Anyone ever do it?
I have a NB Miata with A/C and power steering.
I want Air Conditioning, but only really want Power steering for the odd time my dad drives my car or for tight parking. Otherwise I could do without P/S
Anyone ever adapt an air conditioning clutch to turn on and off the power steering?
Haven't heard of anyone doing that before but it should work. There might be some easier and cleverer options though:
- EHPS conversion. Many of the electric pumps available from production cars aren't good enough for autocross use but are fine for parking (the popular Volvo pump for instance) - these would be fine for your use.
- Column-assist EPAS conversion. Would involve mods to the column and electrical system but you could properly depower the rack and remove the hydraulic PS system completely. You could also have the option of adjusting the level of assistance with this system.
Be warned, a hydraulic PS system with an inoperative pump is a lot harder to turn than a conventional manual steering system. I tried driving a PS vehicle with the belt removed for a year or so, before I finally gave in & fabbed a good PS pump mount. Without a pump turning, the PS gear has to shove oil back & forth through the pump when steering.
OTOH, the racecar has a properly de-powered rack which is only impossible to steer at a standstill w/255 tires. Anything above 5-10mph the steering effort is still higher than PS, but very direct.
Yeah, you really really do not want a fluid filled hydraulic system. There is also a good chance that driving with the pump not turning will push a lot of the fluid out of the reservoir anyway.
Another vote for an EPAS conversion. You definitely don't want to be using the rack to pump fluid.
One other downside of depowering a PS system - there's a torsion spring in the rack input that is used to modulate assist based on input load (deflection vs the rack input from the wheel and the pinion gear that actually turns the rack). Without assist, the steering input force is high enough that the torsion shaft deflects and relies on the splines in the system to transmit force. Nothing wrong with this necessarily, but some PS racks have a lot of steering play when depowered because those splines are not a tight fit and are only really meant as a failsafe, and the torsion spring is quite soft. Other racks have relatively tight splines and/or stiff torsion couplers, and are just fine when depowered properly.
A miata probably doesn't have much issue here, and I'm sure there's tons of them running around depowered with no issue just like the BMWs I'm more familiar with. It's just another aspect of why a true manual rack tends to feel a lot better than a depowered PS rack.
In reply to gearheadE30 :
Back in the day, we didn't do anything about that spring on Miatas. Now, the fashion is to weld it up. I've never done a back to back test on if the difference is perceivable on a Miata.
In reply to Keith Tanner :
The FD guys insist that it makes an enormous difference. I could never tell.
The amount of actual travel in that spring is so minute, it may not be noticeable if it were broken entirely.
In reply to Pete. (l33t FS) :
I can tell you that the steering on my Locost was definitely not spring loaded, and it didn't have the spring welded :) Nobody complained about our aero-equipped turbo race car on slicks with an unwelded pinion either.
Welding the torsion is 1/2 of properly depowering a rack, along with removing the hydraulic seals on the rack itself.
The rack is already disassembled, welding is only a few minutes of a 1-2 hour process. Just do eet!
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