Impeller to stator vane clearance

[durhamgoat]

Two different applications, both related but different...

I have a 550 pump and when installing the impeller you shim the impeller so that the impeller to wear ring distance is minimized. However as the wear ring wears down in diameter you are now shimming the impeller further away from the stator vanes, so assuming that the wear ring is still intact is there a distance away from the vanes that is too far? I am running a 750 motor on a 550 pump and many other people are running this combination and are not having trouble but I am getting cavitation unless I use a smaller exit nozzle, top loader intake, and the stock cone.

I have a 12-17 impeller on a setback maxx 148 pump and when I put it together it seems like the trailing edges of the impeller are a fair distance away from the vanes. Since there is no taper to this pump like there is with a 550 pump I could shim the impeller further away from the vanes or closer if I like, closer might require machining the land area on the impeller hub but that is fine. How far away from the vanes is optimal? I ride fw freestyle (learning) and want to make sure I am getting the best performance out of my pump.

Any help would be appreciated.

 

[speedysprocket]

The closer you get the impeller to the stator, the "tighter" it will make the pump. That distance is another pump tuning. Moving the impeller closer to the stator can be comparable to increasing pitch, putting a larger cone on, or decreasing nozzle size.
So as you move your impeller further from the stator on your 550, the more the pump will slip. But sounds like you need to do that to decrease wear ring clearance to prevent cavation. Sounds like you're stuck where you're going to have to find a decent median between the two. Or get your impeller/wear ring replaced or repaired so you can start over with tight clearances in both places...

 

[Berky]

Right on speedysprocket . I like it tight , it helps hook up .

 

[speedysprocket]

And once you cut your impeller back, I'd say it's easier to shim it back out as opposed to bending the impeller over and over trying to find what's perfect... But that distance should be tuned in conjunction with the pitch, not as compensation, in the perfect tuning world..
And I do like it tight too!

 

[durhamgoat]

So as you move your impeller further from the stator on your 550, the more the pump will slip.

This is exactly what I experienced, the impeller is so far away that it slipped. So by compensating with a smaller nozzle and larger cone I "fixed" the problem but at the cost of water volume out the nozzle?

 

[kevbo]

Two different applications, both related but different...

I have a 550 pump and when installing the impeller you shim the impeller so that the impeller to wear ring distance is minimized. However as the wear ring wears down in diameter you are now shimming the impeller further away from the stator vanes, so assuming that the wear ring is still intact is there a distance away from the vanes that is too far? I am running a 750 motor on a 550 pump and many other people are running this combination and are not having trouble but I am getting cavitation unless I use a smaller exit nozzle, top loader intake, and the stock cone.

I have a 12-17 impeller on a setback maxx 148 pump and when I put it together it seems like the trailing edges of the impeller are a fair distance away from the vanes. Since there is no taper to this pump like there is with a 550 pump I could shim the impeller further away from the vanes or closer if I like, closer might require machining the land area on the impeller hub but that is fine. How far away from the vanes is optimal? I ride fw freestyle (learning) and want to make sure I am getting the best performance out of my pump.

Any help would be appreciated.

Do you have a cambered impeller or straight pitch? A straight pitch behind a 750 will vibrate a lot at low speeds so use a good grate. The blade to stator distance gets too much attention considering what it does for performance.

 

[durhamgoat]

Its a 19 and I've got a good top loader. So are you saying the distance has little bearing on performance?

 

[Berky]

set it 1.2mm to 4.5mm , make sure the leading edge of the stator is parabolic . If your over propped (won't rev quick) go with more space . If your under propped , you get the picture .

 

[kevbo]

Its a 19 and I've got a good top loader. So are you saying the distance has little bearing on performance?

Bend the leading edge down a little, it will run a lot smoother. I never found impeller/stator clearance to make much difference, nozzle size and blade angle are huge by comparrison.