Fast Engineering

"Engineer increases his build speed, producing sentry guns more often."

- Official Bloons Monkey City description

 is the second upgrade of the first path for the Monkey Engineer, costing $300 on Easy, $350 on Medium, $380 on Hard, and $430 on Impoppable. It increases the build speed of Sentry Guns from one every 10 seconds to one every 6 seconds, allowing up to 5 active sentries per engineer.

Trivia

 * The upgrade is useless if the Engineer's Workshop tier 4 upgrade is purchased, because the Engineer will build 3 improved sentry guns as 1/x monkey engineer.
 * If NinjaKiwi goes offline, the maintenance screen will display a modified version of the BMC art for this upgrade, with the sentry gun being replaced with a faulty television.