Jim Becker

For the sake of anyone else interested in this discussion, this web page: >Link
has>Link the text of a General Electric pamphlet from 1943. It includes definitions of these things we are talking about. Bill, I assume that your books all have similar explanations.

I am sure you know much more about aircraft engines than I ever will. I was just trying to make the point that there are turbosuperchargers that meet the definition of "internal." I just happens that they weren't used in WWII or prior aircraft.

The pamphlet says: "A supercharger which is located between the carburetor outlet and the intake manifold of the engine is called an internal supercharger." It goes on and talks about behavior, but THAT IS THE DEFINITION. It goes on with: "A supercharger located ahead of the carburetor in the induction system is called an external supercharger." In the discussion that follows that definition, it says: "An external supercharger is used primarily to obtain full-power engine performance at high altitudes, and is generally driven by an exhaust-gas turbine. A supercharger so driven is called a turbosupercharger." Note that it doesn't say that turbosupercharger is another word for external supercharger.

What makes a supercharger a turbosupercharger is the way it is driven, not which side of the carburetor it operates on.

Bill, I am sure you know this, but for the benefit of anyone else reading this, the Pikes Peak test was done by Dr. Sanford Moss of General Electric.

In the '60s, there were a few turbochargers that got automotive use. The Chevy Corvair and Oldsmobile F-85 both had turbos available from about the same time. The IH Scout was available with a turbo a bit later. This web page:
Link
has a picture and description of the Corvair unit. You can see that the tubrocharger is mounted after the carburetor. That page has a reference to a homemade conversion that put carburetors after the compressor (thus becoming an external supercharger). This page shows it:
Link
If you look at that page, it hints at some of the problems inherent in making that change. The main ones are modifications required to the carburetors themselves. To get by the pressurized venturi area problem that I mentioned in an earlier post, he is pressurizing the carburetor bowl with the boost pressure. Then he had to use a higher pressure fuel pump (with pressure regulation) in order to keep fuel flowing into the bowl. These don't sound that major, but try finding suitable components out of a 1960's standard parts catalog.

The Corvair unit was pretty simple. There was no waste gate. Pressure was limited only by the inherent design of the system. Engine speed had to be fairly high before positive manifold pressure showed. There was no water injection either. A pressure retard was used on the distributor to back the spark off at higher pressures. I don't know much about the Olds or Scout systems, I presume they were similar. The Olds did have a water injection system and probably a waste gate.

There were aftermarket supercharger kits available in the '60s as well. I know there was at least one belt driven supercharger (Paxton maybe) that basicly put the entire carburetor inside a pressurized box. That way they avoided any carburetor modifications (other than maybe jets). But they still needed a higher pressure fuel pump. That too would be an example of an external supercharger that is not a turbo.

The next round of turbocharged passenger cars must have started in the mid/late '70s. At that point, port fuel injection was starting to come into play. So I would guess most, if not all, of those would qualify as external superchargers. Those injection systems could produce enough pressure to not be impacted much by the supercharger air pressure.