On Thu, 09 Oct 2003 12:34:55 -0400, echristley@nc.rr.com wrote:

>> 1) The pumps could
> > have differing efficiencies. That's possible but it doesn't
> > explain the magnitude nor why auto manufacturers would persist
> > with an inferior pump design if reverse engineering a Davies
> > Craig pump could yield such superior results.

How long did it take American manufacturers to wake up to the fact that the oriental's were eating their lunch?  Why would they change out a part that has worked reliably for 100yrs and replace it with something that will provide very little benefits.  Remember most auto engines rarely rev up to 6000rpm, and never for long.  The rotary is notable in that it does rev higher than most, but even then it doesn't stay at those high revs.  It's even more notable in an airplane, as it tends to rev high and stay there.


>>  Homepage:  http://www.flyrotary.com/
>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html

I would like to take a crack at answering #1. I think the failure mode of the mechanical water pump is a soft failure----starts leaking out the weep hole, loud noise from the bearing or seal failing signals most people that something is wrong with the car. Slow loss of coolant is also another signal, especially with the idiot light telling you about low coolant levels. People have many clues before pump fails.

I am in the computer business and when the fan (air pump) stops cooling the CPU you have a warning but if not quickly heeded the processor soon fails. I think the failure mode of an electric motor will give less warning than the mechanical pump will. I write this based on my experience of changing about five water pumps on my 1993 Jeep Grand Cherokee 4.0 Liter engine with 358K miles. Perhaps this is why the manufacturers haven't replaced mechanical pumps with electric ones.

 

Jim Brewer