looking-for-new-steering-rack-feedback/

I have fitted GPS controlled EPAs to my right hand drive '76 260Z - It has variable assistance using GPS and I am very happy with it.

I made the system using an EPAS from a local GM car (Holden Barina) that used the same unit as in the European (GM) Opel Corsa C. I bought the GPS controller from Servtronic who sell direct and also on eBay. The Silvermine EPAS looks like an Opel Corsa B unit, so it is likely that they are using the Servtronic GPS system also. There are good photos and a description on the Servtronic website.

The GPS controller has eleven different settings that allow adjustment of the amount of assistance (versus speed). You have full assistance at low speed up to none at the speed you set. I have mine set to taper from full (literally one finger operation) to zero assistance at about 30mph. This makes parking and city driving very pleasant but has no effect at higher speeds. The transition from full assist to no assist is seamless.

The photo shows an original steering column and my EPAs column together for comparison.

Regards

WM

Now that is an interesting power steering option! Those Opel Corsa C’s are everywhere over here and you can get a complete power steering column with the computer from a junkyard for under €80.

What modifications did you have to do to make the Corsa steering rack fit the Z or does it just bolt up? I imagine you replaced the Datsun steering shaft with the Opel/Holden/GM one or did you have to source one from a different car?

Would you be willing to share some of the part numbers you yourself used? That might make a nice reference point for people in the future.