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Cox Engine of The Month
Venturi length on an Evolution .36?
Page 1 of 1
Venturi length on an Evolution .36?
I bought a new Evolution CL engine that came with 3 different length venturis. What does the length of the venturi do for performance?
Cajun66- Silver Member
- Posts : 75
Join date : 2014-01-03
Age : 49
Location : Baton Rouge, Louisiana
Re: Venturi length on an Evolution .36?
venturi sizes - .225 in (5.7mm), .235 in (6.0mm), .275 in (7.0mm)
It seems all have the same internal diameter that I can research
so the only diff is length and they recommend staring with the 6mm middle size but give no hints why you would select the shorter or longer one
My guess is that you could swap around until you found the strongest power given a certain fuel or propeller or even a certain fuel tank or location
I have never fussed with different LENGTH venturi. Usually we experiment (or copy someone else formula/recipe) with internal diameter. Larger diameters pass more air at the cost of flow velocity. The loss of flow velocity will usually make it hard to draw fuel from a hard tank with no pressure. Smaller diameters speed up the flow and help fuel draw dramatically but limit the air ...both changes have significant effect on torque and rpm
I bet Ken Cook may have some recommendation on what would suggest using the shorter or longer stack...
I love to tinker so I would start in the middle then experiment with the short, and then the long to see what changed....
Then there is fiddling with 10, 15 or 25% nitros, and then there is experimenting with prop diameter and pitch, and then back to fiddling with the venturi to see were best power, reliability, and fuel economy fall
Fun to be sure for a tinkerer....but real frustrating for someone who just wants to start the damned thing and go fly
It seems all have the same internal diameter that I can research
so the only diff is length and they recommend staring with the 6mm middle size but give no hints why you would select the shorter or longer one
My guess is that you could swap around until you found the strongest power given a certain fuel or propeller or even a certain fuel tank or location
I have never fussed with different LENGTH venturi. Usually we experiment (or copy someone else formula/recipe) with internal diameter. Larger diameters pass more air at the cost of flow velocity. The loss of flow velocity will usually make it hard to draw fuel from a hard tank with no pressure. Smaller diameters speed up the flow and help fuel draw dramatically but limit the air ...both changes have significant effect on torque and rpm
I bet Ken Cook may have some recommendation on what would suggest using the shorter or longer stack...
I love to tinker so I would start in the middle then experiment with the short, and then the long to see what changed....
Then there is fiddling with 10, 15 or 25% nitros, and then there is experimenting with prop diameter and pitch, and then back to fiddling with the venturi to see were best power, reliability, and fuel economy fall
Fun to be sure for a tinkerer....but real frustrating for someone who just wants to start the damned thing and go fly
fredvon4- Top Poster
-
Posts : 4001
Join date : 2011-08-26
Age : 68
Location : Lampasas Texas
Re: Venturi length on an Evolution .36?
Diameter is the same. Length is different. I came with the long installed. Seems to run fine. Probably getting into more detail than I can keep up with. It pulls my Ringmaster great.
Cajun66- Silver Member
- Posts : 75
Join date : 2014-01-03
Age : 49
Location : Baton Rouge, Louisiana
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