Description
So what do you do when you've built your motor, strapped on the biggest turbo you can tolerate and basically tuned your forced-induction car to the teeth-but you still want more power? More boost would just blow hot air, and race gas is just is too expensive. One recently popular solution is water/methanol injections systems. Ironically, this is old-school tech that trickled down from supercharged piston aircraft during World War II.
Water/methanol injection (aka water, meth, alcohol injection) works on a simple concept. As turbochargers and superchargers pump higher boost, the pressurized air that comes out of the compressor becomes hotter, which causes power loss and decreases the engine's knock threshold. When intercooling doesn't extract enough heat out of the intake air charge, the next step is to directly spray a mix of water and methanol into the air to extract heat. You could use water, but it takes up space and reduces the amount of total air going into the engine. Pure methanol (or methyl alcohol) would absorb more heat, but it also acts as a fuel, which significantly changes the overall air/fuel ratio. So a 50/50 mixture of water and methanol is used to provide the best of both worlds in terms of charge cooling and allows an engine to make more power with the same boost but lower charge temperatures. The overall effect is like running much higher-octane fuel, which can allow for more boost, ignition advance and a leaner A/F ratio, which reduces the possibility of spark plug misfires.
AEM makes a simple universal water/methanol injection kit for use on forced-induction vehicles. The kit comes with an electric pump; a 1-gallon reservoir; a fluid check valve; all the necessary vacuum, fluid and electronic lines; three different-sized injector nozzles; and a simple boost-sensitive electronics control package that's easier to wire in than a car stereo.
We installed our kit into a '97 SR20DET-equipped Nissan 240SX. The motor had already been built, and the turbo and plumbing had already been upgraded to Blitz hardware. Unfortunately, the Blitz turbo struggled to get past the 400-whp mark (using pump gas and 1.4 bar of boost) on Driftspeed's conservative Dynapack Dynamometer.
Our AEM injection kit was installed by welding an aluminum bung (for the water/meth injector) to the intercooler piping shortly before the throttle plate. For our application, we selected the largest of the three injector nozzles supplied in the kit. The rest was a matter of running the fluid line and vacuum line from the engine bay to the electronics and 1-gallon reservoir in the cabin and trunk of the car. Wiring consisted of power, ground, an optional activation switch and a LED indicator light. While the hardware installation is easy, the injection kit isn't just plug and play. It's highly recommended to have the car tuned on a fully tunable ECU to make additional power. Without proper tuning, an engine will run too rich and lose power. Tuning should also be tailored specifically for the mixture of water and methanol that will be used. A change in the mixture ratio will adversely affect the A/F ratio or preset ignition timing and potentially cause detonation.