Your eGo C Upgrade battery has "variable voltage"...sort of. That is, you can use it on the regulated 3.3volt usual eGo level, or switch it to "unregulated" which will vape more like your Blu (only stronger) betcause it will start out at 4.2volts and go gradually down from there. That will help with the "warmer vape" issue. Here are the instructions from a Joyetech site:
[Quoted...their English, not mine!]
Switching operation and features :
1. From constant voltage output mode to new battery voltage output:
1.1 When the mode is 3.3.v constant output mode, you can lock the battery by 5 clicks (blue LED blinks 3 times).
1.2 By pressing button for 5 seconds, LED will change to orange with 3 blinks. The battery has switched
to variable voltage output mode (battery voltage output mode).
1.3 Then you can use as usual by 5 clicks off and smoke in battery voltage output.
1.4 In new battery voltage output mode, the LED is orange and battery doesn't have power display function.
1.5 When charging, orange LED will blink 5 times in this new mode.
2. From new battery voltage output to constant voltage output mode:
2.1 In new battery voltage output mode, you can lock the battery by 5 clicks again (orange LED blinks 3 times).
2.2 By pressing button for 5 seconds, LED will change to blue with 3 blinks. And the mode has switched to
3.3V constant voltage output mode.
2.3 Then you can use as usual by 5 clicks off and smoke in 3.3V constant voltage.
2.4 In 3.3V constant voltage, the battery features has no difference from present eGo-C battery.
2.5 When charging, blue LED blinks 5 times in this mode.