DIY Water Injection System: Build Your Own for Under $100

Why DIY Water Injection?

Commercial water injection kits from Snow Performance or AEM cost $300–$500+. For naturally aspirated applications where precise boost-referencing isn't needed, a DIY system built from windshield washer components can achieve similar cooling benefits at a fraction of the cost.

Parts List

• Windshield washer pump (12V, from any parts store ~$15)
• Windshield washer reservoir (1–2L, with integrated pump mount ~$20)
• Brass or stainless injection nozzle (200–400 cc/min, $10–$25)
• 6mm nylon or silicone tubing (~$10)
• Push-to-connect fittings and T-connector (~$10)
• Toggle switch and wiring (~$10)

System Design

The washer pump draws from the reservoir and pressurizes fluid to approximately 50–80 psi. This is lower than commercial kits (100–250 psi) but sufficient for basic water injection cooling. Higher pressure produces finer droplets and better atomization — a limitation of the budget approach.

Wiring

Wire the washer pump through a relay to a switched 12V source. Adding a manifold pressure switch (set to activate above 5 psi vacuum reduction) creates a simple load-dependent activation similar to professional systems.

Nozzle Installation

Drill and tap a 1/8 NPT hole in the intake pipe between the air filter and throttle body. Thread in a brass fitting and nozzle. Aim the nozzle slightly upstream to maximize dispersion in the airflow.

Safety Considerations

Always add a low-fluid warning light (simple float switch in the reservoir). On a NA engine, running dry causes no immediate harm — injection simply stops. But know your reservoir level to avoid unexpected loss of cooling benefit.