Performance Review And Installation Of An Injen Cold Air Intake On A 240sx

The Injen cold air intake is a popular modification for the Nissan 240SX, specifically those powered by the KA24DE engine. Beyond just aesthetics and a potentially throatier sound, a well-designed cold air intake aims to improve engine performance by increasing the volume and density of air entering the combustion chamber. In this article, we will dissect the principles behind cold air intakes, evaluate the purported performance gains of the Injen system on the 240SX, and provide a detailed, step-by-step installation guide.

The Science Behind Cold Air Intakes

Internal combustion engines are, at their heart, air pumps. The more air and fuel an engine can efficiently combust, the more power it can produce. The density of the air entering the engine plays a crucial role. Colder air is denser, meaning it contains more oxygen molecules per unit volume compared to warmer air. More oxygen allows for more fuel to be burned, resulting in a larger and more powerful combustion event.

A typical factory air intake system draws air from within the engine bay, an environment often heated by the engine itself. A cold air intake, in contrast, attempts to draw air from a location outside the engine bay, ideally from an area where the ambient temperature is lower. This is often near the fender well or behind the bumper. By relocating the air intake, the Injen system aims to provide a cooler, denser charge of air to the engine.

Beyond temperature, the design of the intake piping is also important. A smooth, less restrictive intake path reduces pressure drop and improves airflow. Factory air boxes and intake tubes often feature convoluted designs and restrictive filters, which can impede airflow. Aftermarket intakes like the Injen are usually constructed with mandrel-bent aluminum or plastic tubing, offering a smoother and wider pathway for air to reach the throttle body. Furthermore, aftermarket performance air filters such as those used in the Injen system are designed to flow much more air than a standard paper filter. This increased airflow is achieved through the use of different filtration materials, such as oiled cotton gauze or synthetic media, which offer less resistance to airflow.

Performance Review: Injen Cold Air Intake on the KA24DE

The Injen cold air intake for the KA24DE 240SX is often advertised as providing a noticeable increase in horsepower and torque. However, the actual gains experienced can vary significantly depending on several factors, including the condition of the engine, other modifications, and driving conditions. It's essential to approach performance claims with a healthy dose of skepticism.

Independent dyno tests of the Injen intake on a stock KA24DE typically show modest gains, usually in the range of 5-10 horsepower at the peak of the power band. While this may seem insignificant, it's important to consider the entire power curve. Some users report improved throttle response and a slight increase in mid-range torque, which can make the car feel more responsive in everyday driving situations. The butt dyno, however, can often be deceiving, as the change in intake sound can sometimes be misinterpreted as a more substantial power increase.

Several factors can influence the actual performance gains:

Engine Condition: A well-maintained engine with good compression and healthy components will be more receptive to performance modifications. An engine with worn rings or leaky valves will not be able to effectively utilize the increased airflow.
Other Modifications: The Injen intake is most effective when used in conjunction with other performance modifications, such as an aftermarket exhaust system, headers, and ECU tuning. These modifications work synergistically to improve the overall efficiency of the engine.
ECU Tuning: The KA24DE ECU is adaptive, but its ability to fully compensate for the increased airflow of the Injen intake is limited. For optimal performance, an aftermarket ECU tune is recommended to recalibrate the fuel and ignition maps to take full advantage of the intake's benefits. This tuning helps ensure the engine is running at its optimal air-fuel ratio (AFR).
Driving Conditions: The benefits of a cold air intake are most noticeable in warmer weather, where the difference in air temperature between the engine bay and the ambient air is more significant.

It's also crucial to consider the potential drawbacks. Some users have reported issues with increased engine noise and the possibility of water ingestion if the filter is submerged in deep water. Injen does offer optional hydro shields that can mitigate the risk of water ingestion.

Installation Guide: Injen Cold Air Intake on a 240SX (KA24DE)

Before beginning the installation, gather the necessary tools and materials:

Injen Cold Air Intake Kit (specific to the KA24DE 240SX)
Socket set with various extensions
Screwdrivers (Phillips and flathead)
Pliers
Wire cutters
Optional: Hydro shield for the air filter
Optional: MAF sensor cleaner
Optional: New hose clamps

Step 1: Disconnecting the Battery

Safety first! Disconnect the negative battery terminal to prevent any electrical shorts or accidents during the installation process. This is a standard precaution for any automotive work.

Step 2: Removing the Factory Air Intake System

Locate the factory air box and intake tubing. Begin by loosening the hose clamps connecting the intake tube to the throttle body and the mass airflow (MAF) sensor housing. Disconnect the MAF sensor electrical connector. Carefully remove the intake tube from the throttle body and MAF sensor. Next, unbolt the air box from its mounting points. There are usually several bolts securing it to the inner fender well. Once the bolts are removed, carefully lift the air box out of the engine bay. You may need to disconnect any vacuum lines or breather hoses connected to the air box.

Step 3: Installing the MAF Sensor Adapter

The Injen kit typically includes an adapter to mount the MAF sensor onto the new intake tube. Carefully remove the MAF sensor from the factory air box. You might want to use MAF cleaner to carefully clean the sensor. Attach the MAF sensor to the Injen adapter using the provided hardware. Ensure the MAF sensor is oriented correctly, as indicated in the Injen instructions. Incorrect orientation can lead to engine performance issues.

Step 4: Installing the Injen Intake Tube

The Injen intake tube is usually installed in multiple sections. Begin by attaching the first section of the tube to the throttle body using the provided silicone coupler and hose clamps. Tighten the hose clamps securely, but avoid over-tightening, which could damage the coupler. Next, connect the MAF sensor adapter to the second section of the intake tube using another silicone coupler and hose clamps. Again, tighten the hose clamps securely. Route the intake tube towards the desired location for the air filter, usually near the fender well or behind the bumper.

Step 5: Installing the Air Filter

Attach the air filter to the end of the intake tube using a hose clamp. Ensure the filter is securely mounted and positioned to draw air from a relatively cool and clean location. If you purchased an optional hydro shield, install it over the air filter at this time. This shield will help protect the filter from water and debris.

Step 6: Connecting Vacuum Lines and Breather Hoses

Reconnect any vacuum lines or breather hoses that were disconnected during the removal of the factory air intake system. These hoses are essential for proper engine operation and emissions control. Double-check that all hoses are securely connected and properly routed.

Step 7: Final Adjustments and Tightening

Inspect the entire intake system to ensure that all connections are secure and that the intake tube is not rubbing against any other components in the engine bay. Make any necessary adjustments to ensure proper fitment. Tighten all hose clamps and bolts to the specified torque values (if provided in the Injen instructions). If torque values are not provided, tighten the hardware snugly, but avoid over-tightening.

Step 8: Reconnecting the Battery and Testing

Reconnect the negative battery terminal. Start the engine and let it idle for a few minutes. Listen for any unusual noises or vacuum leaks. Check the engine for any error codes. If the engine runs smoothly and there are no error codes, take the car for a test drive. Monitor the engine performance and listen for any unusual noises. If you experience any problems, consult the Injen instructions or a qualified mechanic.

Conclusion

The Injen cold air intake can be a worthwhile modification for the 240SX KA24DE engine, offering modest performance gains and improved throttle response. However, it's essential to have realistic expectations and understand the limitations of the system. Proper installation and ECU tuning are crucial for maximizing the benefits of the intake. By following this guide and taking the necessary precautions, you can successfully install the Injen cold air intake and potentially enhance the performance of your 240SX.