Too big a pump for power steering/hydro boost?

[87burbid]

I am building an 86 crew cab 4x4 with a cummins motor, the motor is out of a ford 700 truck chassis (bus) and is set up with the air compressor/power steering pump for the truck. I am doing air ride front and rear so I want to retain the air compressor. I got the specs on the pump and its rated at 4.1 gallons per minute and 2100 psi. A place that does hydraulic brake boosters told me I can only use 2.5-3 gpm and 1200 psi with the stock chevy hydro booster/power steering setup. I dont think its to hard to shim the relief valve down to get it to 12-1300 psi but the 4 plus gallons a minute is just a little too much flow for the hydro system. Any suggestions on how to bleed off some oil and make this pump work? Was thinking about doing a hydraulic assist and that might take a little extra oil but only when your are moving the steering wheel. I havent pulled the pump off to actually see how the drive is set up but I am guessing its going to be different than a stock dodge cummins pump, will check that out this weekend. Anyone messed around with this power steering pump setup?

 

[Fordum]

You would be wasting some engine power, but as long as you have a good cooler on the fluid, I don't see a problem.

Remember, unless a valve opens to send the fluid to a work point, none of the flow is doing anything in any hydraulic setup.

Most hydraulic setups have the pump just recirculating the oil doing nothing most of the time.

With that much flow available, you might have to put some flow controls or restrictors on in some places to slow things down, but the valve is normally supposed to do that anyway.

You always want more flow than you normally use so there is no time lag.

If it makes you feel better, my PTO driven hydraulic pump for my winch on my F250 is rated at 20GPM@2000PSI@1500RPM.

Probably a lot more than I need, but that darn winch is geared so low, its slow as it can be anyway.

 

[boz42]

I too think as long as you get the pressure down the flow will not kill you. I would be scared to double the pressure on the steering box & hydroboost for sure. That much pressure would most likely bow the end cap off the steering box.

Coolers are always a good idea.

 

[miniwally]

Talk to Vanco about the hydroboost, my guess is that you will just need a larger cooler to make it work. Most guys with larger tires and hydroboost complain about no power when they are trying to steer and brake hard at the same time.

You won't have that problem with a big pump.

 

[87burbid]

I think Vanco was the place I called about it. The guy told me the gpm would be too much. Maybe trying to push that much oil through the system would cause it to get hot if its too restrictive huh?

 

[miniwally]

I think Vanco was the place I called about it. The guy told me the gpm would be too much. Maybe trying to push that much oil through the system would cause it to get hot if its too restrictive huh?

Honestly I don't really know, however I do know that Vanco is pretty good. If they don't think it will work I would tend to think you need a different setup.

That's not saying that there isn't a way to limit pressure and flow. I'm thinking some sort of pressure bypass valve that bleeds pressure in excess of 1300psi off thus reducing flow as well?