Fuel Injector Pulse Width Calculator

Pulse Width Formula:

\[ PW_{ms} = \text{duty\_cycle} \times (120000 / \text{RPM}) \]

Injector Pulse Width:

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1. What is Fuel Injector Pulse Width?

The fuel injector pulse width (PW) is the duration, in milliseconds, that a fuel injector remains open to deliver fuel to the engine. It's a critical parameter in engine management systems that directly affects the air-fuel ratio and engine performance.

2. How Does the Calculator Work?

The calculator uses the pulse width formula:

\[ PW_{ms} = \text{duty\_cycle} \times (120000 / \text{RPM}) \]

Where:

\( PW_{ms} \) — Pulse width in milliseconds
\( \text{duty\_cycle} \) — Fraction of time injector is open (0-1)
\( \text{RPM} \) — Engine speed in revolutions per minute

Explanation: The formula calculates how long the injector should stay open based on engine speed and desired duty cycle. The 120,000 factor converts from minutes to milliseconds (60,000) and accounts for 4-stroke engines (×2).

3. Importance of Pulse Width Calculation

Details: Proper pulse width calculation ensures optimal fuel delivery, which affects engine performance, fuel efficiency, and emissions. Too short a pulse width can cause lean conditions, while too long can cause rich conditions.

4. Using the Calculator

Tips: Enter duty cycle as a fraction (e.g., 0.5 for 50%) and engine RPM. Typical duty cycles range from 0.1 to 0.9 under normal operation.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical pulse width range?
A: At idle, pulse widths are typically 1-5 ms. At wide-open throttle, they may reach 10-20 ms depending on engine size and injector flow rate.

Q2: How does pulse width relate to fuel quantity?
A: The actual fuel quantity depends on both pulse width and injector flow rate (cc/min). Multiply pulse width by flow rate to get fuel volume.

Q3: What happens if pulse width is too long?
A: Excessive pulse width can cause rich running, fouled spark plugs, increased emissions, and potential engine damage from detonation.

Q4: Does this calculation work for all engine types?
A: This is for 4-stroke engines. For 2-stroke engines, use 60,000 instead of 120,000 in the formula.

Q5: How does injector dead time affect this calculation?
A: The formula gives theoretical pulse width. Real injectors have opening/closing delays (dead time) that must be compensated for in ECU programming.