Enderle Injector: Tuning and Maintenance

Enderle fuel injectors are renowned for their robust performance and customisability in high-octane racing applications. However, understanding how to properly tune and maintain these sophisticated systems is paramount to achieving optimal engine performance and longevity. This guide will delve into the key components and adjustments of your Enderle fuel injector, focusing on the metering valve, bypass pills, and idle control, along with essential maintenance practices. While the term "bypass" might suggest circumventing a system, in the context of Enderle injectors, it refers to a crucial control mechanism for fuel mixture.

General Installation Considerations

Before diving into tuning, it's vital to ensure correct installation. When mounting your Enderle injector onto a blower or tunnel ram manifold, always tighten the mounting bolts evenly. This prevents any distortion of the injector body, which could lead to fuel leaks or inconsistent flow. Crucially, a gasket or a suitable silicone seal must be applied to the bottom surface of the injector where it meets the manifold. This ensures a proper seal and prevents air or fuel from escaping.

Understanding the Metering Valve

The heart of the Enderle system lies within its metering valve. This sophisticated component manages the fuel flow and is equipped with a dual return line system, each featuring a check valve. The check valve located at the bottom of the metering valve is specifically designed for the idle circuit. It is calibrated to open within a pressure range of 15-20 psi, ensuring a consistent fuel supply for idling conditions. The second check valve, found in the tee fitting, manages the main jet return. This valve opens at a lower pressure, typically between 1-2 psi. Situated directly beneath this main jet return check valve is the main bypass jet. This component plays a critical role in regulating fuel flow. Furthermore, a blank bypass jet is housed under a 9/16 hex plug on the metering valve itself. It is essential to understand that this blank bypass jet should never be removed, as it is integral to the system's design.

The Role of the Main Bypass Pill

Every Enderle fuel injector is supplied with a set of bypass pills, also known as jets. These are not for bypassing the injector itself, but rather for fine-tuning the fuel mixture, particularly at full throttle. The size of the bypass pill has a minimal impact on the idle mixture but significantly influences the mixture under high-load conditions. To achieve a richer fuel mixture, a smaller bypass pill should be installed. Conversely, to lean out the mixture, a larger bypass pill is required. When fitting a new bypass pill, ensure it is properly seated at the bottom of its threads to guarantee a secure and accurate fuel flow.

Bypass Pill Selection Guide

Choosing the correct bypass pill is a critical step in tuning your Enderle system. Here's a general guideline:

It's important to note that these are general guidelines, and actual results may vary depending on your specific engine combination, fuel type, and operating conditions. Dyno testing is highly recommended for precise tuning.

Adjusting Idle Control

The idle mixture is primarily controlled by a turnbuckle located on the side of the injector. To richen the idle mixture, rotate the turnbuckle towards the rear of the injector. Conversely, shortening the linkage (turning the turnbuckle forward) will lean the mixture. This adjustment is exclusively for idle speed and throttle response; it has no effect on full throttle operation. The actual idle speed itself is governed by the butterfly shaft stops, which are positioned on each side of the injector. Adjusting these stops will alter how far the butterflies open at idle, thereby controlling the engine's idle RPM.

The High-Speed Bypass System

For certain demanding applications, an advanced feature known as the hi-speed lean out system is utilised. This system incorporates a bypass pill that is regulated by a high-pressure check valve. Its purpose is to progressively lean the fuel mixture as engine RPMs increase. The opening pressure of this check valve is adjustable via shims, allowing you to tailor the fuel curve precisely to your engine's specific requirements. The check valve actuates when the fuel pressure is sufficient to overcome the internal spring tension. The bypass pill within this system dictates the volume of fuel that is returned to the tank. Adding shims to the check valve assembly will increase the pressure required to open it, thus causing it to open at a higher RPM. Conversely, removing shims will lower the opening RPM. It is crucial to view the hi-speed bypass system as a fine-tuning device. The main bypass pill remains the primary determinant of the overall fuel mixture throughout the engine's operating range.

Essential Maintenance Practices

Regular maintenance is key to ensuring the longevity and reliable performance of your Enderle fuel injection system. It is strongly recommended to drain the fuel system between races or extended periods of inactivity. This prevents fuel degradation and potential blockages. Furthermore, it is imperative to lubricate the fuel pump regularly. Using a dedicated lubricant such as Prolong SPL100, or a similar high-quality lubricant, will protect the pump's internal components. To prevent sticking and drying out of the metering piston, remove the inlet line from the metering valve and apply lubricant directly to the piston. This simple step can save you from significant troubleshooting down the line.

Maintenance Schedule (Recommended)

Important Warning Regarding Fuel Shutoffs

A critical safety and operational note: You must use a 3-way fuel shutoff valve that includes a return line. Employing a standard 2-way fuel shutoff valve will invariably lead to damage to the fuel pump. This is because a 2-way shutoff will trap fuel in the system, causing excessive pressure build-up and potential pump failure. Always ensure your fuel shutoff configuration is appropriate for your Enderle system.

Frequently Asked Questions

Q1: Can I bypass the main bypass jet entirely?

A1: No, the main bypass jet is an integral part of the fuel metering system. It controls the fuel mixture at full throttle. Removing or bypassing it would result in an uncontrolled and likely very rich fuel mixture, detrimental to engine performance and potentially damaging.

Q2: How do I make my Enderle injector run richer at idle?

A2: To richen the idle mixture, you need to adjust the turnbuckle on the side of the injector. Rotate it towards the rear of the injector. This lengthens the linkage, allowing more fuel into the idle circuit.

Q3: What happens if I use a larger bypass pill?

A3: Using a larger bypass pill will restrict the amount of fuel returned to the tank at full throttle. This results in a leaner fuel mixture. Conversely, a smaller bypass pill allows more fuel return, creating a richer mixture.

Q4: My engine is running too lean at high RPM. How can I fix this?

A4: This is where the high-speed bypass system comes into play. You may need to add shims to the check valve in the hi-speed lean out circuit. This will require higher fuel pressure to overcome the spring, causing the check valve to open at a higher RPM, thus leaning out the mixture at those higher engine speeds.

Q5: Is it safe to leave fuel in the system during storage?

A5: It is strongly advised to drain the fuel system between uses, especially for prolonged storage. Stale fuel can degrade, clog filters, and damage internal components. Always follow good practice and drain the system.

By understanding and correctly implementing these tuning and maintenance procedures, you can ensure your Enderle fuel injector system performs at its peak, providing reliable power and control for your high-performance engine.