subaru [subaru?] ecu.

[Dave Williams]

-> [I wonder if you really could build a vacuum tube ECU?]

 Sure.  The Bendix Electrojector in the '50s, and the unnamed system
Rochester played with.  Of course, you had to warm up the tubes before
you could go anywhere, and the Rochester one took up most of the
passenger side floorboard of a full-sized car.  That's why neither
system went into production, and both companies stayed with mechanical
FI.

 The Bosch mechanical system was high pressure, sequential,
speed-density.  The Rochester was continuous flow, low pressure, and
mass air.  Both worked just fine, but the amount of precision machining
required for the control units made them expensive.  It took the advent,
not just of integrated circuits, but of *cheap* ICs, before electronic
systems were practical.