Water Meth

Cooler & Denser intake

Additional Information

Water Methanol Injection/Water Meth

Water meth kits are designed to spray a mist of 50% distilled water and 50% methanol into the cars charge pipe.

The charge pipe or cold side boost pipe is the pipe that leads from the intercooler to the throttle.
The water meth bung is generally placed before the throttle and is only used under load.
The best type of water meth kits are progressive kits – as boost increases, so does volume of water meth mix sprayed into the charge pipe.

Progressive kits are very versatile and can be setup to only spray when required.


Car boost peak is 20 psi, so the range is 0psi to 20 psi. Meth flow starts at 6 psi and runs fully at 12psi. This is done to not waste meth mix and to use the required amount of meth. Older kits would activate at a certain psi and flow fully until you lift off of accelerator. This is inefficient because more water meth is used when not needed.

Reason for 50/50 Methanol to Distilled Water Mix

100% methanol is very corrosive to aluminium, boost pipes and engine blocks are therefore at danger. Methanol is also highly flammable, water is added to take away this corrosive effect and forces ignition only when desired.

Benefits of Water Meth

Reduced pre detonation or knock, from much lower intake temps.
Octane is increased, therefore power is increased
Piston tops, valves, valve seats and charge pipe are actually ‘cleaned’ when meth kit is being used.
Timing can be advanced and boost can be increased when meth is used. This is because the engine runs at consistently lower temperatures.

Water Meth kits are generally used on forced induction cars, but can be used on naturally aspirated vehicles as well.

Project Shift Recommends the AEM Progressive Water-Meth Kit or the BMS Water-Meth kit for integration with the BMS JB4 Chips!

*Picture courtesy of AEM.