As I'm doing a chart with spring for Electic car, i found the following, for the G4S.
I hope they are the same for the E4!!
This is the chart for TM's springs
tm gray 1.9mm 52.0 lb/in
tm orange 1.8mm 41.5 lb/in
tm blue 1.7mm 31.0 lb/in
tm aqua 1.6mm 26.0 lb/in
tm silver kit stock 26.0 lb/in
tm purple 1.5mm 20.0 lb/in
tm pink 1.4mm 17.0 lb/in
tm fuccia 1.3mm 13.5 lb/in
tm green 1.2mm 11.0 lb/in
From rctech
I can give explanation about dimension in mm, I'll only guess that the wire diameter but it's just a guess