Hello jesuitfriar,
The blitz realms (realms with speed x4) follow the rules and mechanics the game speed is multiplied by 4, meaning that accounts' development is 4 times faster than it would be in a normal speed (speed x1) and it is two times faster than realms with speed x2. The slowest realms in version 6 are realms with speed x2.
The production, Gold income, Population growth are faster - х4 than normal speed. Construction and research times are divided by 4. Units’ training time is 4 times shorter, units’ speed is 4 times higher, upkeep is multiplied by 4, traveling times are 4 times shorter. For more detailed information, change the speed number in the upper right corner of the How to play menu -
http://www95.imperiaonline.org/imperia/game_v6/game/help/?lang=en&speed=4 .
The duration of the era is different too – on the 10th week from the beginning the Lords of the realm competition is unlocked; if within 4 months from the beginning of the era none of the alliances has managed to win the realm, the era is closed by Imperia Online’s administration.