Skip to main content

Cold start adjustment

  • Updated

Higher ethanol concentrations require increased fuel injection when the engine is cold in order to achieve a readily combustible air-fuel mixture. 

The Cold Start Adjustment feature allows you to adjust cold-start fuel delivery using the eFlexApp smartphone application, helping the vehicle start more easily in cold conditions.

  • Startup enrichment can be adjusted by selecting an enrichment level from the choices below.
  • See "Start Info" on eFlexApp for the data of last start (ethanol content, temperature and enrichment time).
  • The custom option is only available if custom adjustments have been made with eFlexTuner software.

Buttons

  • 3 = Richest
  • 2 = Richer
  • 1 = Richer
  • DEFAULT = Factory settings
  • -1 = Leaner
  • CUSTOM = Adjustments made with eFlexTuner Software

👉Read more: Check product specific eFlexApp features

Adjustment with the eFlexTuner PC Application

Cold start tuning is largely based on trial and error: values are adjusted, the engine is started, and the results are evaluated to determine whether the change and direction were correct. 

Only a limited number of start and adjustment attempts can be made consecutively, as the engine's internal temperature changes quickly. 

Cold start tuning can be adjusted in three phases:

1. Startup Crank (starter motor begins turning the engine)

  • Adjust this map if no combustion events occur during the first 1 to 2 seconds of cranking, meaning the engine does not show any sign of starting.
  • The goal is to inject a sufficient amount of fuel into the intake ports and combustion chambers at the beginning so that enough fuel vapor is produced for a quick start.
  • The map values are used only during the first few injection events at the start of cranking.
  • Primarily adjust the Crank [Corr %] value in the map.
  • The number of injection pulses (Pulse count [pcs]) usually does not need to be changed.
  • You can modify the values in relatively large steps, for example 30 to 40 at a time, to find the correct direction.

2. Startup Crank Hold (starter motor continues turning the engine)

  • Adjust this map if the engine briefly tries to start at the beginning, but the RPM does not increase and the engine does not continue running without starter motor assistance after the first 1 to 2 seconds.
  • Primarily adjust the Crank hold [Corr %] value:
    • Values can be changed in relatively large steps, such as 30 to 40 at a time, to determine the correct direction and amount.
    • The number of injection pulses (Pulse count [pcs]) can be increased by a few counts if fuel quantity changes no longer improve the starting behavior.

3. Startup Warmup (post-start enrichment)

  • Adjust this map if the engine starts but runs poorly or stalls a few seconds after starting.
  • This cold start phase has two stages:
    • The enrichment amount specified by Warmup [Corr %] is maintained for a specified period (Hold duration).
    • After that, the enrichment is gradually reduced to zero during the Decay duration period.
  • Primarily adjust the Warmup map.
  • The Hold and Decay times are generally already quite long, and they can usually be reduced if the Warmup values are increased significantly.
  • This is the first startup adjustment phase that can also be tuned using measurements.
  • If you have an OBD diagnostic device capable of reading Short Term Fuel Trim (STFT) or a wideband air-fuel ratio meter, the Decay time can be adjusted based on those measurements.

Remember to save the settings permanently to the eFlexFuel control unit!

👉 More information about using the eFlexTuner software can be found in the user manual: eflextuner-en.pdf