Originally posted by "solo_mata_me"
That is speed shifting. I refuse to believe that you have not ever heard of shifting without the clutch. Tony (now flies w/USAF) and I used to do this all the time with the ACE autoparts trucks to perfect our techniques. We'd use the clutch to get off the line and that was it. It is all about timing and knowledge of the transmission/engine.
Granted, the transmissions you listed were designed to be shifted w/o a clutch, but experiance with other transmissions tells me that other transmissions than the ones you listed can be shifted without the clutch.
Anyway, back on subject.
no, actually he was right, powershifting is shifting without lifting the throttle. speed shifting is when you start selecting the next gear before the clutch is to the floor (but still lifting the throttle). the idea is that you can time the shift so that just as the shifter hits neutral, the clutch is disenged, allowing a quicker shift to the next gear.
speed shifting is what you do when power shifting results in wheelspin in the next gear.
what you are talking about is clutchless shifting and i would think its not really wise practice in drag racing since you have to wait for the revs to drop before you put the car in the next gear. (else you wanna destroy the synchromesh).
in a non-synchronized racing transmission (purpose built race car), clutchless shifts are used to extend the life of the gearbox and clutch.