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View Full Version : Water Pump - How many impellers is best?



sammy
02-08-2008, 11:13 AM
I am debating replacing my water pump. I know the original has 4 impellers. I have seen pumps with 5 and 6 impellers. I have even seen a mention that pumps with 6 impellers rob power from the engine.

Do more impellers help with cooling for normal street driving? If so, what is the best number of impellers?

martx-5
02-08-2008, 12:27 PM
Actually, the difference between four impellers and six is not that much as far as horsepower consupmtion. The biggest difference in the six bladed TR3-4 pump is the fact that the impellers are set at an angle rather then radially from the pump shaft. This cuts down on cavitation and is generally more efficient at moving coolant around. I don't remember seeing a pump with five impellers, but the ones I've seen available are either the original four or the six bladed type. The six bladed type is a lot more expensive then the original. For most apllications with a stock motor, the original should be fine. Of course, that didn't stop me from spending the big bucks for a six bladed pump! /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

Edit: Actually, I'm still waiting for Ken from BF&E to send it to me. He said this week. Seems to be a hang up in the UK! /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

PeterK
02-08-2008, 01:44 PM
Five blade is a new (expensive $148) https://www.bpnorthwest.com/.sc/ms/bdd/ee/10125/Water%20Pump%205-Vane%20TR3-TR4A one from bpnw. Never seen one before they listed it and they claim that 6-vane robs HP. I'd say bunk but that's just MHO. I'd like to see the data to back up their claim.

I have the 6-vane in my motor. Didn't feel any HP rob when I installed it but would suspect even if claims are founded, the HP rob wouldn't be a significant whole number.

Geo Hahn
02-08-2008, 02:53 PM
You want Googol -- maximum number of impellers before infinity.

tomshobby
02-08-2008, 03:16 PM
In preparation to rebuild my pump I did some extensive research contacting people in the water pump industry. The consensus was that vane clearance in the housing is very important to avoid cavitation. I found that my original pump rebuilt to the correct specs is very efficient and cools dramatically better than before it was rebuilt.

https://www.britishcarforum.com/tikiwiki/tiki-index.php?page=Water+Pump+Part+3+assembly
"The spacing between the vanes of the pump and surface in the mating housing needs to be about .030. If much more the pump can have a tendency to cavitate. If it is too close the pump may rub or just work harder.

Geo Hahn
02-08-2008, 05:21 PM
I have noticed than some after-market (4-vane) pumps have vanes that are quite a bit shallower than the originals.

Not sure if more vanes are better but am pretty sure that shallower vanes would be less effective.

RobT
02-08-2008, 06:41 PM
You want Googol -- maximum number of impellers before infinity.

A Googolplex is bigger....

https://en.wikipedia.org/wiki/Googolplex

But probably tough to fit into a standard housing.

DrEntropy
02-08-2008, 06:47 PM
naah. Th' vanes are just thinner and spaced really-REALLY close t'gether! /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

Lou Metelko
02-08-2008, 10:02 PM
I also thought it would be good for the cooling in the TR2 to install a six vane pump. There was absolutely zero difference in the cooling results. The grossly over priced six vane broke a relatively short time later and to add insult to injury the warranty was non existant.

There are other places to waste your money on these cars, just don't do it on the "high capacity water pump".

Lou Metelko
54 TR2 TS981L

02-09-2008, 04:45 AM
Any thoughts on the 6-bladed aluminum water pumps from the likes of Racetorations over in the UK? I have their aluminum water pump housing (6 pounds lighter) that works well. (My OE iron water pump housing was so corroded and rusted as to be useless.)

DrEntropy
02-09-2008, 09:49 AM
You DO like that bling factor, don't-cha!

Only thing to be concerned over, IMO, would be the possibility of electrolysis. Not a big "real world" worry if the coolant mix is maintained, tho. Aluminum bein' softer than cast iron would suggest a bit faster internal wear rate, too. But again: not much of a "real world" issue.

70herald
02-09-2008, 12:07 PM
Any improvement in water flow / energy loss from the 5 bladed pump is likely due to the blade design and not the number of blades. Blades pointed straight out is really not an efficient design. sure is expen$ive!