Wednesday, October 5, 2011

Always Nice to Have a Basic Understanding of What you’re Trying to do

A carburetor is defined as a device for breaking up gasoline into a very finely divided state and mixing it with air in automatically varying proportions to meet the variable running conditions of a gas engine.  Ok now that sounds simple and it was when gasoline was available that was of a high test it was. 
So to actually get this all to work a few things are required for a carburetor.  A fuel supply is needed, air is needed to mix it with and the motive force of a vacuum to make it all flow and do its thing of producing homogeneity of mixture, which is the ideal objective for burning in a combustion chamber.   
One of the ways to make this all happen inside a carburetor is to use the Venturi Principal in the internal structure of the carburetor body.  All carburetors use this principle in some form or another.  Now it’s my understanding that using a venturi effect helps create a pressure differential which is lower than the atmospheric pressure the carburetor is operating in.  Of all the ways to get this effect one way is to machine a true venturi inside the throat of the carburetor body.  An example of this would be having an inlet of 32mm and in the area of the fuel supply valve the throat would taper to 30mm and then taper back out to 32mm on the combustion chamber inlet side.
Now obviously there are other considerations in design that I’m ignoring in my search for understanding.  My basic interest is in trying to find a simple carburetor that is fairly easy to tune for different operating conditions, altitude, fuel octane, and top end, mid range or low end performance.  But it remains pretty simple in design and construction.
All in all it seems that my best choice is still probably going to be a Lectron.  The current Lectron pretty much meets all of my requirements.  Plus it’s cheaper than all the alternatives and spares are very available since it’s still being produced.  But as always I could be dead wrong and your mileage may vary.  We shall see down the road when I get my engine built and try and feed it a homogeneous mixture of gasoline and air with a bit of spark added.

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