Electric Power Steering: Manual vs GPS for 280Z Autocross/Daily (Quick Steer & Wide Tires)

[3ricchu]

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!

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[74_5.0L_Z]

I don't have experience with the EPS.  I am interested.

 

I do autocross with wide tire 275/35-15 on 15x10 wheels on all four corners.

 

While moving, the effort to turn the steering wheel isn't terrible.  I try not to turn the wheel while the car isn't moving because I feel that I might over stress the steering rack.

 

The 280Z has a slower rack than the 240Z.  For autocross, I would swap to am240Z rack.  I measured the difference between the racks in a thread several years ago.  Going from memory, the 280Z rack moves 1.59 inches per revolution of the steering wheel, and the 240Z rack moves 1.81 inches per revolution of the steering wheel.

 

The faster rack would benefit more from the power steering, but is usable without as long as the vehicle is moving.

 

 

Edited June 14 by 74_5.0L_Z

[jhm]

Ditto for me....I'm in exactly the same situation as both of y'all; so I'm interested to see what kind of responses there are.

 

One nugget of information I can share is that most of these EPS units are HEAVY; and additional bracing is typically needed on the stock steering column mounts/bracketry.

[calZ]

The "rumor" about Silvermine comes straight from the Z Power Steering site, but it isn't necessarily wrong. I believe Silvermine uses an EZ-Steer kit to make their units. Those are designed for ATVs that weigh more than most Zs and experience a lot rougher roads than a car does. They likely don't have the factor of safety of an OEM automotive unit like the ZPS, but it's up to you if that matters. I have seen multiple people who run the Silvermine kit on track and have never seen a complaint, and the EZ-steer kits get used on street rods a lot. If there were an issue with the SM units, I would have expected to see some firsthand accounts of failure online, but I've never even heard secondhand of one having issues.

 

Here's a discussion we had years ago about delay with these units. 

 

Interestingly, the only complaints were about force-sensing units. 

 

The GPS is also only necessary if your car is stock without an electronic speed signal. I'm not sure how your car is setup, but with a VSS signal, there would be no chance for lag. If you have an aftermarket ECU, you could even setup a custom assist curve if you wanted.