Freestyle Set-back vs non set-back
- Thread starter nutz
- Start date
- Location
- detroit MI
i would go up to a non setback 155 before paying for a smaller setback. more volume of water for flatwater freestyle seems to be the best way to go. i def like a even stock 155 over a setback 144 mag. jsut my prefference
DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
I wish I had a better understanding of pump dynamics, there are a lot of unknowns I’d like answers for but I can tell you with confident a pump of a larger diameter is capable of processing more water than a pump of a smaller diameter running the same pitch at a given RPM.
I don’t understand the whole setback aka “water in front of the pump” theory. In my head the pump tunnel is way more important. In my eyes the entire lake is your “set back volume” the prop should beable to pull water from the lake without dropping pressure.
What I believe everyone has to find out is at what RPM is there drivetrain making the power. They then need to find out given that RPM how they can get there pump to move the most water “efficiently”. That’s just how I think about it. I don’t have any pump tuning wisdom to spread around obtained from good old faction trial and error. Not sure if that helps you any. Asking someone like Phil Clemmons that’s phenomenal at pump tuning would be my first step.
I don’t understand the whole setback aka “water in front of the pump” theory. In my head the pump tunnel is way more important. In my eyes the entire lake is your “set back volume” the prop should beable to pull water from the lake without dropping pressure.
What I believe everyone has to find out is at what RPM is there drivetrain making the power. They then need to find out given that RPM how they can get there pump to move the most water “efficiently”. That’s just how I think about it. I don’t have any pump tuning wisdom to spread around obtained from good old faction trial and error. Not sure if that helps you any. Asking someone like Phil Clemmons that’s phenomenal at pump tuning would be my first step.
Ducky
Back in the game!
- Location
- Charlotte, NC
The Skat website makes it sound like set-back pumps make no improvements vs a non-set back pump in freestyle.
From the website:
"Although our Set-Back Pumps and their Standard cousins are equal on acceleration, hook-up, and mid-range speed, testing has shown that our Set-Back models have an added advantage in top-end speed. This application is ideal for Endurance or Off-Shore racing where it can be used to its full advantage."
From the website:
"Although our Set-Back Pumps and their Standard cousins are equal on acceleration, hook-up, and mid-range speed, testing has shown that our Set-Back models have an added advantage in top-end speed. This application is ideal for Endurance or Off-Shore racing where it can be used to its full advantage."
- Location
- the jetski grave yard
a old pro racer told me that a setback pump makes the boat feel/ride/handle like its longer which is better for racing. it would not surprise me at all to find out that the setback does nothing advantageous for freestyle. i'm lucky i can afford to buy into the BS that makes me think i just gotta have this or i'm getting less. setback means more $$$ for special shaft so i dont know why skat isnt saying setback is a must. everybody else is...............
- Location
- San Marcos, CA
Set-back pumps are the best pump for flatwater freestyle. They allow more water into pump area and therefore create more thrust.
- Location
- detroit MI
okay ill bite and play along. please explain further how this is logical. anything after the prop and any extra volume of tube creates loss an in pressure and more restriction and flow for every inch longer it is.
and conversely a longer tunnel is front of the impeller will require more power to pull up to the impeller.
and conversely a longer tunnel is front of the impeller will require more power to pull up to the impeller.
speedysprocket
Alex
- Location
- Chesapeake, VA
The advantage I see with a set back is that you have that little bit of extra water still in the tunnel to add that tiny bit of extra thrust once the grate leaves the water. The draw back is that once you get back in the water, the prop is that much further from the water and takes a tiny bit extra to get that water to the prop...
SpaceCowboy
breaking something
- Location
- Ypsilanti Michigan
I think this topic has a lot to do with pump tunnel/intake design as well to compliment the pump you run.
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
I though that awhile back also but after trying to put numbers to it, it does not make since, to me. I'm guessing a prop can chew thru well more than the 2" of setback water probably just using 1 of the 3 blades, but say a full 360 spin will defiantly get it. At say a conservative 4000 RPM aka 66 RPS(second) it would be such a small fraction of time there is no way anyone would know or could feel a extra .001 second.
DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
conspiracy theory #2
After watching some high speed video of a water balloon popping in slow mo I think that the second the pump intake drops pressure aka leaves the water all the water in front of the prop just collapses. Sure it may still go through the prop but there is nothing feeding it and no power to be made.
ok busting out the popcorn after that one
After watching some high speed video of a water balloon popping in slow mo I think that the second the pump intake drops pressure aka leaves the water all the water in front of the prop just collapses. Sure it may still go through the prop but there is nothing feeding it and no power to be made.
ok busting out the popcorn after that one
- Location
- Cruising Around
Well as far as having extra water for the pump to process after leaving the supply, I believe you are assuming that the pumps in our skis operate on a "suction" principle where as "head pressure" does not affect the processing. Lots of literature on how these pumps function as their principle is very similar to the very squared away jet boat market.
- Location
- detroit MI
- Location
- Ontario, Canada
I'm eating a greasewheel while I read this one 
...and watching Star Trek TNG.
...and watching Star Trek TNG.- Location
- San Marcos, CA
Here is Blowsions reasoning on the set-back pump...
the Skat-Trak Set-Back Pump option moves or "Sets-Back" the stator section and impeller by reducing the length of the vanes. Not only does this open up the intake area before the impeller, allowing for more water to be stored in the inlet section, but it also puts the impeller closer to the venture nozzle creating less drag on the water flowing through the stator section. The stator vane and wear ring housings are not shifted. Only the stator vane section is internally moved back. When you compare the craftsmanship of the Magnum Pumps to their stock OEM counterparts, the difference is visually noticeable, and beyond compare in performance.
... I spoke with Jordan @ Blowsion about this and he explained it pretty well. He is there lead mechanic and has built many skis with many different configurations and he swears that the set-back is the only way to go.
Hope this helps!
the Skat-Trak Set-Back Pump option moves or "Sets-Back" the stator section and impeller by reducing the length of the vanes. Not only does this open up the intake area before the impeller, allowing for more water to be stored in the inlet section, but it also puts the impeller closer to the venture nozzle creating less drag on the water flowing through the stator section. The stator vane and wear ring housings are not shifted. Only the stator vane section is internally moved back. When you compare the craftsmanship of the Magnum Pumps to their stock OEM counterparts, the difference is visually noticeable, and beyond compare in performance.
... I spoke with Jordan @ Blowsion about this and he explained it pretty well. He is there lead mechanic and has built many skis with many different configurations and he swears that the set-back is the only way to go.
Hope this helps!
- Location
- the jetski grave yard
thats the BS story that gets everybody to think thats whats needed. 2" more water before the prop is going to mean exactly nothing. thats one of the problems in all aftermarket parts makers and sellers, they dont tell the truth about their product. they hype it up so they can make money. its up to the consumer to see thru the smoke, not up to the seller to advertise the truth.
- Location
- detroit MI
and people swear that big bore stock stroke is the way to go..... yet math and engineering principles say that it is actually the opposite.
- Location
- Edmonton, AB
How many freestyle skis have you built with 144 mags and with stock 155 pumps.
This is just bad information, blind leading the blind