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Single Port Water Methanol Injection Still Keeping Pace with New Direct Port Water Methanol Systems?
Direct port water methanol injection setups have gained popularity in recent years, and it’s easy to see why as the array of feed lines and injection nozzles turn an intake manifold into a work of art that screams power!

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Single Port Water Methanol Injection
Still Keeping Pace with New Direct Port Water Methanol Systems?

Direct port water methanol injection setups have gained popularity in recent years, and it’s easy to see why as the array of feed lines and injection nozzles turn an intake manifold into a work of art that screams power! This system of providing a water methanol nozzle for each intake runner is gaining traction in a serious way so we decided to discuss the science behind it and look at the results compared to single point injection.

Aesthetics aside, the direct port system has been touted as a superior way to inject water methanol because it will ensure that each cylinder receives the exact same amount of spray and therefore no cylinder can be starved. This is felt to provide more precision and has been somewhat driven by the evolution of gasoline engines as they have moved from throttle body injection , to sequential multi-port fuel injection and now to direct injection. It has been made a bit of a universal truth that if car manufacturers have found injecting closer to the cylinder is better there is no reason not to follow their lead.

The popularity of direct port injection for water methanol systems has also been driven by carbureted engines when a poor manifold design could lead to cylinders being starved and consequently damaged by running lean. These stories have stuck around even after sequential fuel injection has ensured every cylinder receives the same amount of fuel. It’s easy to see why the direct port injection systems have become the perceived pinnacle of water methanol injection when we take these accounts at face value.

We want to take a more in depth look at the science behind these widely held beliefs and look at the real-world comparison of a single point injection system and a direct port injection system. For the purposes of this article a single point injection system will be defined as one or two nozzles mounted in either a throttle body spacer plate or the intake tube/charge pipe.

A single point injection system sprays a mist into a uniform volume of air as it moves through a charge pipe of the throttle body. The air speed and heat carries the vapor along with it as the manifold directs the incoming air to each cylinder. The argument is that this method cannot ensure the same amount of vapor reaches each cylinder because the closest cylinders or those with the shortest runners will get the most vapor. Aside from modern intake manifolds being very well designed to ensure that every cylinder gets comparable air volume and velocity, this theory does not take into account intake valves opening at different times.

The theory that the water methanol vapor will follow the path of least resistance and over feeds the nearest cylinders assumes the intake valves are always open drawing a constant stream of air. In a 4 stroke engine, the intake valves are potentially open only about 25% of the time; therefore, the air demand is a variable condition inside a manifold. The best way to think of the conditions in a forced induction manifold is that rather than a river following the easiest path we have a compressor tank with a row of valves being opened at different times. The air volume and accompanied vapor is waiting in the intake runners at the same pressure waiting for the intake valve to open. So the Intake manifold on a forced induction vehicle acts as a kind of reservoir holding the pressurized air charge until each cylinder is ready for it.

We have conducted testing on a “Log Style” intake manifold on an inline 6 cylinder engine to prove the actual operation and behavior behind the airflow. This long type of intake manifold requires the air to pass the first few cylinders to reach the rear ones, and by the theory of uneven cylinder feed the first cylinders should have been over cooled while the rear cylinders began to run hot. For this test instrumentation was placed in each cylinder to record heat levels as the engine was run with water methanol injection from a single point. All cylinders showed comparable temperatures ranges which indicate that the air/vapor mixture fills up the intake manifold and is then alternately drawn into each cylinder ensuring that an even mixture is maintained.

This describes a forced induction manifold operation where the incoming air charge is pressurized and forced against the intake valves, which accounts for the vast majority of vehicles operating with a water methanol system. With it being proven that the vapor will be evenly distributed among each cylinder from a single-point injection system we can look at the power aspect of the argument; Does a direct port setup allow the water methanol system to make more power?

The power to be gained from water methanol injection systems depends entirely on the level of heat and octane deficiency they have to treat. Water and methanol are added to the incoming air charge until the cylinder environment is optimized to be able to run ideal timing and fuel maps. Because we have shown that regardless of the injection point all cylinders are receiving an equal share of the vapor, the power to be gained relies entirely on the ability to inject the appropriate amount of fluid at the appropriate time to provide the necessary benefits.

Most gasoline engines up to approximately 1,000 RWHP will receive ample injection from only 2 large nozzles mounted in a common air area for the engine. Too much flow will actually bog an engine down and cost power because the cylinder does not have the heat to create a clean burn. This is an important consideration when deciding if a direct port injection system is right for you because as the number of nozzles increases, the amount of fluid injected will climb.

For instance, on a V8 engine with 8 of our smallest nozzles (#1 60ML/MIN), that engine will need to be making about 850+ forced induction horse power to make efficient use of the fluid. This is even more important in smaller 4-cylinder engines where the engine should be making at least 400+ HP and over 23 pounds of boost to make use of the smallest nozzles. These levels of power are generally attainable but we do want to stress that lightly modified engines should be very cautious going to this setup as most customers will lose HP due to over injection.

Additionally, any time nozzle size is changed on that engine the step up in flow will be very drastic: in the instance of the V8 direct port application, going one size up in nozzles will double the flow the system can provide, from 1,000 ml/min to 2,000 ml/min. For this reason, we look at direct port injection system only on very high horse power street/race engines. These extreme power engines are able to make use of this level of injection and the direct port systems can be very beneficial.

The goal of this article is to help customers decide if a standard water methanol injection kit is right for your build or if it is necessary to go with a direct port injection set up. Our recommendation is to discuss with the tuner who will be working on your vehicle and get a good grasp of HP, boost, and heat potential. If the vehicle is predominantly a street build where these high HP numbers will not be reached we recommend using a standard injection kit to mount 1-2 nozzles in a common air area going into the manifold. These types of kits will be able to handle vehicles making up to around 1,000 HP at a very reasonable price. If cost is not a issue and your vehicle will be making these high HP numbers your manifold very well be a water methanol hard line masterpiece!

Snow Performance features a nozzle selection guide which will indicate the largest amount of fluid we have estimated your engine will be able to make use of. This can also be used as a rough gauge if a direct port manifold will be feasible for your application.

We make both standard injection kits as well as plumb custom direct port manifolds depending on your needs! For more water methanol reviews, articles, and products check out our YouTube Channel.