The power transistor that Bosch uses in their own ECUs is now available to the hobbyist. This is a mod kit for installing a BIP373 in a Megasquirt, or replacing a VB921 with a BIP373. This kit includes a Bosch BIP373, mica insulator, mounting hardware, and a 330 ohm resistor (used for MS1/Extra and MS2/Extra mods).

We're introducing the Bosch BIP373 as a replacement for the now discontinued VB921 coil driver transistor. These are almost a drop-in replacement for the 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.

Here's an illustration of the correct way to install one on a heat sink:

We've tested these with MS1/Extra, MS2 standard code, and MS2/Extra.