Yet another inlet PSI question

# Thread: Yet another inlet PSI question

1. ## Yet another inlet PSI question

I drilled and tapped my suction for inlet psi @ 9oclock. It reads between 32-37psi, depending on shoe/depth, and nozzle size. 35-37 with my best (to date) setup in the boat.
A few weeks later I stopped by Jack's shop and he advised me that a better place to take a reading from would be up higher, at about 10-11oclock, as the top of the impeller is harder to load.
So yesterday I took the boat out for the 1st time since adding the 2nd tap. 1st couple passes the low tap read 35psi. I then switched to the high tap and saw consistent readings of 36-37psi, though I'd have thought it'd be less than the low tap.
Anyone have any ideas why the high tap might see more psi than the low?

2.

4. on the wall of the suction piece, the closer to the impeller, the higher the pressure.

basically. you are scooping a column of water at the same speed the boat is travelling. at the intake opening, pressure is close to atmospheric, but the velocity up into the suction piece is high (i.e., if you were removing water as fast as it entered, suction pressure would be 0). the closer it gets to the impeller, the more the water molecules slow down. since the velocity energy must be conserved, velocity energy converts to pressure energy.... basically...

5.

6. Originally Posted by bp298
on the wall of the suction piece, the closer to the impeller, the higher the pressure.

basically. you are scooping a column of water at the same speed the boat is travelling. at the intake opening, pressure is close to atmospheric, but the velocity up into the suction piece is high (i.e., if you were removing water as fast as it entered, suction pressure would be 0). the closer it gets to the impeller, the more the water molecules slow down. since the velocity energy must be conserved, velocity energy converts to pressure energy.... basically...
WOW!!!! Thats a mouth full!!!!!!!

7. There's someone on this forum that told me, when he gets done doing his magic to the pump >>> 8-lbs is plenty and no more is needed.
My lips are sealed to whom that person is

8. Originally Posted by bp298
on the wall of the suction piece, the closer to the impeller, the higher the pressure.

basically. you are scooping a column of water at the same speed the boat is travelling. at the intake opening, pressure is close to atmospheric, but the velocity up into the suction piece is high (i.e., if you were removing water as fast as it entered, suction pressure would be 0). the closer it gets to the impeller, the more the water molecules slow down. since the velocity energy must be conserved, velocity energy converts to pressure energy.... basically...
Where's MikeT when I need him

9. Originally Posted by zacho!
Yup. A real nice MPD open center one.
What kinda inlet pressures are you seein' high and low?

10. Originally Posted by HammerDown
There's someone on this forum that told me, when he gets done doing his magic to the pump >>> 8-lbs is plenty and no more is needed.
My lips are sealed to whom that person is
Timinator?

11. Originally Posted by cyclone
Timinator?
I'll never tell...

12. Originally Posted by 75 TX
Yup. A real nice MPD open center one.
What kinda inlet pressures are you seein' high and low?
I run a "hand me down" loader. Flat shoe, around 20#'s high and 30#'s low, v-hull. I think it runs incredible, but I'm sure a pro would tell me different. One of the really fast racers here in tucson said I need a center blocker for more lift ... at some point Ill be able to work with JM, who built the said racer's pump.

13. Originally Posted by HammerDown
I'll never tell...
he's stated as much before. Can't say I agree with it but would like to see some sort of test to prove it.

14. Originally Posted by wickedsanger
WOW!!!! Thats a mouth full!!!!!!!
just a basic description. the long version would be a mouthful. it is what it is.

Originally Posted by HammerDown
My lips are sealed to whom that person is
doesn't matter, everyone knows who it is. unfortunately, this has nothing to do with the op's question. also unfortunately, "your guy" has never had a boat on a track to demonstrate it.

Originally Posted by cyclone
he's stated as much before. Can't say I agree with it but would like to see some sort of test to prove it.
it would be very interesting to see an actual data file with 3-4 suction pressure taps, top and bottom, along with a couple bowl pressure taps, and see what the trends are when you're trying to maintain 8 psig suction pressure at 110-130.

15. Originally Posted by 75 TX
Anyone have any ideas why the high tap might see more psi than the low?

Its tottally normal that the high inlet is higher. In fact your low and high are pretty equal, I'd say your doing real well with your setup.

16. Originally Posted by bp298
just a basic description. the long version would be a mouthful. it is what it is.

doesn't matter, everyone knows who it is. unfortunately, this has nothing to do with the op's question. also unfortunately, "your guy" has never had a boat on a track to demonstrate it.

it would be very interesting to see an actual data file with 3-4 suction pressure taps, top and bottom, along with a couple bowl pressure taps, and see what the trends are when you're trying to maintain 8 psig suction pressure at 110-130.
I'd like to see a boat that goes 100+ with only 8psi inlet pressure. that would be an accomplishment.

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