Version2:Hardware/Engine Board

Engine Management & Control Board

A separate PCB from the flight computer board, dedicated to engine and power management.
Philips LPC2132 or LPC2134 microcontroller (ARM7)
I really like this idea because everything related to the power and propulsion system is separated from the core electronics (e.g. we could have a different engine board for a brushless motor drive system and Lithium batteries, with onboard BLDC motor controller and power supplies, minimizing heavy cabling and unused circuitry on the main board)

hall effect sensor for spark timing (and frequency counter for RPM)
thermocouple interface for exhaust gas temperature sensor
maybe a thermistor or digital temperature sensor for air temperature
spark ignition: 300V DC-DC step up converter (torrodial transformer, MOSFET switcher on the primary, fast diode bridge rectifier), 0.47 uF capacitor, MOSFET for discharging capacitor through ignition coil.
mixture heater output (7.2V (or whatever the bus voltage is) switched/PWM output for a nichrome wire heater coil in the engine inlet manifold. Would be desireable if the CPU could measure the resistance of this heater to estimate inlet mass flow (proportional to cooling of the heater coil). Only needs to be <10W peak, maybe <3W average.
servo outputs for the throttle and mixture valve servos. Possibly other servo outputs too.
Perhaps a switch/button and a few LEDs that will indicate state when starting the engine.

3-phase rectifier for alternator
alternator output voltage should be ~7.2V at cruise RPM.
simple Li-Ion battery and charger so we don't loose power immediately if the engine stalls. Probably easiest if this is a two-cell battery (7.2V). We don't need to worry about powering spark ignition, the mixture heater, or the engine servos from battery backup, as they aren't necessary when the engine/alternator dies.
7.2V ground power input. This would connect to the output of the alternator rectifier (and thus could power everything). This should have a battery-pack-friendly connector so we can fly with a big LiIon pack until the alternator is working properly.
4.8V switching power supply for servos (need to make sure the output ripple is well controlled and the regulator is stable under an extremely variable load of servos).
a shutdown-able servo bus (P-channel FET) for the engine servos as they don't move much. Need to make sure that servos don't jitter at all when power is turned on and off, as a small jitter could stall the engine.
3.3V linear power supply for engine board electronics
7.2V bus voltage output to power flight computer board.