Recommended flyback for GenBoard/VerThree: DD flyback
In ancient times, the
- high voltage flyback was the recommendation for highZ injectors, when max 2 injectors (preferrably just 1) used per bank
- and low voltage flyback for lowZ injectors (or when multiple injectors per bank are used)
Since the precise injector opening is configurable (this is a nice feature that not many ECMs have, and no other opensource ECM) usually the low voltage flyback is used also for highZ injectors. In the worst case, there is some adjustment needed (see GenBoard/Manual/Config/InjectorOpening) to smoothen idle if the injector opening parameters were guessed badly originally.
- The left drawing is a high voltage flyback, used only when PWMing is not applied (thus PWM% = 100, recommended for highZ injectors). The flyback voltage drop is
- 0.7V + 6.8V or
- 0.7V + 20V
- The right side drawing is a low voltage flyback for lowZ injectors, where PWMing can be applied. The voltage drop is
- 0.7V + 0.7V for a configuration as on the picture or
- 0.7V + 0V if there is only one diode (or the second is shorted). The 0.7V + 0.7V is preferred by some installers, as the 2nd diode provides protection against the most common (still very rare) failure mode of diodes (when it is shorted)
Notes:
- never have a fuse in the flyback path. The fuse must be outside of the path, as the drawings suggest
- we recommend using separate channels for each injectors
- if one puts in the transient protection diode with anode on the switched side, he'll not get the left side highZ configuration, but the right side low voltage flyback (0.7V + 0.7V) type
- the low voltage type can be used for highZ setup safely, but injection time related parameters are harder to set since injector closing will take longer:
- the low voltage type is definitely suggested if capability of driving highz or lowz injectors is required without HW change.
A [DD flyback picture with 0.7V + 6.8V]
![[DD flyback picture with 0.7V + 6.8V]](http://www.american.hu/GenBoardv31/GenBoardv31_assembled/GenBoardv3.1_TOP_04.JPG){kind=link}
Notes:
- the placement of the red wire is suboptimal: the best connection is between 4th and 5th diode, so 4 flyback paths are on one side and the other 4 flybacks flow from the other side of the onboard flyback trace. The reason for this is that the red 0.61mm2 wire can handle much more current with less heating than the PCB trace. This is more important when PWMing is used. Without PWMing the flyback heat dissipation is not significant.
- the red wire connects the flyback rail to the EC36 connector, which must be directly connected to the injector common with no fuse in between. This is done regardless if you're using HighZ or LowZ injectors.
- low voltage flyback looks similar, but the diodes connected to the flyrail are reversed (and usually not transient suppression diodes, just normal diodes).
See
- GenBoard/Manual/Flyback/Testing for how to test flyback.
- GenBoard/VerThree/RescueKit to verify what diodes you have
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