How to Set Injector Flow-Rates and Set Injector Dead Times

Anyone who as installed aftermarket injectors before probably ran across the issue of not having accurate injector dead time values to enter into their tuning software or having an engine run too rich or too lean using the fuel injectors advertised flow-rates. Having accurate injector dead time settings (also known as injector lag time or latency) is critical for a quality idle as well as maintaining air/fuel ratios when there are lots of accessory loads on the engine (ie: headlights, heater, etc.). Here is our recommended method for setting flow-rates and getting the dead times dead right:

1. Do a full tune using stock/OEM injectors with OEM injector dead times. If you are tuning a boosted car, etc. that the stock/OEM injectors cannot provide enough fuel for, just tune the idle and part throttle areas of the fuel and ignition maps fully.

2. Turn off all accessories (headlights, heater, stereo, etc.)

3. Hold the throttle steady at 3,000 rpm after tune is complete and take note of your air/fuel ratio. WRITE IT DOWN.

4. Allow the engine to idle and take note of your air/fuel ratio. WRITE IT DOWN.

5. Install your aftermarket fuel injectors.

6. Set your injector size setting in your tuning software to the new injectors' published flow rate/size.

7. Hold the throttle steady at 3,000 rpm and adjust the "injector size" setting higher or lower until you reach the same air/fuel ratio that you wrote down in step 3 above. Adjust the injector size lower to richen/increase fuel. Adjust the injector size higher to lean/decrease fuel. Upload or program the changes to your ECU and repeat this step until you reach the same air fuel ratio as in step 3. You will most likely end up with a value that is different than the published injector size, this is correct and not an issue.

8. Allow the engine to idle. Now go to your injector dead time/latency tables and take note of the injector dead time value for the voltage that you are currently seeing in your tuning software. For example, if you are currently seeing 14.0 volts, only adjust the box for 14.0 volts. Adjust the value in the box for the voltage you are currently seeing in your tuning software higher or lower as needed until you reach the same air/fuel ratio that you wrote down for step 4. If the engine is running richer than the value from step 4, decrease the dead time value. If the engine is running leaner than the value from step 4, increase the dead time value. Upload or program the changes to your ECU and repeat this step until you reach the same air fuel ratio as in step 4.

9. Turn on your headlights, heater, etc. to produce an electric load on the engine until you see your voltage go lower (ie: down to 12 volts). Now go to your injector dead time/latency tables and take note of the injector dead time value for the voltage that you are currently seeing in your tuning software. For example, if you are currently seeing 12.0 volts, only adjust the box for 12.0 volts. Adjust the value in the box for the voltage you are currently seeing in your tuning software higher or lower as needed until you reach the same air/fuel ratio that you wrote down for step 4. If the engine is running richer than the value from step 4, decrease the dead time value. If the engine is running leaner than the value from step 4, increase the dead time value. Upload or program the changes to your ECU and repeat this step until you reach the same air fuel ratio as in step 4.

10. You can now either calculate or interpolate values to the rest of the boxes, or you can work on other boxes by producing even further load (ie: disconnect the battery and allow the engine to run on the alternator only, etc.

You are all done. You can now enjoy your dead-on injector dead times and accurate air/fuel ratios. Happy tuning.