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.
As it turns out, fuel isn't the only piss swill California has to offer. We got hosed when it comes to methanol, too. AEM recommended using low-temperature windshield-wiper fluid, which is a mix of water and methanol. Unfortunately, the rarely snowy state of California has just recently decided to outlaw the stuff and only offer wiper fluid that works in above-freezing temperatures. This means the methanol content in these mixes is very low, making our injection system more water than meth. With the help of Koji, head tuner at Driftspeed in Lomita, California, we tried to retune the car's A'PEXi Power FC ECU regardless to see if we could make any power gains. Even with a much leaner A/F ratio and more ignition advance, the car made the same power. But it did allow us to find a little more power by increasing the peak boost from 1.4 to 1.6 bar (20 to 23 psi.)
The next day we tried again, but this time with a true 50/50 mix of VP Racing 99 percent pure M1 Methanol with distilled water. After retuning the WOT A/F ratio, we found that the higher methanol content allowed us to advance the ignition timing a significant bit more than before. At the same boost, we were able to lean out the A/F ratio at full boost by one point as well as adding a couple of degrees of timing on average. Since the Power FC did not have switchable tuning maps, Koji had to tune the car and the water/methanol injection rate so that injection only occurred at high boost and smoothly transitioned with the base map where methanol was not used.
With the proper mixture and an experienced tuner, we were able to pull out quite a bit more power. Most of our gains were before peak power, where the turbo hits its flow limits. The water/methanol injection also allowed us to turn up the boost and make power at 1.6 bar, whereas 1.4 bar was the original limit of our pump gas, the turbo and the engine. If you're just looking for a little more power without more lag or a complete hardware teardown, water/methanol injection is an affordable option. A 50/50 mixture in the 1-gallon tank will easily last a tank of gas even for the most lead-footed of drivers, and is a lot cheaper than buying a tank of the equivalent 100-octane race gas.
Specifications & Details
'97 nissan 240SX
Engine: 2.0-liter SR20DET (red top)
Relevant modifications: Blitz K3 turbo kit, Tomei ProCAM w/ solid lifters, Supertech internals, GReddy intake manifold, A'PEXi Power FC and GP Sports exhaust
-Fully integrated universal kit for all forced-induction vehicles
-Includes three different injection nozzles for different power applications
-Integrated pump controller with boost sensitive tunable injection rate
-Effectively raises fuel octane by several points
|WITH INJECTION KIT AT 1.4 BAR|
|+ 31.5 hp|
|+ 25.4 torque|
|BEFORE 378.8 whp and 294.1 ft-lbs|
|AFTER 410.3 whp and 319.5 ft-lbs|
|WITH INJECTION KIT AT 1.6 BAR|
|+ 16.3 hp|
|+ 21.5 torque|
|BEFORE 410.3 whp and 319.5 ft-lbs|
|AFTER 426.6 whp and 341.0 ft-lbs|