Corvette ZR1 power steering rack: next project? (Page 36/37)
Steven Snyder SEP 24, 01:19 PM

quote
Originally posted by Rickady88GT:

You may look into the pressure spring?
It works like a oil pressure relife valve. More spring more presure.
The pumps I have used so far have never made to much "boost".



It's my understanding that the spring just controls the bypass pressure, which really only matters when the fluid is very cold or the steering rack hits one end of its travel. The amount of fluid flow determines the steering assist by how fast it fills the cylinder in the rack.

I found a shop in the San Fernando valley that can rework the spool gear in the rack to change the assist. Alternatively, restricting the flow from the pump will work as long as there's still enough maximum flow to accommodate rapid change in steering angle.
FieroWannaBe SEP 24, 01:58 PM
Power (HP) = Flow (GPM) X Pressure (PSI) / 1714 (the basic hermaphroditic approximation of fluid power.)
The simple fact is for less power you can lower either of the two inputs, lowering the pressure will lower the gain in the cylinder, lowering the flow will slow the fill time of the cylinders. Either the system pushes less or the driver pumps more. I think it may be wiser to have a stiffer torsion bar installed in the rack with reduced flow to the rack, combined with a lower system pressure. (A weak torsion bar with heavier input shaft torque sound to me like a recipe for failure.)
Steven Snyder SEP 25, 01:59 PM

quote
Originally posted by FieroWannaBe:

Power (HP) = Flow (GPM) X Pressure (PSI) / 1714 (the basic hermaphroditic approximation of fluid power.)
The simple fact is for less power you can lower either of the two inputs, lowering the pressure will lower the gain in the cylinder, lowering the flow will slow the fill time of the cylinders. Either the system pushes less or the driver pumps more.



That's a bit of an oversimplification in the case of power steering since there's a flow metering valve (the spool valve/torsion bar assembly) in the system, but reducing the pressure should reduce the flow gain and cause no other problems as long as the spool valve can source enough flow from the pump. So I can reduce the pressure to reduce the flow gain, as long as the bypass pressure isn't so low that the pump no longer flows enough fluid to the spool valve.


quote
I think it may be wiser to have a stiffer torsion bar installed in the rack with reduced flow to the rack, combined with a lower system pressure. (A weak torsion bar with heavier input shaft torque sound to me like a recipe for failure.)



Good point. I imagine the torsion bar was designed to hold up to being torqued hard with the rack limited out (or the wheels stuck), so it probably isn't a failure point, but that's certainly a consideration.

[This message has been edited by Steven Snyder (edited 09-25-2012).]

FieroWannaBe SEP 25, 03:54 PM
The pump has a fixed displacement and operates at a extremely large rpm range at system pressure and flow under almost all conditions, a lower pressure should not greatly affect flow rate. Remember we are dealing with a largely immeasurable compressible fluid.
Steven Snyder MAY 29, 05:56 PM

quote
Originally posted by FieroWannaBe:
A weak torsion bar with heavier input shaft torque sound to me like a recipe for failure.



Looks like you are right.

From: http://spece30.com/forum/10...ering-pinion-failure

quote





Obviously this is the most extreme case (track car with a completely depowered power steering rack) but still relevant.

[This message has been edited by Steven Snyder (edited 05-29-2014).]

motoracer838 JUN 10, 11:50 AM
Rick, I sent you a pm a while ago asking about the rack adapters, did you get it???

Joe
Rickady88GT JUN 18, 01:17 PM

quote
Originally posted by Steven Snyder:


Obviously this is the most extreme case (track car with a completely depowered power steering rack) but still relevant.




Is that the steering spool assembly from the Vette?
And no hydro pump?
Rickady88GT JUN 18, 01:19 PM

quote
Originally posted by motoracer838:

Rick, I sent you a pm a while ago asking about the rack adapters, did you get it???

Joe



Sorry, I have to look into it? Can you re-send it?
motoracer838 JUN 19, 05:34 PM

quote
Originally posted by Rickady88GT:


Sorry, I have to look into it? Can you re-send it?



message sent.

Joe
Steven Snyder SEP 11, 06:19 PM

quote
Originally posted by Rickady88GT:

Is that the steering spool assembly from the Vette?
And no hydro pump?



BMW E30 with no hydro pump