Blaster Exit Nozzle & hydro dynamics 101

[ItsRixter]

Two questions for those fluid dynamics experts out there.

I'm going to do a B1 Kawi 1100 build. I'm going through spare parts I have and noticed I have two drop nozzles. One has slats/ splines in the exit nozzle the other does not. Additionally, the one nozzle is slim the other is more ballon shaped.

1) What are the pro and cons with the spines? I assume it prevents the water to swirl through vs go straight out.

2) What are the advantages/ dis advantages with a slimmer nozzle vs the more ballon shaped one (black one in the photo)

 

[wanderer1]

You could've called Pro Tec and asked them since they made it and not the guys on here. ProTec told me they found and felt the fins coupled with the bell shape aided in more thrust by straightening the flow,smoother transition at the exit and more volume in the reduction nozzle. Radar testing showed a loss of 1-2mph on top end turning same RPM using the ProTec reduction nozzle.

 

[ItsRixter]

You could've called Pro Tec and asked them since they made it and not the guys on here. ProTec told me they found and felt the fins coupled with the bell shape aided in more thrust by straightening the flow,smoother transition at the exit and more volume in the reduction nozzle. Radar testing showed a loss of 1-2mph on top end turning same RPM using the ProTec reduction nozzle.

Good call. I called ProTec and they recommend using the black one. Not much detail other than it was "designed to have more thrust". Interesting the bell or bulb shape of the nozzle allows more water yet aftermarket nose cones are bigger to fill more space....seems like those are working against each other