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Post by Garf on Jul 25, 2004 12:42:11 GMT -7
I have a Magnum GP 25 with a TT 25 P&C installed. I'm trying to dial it in for stunt use. The TT venturi doesn't fit properly, so I will likely have to make a custom. I don't like the NVA location as it is almost against the prop. I have the TT rear NVA but I need to find longer screws to be able to mount it. What I need to know is the venturi bore both for the thru center NVA and the sprinkler venturi.
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Post by downunder on Jul 25, 2004 17:47:17 GMT -7
Len Neumann on SSW suggests a ball park figure for any stunt engine as a ratio between engine size and venturi area. His ratio is around 20:1 so for a .25 engine the venturi area should be .0125 square inches. This holds whether it's a sprinkler type or normal. Of course, you have to take into account the area blocked off by the needle valve or sprinkler.
This ratio is only a guide and may vary according to engine size because I just checked my ST G51 and it's ratio is almost 31 (the higher the number the smaller the venturi area is compared to the engine size).
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Post by Garf on Aug 8, 2004 17:09:28 GMT -7
I'm going to need some longer backplate screws to mount a remote needle valve on this engine. What is a good source for these?
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Post by S. O'Bat on Oct 10, 2004 20:01:00 GMT -7
Du-Bro rack in your LHS should have plenty of 2.5mm and 3mm screws, in various lengths. If you don't find'um in the usual R/C Airplane section, look over in the R/C Car section. Personally, I would put the NVA through the venturi, whether I drill the case or put it above the case. There are advantages to both. Avoid the RNV unless you are using a bladder pressure tank. IMHO. Spiffy new forum...this is my first post here. "Git 'er done".  Steve |
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Steve