Injector End Angle Calculator - Calculator Academy

Enter the engine speed, injector pulse width and desired end angle into the calculator to determine the injector timing.

Injector Timing / End of Injection Calculator

Use the main mode to place end of injection in the cycle. Use the sweep helper to compare multiple end-angle targets at the same RPM and pulse width.

End of Injection Calculator

Timing Sweep Helper

Enter RPM, pulse width, and your desired end angle. BTDC and ATDC are interpreted around the 360° reference point. Results show start of injection, crank degrees consumed, cycle usage, and a quick timing-window note.

Engine Speed (RPM)

Injector Pulse Width (ms)

Desired End Angle

End Angle Reference

Compare a range of end-angle targets at one RPM and pulse width. This is useful when you want to test several candidate end-of-injection values without re-entering the same setup each time.

Engine Speed (RPM)

Injector Pulse Width (ms)

Sweep Start

Sweep End

Step Size

Sweep Reference

Related Calculators

Injector End Angle Formula

The following formula is used to calculate the injector end angle for a given injector start angle, injection duration, and engine speed.

\theta_e = \theta_s + D \, S \times 0.006

Variables:

θ_e is the injector end angle in degrees (crank degrees)
θ_s is the injector start angle in degrees (crank degrees)
D is the injection duration in milliseconds
S is the engine speed in RPM

To calculate the injector end angle, convert the injection duration into crankshaft degrees using Δθ = D × S × 0.006 (since 0.006 = 360/60000), then add that angle change to the injector start angle. If you are working on a 4-stroke 0–720° reference, you may wrap the final angle into your preferred range as needed.

What is an Injector End Angle?

The injector end angle is a critical parameter in internal combustion engines, particularly in fuel injection systems. It represents the crankshaft angle at which the fuel injection process ends. Accurate calculation of the injector end angle helps ensure appropriate fuel delivery timing, combustion efficiency, and engine performance. This parameter is used for tuning and calibrating the engine control unit (ECU) to achieve desired performance and emissions standards.

How to Calculate Injector End Angle?

The following steps outline how to calculate the Injector End Angle.

First, determine the injector start angle (θ_s).
Next, determine the injection duration (D).
Next, determine the engine speed (S).
Finally, calculate the injector end angle using the formula (θ_e = θ_s + D × S × 0.006), with D in milliseconds and S in RPM.
After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Injector Start Angle (θ_s) = 30 degrees

Injection Duration (D) = 2 ms

Engine Speed (S) = 3000 RPM

Injector End Angle (θ_e) = 30 + (2 × 3000 × 0.006) = 66 degrees

Follow-Up Calculations

If your injector end angle lands around 405° crank angle on a gasoline tune, the next sanity check is whether the commanded fuel still matches the combustion target. You can convert your air-fuel target to lambda — for example, 12.8:1 gasoline is about 0.89 lambda — so the timing you choose still supports the mixture the engine actually needs.

If the injector has to finish its pulse by roughly 40° before intake valve closing at 6,500 rpm, the engine is being tuned for a very specific resonance band. You can match the intake runner length to that rpm; a runner in the mid-teens of inches is often aimed at a similar mid-to-high rpm torque peak, which helps the cylinder fill when the fuel event is happening.

A late injection end angle usually points to a high-rpm build, and those same builds need enough exhaust flow to keep backpressure from hurting power. You can size the exhaust for the same power band — for example, a 300 hp street setup often lands near a 2.5-inch system, while larger power levels typically need more diameter to move the spent gases out cleanly.