View single post by Esprit2
 Posted: 09-25-2019 03:34 pm
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 460
redracer wrote:
...for a while in the mid '90s, all the impeller shafts were short, so I tack welded the impeller to the shaft inside(no problems, thank goodness). I had 2 original pumps from one of my dealer buy-outs that had the longer shaft which Dave Bean wanted, but I didn't want to give them up, and now there are longer shafted one available.Bruce,
The 9XX 4-cylinder engines are decades out of production, and Lotus hasn't provided many of the parts for a long time. We rely on the independent Lotus & Jensen-Healey parts specialists, and I really do appreciate their efforts. But it would sure be nice if they would put their heads together on some items (like the water pump bearing) and agree on a common, 'correct' configuration.... like a long impeller shaft.

The attached JPEG shows the difference in shaft lengths between two bearings I received from different vendors. Note that the bearing's OD is smooth on one, and has two grooves around it on the other. I have another bearing with one groove, and it's impeller shaft is yet a different length. And they're all sold as being "Lotus" water pump bearings.redracer wrote:
I assume the angle for the impeller-to-housing is the same and wonder if anyone has done a flow test to see how much more water is flowing through the LOTUS impeller vs. the original J-H impeller?They all appear to be the same. The Turbo impeller nests into the housing like it belongs there... once you shorten it's nose.

I've never seen any published performance specs for the various 9XX water pumps... like flow rate and pressure. Conversationally, the Turbo water pump was said to be a flow-rate upgrade that was required to keep up with the heat load of the 910 Turbo engine. Besides the impeller, the pump's scroll housing was enlarged to better accommodate greater flow. How much greater? No clue. But it's also said that if you don't wish to deal with some of the other issues involved with swapping-in a full Turbo pump, that just installing the Turbo impeller into a 907 pump housing will produce about 70% of the flow improvement... however significant that improvement is. I can say from experience that the 910 impeller in a 907 housing does make a difference.

Once the improved pump was tooled-up, a slightly modified version (machined off a large boss) was also used on the 912LC & 912HC. "IF" you were to install a 'Turbo' pump on your 907, it would be better to buy the 912 version without the big, intrusive boss... it's a more direct fit. I just speak of Turbo impellers all the time, since the 912 was never sold on this side of the pond, but Turbo Esprits were.

Tim Engel

Attachment: Water Pump - 9XX Parts - Bearing.jpg (Downloaded 121 times)