Interesting thread here that I'd like to revive:

 

If the the pump with cast impeller is more efficient than the pump with stamped impeller, then why does Subaru prescribe the latter for turbo applications and the former for non-turbo applications?

Hm.....can you provide more info? It seems like the cast would be the choice for the turbo, and if stamped were to be used it would be for the n/a?

The only thing i can think of is stamped is lighter then cast.

 

nipper

Hey Porc, where have you and your photo skills been?

 

Well, after reading "Hillier's Fundamentals...." posted by Legacy777, I went back and read this old thread on the two different types of pumps:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=52560&highlight=water+cavitation

 

The OP in this thread says:

 

So of course I run it past my 86 year old Dad, the civil structural PE. His take is the one with the steel impeller would be the more efficient of the two pumps and recommends using that one.

 

When I do a part number search:

21111AA007 (cast impeller) = for non-turbo applications

21111AA110 (stamped impeller) = for turbo applications

 

I would presume that that the stamped impeller would be the "high velocity pump" intended to address the excess heat produced by the turbo charger.

 

I'm thinking perhaps the key word may be "efficiency" as distinct from "flow." In other words, the cast impeller design may rob less energy from the engine to make it spin, but in this case, the stamped impeller actually creates more flow.

You got them backwards.

 

The cast impeller is of the curved vanes, and has a higher flow.

 

The stamped impeller is more then likely the straight vanes, and has a lower pumping efficiency, which consumes less power from the engine at a given rpm.

When I do a part number search:

21111AA007 (cast impeller) = for non-turbo applications

21111AA110 (stamped impeller) = for turbo applications

 

I would presume that that the stamped impeller would be the "high velocity pump" intended to address the excess heat produced by the turbo charger.

 

I'm thinking perhaps the key word may be "efficiency" as distinct from "flow." In other words, the cast impeller design may rob less energy from the engine to make it spin, but in this case, the stamped impeller actually creates more flow.

 

You have it right as to which pump has cast and stamped impellers, but, both of those pumps are for Non-Turbo applications.

 

I believe that all the late model turbo water pumps are stamped impellers. I don't think it has to do with "flow efficiency", I think it has more to do with cost and / or weight. IMO.

Edited December 11, 200817 yr by WAWalker

You got them backwards.

 

The cast impeller is of the curved vanes, and has a higher flow.

 

The stamped impeller is more then likely the straight vanes, and has a lower pumping efficiency, which consumes less power from the engine at a given rpm.

 

Yes, I read that great google link you posted, but the section on water pumps lacks a bit of clarity. It states that "the stamped impeller is very cheap but has a very low pumping efficiency and as a result energy consumed lowers the fuel economy of the engine."

 

As already quoted by porcupine, "the cast impeller, shrouded in a manner to give flow about three times greater than the stamped type, is favored."

 

The only question then is whether this "three times greater flow," is factored at a given rpm or a given level of energy required to turn the impeller.

 

If the latter, then it's possible that although the pump with stamped impeller may be less efficient it produces greater absolute flow at a given rpm.

 

 

 

You have it right as to which pump has cast and stamped impellers, but, both of those pumps are for Non-Turbo applications.

 

Man, I feel a little silly -- misread the inventory data. This makes my first point moot as this was my entire premise for raising this question.

 

 

I believe that all the late model turbo water pumps are stamped impellers. I don't think it has to do with "flow efficiency", I think it has more to do with cost and / or weight. IMO.

 

Yeah, who the heck really knows at this point, but I suspect you're right.

i prefer using cast as well.