Monday, November 28, 2016

Saginaw steering pump pressure relief modification, now 1,600 psi brake pressure

With Hydroboost brakes more steering pressure equals more brake line pressure. PSC sells a new Saginaw P style pump made by Delphi which is supposed to be set for 1,650 psi.
After installing it I found it didn't quite make the pressure spec. I'm shooting for 1,650 psi pump pressure by making a new flow valve plug with a 20% smaller area seat for the relief valve ball. The thread on the plug is 3/8-24 so I started with bolts of like thread and went from there.
 Had six flow valves to fiddle with!
Springs and balls were the same on all. There were two different lengths of valves and corresponding plugs. The orifices and seats were the same on all. Had a few shims to work with too.
Had four bolts to use and they needed the hex changed to 7/16" from 9/16"
Made a fixture to hold plugs for machining. Here is a screen ready to go in.
New plug, original plug with screen removed and original plug unmolested.
Made orifice .052" closest I had to .050" original
New plug with 20% less seat area.
Rolling screen in.
Screen rolled in new plug and original plug
Valve ready to test
 where screen goes
With no shim the spring is very close to coil bind so I didn't pursue shimming the spring. No shims on the valve is about 1,400 psi.
 After some more fiddling we got 1,650 psi from the Saginaw pump. Ended up shortening the end of the flow valve where the plug screws in .015"

rear brake pressure 40mm master 80mm front and mid, 66 mm rear calipers
front brake pressure 40mm master 80mm front and mid, 66 mm rear calipers
There is some concern running the steering box at a higher pressure than It really needs. To lower the pressure just to the box I put in an additional relief valve before the box. Sun Hydraulics has all this stuff.
              I selected a AEJ manifold in steel
           The relief cartridge I selected was an RDBALAN
                    Ready to install with Oring boss adapter fittings
To install I got a 20 inch hydraulic hose to go from the hydroboost outlet to the manifold and used Bob Stones kit original hose from the manifold to the steering box. Bob's hose clocked OK to hook up this way. The return tees in before the cooler. I set the pressure to be just enough to turn the wheels while stopped.

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