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  • November 13, 2019, 07:07:56 PM

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Author Topic: Novarossi .21 venturi help  (Read 558 times)

Offline Tim Stone

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Novarossi .21 venturi help
« on: June 20, 2019, 05:59:59 AM »
   Maybe someone can help save me some time. What venturi size are you using on NovaRossi .21 on crankcase pressure?
And diameter of pressure tap? Thanks I could not find much when I searched.

Online Motorman

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Re: Novarossi .21 venturi help
« Reply #1 on: June 20, 2019, 07:03:55 AM »
Pressure tap can be 4-40 fox or K&B unit. Don't over tighten it or it will snap off. Use loctite and barely snug it. I've actually gone to a 6-32 nipple but with a restrictor in the line that has a #69 drill hole and is also a check valve. Side note the old KK check valves for 1/2a aren't big enough. Venturi? what venturi. Is it for upright cowled in or profile? Beyond a certain size there is no gain but you can go .440" if you have good height and shape to prevent the prop blast from blowing the fuel out. You're also dealing with centrifugal force slinging the fuel out on a profile. On my proto I have a .400" that's 3/8" above the crankcase. The choke is down by the spraybar and it has about 10-12 degree taper. I use 7075-T6 because the sections get pretty thin. Enough secrets for now lol.


Motorman 8)
« Last Edit: June 20, 2019, 07:21:47 AM by Motorman »
There will be a sunny day and we will fly our airplanes.

Offline Les Akre

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Re: Novarossi .21 venturi help
« Reply #2 on: June 21, 2019, 02:43:52 PM »
Hi Tim

The motor I used many years ago, came from Gillot with the Venturi the same size as the crank bore, I would at least start there.

Les

Offline Tim Stone

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Re: Novarossi .21 venturi help
« Reply #3 on: June 26, 2019, 08:46:02 AM »
Hi Tim

The motor I used many years ago, came from Gillot with the Venturi the same size as the crank bore, I would at least start there.

Les

Thanks Les it is hard to argue with Tim Gillotts' methods.

Offline Tim Stone

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Re: Novarossi .21 venturi help
« Reply #4 on: June 26, 2019, 08:47:01 AM »
Pressure tap can be 4-40 fox or K&B unit. Don't over tighten it or it will snap off. Use loctite and barely snug it. I've actually gone to a 6-32 nipple but with a restrictor in the line that has a #69 drill hole and is also a check valve. Side note the old KK check valves for 1/2a aren't big enough. Venturi? what venturi. Is it for upright cowled in or profile? Beyond a certain size there is no gain but you can go .440" if you have good height and shape to prevent the prop blast from blowing the fuel out. You're also dealing with centrifugal force slinging the fuel out on a profile. On my proto I have a .400" that's 3/8" above the crankcase. The choke is down by the spraybar and it has about 10-12 degree taper. I use 7075-T6 because the sections get pretty thin. Enough secrets for now lol.


Motorman 8)

Thanks I appreciate it.

Online bob whitney

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Re: Novarossi .21 venturi help
« Reply #5 on: June 27, 2019, 08:18:41 PM »
Time just looking at some old notes and see where one of the fastest 21 SS had a 390 venture in it
rad racer

Offline Tim Stone

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Re: Novarossi .21 venturi help
« Reply #6 on: June 29, 2019, 10:20:22 AM »
Time just looking at some old notes and see where one of the fastest 21 SS had a 390 venture in it

 Thanks Bob I appreciate it.

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