Wright SGR-1820 vs R-1820?

[vikingBerserker]

I've spent several hours trying to figure out what the difference is between a Wright SGR-1820-XX vs an R-1820-XX engine and I cannot figure it out. Does anybody know?

 

[Shortround6]

The G stands for reduction gear, engines without the R were direct drive.
The S might stand for supercharged.?

Once all 1820s were supercharged and used reduction gears the S and R might have been dropped?

In any case here is the FAA type certificate for the R-1820 series, both geared and ungeared which shows that the G stood for geared.
No real clue as to what the S stood for?
https://rgl.faa.gov/Regulatory_and_...00705bbc87d578525670e00653f09/$FILE/ATC98.pdf

Correction, type certificate for the R-1820F series.

 

[vikingBerserker]

Thank you!

 

[MiTasol]

I seem to remember that the mil designation was R- and civil engines had the prefixes but I cannot guarantee it.

 

[cvairwerks]

The SGR-1820 should be a geared 1820 with an external supercharger...With the development of the G series engines, the external supercharger was dropped and the case got an internal one. They produced only about 710 hp, and I believe the DC-1 and DC-2 were the only aircraft that used them from the data that I found.

 

[Simon Thomas]

S = higher supercharger ratio per Model Designations of U.S.A.F. Aircraft Engines (USAF Engine Models )

Seems to be applied often but not always as a modification of an existing model, and was used widely for the E and F models, a limited number of G engines and not at all from the G100 onwards.

 

[vikingBerserker]

Thank you gents!