One Question: AEM Performance Electronics Schools Us On Water/Methanol Injection

In the course of developing content for our One Question series here on Front Street, Kyle and I will toss ideas back and forth to one another before we submit them to the expert for an answer. The point of us collaborating on the question is to ensure we’re capturing the relevant details of the concept while providing the expert with a single question that can provide a quality answer. For this particular installment, we enlisted the assistance of Sam Chaysavang, Technical Sales Specialist at AEM Performance Electronics. Prior to joining AEM, Sam tuned racecars at Road Race Engineering for 11 years, where he prepped engines for everything from NHRA drag competition to the Pikes Peak Hill Climb. Tuning water/methanol injection used in racing applications has always been a bit of a mystery to me, so we enlisted Sam to provide an education.

I was completely positive that my initial question to Sam could be answered in a couple of paragraphs, so I fired it off and awaited his answer. Boy, was I wrong! Strap in for an expert lesson with Sam.

What is the best way to make tune changes to take advantage of the use of water/methanol injection on a boosted gasoline engine?

Sam Chaysavang: To answer this question, we should first answer the question: “Why inject water/methanol into a high-performance forced-induction race engine?” The short answer is: When used properly, it can play a vital role in getting the most out of boosted gasoline engines, by decreasing an engine’s threshold for knock or pre-ignition under high boost loads. Now, let’s break down the sum of these parts.

What is Detonation and Pre-Ignition?

The enemy of any engine when targeting big boost to achieve more power is knock (or detonation), which is uncontrolled combustion after the spark event. An even worse enemy is pre-ignition, which is when the air/fuel mixture combusts due to an extreme heat source in the combustion chamber prior to the spark event. People sometimes interchange those terms but they are two different things, and the simplest explanation is that both knock and pre-ignition are forms of uncontrolled combustion. However, since pre-ignition occurs BEFORE the spark plug fires, you experience a random, extremely advanced combustion event in the cylinder that can melt spark plugs if you are lucky and crack rings and ring lands (or worse) on a bad day. It can even be severe enough to bend connecting rods if you win the sadness lottery.

Several factors play into causing these events. Some of the major players are cylinder temps, hot spots in the cylinder, high cylinder pressures, and commonly poor fuel octane. This is where water/methanol injection can be applied to essentially kick all of those factors out of the party.

Water/Methanol injection

The most elegant way to tune for WMI is with a standalone ECU. In this example the Infinity ECU switches between Lambda0 and Lambda3 target tables when the pressure switch grounds the ModeSwitch analog input to change ModeSwitch value from 0 to 1. Or, if using AEM’s Failsafe device you can invert the ModeSwitch input so that when it receives a ground signal from the Failsafe if there is a fault, and the ModeSwitch value will go from 1 to 0. This will also make the ECU switch from IgnMap_1 to IgnMap_3 when the WMI system is spraying. You can see the differences in the Lambda targets as well as ignitions maps between system on and off. Boost is increased by BoostTargetTable4, which will add 68.9kpa (10psi) to the current boost target defined by BoostTargetTable1 which is 260kpa (23psi) for a total of 319kpa (31.75psi) for boost target when the WMI system is active.

How can Water/Methanol Injection Prevent This?

Water/methanol injection works by lowering cylinder temps, quenching hot spots, and increasing effective fuel octane to support higher cylinder pressures. The water component of the mix has a high latent heat of vaporization, meaning it requires a metric ton of heat energy to convert it from a liquid state to a vapor state; this cools the combustion chamber down drastically. The other component, methanol, has an extremely high octane value of 113 to 119 octane (R+M/2), which will support the extreme effective compression ratios seen by boosted engines at boost levels upwards of 25–35psi without any signs of knock or pre-ignition.

Another benefit of water/methanol injection is that it cools the air intake charge, due to the water/methanol mixture vaporizing prior to reaching the cylinder. During tuning sessions, I’ve seen condensation collect on the outside of intake manifolds of water/methanol injected engines on humid days due to the reduction of intake temps to below ambient. This is possible because the vaporization process of the water/methanol mix is endothermic. The same process is the reason your hands feel cold when you have rubbing alcohol on them.

If a standalone ECU does not have map switching but does have nitrous control that is not controlling nitrous, then that function can be used for WMI control. These log files are from an AEM Series2 EMS using the Nitrous controls for water/methanol injection control. Notice the positive timing adder and negative fuel adder and the timing change when the Nitrous value changes from 0 to 1. In the bottom log, WMI is activated. 

Why Not Just Run Race Gas?

At $15.00 to $20.00 USD per gallon, race gas is considerably more expensive than running water/methanol injection with pump gas, and you don’t get any of the cooling properties of the water/methanol mixture. I used to buy methanol from a local racing supply store for $4.00 a gallon, and after mixing it with $1.00 a gallon distilled water at a 50/50 solution I had a total of two gallons for only $5.00, and one gallon supplied more than enough injection for a 16 gallon tank of pump gas. Since I only injected the water/methanol at a set boost level, I’d race for weeks on that single purchase.

How Do I Tune for Water/Methanol Injection?

Now that I’ve explained why water/methanol injection is one of the greatest things since sliced bread, here is the skinny on how to implement and tune for it on a boosted gasoline race engine. I’ll cover a few methods and examples; the first one will be from my experiences tuning with a standalone ECU, in this case, AEM’s Infinity ECU.

I begin with dialing in the engine in on whatever regular premium pump gas is in the tank, finding that sweet balance of increasing boost levels to increase airflow for more potential power. At some point, this increase in boost requires a decrease in ignition timing to prevent knock. Typically, I get to a point where a 10-20 horsepower gain from a 1 pound increase in boost ends up being lost to the 1–2 degrees of timing reduction needed to keep the engine from knocking.

Once I find the boost limits of the fuel in the tank, it’s time to add water/methanol injection into the mix. There are several things that should be considered. Our goal with the injection is to allow for more boost and more timing with the aid of a secondary fuel delivery system, and have the engine management system switch to a second set of fuel, timing, and boost target maps when the water/methanol system is armed and spraying, then switch back when the system stops spraying or in the unlikely event the system shuts down (which can be caused by something as simple as forgetting to top off the tank).

Water/Methanol injection

AEM’s WMI systems feature both Boost Dependent controllers (pictured), with 35 PSI standard and 40 PSI HD internal MAP sensors, and a Multi-Input Controller that allows users to program flow start and full pressure points using MAF, IDC or external MAP sensors for higher boost applications. Once start and full pressure is set, the controller interpolates the points to deliver a smooth, linear flow curve.

Switching maps can be achieved with something as simple as a pressure switch tee’d into the injection line to detect when the system is active to send a signal to the ECU to switch to the second set of maps with increased boost targets, increased timing values, and leaner and meaner air/fuel ratio targets. This is implemented through the use of one of the four available Lambda target tables, four timing tables, and eight boost target axes that the AEM Infinity ECU offers by incorporating the “ModeSwitch” function of the ECU. To achieve this, the pressure switch is wired from ground to an analog voltage input of the ECU and defining that input as the “ModeSwitch”. When the pressure in the injection line gets high enough to activate the switch, it sends a ground to the ECU to tell it to switch maps to the water/meth injection maps. This same ModeSwitch input is also set as the Y-axis for one of two generic fuel trim tables that can be used for any reason and is a percentage fuel trim on the final fuel injection pulse. The X-axis of this table is set to RPM to allow fueling reduction from the fuel injectors at different RPM points only while the water/meth is spraying to account for the extra fuel provided by the water/meth injection.

With the WMI system implemented, you typically could achieve an increase of 10~12 PSI of boost, 10~12 degrees of timing, and leaner air/fuel mixes closer to 12.0:1, which can result in an increase of 80~200 horsepower. Of course, this depends on turbo and engine setup as well as how octane limited the engine was without the water/methanol injection system engaged.

What if my ECU Doesn’t Have Map Switching?

One trick method I’ve used to control WMI if an ECU has nitrous control functions but not a multiple map switching feature is to implement the nitrous control features for the water/methanol control, but in the opposite fashion of how you would control the nitrous. Instead of retarding timing and adding fuel when nitrous is active, you can potentially use these same trim options to subtract fuel (to account for the extra fuel added by the water/methanol) and advance timing. If the ECU doesn’t offer multiple boost targeting options, boost switching can be done using a 2-stage manual boost controller that allows for a high/low boost setting by switching between two manual controllers via an electronic solenoid controlled by the injection line pressure switch or AEM Water/Methanol Failsafe Device, which will also send the ECU the “nitrous on” command to active those trims.

Piggyback and reflash tunes are very popular and there are also ways to implement water/methanol injection using them. While I don’t have much experience using SCT I do have experience tuning with HPTuners. I set up water/methanol injection on a GenIII GM PCM by using HPTuners’ 3BAR MAP Speed Density custom Operating System, which anyone should already be using if they’ve got a boosted LS. In addition to the water/methanol injection kit, I always required an AEM Water/Methanol Failsafe device to handle the safety side of things.

Water/Methanol injection

A quick and dirty illustration on how to configure a WMI setup for tuning using HPTuners software.

Once installation of the system was complete I would tap into the ground output wire on AEM’s water/methanol injection controller that sends a ground signal out to control an optional shut off solenoid to open the solenoid to allow fluid flow when the pump is commanded to turn on, and shut off flow when the system tells the pump to turn off. I used this ground output to trigger a relay that cut the ECU’s intake air temp signal and routed it through a 50ohm resistor to ground, tricking the ECU into thinking air temps are at 290F~300F. A 12-volt supply for relay control was supplied by the Water/Methanol Failsafe Device as it has a 12v output that can be programmed to turn off if the fluid flow is above or below set parameters, indicating an injection system fault.

Boost high/low switching was done using a dual-stage manual boost controller that used a solenoid to switch between two manual controllers. This solenoid was controlled via the Failsafe Device’s ground output with fused, switched 12v supply to the other side of the solenoid. In the event of a fault, the 12v supply to the relay coil was cut, reverting the ECU back to using the real air temp signal and not the 290–300° Fahrenheit value, and the ground was cut to the dual-stage controller, dropping boost back down to safe levels. That was the hardware setup; now we’ll move on to tuning with the software.

HP Tuners uses a function they call Power Enrichment for wide-open throttle fueling and this function has air temp compensations that are zeroed out by default. These compensations are also available for spark timing as well, and I would exploit these compensators for when the water/methanol injection system was armed and spraying, forcing the ECU to switch to a 290° F (or more) air temp value. Tuning for the system was accomplished using these compensators at these high air temp values by entering positive timing values and entering negative values in the IAT Adder tables for spark timing and power enrichment. It’s a little bit of “rocks and sticks” level of tuning when compared to tuning for WMI with a standalone ECU, but it worked.

Water/Methanol injection

Matching flow to horsepower is important. AEM provides different nozzles for its injectors that allow you to match flow, and offers water/meth injector kits for ultra-high HP applications that need more than one injector. They also provide a handy reference chart for matching flow with boost to horsepower:

Protecting the Engine from WMI Shutdown

By using a simple map switching method in the Infinity, in the event of a failure the ECU will know that there isn’t pressure in the injection line and will not switch maps to the water/methanol maps, or if pressure drops suddenly it will switch back to a set of maps tuned for no injection.

The potential downside of using a pressure switch is in the instance of a clogged injection nozzle, which is why I always like to incorporate the AEM Water/Methanol Failsafe Device into the system regardless of what WMI kit is being used or what control device is being used to tune for it. It’s a gauge-based failsafe system that you can set up in multiple ways to alert you to a system failure and take preventative measures. In my case, I used it because it delivers the same map switching function but bases it off a user programed minimum and maximum flow range for the entire injection map that is measured by a flow sensor. Since this method could be implemented with any engine management that has an option for input based map switching, I’ve also used it on other ECUs beside the Infinity.

FS: And there you have it, folks. More information than you ever wanted to know regarding the use of water-methanol injection with boosted vehicles.

Much thanks to Sam for taking time out of his busy schedule to answer One Question for us. Check out previous installments of One Question content right here.



Go to Top