Maximum Torque occurs at a 13.2:1 Air Fuel Ratio.
Transitional Fueling and Maximum Boost Air Fuel Ratios are about 12.5:1.
Water Injection is most efficient with a 50/50 water alcohol (or methanol) mixture.
Methanol, as an additive, is not a practical choice as it is prone to pre-ignition in higher than 50/50 percentages, is not safe to handle, and is not readily available. It's a good choice, but not necessarily the most practical one when you need some in a hurry. Methanol is usually found where racing fuels are sold.
Denatured (ethanol) alcohol, typically 95% pure, is available in paint, hardware, and Home Depot type stores in gallon containers for about $10.00. Expensive but available everywhere. Isopropyl alcohol can be used but it is often 30% or more water by content
Water Injection allows ignition timing to be more aggressive or closer to stock. In other words boost does not automatically mean retard your timing.
Excessive amounts of ignition retard will cause a loss of power and overheating.
Water to Fuel ratios should be based on weight and not volume.
Water weighs 1 001,21208 kg / m3
Alcohol weighs 792.516157 kg / m3
Air weighs 1.29180898 kg / m3. It takes about 4.24752699 m3 of air per 100 horsepower. It takes about 5.44310844 kilograms of air per 100 horsepower.
Water or Water / Alcohol to Fuel Ratios are between 12.5% to 25%. This means Air to Fluid Ratios are between 11.1:1 and 10.0:1 with water injection.
Maximum water delivery should be in higher load low to mid rpm ranges tapering somewhat at peak rpms where load is less.
Atomization of the water mixture is directly related to it effectiveness. Finer droplets cool the inlet charge better and with less mass they navigate the inlet plenum easier for more equal water distribution.
Don’t flow water through an intercooler.
Atomized water, just like fuel , does not like to make turns thus making accurate distribution something to think about. This is why port fuel injection is the norm. Water is a fluid just like your fuel. Using two staged nozzles at high pressure is the best practical solution. Using individual port nozzles is a bit complicated for a large # of cylinders and makes control difficult.
The introduction of water will allow higher boost pressures to be run without detonation. Higher pressures will increase torque. It’s always about torque.
Racing high octane gasoline should be used for all forms of competition and for higher than normal boost levels. Water injection as well as charge cooling should be used with racing gas. 91/92 Octane pump gas simply will not cut it. Water spray cooling of the intercooler is a good idea.
Fuel Injectors operate in the 1 Millisecond range (.001 second) and are not capable of long term usage for H20 as they will corrode or rust shut in a very short period of time. Unless a solenoid can open as fast as a fuel injector it should not be used to "pulse" water injection events as flow is not directly related to "duty cycle".
Varying voltage to water injection pumps or using similar schemes is a recipe for disaster. You have to eliminate the variables, not increase them.
Fuel Injection pumps cannot be used for water injection. Water is conductive. Gasoline is not. Water will corrode an efi pump shut in a very short period of time.
Water injection has a cooling effect on the engine head, valves, and cylinder. Exhaust temperatures (EGT) are largely unaffected at recommended water / fuel ratios.
The cooling of potential hot spots in the combustion chamber defeats pre-ignition, the most destructive form of uncontrolled or unplanned combustion.
Higher static compression ratios will require a higher percentage of water or water / alcohol.
No, water does not burn. We are not combusting the hydrogen in the H2O.
At around 13.2:1 or fuel air ratios of .75, EGT’s will peak.
People will try to selectively edit their way to get you to use water injection by stating "One can basically double the power output of an engine using water/methanol" and "It was used effectively in Formula 1 before being banned for adding too much power". This is pure bunk. Water or water/alcohol/methanol does not make power...superchargers and turbochargers make power. The cooling effect of the water injection only allows you to run higher boost pressures and leaner mixtures without engine damage. The increased density or higher pressure ratio is what makes the power, not the water. The last time we checked water wasn't a very good fuel. Water Injection definitely does not give "a 5-15% increase in fuel economy" as some marketers clain.
Ferrari suspended water in their fuel during their 1980’s Formula1 period. We don’t recommend that you try this...although Acetone will mix with water.