Tom Wilson
March 1, 2013
Cooling intake air temperatures pays off. Using a stock engine tune simply adding water/methanol from a Snow Performance kit chilled the Laguna Seca’s inlet air 23 degrees, thus adding 1 degree of ignition timing and 8 hp. Dyno-testing was performed on Rocky Mountain Competition Research’s Dynojet in Colorado Springs, Colorado.

Water injection has been around forever, but after going in and out of fashion for decades, it's gaining a firm foothold in the performance-car world. A big reason is Matt Snow at Snow Performance is dedicated to educating the world that water is less expensive than race gas, and almost as easy to install. His line of computer-controlled water/methanol injection kits has proven popular with supercharger fans where boosted induction air temps are hot enough to bake a turkey, and now he's showing naturally aspirated powerplants benefit from water as well.

So what is the big deal with water injection? It sure doesn't sound like a good way to build a big fire in the combustion chamber, after all. Well, in a nutshell, that's the point. With high compression, boost, or low-octane gasoline (and by that we mean any modern pump gasoline) it's easy for cylinder temperatures and pressures to spike over safe levels. The classic hot-rodding ways of avoiding momentarily excessive cylinder pressures are to raise the fuel's octane, lower the compression ratio, lower blower boost, or retard ignition timing. Obviously all of these reduce efficiency and cost power, but can be necessary to avoid engine damage.

But spray a little water into the intake stream at the right time and peak combustion pressures are lowered as well. The water changes state into a vapor, absorbing heat in the processes. Voila, it's as if your pump gasoline was suddenly C16 race juice. What little space the water takes up in the air-fuel mixture is more than compensated for by the ability to retain advanced ignition timing, boost or what have you. And just a little water does the cooling trick, without quenching the main combustion by any meaningful degree.

Even better than plain water is a 50/50 mixture of water and methanol. In car circles this is often referred to as simply water or water/meth, while over at the airport it's called anti-detonation injection. The flyboys were the first to put methanol in the water to reduce freezing at altitude, but everyone has found methanol has an evaporative cooling property, and unlike water, is also a high-octane fuel so it actually gives a little urge to the mixture. The fuel component of methanol is not a primary factor when running small amounts of water, but as the boost and power go up, it can help retain some power.

Obviously, the hotter the intake charge, the more effective the water/methanol injection, which is why it's a natural for blower motors. The water is sprayed into the mixture downstream of the blower where intake temps are highest, giving the maximum evaporative effect. But as Snow Performance's testing shows, water/meth is useful on naturally aspirated engines as well. This is of practical use on endurance applications where the engine runs at WOT for extended periods-in other words, at open-track or road race events where the fun typically lasts 20 to 30 minutes at a time.

In such applications, water injection is used not so much to boost power, but to retain power by not heat-soaking the engine, causing the engine management to retard the ignition timing either because the software says to at elevated coolant temperatures or because the knock sensors are hearing things. If you've tracked your Mustang and sensed it was getting lazy as the session went on, then you know what we're talking about.

To put some numbers to it, Snow Performance ran a series of chassis-dyno tests, plus some instrumented road miles, to document what their water/methanol kits can do on a naturally aspirated 2012 Boss 302 Laguna Seca. And just to maintain everybody's attention, they also included a 50-horse shot of nitrous in their test program as well.