does anyone have any clear pics of the EHPS in the prototype fiero? Boomtastic did on an old thread but they don't pull up anymore

There are several forum members that have adapted electric power steering to their Fieros. Member Spoon is one who did a great job. Another member adapted a power unit on the steering column. Ask around and you'll find info on the modification.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Original Thread
https://www.fiero.nl/forum/A...0825-1-015192-5.html

[This message has been edited by Chief (edited 09-02-2016).]

quote Originally posted by Chief: Original Thread https://www.fiero.nl/forum/A...0825-1-015192-5.html

Try this... Here they are! The WCF sponsored 89/90 Fiero pics!

I believe that some power steering racks that were used in Fieros are the 85-89 Mercury Merkur, 80's F-Body and Corvette units but don't quote me on this.
See this thread: https://www.fiero.nl/forum/A...060811-2-073100.html

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-02-2016).]

thank you!! is there any pics of the wiring going in to the fan?

quote Originally posted by predmeister: thank you!! is there any pics of the wiring going in to the fan?

There are no other pictures that reveal anything else. What you can not see is the switch that controls the steering effort with the aid of the VSS. This same system was made by Saginaw and carried over for use on the GM EV1. When all of the EV1s got scrapped the power steering units showed up on eBay and sold from $200 to over $1000. There is some documentation of that on this forum however the units soon sold out and one or another will turn up from time to time. None that I know of included the steering column switch.

If you can find this article it will enlighten you: Forbes, J., Baird, S., and Weisgerber, T., "Electrohydraulic Power Steering - An Advanced System for Unique Applications,"

In case you are too young to know what the EV1 was, they were electric vehicles only leased to a select number of people in California GM took them all back and scrapped them all. This after legislation that required all dealers to sell a certain percentage of electric cars by the year 2000 was dropped. There is a documentary on this: Who Killed the Electric Car?

https://assets.blog.hemming...//2013/06/033173.jpg

[This message has been edited by Chief (edited 09-04-2016).]

Description of EHPS:




The steering sensor is mounted on the steering column it is basically a switch that detects movement (clockwise-counter clockwise).
The brush wear detection switch is on the electric motor and warns of worn brushes.
The engine control computer is a signal from the ECM that wakes the PSC (or ECU as noted above) when the engine is running.
The rest is explained above.

[This message has been edited by Chief (edited 09-17-2016).]

chief, where did you get this chart from? very cool

The steering sensor *can* be nixed from that block diagram; you can implement power steering without knowledge of the steering angle.

These days, the motor could be AC brushless to eliminate the issue of brush wear.

quote Originally posted by Dennis LaGrua: I believe that some power steering racks that were used in Fieros are the 85-89 Mercury Merkur, 80's F-Body and Corvette units but don't quote me on this.

80's F-bodies would not have had rack and pinion steering. The 4th gen's did have it though.

Gary

quote Originally posted by predmeister: chief, where did you get this chart from? very cool

From this article : Forbes, J., Baird, S., and Weisgerber, T., "Electrohydraulic Power Steering - An Advanced System for Unique Applications,"

quote Originally posted by Chief: It is crucial as it ACTIVATES AND deactivates THE ELECTRIC MOTOR when the steering wheel is turned. Otherwise it will run all the time.

The crucial measurement in power steering is driver input torque, NOT steering angle.

The function of power steering is to provide an assist torque which is proportional to the driver's input torque.

In the case of hydraulic power steering (whether engine-driven or electric pump), the twist of the torsion bar causes pressurized fluid to push on the right or the left side of the rack's piston.

In the case of purely electric power steering, the twist angle of the torsion bar is electronically measured, and then the electric motor provides assist torque accordingly.

Either way, it come down to the driver twisting the torsion bar with the torque from his arms. Position is not a key parameter.

[This message has been edited by pmbrunelle (edited 09-24-2016).]

[This message has been edited by Toddster (edited 07-16-2019).]

Cool pics; I had not seen these before.

I especially like the internal memo discussing the technical difficulties they were having with the WS6 cars.

It shows that things are largely the same some three decades later:

• The factory wants wider tolerances
  
• Marketing wants more features that they can sell
  
• Test results are not fully repeatable

I have a lot more, I even have the original Diagnosis and Service Manual for the EHPS, schematics, etc. I might see about reproducing it one day. it is really rare. It shows Suty cycles controlled by the VSS for how much assist it gives at certain speeds, etc.

[This message has been edited by Toddster (edited 07-16-2019).]