[dcb]

Originally Posted by diesel_john

Throttle Body Injection (TBI) is not timed to the engine.

Hmm... this data was from a tbi metro, you can see inj count going through the gears then stabilizing in 5th gear to be proportional to vehicle speed (vss count). I believe that at least some TBIs, while not critically timed with valve position, do use an injector signal proportional to rpm. In fact the metro seems to fire 3 times per 2 revolutions. When we hit the 38 in inJcount we have just shifted to 5th gear. Shifts are at 40->34, 51->37, 50->42,49->38 . Counts are total for one second.

byte vssCount[]={ 0 ,2, 6,10,13,15,18,20,22,25,25,27,28,29,28,28,28,26,26,25,24,23,24,23,24,24,24,24}; 
byte injCount[]={37,40,34,51,37,43,48,50,42,46,49,38,37,39,38,37,37,36,34,33,32,32,31,32,31,32,32,33}; 
unsigned long injHiMS[]={69002,117777,101972,138435,148117,174988,98775,164693,165873,176190,113628,148571,120702,58276,39501,37891,38435,37369,37006,37142,39433,62879,71179,71995,77074,95215,86281,75419};

Note, this was gathered with a laptop running sound recorder, I suppose one could use the same technique in lieu of a real oscilloscope if the signals aren't making sense.