News:



  • March 29, 2024, 01:53:18 AM

Login with username, password and session length

Author Topic: Increase Nitro or bigger venturi for more power?  (Read 609 times)

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4209
Increase Nitro or bigger venturi for more power?
« on: April 24, 2019, 05:44:21 PM »
Guys,
I found my Ringmaster needing a bit more power to get through the OTS vertical 8's in the wind. The ship has a OS Max 25, with a 0.25" venturi and ST NVA. Had been running a 9x6 APC and 7% nitro, 26% oil fuel. If we go a bit lean (from a very rich 2 cycle to a kinda rich 2 cycle) the ship picks up a just a bit of speed and will do OK. Looking at the set-ups for the FP20/25 they have venturi's of around 0.265", for the old MAX this is a bit outside the range of rpm needed for good pumping but maybe a 0.257" would work and still have a good neeedle. Seems the 0.25" might be a bit small with the ST NVA,  but I get very consistent needle settings.  I would like to see if I can get to a 9 3/4 -10" diameter 5"ish pitch prop (narrow blade) to get a little more pull through the top without stressing the engine to much.

Question is can going up to say 10 -15% nitro with the current set-up give the power boost that you would get if I went to a larger venturi say 0.257"?

Best,     DennisT

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13717
Re: Increase Nitro or bigger venturi for more power?
« Reply #1 on: April 24, 2019, 07:39:56 PM »
Guys,
I found my Ringmaster needing a bit more power to get through the OTS vertical 8's in the wind. The ship has a OS Max 25, with a 0.25" venturi and ST NVA. Had been running a 9x6 APC and 7% nitro, 26% oil fuel. If we go a bit lean (from a very rich 2 cycle to a kinda rich 2 cycle) the ship picks up a just a bit of speed and will do OK. Looking at the set-ups for the FP20/25 they have venturi's of around 0.265", for the old MAX this is a bit outside the range of rpm needed for good pumping but maybe a 0.257" would work and still have a good neeedle. Seems the 0.25" might be a bit small with the ST NVA,  but I get very consistent needle settings.  I would like to see if I can get to a 9 3/4 -10" diameter 5"ish pitch prop (narrow blade) to get a little more pull through the top without stressing the engine to much.

Question is can going up to say 10 -15% nitro with the current set-up give the power boost that you would get if I went to a larger venturi say 0.257"?

      This is a 25-S (baffle piston)?

    Brett

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6824
Re: Increase Nitro or bigger venturi for more power?
« Reply #2 on: April 24, 2019, 07:54:44 PM »
  Yes, is it the older .25S? If so, you are choking it down with the ST NVA. If you have a slightly larger venturi, try that first. Or find an original OS NVA, but you probably drilled everything out to to accommodate the ST unit. A foot or so shorter lines might help. But I think you'll find that older .25 won't pull much prop, and no sense comparing to to an FP-20 or .25. These are way different animals. The easiest ti try would be 10% nitro and/or shorter lines.
   Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline RandySmith

  • Administrator
  • Trade Count: (0)
  • Admiral
  • *****
  • Posts: 13747
  • Welcome to the Stunt Hanger.
    • Aero Products
Re: Increase Nitro or bigger venturi for more power?
« Reply #3 on: April 24, 2019, 10:47:45 PM »
The venturi needs to be opened  first  try  drilling it out  to .275,  That is more in the  range  when  using a  .157 diameter  spray bar

Randy


Advertise Here
Tags:
 


Advertise Here