Too Much Time On My Hands
Posted: Fri Feb 08, 2013 2:53 pm
One day I was sitting around wondering "how do you go about selecting the right carburetor size for a given engine?". That ultimately lead to a spreadsheet calculator into which you plug in engine displacement, assumed volumetric efficiency and a series of RPM values, and voila - out come CFM numbers.
The next step came from wondering whether I could get rated engine power outputs to align with theoretical power outputs given typical values for engine efficiency, fuel air ratio, thermal energy contained in gasoline, etc.
These screenshots show how it came out. Not bad at predicting horsepower.
Maybe I could work for Edelbrock.
Note the CFM for a 440 at 5,000 rpm is 637. Then note the predicted horsepower for that flow would be about 375 HP. It's a miracle. Actually, I adjusted the amount of gasoline per cubic foot of charge and the engine efficiency to get it close, BUT, the numbers I used are in fact realistic.
The next step came from wondering whether I could get rated engine power outputs to align with theoretical power outputs given typical values for engine efficiency, fuel air ratio, thermal energy contained in gasoline, etc.
These screenshots show how it came out. Not bad at predicting horsepower.
Maybe I could work for Edelbrock.
Note the CFM for a 440 at 5,000 rpm is 637. Then note the predicted horsepower for that flow would be about 375 HP. It's a miracle. Actually, I adjusted the amount of gasoline per cubic foot of charge and the engine efficiency to get it close, BUT, the numbers I used are in fact realistic.
