The ECU uses three different ignition maps to fuel the car during startup.
The cranking map ensures there's fuel and sparks available and that everything is ok, then it transitions to the ignition map which provides a richer mix for startup (like putting on the choke), then once the engine has fired it transitions out of the ignition map into the main running map.
The length of time a car spends in each map is set in the ECU programming. On my car, we have set the ECU to hold the crank map for a minimum of 3 seconds in order to start building oil pressure before the engine is allowed to fire, but many engines will exit crank mode as soon as the ECU has got a valid response from the crank sensor and the injectors. I think the logic is that people prefer their car to start immediately and aren't that worried about building oil pressure.
Tim,
This explains something that I have noticed for years my existing and previous Subaru's take a while to start while our Mazda's vy comparision appear to start instantly.
I guess from you post, that the Subaru ECU waits a number of seconds to allow the engine to transfer to the first starting map to allow the Oil Pressure to build up before starting while Mazda may be less concerned on this point or use a more instantly responding oil circulation system.
