Minimum Injector Pulse and Short Pulse Adder

Can some one explain in detail what the Minimum Injector Pulse, Default Injector Pulse and Short Pulse adders actually do?

How important are they with injector operation?

Are these 2 aspects that really need to be spot on with no margin of error?

The Small Pulse Adder (SPA), is an adjustment made to the commanded Injector Pulse Width (IPW) when it is operating in its characterized non-linear state. An injector has issues maintaining a linear Injector Flow Rate (IFR) during small pulse operation. Good injector manufacturers/suppliers will go to great lengths to test and define the adjustments made to the linear IPW calculation based on the injectors mechanical and electrical variances at pulse widths less than 4ms or what is defined as Short Pulse Limit.

The Min Injector Pulse is the absolute smallest pulse width that the PCM can command at any time. It has to alot to do with how well the injector can accurately operate in small pulse width situations like idle or decel. It includes the addition of the Small Pulse Adder.

The Default Injector Pulse is the pulse width that will be used when the IPW is less than the Min Injector Pulse.

I believe the most important of the 3 parameters is the SPA. This helps stabilize the fueling and reflects in a much better idle quality and ease to tune. The Min Injector Pulse is more important when using larger injectors as it can limit how low the IPW can go, and if not low enough, may be supplying more fuel than is needed during idle. This scenario will increase the idle rpm and force the idle adaptive spark (under/over speed) to decrease to much lower degree's in an effort to bring the idle rpm back to the desired rpm...too much retarding of the spark and the next thing is glowing headers or worse, damaged valves.

Ed M

Quote:

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Originally Posted by mowton

The Small Pulse Adder (SPA), is an adjustment made to the commanded Injector Pulse Width (IPW) when it is operating in its characterized non-linear state. An injector has issues maintaining a linear Injector Flow Rate (IFR) during small pulse operation. Good injector manufacturers/suppliers will go to great lengths to test and define the adjustments made to the linear IPW calculation based on the injectors mechanical and electrical variances at pulse widths less than 4ms or what is defined as Short Pulse Limit.

The Min Injector Pulse is the absolute smallest pulse width that the PCM can command at any time. It has to alot to do with how well the injector can accurately operate in small pulse width situations like idle or decel. It includes the addition of the Small Pulse Adder.

The Default Injector Pulse is the pulse width that will be used when the IPW is less than the Min Injector Pulse.

I believe the most important of the 3 parameters is the SPA. This helps stabilize the fueling and reflects in a much better idle quality and ease to tune. The Min Injector Pulse is more important when using larger injectors as it can limit how low the IPW can go, and if not low enough, may be supplying more fuel than is needed during idle. This scenario will increase the idle rpm and force the idle adaptive spark (under/over speed) to decrease to much lower degree's in an effort to bring the idle rpm back to the desired rpm...too much retarding of the spark and the next thing is glowing headers or worse, damaged valves.

Ed M

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Thanks a bunch. Great information.

bringing this back.

I set both limits, the IPW and the DIP, to .350, and left the SPA and the Short Pulse Limit to stock values. When I scan, IPW is reading 1.7 to 2.0.

Do I need to change the remaining stock values to achieve the .350?

Thanks!