Kfrs, Kes and other mystery letters

[Tzaw1]

Does anybody know, what do mean letters in names of engines Gnome Rhone?
For example:
18Lars
18 - 18 cylinders
L - the series L
And remaining?

[jerryw]

"L" is the manufacturer's SERIES reference.
"r" means REDUCTEUR (= reduction gear)
"s" means SURALIMENTE (= supercharged)
"a" is part of La (indicates a SUB-SERIES)

[Tzaw1]

Thanks.