Water / Methanol Injection - What it is & How to Tune for it.

The problem
We want to make our cars faster, and to do this the tuner tells us he'd love to lean the fuel some more, add some more ignition timing and turn up the boost to increase the horsepower. However, your car is at the limit, he says, and you cannot add anymore timing, or boost to make more power. Increasing any of these three, or all of them, will lead to too high cylinder temperatures and higher temperatures increases the likelihood of detonation.

While your engine requires heat to ignite the fuel and expand the gases to give you torque, heat is also one of the biggest enemies to your engine. Removal of any amount of unwanted heat is therefore welcomed.  Too much heat leads to detonation and detonation leads to preignition that causes broken ringlands, bent rods and spun bearings. To prevent detonation your tuner uses a richer air/fuel ratio, lower ignition timing (firing spark later), and a lower boost target.

Lowering the AFR and firing the spark plug later robs the engine of power, as the fuel ratio is not optimal and neither is the ignition advance near MBT (maximum brake torque). Lowering boost is obviously not going to make you go any faster either! So what can be done to squeeze more power out of your engine?

The solution
Spraying a fine mist of water in the intake to cool the inlet temperatures and promote in-cylinder cooling. This is called water/alcohol injection. The mist of water/alcohol is minute enough to prevent drowning out the combustion process in the cylinder, but just enough to remove some of the bad heat. The cooler intake charge allows (slightly) more airflow and the cooler combustion chamber allows more boost, higher ignition advance and leaner air fuel ratios (AFRs).  The ideal gasoline AFR is 12.5:1, but to keep the cars safe from detonation they are usually forced to be richer at 11 - 10.6 AFR in turbo charged vehicles.

With water/alcohol injection leaner AFRs can be used, and 12.5:1 AFR is quite common. Gains of 10-20% in horsepower are the norm, and even higher if the petrol was of low octane to begin with. Water injection on top of  90 octane gasoline can give the impression that 100+ octane is being used!

How is it controlled?

Simple water injection system

The mixture is administered via a water methanol injection system. This usually comprise of a dedicated pump, reservoir, fuel line, solenoids, nozzles, some wires and a controller to manage the flow. Kits can be as simple as a pump, reservoir, solenoid and a pressure switch and a nozzle; or as complex as all of that plus a pulse width modulated controlled injector with failsafes on top of failsafes.

All kits have trigger points that either depend on engine speed, measured airflow, measured boost or a combination of those.

Sub-optimal systems are simple injection systems with an on or off approach. They are either on when the right boost is met or off when it isn't. These are not recommended as optimal delivery methods. Turning on full blast at a boost or rpm point will mean that the midrange will get a lot of flow but the top-end will not. Essentially running out of injector flow like regular injectors do. If you use a bigger nozzle the midrange will bog, or require an aggressive tuning approach.

 

A more complex WMI system

At wide open throttle your RPM increases and so does the airflow. This leads to a gradual increase in fuel flow requirement. This is what happens in 99.9% of cars on the road. When you introduce water or methanol into the system ideally its flow should follow the same pattern: more RPM, more air, more gasoline (or diesel), and more water/meth.

Turning on your water (or meth) at once with nothing to scale its flow will result in either a setup with a bogging midrange, or one that will have enough flow in the midrange but not enough for the top end as the airflow and fuel flow requirements increase. Therefore, this setup is limited to a punchier midrange output but a less exciting top end.

The more advanced systems can inject to match and follow the flow of incoming air based off the airflow sensor, or they can follow the main injector duty cycle. This will ensure the water/methanol to fuel, or water/methanol to air ratio is linear. Obviously, larger nozzles can be used as the flow is not controlled by the size of the nozzle, but by a controller through a PWM solenoid (pulse width modulation). This is exactly how the gasoline injectors in your cars work, so mimicking that system is not a bad idea! This setup will show a flatter torque curve and nice top-end power.

Where to place nozzle?

The location of the nozzle is usually best placed at 6-12 inches before the throttle body. Some users have it even further upstream and some have direct port injection – injecting into each intake runner. There are also setups that injects before the turbocharger and those that do a combination – injecting before turbo and after intercooler.

Do not install it between the turbo and the intercooler as It will only heat up the charged   mixture closer to ambient temp, or even warmer if it was heatsoaked!

What mixture to use?

100% water will give the best combustion chamber cooling while 100% methanol will give the best intake charge cooling and also add a small bump in your octane number. 100% methanol has the highest fire hazard and wear and tear on various parts of the kit. It is also the easiest to make power with. 100% water needs aggressive tuning to extract the last bit of power. A 50/50 mixture of water and methanol is said to be best compromise. This is mixture not as hard to tune as pure water, and is easier on the pockets as 50% of the content is free!

How do I tune for it?

Before tuning for meth you have to do a system check, a failsafe check and then the actual tuning.

System check

Before you drill a hole in your intake, you are going to do a bench test of the nozzle and pump to ensure they are working correctly. Use pure water only as to not waste any of the methanol! Connect the pump straight to the nozzle and get a stop watch and an empty bottle ready. There should be no solenoid or anything between the pump and the nozzle. Place the nozzle into the bottle and at start the pump and the stopwatch at the same time. On the one minute mark remove the nozzle from bottle and turn off the pump/car. Measure the flow in the bottle and observe if it satisfied the expected flow of the pump and nozzle.

Now that we know the pump is building correct pressure and flow, and the nozzle is doing well, we connect the system in the way it was designed to be used. This means solenoids and everything should be present and all wire splicing has been done.

Ensure the system is connected properly by doing a dry run with the nozzle connected but not injecting into the car. You can point the nozzle towards your windshield for now. Take a nice 2^nd or 3^rd gear pull to see the system working, spraying on your windshield. Once you are satisfied with the flow then all is good.

Failsafe check

You are going to test the failsafe of the system. Whether this is a low level check, a low pressure, a low flow or any other condition, you will have to check this by simulating those conditions. If a boost cut is the failsafe then lookout for this effect on the car when you create the failsafe condition.

After that is done and you are satisfied that the system is up to the task in every way, drill and test fit the nozzle. Everything should be connected and ready to go as this is the final configuration of the hardware.

Tuning

Up to this point your reservoir had pure water in it. Dump it. Now, pour the correct ratio of water and methanol in the reservoir. Make note of the ratio you used as this will have to be maintained from here on out. A change in the ratio of water to methanol will require a retune.

Find out how much of that mixture you will need to use for your setup. This will determine the nozzle size. A good website tool for this is found here. If you are tuning a fixed flow system .75 x the max duty cycle is a good starting point. For flow controlled system ignore that and use the maximum calculated nozzle size. Proceed to the next step.

With your nozzle size figured out and installed, and your AFR gauge working correctly, take a pull in 3^rd gear with the injection system DISABLED to see what your AFR ratios are at the respective RPMS. If you don’t have a system to log to a laptop you will have to eyeball this and remember it.

Set the system to inject the methanol at whatever boost or airflow you want to have it running.

With an idea of where your gas AFRs are, ENABLE the injection system and note how much the AFR has dropped in the area of the log that it is injecting. Since this is your first time tuning this, I will recommend no more than a .5 to 1.0 AFR drop. If less than 0.5 you are injecting too little. If more than 1.0 you are injecting a lot! Write down the original AFR (call it GAS AFR) and the new AFR (call it WMI+Gas AFR).

Since your fuelling and injection flow has been worked out, lean the mixture back a little closer to where it was and begin increasing your boost while monitoring knock and AFR. A good starting point is to add half of the AFR drop. So if your AFR dropped 1 full point, lean it out 0.5 points leaner. Eg 11 AFR drops to 10.5, lean it out 0.25 or 10.75.  

Once your boost targets have been safely met (fuelling ok, boost ok, knock free). Proceed to add some timing. I find that 15% more timing at a time will be a good increment. This means that if you were at 10 degrees, increasing to 11.5*. Or if you were at 20*, increase to 23 degrees. Listen for knock with your knock device. If knock is encountered remove some timing until it goes away.  

At this point, you should not be doing single gear pulls only, but also 1-2-3 pulls, or even 1-2-3-4 pulls. You have to really work the engine up to ensure that it is not knocking when it is driven as how it WILL be driven.  So add the timing, do a 1-2-3 or 1-2-3-4 pull, then do a single gear pull to measure the power. If there is no knock, you are doing well.

One thing to remember is that WMI systems can have you increasing timing way beyond what would continue to give power (MBT) and yet your cylinder pressures will be rising. A cylinder pressure too high will bend connecting rods, bust bore walls, and lift heads if the build is not prepared for it!

Ideally, by this you would have been increasing timing to a point where adding 2 or so degrees more in the top end does not increase power. This would mean you are currently at MBT, or maximum brake torque.

I highlighted ‘in the top-end’ because unlike the top-end, the midrange will see highest cylinder pressures, and as such, you have to be careful the amount of timing you add in that midrange area. Again, too much cylinder pressure from timing can bend rods, bust bore walls, and lift heads!

At this point, you are almost finished. Lean the car out some more and do your 1-2-3-4 pulls. Allow the car to cool down between each set of 1-2-3-4 pulls. It is important to know your current GAS AFR. This is the AFR your system will see if your meth system completely fails.  If you started out at 11 AFR and the meth dropped it to 10.7, but then leaned it back to 11:1 AFR, then your GAS AFR is now approximately 0.3 points higher. Or 0.3 +11 = 11.3 AFR. This is an approximation, and this is where your fuelling will be if the system suffers a nozzle clog or something of the sort preventing the mixture for injecting.

Continue to fine tune boost, afr and timing until you are satisfied.

Congratulations, you have tuned your car to your WMI system!