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Speed sensitive steering is a feature available on many different cars. Its job is to give the car a more stable and heavy feel at highway speeds, and to make the car less prone to sudden changes in steering angle at speeds where such a move would be dangerous. It also allows more steering assist at low speeds for parking maneuvers.
Speed sensitive steering is great, but that's not what our 2L (Turbo&NA) DSMs are equipped with. We have RPM sensitive steering, which acts somewhat the same. It will decrease the steering boost at highway speeds because the engine is turning 3500-4000 RPM, but unfortunately it severely cuts the steering boost in the upper-rev range, regardless of what gear the car is in. 6000 RPM through an auto-x slalom results in minimal steering assist, followed by a sudden lack of any assist. Not exactly what an auto-x driver is looking for.
The steering assist reduction is caused by a valve in the power steering pump itself. We will be adding a spacer to preload the spring inside the small assist varying valve that closes at high RPM. This will stop it from restricting the flow of PS fluid out of the pump at high RPMs, but will not raise the maximum pressure of the fliud leaving the pump.
Some people have in the past shimmed the flow bypass valve in the pump. This is a separate assembly that sits below the assist varying valve. This resulted in more steering assist at high speeds, but accomplished this in a bad way. The flow bypass valve is there to relieve the high pressure created when the pump spins faster (high RPMs) and the flow exceeds that which is needed by the power steering system. If you shim this valve the fluid has nowhere else to go, and its pressure will increase far beyond the factory levels. I tried this, but after a 15 minute drive at moderate speed my fluid boiled and I lost steering assist. Not good.
Warning: This modification may change the way your vehicle
reacts to steering input; perform it at your own risk. I personally
found it made very little difference in the steering response during
normal driving, and was only noticable during extreme maneuvers. It
should not cause premature wear of any parts of the power steering
system. Your mileage may vary.
Written by: Matt Price (Updated by Corey Kaye for 2G DSM's)
Last updated: 12/22/99 (07/05/2000)
Comments? E-mail me at LIL4X4@Hotmail.com (firstname.lastname@example.org)
You will want to figure out a way to either drain the power steering reservoir or divert the flow of power steering fluid around your alternator into an oil change pan, as a significant amount of it will flow out of the top of your pump during this fix.
|1. Locate the power steering pump. Clean off any dirt or debris around the pump. It is important to not comtanimate the power steering fluid. Unscrew and remove the 17mm nut and locking washer. With this nut off you can lift off the ps line. Get a rag ready you will have fluid everywhere! Carefull not to let any drip on the belts or the alternator below.|
|2. I found the only way to remove the ps value was to bend back a small metal tab (#1). With the tab out of the way you can use a deep socket or a wrench (23mm) to unscrew the valve unit (#2). Once the valve is removed ps fluid will start to flow out of the ps pump. You will need something to plug the hole. I had a large rubber stopper sitting around that worked fine.|
|3. This is the ps valve housing removed from the ps pump.|
||4. Inside the valve housing is the following pieces.
It appears that ps fluid flows out of the five hold in the top of the
Valve. As the pressure rises the Valve is pressed up into the housing
and the four holes on the side of the Valve get plugged off leaving
only the top center hole. For me, I started to lose ps assist around
5,000 RPM's and by 6,500 RPM's I had lost almost all assist.
I tried streching the spring but as soon as i pinched it back together it retuned to it's original size. Afraid I was going to break it I decided that stretching it wasn't the answer.
|5. Using a piece of standard brake line i was able to fashion a small spacer. According to the 1G PS VFAQ Matt used a 3.75mm spacer. I filed my spacer (ring) down to about 1mm and was just bairly able to fit it in.|
||6. With all the pieces in order reassamble the value in the valve housing.|
|7. Replace valve in ps pump, clean up excess fluid and top up resovior as necessary.|