$txt['youtube'] = 'YouTube'; $txt['youtube_invalid'] = '#Invalid YouTube Link#'; Performance Impeller

Author Topic: Performance Impeller  (Read 19241 times)

0 Members and 1 Guest are viewing this topic.

Offline cjyoung

  • Newbie
  • *
  • Posts: 2
  • Location: Texas
  • Cool Points: 0
Performance Impeller
« on: July 07, 2015, 01:16:09 AM »
There are several posts about engine performance for the Honda engine in my mokai, but I haven't seen anyone talking about changing out impellers for more torque, top speed, etc... My experience with boats has mainly been outboard motors where prop pitch and size is very important to overall boat performance.  I assume that this is true for jet drives as well.  Does anyone on here have experience with tuning or replacing their impeller to achieve more top speed?

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #1 on: July 07, 2015, 10:36:36 AM »
Since Mokai makes their own pump, there are no replacement impellers. As a result, nobody is keen on the idea of modifying the one they have and risk ruining it. You MIGHT be able to talk Mokai into selling just an impeller, but I wouldn't count on that being an easy task. Then unless you have special tools, you could not tear the pump down to change the impeller. I firmly believe there is a ton of performance to be gained from a more efficient impeller/pump design, but so far the market has been way to small for anyone with the capability to be interested in taking it on. Just isn't worth the investment for the big companies to mess with, and too big of an undertaking for someone like me to think about it.
Tom

  >:D    

_________________________

www.PainlessClutch.com

Offline Heavynets

  • Jr. Member
  • **
  • Posts: 66
  • Location: Indianapolis area
  • Cool Points: 5
  • Engine: EX-21
  • Model Year: 2010
Re: Performance Impeller
« Reply #2 on: July 17, 2015, 11:28:48 AM »
I've thought about that myself.  A new turbine could be 3-D printed for probably less than $200.  The problem is that I have know idea of what a better design would be.  Trial and error R&D could be quite expensive.

Peter (from Russia) made a turbine for his boat that only had 3 blades.  I wonder if that would be an improvement over Mokai's design.

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #3 on: July 17, 2015, 12:31:44 PM »
A three blade overlapping impeller is more efficient that what Mokai did. If it wasn't, then EVERY other jet boat manufacturer would not make them that way. Those people use what works, they've spent millions in R&D to figure that out. SeaDoo, Polaris, Yamaha, Berkeley, Hamilton.. Every jet pump I've ever seen has a 3 or 4 blade impeller that has a varying degrees of overlap. I don't think that the new impeller could be made to work with the factory wear ring design though, it's too shallow and at a taper. Real jet pump impellers are much deeper with no taper, I'm sure this affects performance too.

So.... there really needs to be a whole new design to make use of the more efficient technology. While 3D printing could be used to come up with a semi working prototype, cost would prevent the next level to source out castings and machining to come up with a product. Then you have to sell it and make a profit. If there were millions of Mokai boats out there, there would be a market for something.. with only thousands, you would be spending allot of money with no return. That's just how I see it anyhow.

I feel if Mokai really wanted to make a better boat, they would quit farting around with servos and non functional cold air intakes and address the potential the boat has while fixing the problems that have been ongoing since the beginning. Redesign the pump so it's a real jet pump, make it so it will last and not fill up with water after a few hours of use....
Tom

  >:D    

_________________________

www.PainlessClutch.com

Offline Odie

  • Mokai Maniac Member
  • ******
  • Posts: 979
  • Location: NC
  • Cool Points: 17
  • Engine: RS
  • Model Year: 2008
Re: Performance Impeller
« Reply #4 on: July 17, 2015, 05:34:16 PM »
I'm curious, is the current impeller investment casting? 

Offline Heavynets

  • Jr. Member
  • **
  • Posts: 66
  • Location: Indianapolis area
  • Cool Points: 5
  • Engine: EX-21
  • Model Year: 2010
Re: Performance Impeller
« Reply #5 on: July 17, 2015, 09:32:48 PM »
I wasn't planning on going into business, just make one for me.  The 3D printed turbine is the final thing, not just for a a prototype.  It may not be the optimal design due to Mokai's initial design limitations, but it may be an improvement over the current design.  It will probably require a little machining, but that's not a deal breaker for me, if I decide to do it.

if it works the CAD file could be made public for anyone that wants to have one made.  Now if I just knew the optimal pitch.

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #6 on: July 18, 2015, 01:12:58 AM »
How strong would the 3D printed part be? The impeller is the "nut" that tightens the axle to the bearings and needs to withstand that as well as the shaft seating to it and tightening down against it. Then there is the wear factor if you're running through any debris or shallows. Would love to see somebody make it happen though, if I had the ability and know how I would have played with this a long time ago.

Tom

  >:D    

_________________________

www.PainlessClutch.com

Offline Heavynets

  • Jr. Member
  • **
  • Posts: 66
  • Location: Indianapolis area
  • Cool Points: 5
  • Engine: EX-21
  • Model Year: 2010
Re: Performance Impeller
« Reply #7 on: July 18, 2015, 09:00:17 AM »
Strength is a function of not only the material, but also the design and directions of the various loads.  It is therefore hard to answer your question.  As for the material, I would probably use 420 Stainless Steel infused with bronze.  It has a final composition of approximately 60% steel and 40% bronze.  This is a standard product for one 3D printing supplier.  However, almost anything is available including carbon graphite, kevlar and fiberglass impregnated plastic.

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #8 on: July 18, 2015, 09:21:45 AM »
3D printing has come a long way since I last paid attention to it. Did not know metals were an option now, this would be a game changer if you have a source for the process at an affordable level. Is the finished stainless/bronze piece able to bend, or is it too brittle? Wondering how it would handle impact, such as hitting a rock at 4000 rpm. Interesting stuff.  ;D
Tom

  >:D    

_________________________

www.PainlessClutch.com

Offline Odie

  • Mokai Maniac Member
  • ******
  • Posts: 979
  • Location: NC
  • Cool Points: 17
  • Engine: RS
  • Model Year: 2008
Re: Performance Impeller
« Reply #9 on: July 18, 2015, 07:20:51 PM »
Investment Casting  + FDM is a marvelous marriage of past and present. It offers a low production cost after all engineering plus trial and error is done.  The cost of the engineer and trial and error?

Offline XYZER

  • Jr. Member
  • **
  • Posts: 62
  • Location: Oregon
  • Cool Points: 5
Re: Performance Impeller
« Reply #10 on: July 21, 2015, 09:15:07 AM »
We have 2 metal 3D printers here at work. It is currently printing in Inconel. There is no strength problems. We have made a few turbo impellers out of the Inconel and not sure how testing has gone. Getting a model with the improvements is part of the problem. You could end up making several before you found the sweet one for your target rpm. Got a model?
https://www.youtube.com/watch?v=DXh1AbX5j20

Offline Heavynets

  • Jr. Member
  • **
  • Posts: 66
  • Location: Indianapolis area
  • Cool Points: 5
  • Engine: EX-21
  • Model Year: 2010
Re: Performance Impeller
« Reply #11 on: July 22, 2015, 11:15:08 PM »


Here is a rough sketch of a 5 blade turbine in a 3D CAD format (STL file).  I may try to design one this winter.  Too busy right now.

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #12 on: July 22, 2015, 11:57:44 PM »
Very impressive, wish I had learned CAD. Was good at mech drafting / drawing when I was in school, but I wanted to play with wrenches and grease instead.

Why 5 blades? There are 8 now, the "standard" on many other pumps is 3. The fun part is figuring out what thread size is inside it, left hand threads at that. I have several pumps I'm rebuilding right now, will have to see if I can figure that out.

Tom

  >:D    

_________________________

www.PainlessClutch.com

Offline Hillbilly

  • Mokai Maniac Member
  • ******
  • Posts: 793
  • Location: Greensburg, Pa
  • Cool Points: 35
  • Engine: Subaru
  • Model Year: many
Re: Performance Impeller
« Reply #13 on: July 23, 2015, 07:07:42 AM »
Mine has eight.  Thought about cutting four off from a spare

Offline Painlesstom

  • Painless Tom
  • Administrator
  • Mokai Maniac Member
  • *******
  • Posts: 5719
  • Age: 44
  • Location: Georgia
  • Cool Points: 55
  • Making Your Mokai... A Better Mokai!
    • Painless Products
  • Engine: EX21 w/17 head - ES
  • Model Year: 2003 / 2011 / 2015
Re: Performance Impeller
« Reply #14 on: July 23, 2015, 07:52:05 AM »
Cutting out 4 without making the others wider to fill the gap, would just move half as much water at a faster rpm in my opinion. You aren't changing anything to make up for the 4 missing blades.
Tom

  >:D    

_________________________

www.PainlessClutch.com