For another perspective on this, look at some of the centrifugally blown engines offered in the US in the 1930s.
Auburn replaced their 150HP V12 with a supercharged straight eight of the same horsepower. Graham replaced a 120HP straight eight with a supercharged 6 also with the same HP as the engine it replaced.
For a 6=8 and 8=12 equation, the HP increase from supercharging would have to be 1/3 to 1/2.
These were both conventional inline flathead engines, with centrifugal blowers belt driven off the crankshaft.
The supercharger did nothing at low speeds which is good because it prevented knocking and damaging the engine.
At medium to high speeds when the conventional engine was running out of puff, the supercharged engine came into its own.
Thus they could tune the engine for economy, smoothness, and low speed pulling power and at the same time, the supercharger gave them the high speed performance of the most sophisticated performance engine.
The supercharger was simple reliable and had no adverse effects, they even figured it improved economy and low speed running by "homogenizing" the incoming mixture even when it was not providing pressure.
It has seemed to me for a long time that the centrifugal blower and the flathead engine is a marriage made in heaven. The blower overcomes the built in drawbacks of poor breathing and low compression found in the typical flathead, while keeping the virtues of simplicity, smoothness, economy and excellent low to medium speed pulling power.
Last edited by Rusty O'Toole; 04/09/08 12:20 AM.
