High impedance (high-Z) injectors 7 Ohm or higher
PWM-ing (and the low-Z extension board) has no advantage here. The easiest method is to
- use the default 30V flyback.
- and then the default setting must be used: PWM-ing must be disabled in injector settings with
- injector PWM time=25.5 msec
- injector PWM duty=100% ... because any other setting might cause damage.
Medium-impedance (medium-Z) injectors 5-7 Ohm
The 1680 cc/min Bosch falls here (5.9 Ohm). Can be driven as either high-Z or low-Z.
Low-impedance (low-Z) injectors less than 5 Ohm
See "LowZ extension" (4 or 8 channel)
- must be used with the 200V IRF640 FET (not the FQPF20 black insulated 60V FET)
- normally installed inside the ECM case
- the EC36/23 flyback pin (which goes to the injector +12V in the harness) must be connected with min 0.75mm2 wire to the anode of big throughole "1k5e30" 30V unidir transient diode on the extension board
- alternatively outside (if the assembled v3 is equipped with 30V flyback and IRF640 200V FETs, which is default since 2010-12).
- requires a 30V unidir transient diode if the assembled v3 has low-voltage flyback inside. (only for those who know what they are doing).
Using 4+1 or 8+1 wires in any case (v3.7 has extra throughole pads for these).
- One wire for each (4 or 8) injector output
- and one "flyback wire" connected directly (no fuse between) to Injector common (the shared pin of injectors, which gets +12V when ignition or ignition+fuelpump is on).
Note about the 4 channel Low-Z board when installed outside the ECM
The 4 channel version uses A,B,C,D injector outputs (EC36 pin 7,19,8,20) when installed on top of v3 as a daugther-board.
Please use the same pins if installing outside. VemsTune will give validate warnings if using 4 injector channels with PWM-ing other than these A,B,C,D injector outputs.
In case of the 4ch lowZ-extension only:
- from the mainboard flyback rail (if the 30V unidir transient diode is missing from the mainboard for mechanical clearance reasons) a 0.75mm2 (red on the pic) wire is connected to the cathode of the 30V unidir transient diode (on the extension board).
- This completes the flyback path for the 4ch that does NOT have the low-Z extension => therefore not needed for the 8 channel extension
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