Dead time with intervalometer and bulb timer

[eloml]

Hi,
I use the ML intervalometer for astro-imaging. Typically, I take 60 sec subs in bulb mode and get an image every 63 seconds. The additional 3 seconds per image I attributed to the storage of the raws and perhaps some lazyness of the intervalometer.
But recently I astro-modded a 1100D (filter & mirror removal, cooling). Thereby I also replaced the shutter by an emulator and did some tests with short exposures. When I came to exposure times below one second I left the bulb mode and selected the exposure time directly. And suddenly, the time loss of 3 seconds was reduced to half a second per image!
Is this a know effect, and if so: where does it comes from?

[a1ex]

Mode switch, conservative delays, restoring previous settings...

Feel free to optimize it. Tweaking it for your particular purpose is probably easy. Doing so without breaking existing functionality (e.g. bracketing in bulb mode, bulb pictures from Lua scripts, compatibility with old and new models) is a bit harder.