The supercharger wagon raises the effective level of nearby wagons by one level while active. The range of the boost begins at one (directly adjacent wagons) and increases by one per additional upgrade of the supercharger, up to a maximum of three wagons distance in either direction. This effective level can increase the storage capacity of other wagons beyond their normal maximum, including the number of tracks held by the Crafter, and the wood and iron stack size of the Storage. This effective level also applies to passive wagon benefits, such as the Ghost.
The supercharger wagon requires iron to be loaded to operate, and gradually consumes the iron while outside of the shop. The supercharger wagon cannot be automatically loaded by other wagons. If the supercharger wagon is inactivated, boosted wagons will not eject excess commodities above their normal maximum.
The supercharger wagon appears to give benefits beyond level three if other wagons are already maximally upgraded. In other words, maximally upgraded wagons craft instantly instead of rapidly, hold additional commodities, have range increased, etc. beyond their normal maximum tier-three stats and create a tier-four wagon.
The supercharger wagon effect stacks, meaning that carts within the range of multiple supercharger the amount, which wagons are boosted, is determined by the number of supercharger wagons properly affecting the given wagon. Supercharger wagons do not affect each other, however.
Note: A supercharged level three crafting wagon appears to craft tracks almost instantly. It may not be possible to complete the quest to keep the crafting wagon occupied for any amount of time, even with an auto-pickup wagon, as the crafting wagon will fill with new tracks too rapidly to use and allow further crafting, and/or the resources in the storage wagon will immediately exhaust.