What Is the Injection Duration / Fueling Time Map in Diesel ECU?

The Injection Duration Map controls how long the injector stays open, usually expressed in crankshaft degrees. This determines the total quantity of fuel delivered per injection cycle crucial for:

• Power output
• Torque delivery
• Smoke and soot control
• Fuel economy
• Combustion temperature

In modern diesel ECUs like Bosch EDC16/EDC17, injection duration works hand-in-hand with Fuel Quantity, Rail Pressure, and Start of Injection (SOI) to form a precise, interdependent fuel delivery model.

 How It Works: Simplified

Think of duration as "fueling time".

Longer duration → More fuel → More power
Shorter duration → Less fuel → Lower emissions

But it’s not linear — because higher rail pressure injects the same amount of fuel faster.

So, duration must always be calculated relative to pressure and desired IQ (Injected Quantity).

 Formula (Conceptual)

Injected Fuel (mg) = Injector Flow Rate × Injection Duration × Pressure Correction

The ECU uses internal models and lookup tables to convert IQ request into an appropriate duration based on:

• RPM
• Rail Pressure
• Engine Temperature
• Operating Mode (pilot, main, post)

 Types of Duration Maps in ECU:

• Main Injection Duration
• Pilot Injection Duration
• Post Injection Duration
• Total Duration Limits
• Rail Pressure-Compensated Duration

Each of these has its own tuning function  and mastering them gives you full fuel control from cranking to full throttle.

 How to Find Diesel Duration / Time Maps in WinOLS:

In WinOLS, typical duration maps:

• Are 2D or 3D maps
• Indexed by RPM and Rail Pressure
• Values in degrees of crank angle
• Axis often labeled in bar (rail pressure) and RPM

 Steps to Identify:

1. Use known map pack references or damos if available
2. Visually scan for maps where value patterns increase linearly with rail pressure
3. Duration maps have a "ramp-up" shape  more pressure = shorter duration for same fuel
4. Use axis spotting to match known PR and RPM ranges (e.g., 1000–4500 rpm, 300–1600 bar)

 What You'll Learn in This Episode:

In this practical training session, we teach:

• How Injection Duration affects combustion and power
• How to locate all types of duration maps in WinOLS manually
• How to adjust duration for safe performance without excess smoke or EGT
• How to synchronize duration with rail pressure and SOI
• The dangers of over-injection and how to avoid them

 Tuning Notes & Best Practices:

• Duration must match SOI to avoid incomplete combustion
• Too much duration = smoke, high EGT, possible DPF damage
• Raising rail pressure allows for shorter durations with the same IQ
• Always log rail pressure and combustion feedback when tuning duration

 Why This Map Matters:

Injection Duration is the foundation of fuel control. You can’t properly remap diesel engines without a full understanding of this map and how it scales with pressure and RPM.

It defines the real-world result of your tuning logic.
IQ = intention → Duration = execution.