This is the first layer of the system, the Base Layer, featuring 8 x 40 automotive relays, 8 x SMT high side switches, 4 channel 16 bit current sensing, fuse box, bus bars and motor controllers. It's vital to be thinking ahead at this stage to the next 3 layers as we really don't want to have to remove the other layers to get access to this one again in the future. We probably don't need all 8 relays, but they're wired up anyway, with their associated connectors, most of which can be 20 Amp except for the starter motor solenoid and the glow plugs which use 60 Amp Deutch DTHD series ones. There's a lot of connectors! Most vehicles combine circuits into one multi-way connector which is a lot cheaper way of doing things, but not easy to hack and soon degrades into an unfathomable mess, even with good labeling. Many of these connections will drive double acting hydraulic cylinders, each of which needs two connections - one for forwards and the other for reverse, the default 'null' position being positionally locked in place by static hydraulic oil rather than neutral.