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| Another version of how not to build a model engine |
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| NickG:
S, THat extension to the inlet manifold might affect things. You have now brought another variable into the system and you don't know the effects. Good work though, hope you find a solution. We want to see a video too!! nick |
| sorveltaja:
Bernd, you're right, there isn't venturi. I have wondered, how does one affect the engine's behaviour :scratch:. Many of the old engines have just straight tube as venturi. Here is an example of an engine, that is roughly about the same size as the current project, although it's two-stroke: http://www.modelenginenews.org/schroeder09/index.html I'm not sure, if 2 and 4 stroker carbs are comparable, but on that Schroeder's 09, the carb throat is quite big (4.37mm(0.172")). I'm bit confused about those :smart:. Nick, the extension piece doesn't seem to affect, as the engine behaves like it did before it. Anyway, I'm also looking forward to shoot a video of it running. If lucky, at this week. |
| John Hill:
At the risk of showing myself to be a complete Wally I will venture my thoughts on the venturi... A venturi causes a change in pressure in the airflow and I assume a carb with a venture will more readily atomise or evan vaporise the fuel. So I assume that where a venturi is not used the fuel must be more volatile. |
| Bernd:
Ok, I looked at the Schroeder 09. I can see that it dosen't have a vebturi. Well it was guess as to what might be wrong. Looks like you don't need one to run the engine. Keep up the good work. I'm sure you'll get it straightened out eventually. Bernd |
| bogstandard:
You will find that you will get very little fuel suction as you have it. The way the one you showed works is the spraybar acts as a backwards venturi. Instead of having the curved in walls of a standard venturi, speeding up the air flow and thus the drop in pressure, the airflow around the spraybar speeds up the airflow and it is that which causes the pressure drop, and so the fuel is sucked into the inlet. It is not as efficient as a venturi, but it is good enough for these small engines. C-o-C explains the principle. Bogs |
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