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Re: HP drawn by the power steering pump.

Hi everybody,
 here is my 2 cents on the power of the steering pump.

Alan is making some calculations here (deleted),
and at some point he says:

>WORK by EACH PISTON per stroke  = 2200 x .196 x .2  in-lbs
>                                = 86.5 in-lbs
>                                = 7.2 ft-lbs

Well that's right if pressure is constant from the begining to the end of
the cycle. I think that the case would be that pressure starts at 0 and builds
up to 2200, assuming that the relation pressure-distance is linear,
the formula would be 1/2 x 2200 x .196 x .2 ie. the result would be
half (3.6 ft-lbs).

(more deleted here, with my assumption power used is 1.5HP at 1000rpm)

>Can someone go over these numbers, I think I'm on the high side
>but still hav'nt spotted where the problem is. It may also be
>my incomplete understanding of what the pump is doing when
>there is no fluid being drawn from any of its outputs.

Well I haven't seen a schematic of the pumps, so I comment from what I
understand. (yes, I will buy the Bentley for a christmas present to myself...)

>Since all this power is converted to HEAT if it is not used,
>that implies the pump is self heating to the tune of 4 or 5 KW
>at highway cruising speeds. I find this a little steep
>and hard to believe.

Why should it be converted to heat ? If no compression is to take place then
no energy will be drawn, therefore nothing to be converted to heat. (well, again
haven't seen how the think works).

>I still think the pump is running a half HP at 1000 rpm, and
>one to two HP at cruising speeds.

I agree with you, 2 or 3 HP (about 2KW right ?) seems high to me too.


 (in a borrowed 924 until my valve problem is fixed, hopefully tomorrow).