Okay, so you’ve built your manual boost controller and want to know what to add next? Water injection is the answer. Okay maybe if the original question was “what’s the last thing you want to spray into your engine?” On turbo cars water injection helps cool the injection charge as it enters the engine. Compressing air generates a lot of heat and the hotter the air/fuel mixture is when it enters the engine the more likely it is to detonate. You can use a water/alcohol mixture to cool your intercooler or you can spray it into the intake air. This guide shows you how to assemble a home built water injection system that has been proven to reduce intake temperatures by 90F. It also includes notes on how to do this without hydrolocking your engine. Handy!