power steering losses reduced
 

Traditional hydraulic power steering systems are powered by a belt-driven hydraulic pump. My 1989 Ford Van uses a Saginaw "canned-ham" power steering pump, as do most GM cars and trucks of similar age. Fords typically used their own pump setup but put Sag's in the vans. These pump typically run 2.0-4.5 gpm and 700-2,400 psi.

http://www.rockauto.com/info/1/207878f-bot__ra_p.jpg

Borgeson’s pressure-adjusting kit (part number 899001) includes a clamping tool, six shims, and installation instructions for lowering the bypass pressure on all GM self-contained and Type II power steering pumps.
http://image.hotrod.com/f/38840528+w...usting-kit.jpg
Here's a little chart showing how it works.
http://image.hotrod.com/f/39454847+w...sure-chart.jpg
These kits are used most commonly by hot rod drivers looking for more steering "feel" on the race track. I'm interested in using one for the same reason (not on the racetrack though, just tired of my numb steering feel and think reducing the over-corrections it causes waste fuel) and think maybe reducing the pump's output can reduce the hp-loss of the belt drive. At the lowest normal rates (2.0 gpm and 700 psi) the pump has an input requirement of .82 horsepower. This is well below the stock settings of my van. It's closer to 1.93 horsepower. I may not be able to tolerate the pump running at its lowest possible setting but if I could, I think 1.1hp for ~$20 is a pretty good deal and might even be directly noticeable in mpg. Thoughts?

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Anything that reduces hp required is good. :thumbup:


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The power steering system only develops those high pressures when the steering wheel is turned. When driving straight the pump is allowed to full bypass, only developing a max of 100 to 200psi.
Even then it still takes around 1 hp to turn it.

Pressure reduction will make absolutely no difference in MPG.

I am one of the few people to study the at rest state of power consumption on a Saginaw type 1 pump, here:
http://ecomodder.com/forum/showthrea...ing-29002.html

That lead me to this, the only way to further reduce parasitic P/S losses is to remove the pump from the system, here:
http://ecomodder.com/forum/showthrea...ion-32895.html

Yeah I've read your threads. Interesting stuff with hpus and whatnot. If mpg was my only reason for considering the pump mods I wouldn't. That being said, the bypass valve is exactly what I plan to modify. By reducing the preload on the bypass valve spring, the pump will be allowed to full bypass more often, reducing its power drain just like driving straight more of the time. The flow control orifice can also be modified (my second stage of planned mods) to allow fewer gpm max flow.