Nozzle bore vs impeller pitch change

[Jcary85]

Hey all,
I’ve recently been playing with nozzle size inserts and have had varying results. I’m curious if anyone can provide a semi-scientific explanation on what should be expected when going to bigger/smaller nozzle sizes vs pitching down/up? A smaller nozzle size has a similar “tightening” effect to pitching up, but what different effects should be expected with each?

Thanks!!

PS I’d be trying the pitch changes myself but my impeller is verrrrry stuck at the moment and I’m switching to a ninja pump soon so I don’t feel like messing with it.

 

[dcg5116]

Interested in this as well. Also..... X2 on the verrrrrry stuck impeller in one of my spare pumps.

 

[DylanS]

Hey all,
I’ve recently been playing with nozzle size inserts and have had varying results. I’m curious if anyone can provide a semi-scientific explanation on what should be expected when going to bigger/smaller nozzle sizes vs pitching down/up? A smaller nozzle size has a similar “tightening” effect to pitching up, but what different effects should be expected with each?

Thanks!!

PS I’d be trying the pitch changes myself but my impeller is verrrrry stuck at the moment and I’m switching to a ninja pump soon so I don’t feel like messing with it.

As far as the science goes I might not be spot on but what I can tell you is that you’ll want to settle on a pitch (unfortunately can only really be done by trying different props/experience) then make your fine tuned adjustments via cone/bore/spacing.
If you’re running the one that’s stuck on and you have adjustable rings (very cool stuff btw been following that on Facebook) it shouldn’t be too hard to go for a burn, come back and swap rings, then go for a comparison run.
You’ll be able to optimize the prop you have in even if it’s not the perfect pitch.
A bigger bore reduction/steering nozzle takes load off of the motor and allows the pump to push a larger volume of water out quite a bit faster which results in better “low end thrust” but can result in less velocity and less top end performance. There are also tapered bores on most nozzles in varying angles that most claim to work far better than a strait bore. We used to wrap carbon around stock nozzles and hog them out like crazy to experiment. There is a point of diminishing return on boring them though!
I read somewhere that you want to bore the nozzle until you just about slip your prop when riding then come back down in size to be roughly in the right ballpark but I’ve never tried it and can’t tell you how well it works.

Unfortunately pump tuning is super labor intensive and expensive and I’ve come to find it soooo much easier and cheaper in the long run to get ahold of Brian at Torrent (or another professional) and get the right pitch prop and setup from someone who has a lifetime of experience over me. Just one less headache to worry about when dialing the ski in IMO.

 

[Jcary85]

As far as the science goes I might not be spot on but what I can tell you is that you’ll want to settle on a pitch (unfortunately can only really be done by trying different props/experience) then make your fine tuned adjustments via cone/bore/spacing.
If you’re running the one that’s stuck on and you have adjustable rings (very cool stuff btw been following that on Facebook) it shouldn’t be too hard to go for a burn, come back and swap rings, then go for a comparison run.
You’ll be able to optimize the prop you have in even if it’s not the perfect pitch.
A bigger bore reduction/steering nozzle takes load off of the motor and allows the pump to push a larger volume of water out quite a bit faster which results in better “low end thrust” but can result in less velocity and less top end performance. There are also tapered bores on most nozzles in varying angles that most claim to work far better than a strait bore. We used to wrap carbon around stock nozzles and hog them out like crazy to experiment. There is a point of diminishing return on boring them though!
I read somewhere that you want to bore the nozzle until you just about slip your prop when riding then come back down in size to be roughly in the right ballpark but I’ve never tried it and can’t tell you how well it works.

Unfortunately pump tuning is super labor intensive and expensive and I’ve come to find it soooo much easier and cheaper in the long run to get ahold of Brian at Torrent (or another professional) and get the right pitch prop and setup from someone who has a lifetime of experience over me. Just one less headache to worry about when dialing the ski in IMO.

Thanks man appreciate the Info. FWIW I’m really just playing around for fun. I’ve got a new ninja 160 on order with prop and all from Brian. Just like to understand what adjustments impact what.

 

[DylanS]

Thanks man appreciate the Info. FWIW I’m really just playing around for fun. I’ve got a new ninja 160 on order with prop and all from Brian. Just like to understand what adjustments impact what.

I understand, I’m the same way!
Maybe pick Brians brain I’m sure he’d have some interesting things to say

 

[kevbo]

I have made and tested various nozzle diameters on kawasaki 140 and Yamaha 144 pumps. My findings were, larger nozzles made noticeably better thrust until the ski was going fast. Smaller nozzles kept top speed better than large ones do. The short aftermarket cones didnt seem to hurt but were a waste of money. Our piped engines have a narrow power band so its critical to find an impeller that gets to the pipe just fast enough. If you go too low in pitch, response will be good but thrust will begin to fall off.