There have been a number of threads on multiple carburetors. Often I have posted that mathematics and physics are the enthusiast's best friend. But believe it or not, history is also an enthusiast's friend.
When one goes to the license bureau to acquire a license for one's automobile (at least here in Missouri), one pays based on taxable horsepower (one can get some really interesting answers by requesting a definition of "taxable" horsepower from the license clerks)
But taxable horsepower dates back to the early days of the automobile industry in the USA, when a government official asked a representative of (A)merican (L)icensed (A)utomotive (M)anufacturer for a way to calculate horsepower. The internet states this occured in 1908. My sources say that A.L.A.M. contacted Cadillac, and one of the Cadillac engineers, in 1911, gave them the equation:
HP = D (squared) times N divided by the constant 2.5
Or
Horsepower is equal to the piston diameter multiplied by itself times the number of cylinders divided by 2.5
This was a very credible figure for horsepower for the low RPM engines of the time (either 1908 or 1911).
This equation was also adopted by the Royal Automobile Club of Great Britain.
So what does this have to do with multiple carburetors???
The British government since long ago (especially on tea
) has been very interested in taxes; and they were much more aggressive on taxing automobile engines, but they often used displacement. So the British manufacturers tried to squeeze more power from smaller engines (improve volumetric efficiency). Note that, while there are exceptions, most of the British factory built (and engineered) engines used setups where the number of carburetors was half the number of cylinders (a four cylinder had two carburetors, a six cylinder had three carburetors). Rarely, but it happened, a six cylinder would have two carburetors, AND THE MANIFOLD AND CYLINDER HEAD DESIGN WOULD BE ONE CARB FEEDING TWO BANKS OF THREE CYLINDERS! The idea with multiple carburetors was better A/F density to all cylinders, thus improving the volumetric efficiency. The carburetor size would be determined by the displacement, and the number of carburetors.
And while it may have occurred, I have NEVER seen one of these engines which used progressive linkage.
Just something to consider when considering the installation of multiple carburetors.
Of course you can also consider our government using a horsepower equation more than 100 years old!
Jon.
