The power transistor that Bosch uses in their own ECUs is now available to you! This is a ‘mod kit’ for installing a BIP373 in a Megasquirt, or replacing an older or damaged VB921 with the much improved BIP373. This kit includes a Bosch BIP373, mica insulator, mounting hardware, and a 330 ohm resistor (used for MS1/Extra and MS2/Extra mods).
These are almost a drop-in replacement for the (long ago discontinued) VB921, except that they must be installed with a mica insulator as they have a metal backed case. Other than that, they work with exactly the same circuits as the VB921. We have a page that goes into more detail about these transistors here. These have held up very well in our tests, even when we’ve deliberately tried to break them. But like a VB921, they still provide current limiting to protect the other components of your ignition circuit.
We’ve tested these with MS1/Extra, MS2 standard code, and MS2/Extra.