Can someone quote the oil pump gear tooth numbers please, old style vs new style.

New type; 32 / 14.

Old type; 19 / 12.

Thanks, just doing some research and a bit of thinking. Assuming the new gears only fit into a new style oil pump housing, the gear ratios (between driver and driven gears) is quite different - old style 12/19 = 1.583 : 1, new style 14/32 = 2.286 : 1. So the newer oil pump design means the water pump shaft turns slower for given enging rpm's. This leads me to think that the new style water pump impeller is so designed to give correct coolant flow for lower revs ?? Just my thoughts, unless others have design info from BMW to support this thinking ........ what happens then if an old cast iron impeller is used with the new gearing ?

Dennis,
Excellent observation.

It would be interesting to know if the design has been modified to change the oil flow rate or to change the speed of the water pump shaft.
This is not obvious as smaller teeth will create smaller oil pockets but the increase of the number of teeth will push more smaller oil pockets for each revolution. It may result to an equal output flow between both gearing arrangement.
As for the water pump impeller, the old cast one needs a faster speed to push an equal amount of water. The volume of water displaced on the old one is smaller due to the space taken by the physical size of the turbine.

FYI: These oil pumps create pressure through the meshing of the gear teeth, which forces fluid around the gears to pressurize the outlet side.



CF

Yes Bert, correct in all of your reply, we are on the "same page" here. Note that in almost all cases in my experience, gear pumps have equal size gears, but, typical of the Germans, they must be different ! I suspect that the newer gear design with more teeth is slightly more efficient as there is less bypass possible across the ends (faces) of the gear teeth. I suspect the pressed steel impeller is a more efficient design to compensate for the lower rpm's. I also suspect that delivered oil pressure (after the relief valve) is the same as with the old design, possibly with less by-pass over the relief valve. Someone may have indicated oil pressure figures for us ?? I have a test gauge but have never taken the time to connect it and test. I reckon Ajays would know the oil pressure, I bet he has it recorded somewhere !