[Jamie '92 968]

I have seen a lot of discussion on the steering feel of our cars.
Mine has always felt a bit vague with a soft feel and lack of centering force.
It sounds like I am far from alone in this observation.

I've been paying attention and trying to learn all I can about the steering and suspension that might affect this issue and I have some question I cannot seem to find an answer to...

I seem to remember reading somewhere that the boost on our power steering is speed sensitive, reducing boost at higher speeds.
Is this true?
How does it work?
Is there a failure mode or malfunction of this feature that might lead to overboost at higher speeds and the vague, soft feel that some have observed?

Always anxious to learn....

Thanks,
Jamie

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[banditsc]

Steering feel seems to vary between cars. I'd like mine to have a little less assist, one option I was given was to have my pump rebuilt to put out less pressure, that would also increase steering rack life. Changing out your rubber rack bushing to something more solid like derlin should help decrease some of the vagueness.

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[Fox944]

my wheel feels as if i dont have much steering assist at all. Especially once the car warms up.

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[Ryan]

Could be an allignment issue as well. This can effect the steering feel quite a bit.

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[rxter]

My wheel feels quite dead on center - compared to my RX8 which has telepathic steering. Actually feels a bit like bias-ply tires on an old Ford. Sort of hunts around.

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[Fox944]

RX8's steering feel is damn good.

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[Jamie '92 968]

Can anybody confirm the speed sensitive boost thing?

I did some searching on the web and found some discussion on the Pelican Parts forum about how the 944/951 have this feature.
It was stated that for those cars the boost is turned off above about 40 mph.

True for the 968?

Jamie

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[Fox944]

I cant attest to anything of that nature, as i now believe my PS isnt working properly. No noise. I have boost at low speeds when the car is cold. After it gets hot, its as if i have no boost. I recall using both hands to turn the wheel when parrallel parking in NYC, as the steering would get really heavy once the car was warm. At speeds on the freeway, the steering feel is always the same, cold or hot.

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[DaveN]

I would suspect the PS pump vanes. Low temp with viscocity will give you some PS but once warm the oil is too thin so get pushed around by failed pump vanes. Had the exact same thing on my Jetta; vanes broken.

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[Oily]

Over the past few months the steering on my car seems to have deteriorated. Recently I have been experiencing play in the steering wheel. At speeds over 80mph I can move the wheel 2 or 3 degrees with no affect to the direction of travel. It seems to get worse as the speeds increase. Not a fun place to be....

In an attempt to rectify the problem I have got new front control arm rear bushes, they went on last night. I will test the car at the weekend with them on and let you know the result. The new bushes are original Porsche items. When I visually compared the old with the new bushes, it appears as if the inner section of the old ones have rotated through nearly 90 degrees in the outer housing, meaning that the two rubber sections were where the two solid sections should be. It may be that the steering geometry changes as the speed increases as a result of this.

I'll let you know.

Cheers

Oily

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[Cloud9...68]

I wonder how much it would help to thoroughly flush and refill the power steering fluid. I did this on our minivan, and it eliminated a very loud whine the steering was making, particularly near the locks, moreso when cold. I can't say it had much impact on steering feel, though. I've been meaning to do this on the 968 just as a prevntative measure, but haven't gotten around to it yet, largely because the steering feel of my car is actually pretty good - just about right, in fact, to my taste.

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[flwbyu]

I have always had mixed feelings about my steering. Sometimes it feels right on and other times the steering seems distracted by the smallest thing, hunting around the various differences in the pavement surface.

I am currently having the steering rack rebuilt. So, it will be interesting to see how that effects things. I have tried various tires and have the factory 17" wheels. So, I continue to search for the solution.

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[ds968]

I wonder if there is a really thick ps fluid out there ( maybe for trucks, or tractors, or caterpillars [img]style_emoticons/<#EMO_DIR#>/huh.gif[/img] ) and if so what effect, if any, that might have if we used it...or, could it damage the system ?!

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[banditsc]

Thicker fluid would most likely increase the pressure in the system and blow out the rack seals. The best bet for less steering assist is an underdrive pully or have the pump rebuilt to put out less PSI.

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[pure&amp;simple]

When I got my car, it had 108,000 miles on it, and original suspension. I replaced the suspension with coilovers, and added upgraded castor blocks and sway bar mounts, but after a while I noticed something funny about the steering. It had great precision and on-center feel, but during cornering I found I had to feed in more and more steering to maintain my trajectory as the g-forces built (this is before understeer sets in - the tires were not slipping). After I had Racer's Edge control arms (with solid bushings) and the Rack Tack steering rack bushing installed, the problem went away. I suspect there is probably a variety of ways in which deteriorating bushings affect steering and handling.

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[Jamie '92 968]

So nobody knows anything about this speed dependent boost on the power steering...

Searching the PET, I found something called a "pressure transmitter" 944 606 209 00 with a wiring harness as part of the PS system of a 944S. Nothing like it is found in the 968 PET.
Anybody have any idea what this does?

Jamie

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[banditsc]

The 944S was the introduction of 16v to the 4cyl. For whatever reason they decided they needed to kick up the throttle when the steering wheel went to full turn. It was actually a pretty bad decision, they power wire wasn't fused and it rubbed in the engine bay and caused a few fires, which lead to a recall to reroute the wire and put a inline fuse on the circuit. Most people with a S have a regular pump on there now.

The onyl speed sensitve part of the pump would be how fast the engine is turning, it doesn't know how fast you are going. I suppose the pump could decrease pressure when it starts spinning at a certain RPM. But just guessing there.

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[flash]

it's a pump - it levels off at a point

i don't exactly know why the feel varies so much from one car to the next - the white car has quite a bit of resistance, and i like that - the blue car was moderate before i changed to the really big tires, now it's a bit heavier - other cars i have driven are really light

toe set will play into this a lot, as will castor setting

but still, i don't understand the pump variations, which seem to be significant

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[Jamie '92 968]

OK.

I did some more searching this afternoon and found what I remember reading many years ago.
This is from a sales brochure from an '89 944

   

Sounds like a nice design.
Even though it says "when driving at higher speeds it again automatically adjusts itself to the lower level torsional forces", I think this is just referring to the nonlinear nature of the boost that is shown in the graph.
I could never understand how the boost was supposed to react to the car's speed, but this explains that it is an indirect relatonship.


Does the 968 behave similarly?

I would love to know more about how the system accomplishes this, and the possible failure modes.

Jamie

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[968 GUY]

I know that the steering feels much different between my 6-speed and the tip. The tip is much more firm, almost to the point of hard. The 6-speed has been lowered, not sure if that would change steering feel, but I did have it aligned in a very good shop in Bremerton,Wa.(MaxRpm) before driving cross country to Ga. Car drove as if on rails, esp. at 90-95mph. The tip, I am not sure of the history of the suspension service on it, has 80k mi., prob could use an alignment, that may make a diff. The steering feel on the 6spd is just how I like it, not too soft or too stiff. The 951, I have no complaints about, other than a bit of clunking at full lock while backing.(from the front susp.)

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