I was just curious as to what makes a 550 different from say a 1600. what part of them is it that it altered to provide so much more fuel. Is it as simple as the nozzle?? or is there much more to it? Thanks for an explanation in advance. Also, if i put gsl-se 680's in my T2, would some sort of injector controller (i.e. s-afc) be required to get them to operate at 680cc instead of 550?? How about with even bigger aftermarket injectors?

 

They're bigger, that's all. The same way a 2.5" exhaust flows more than a 2" one.
If you put 680's in, at full load the ECU will be squirting in 12% more fuel than it thinks it is, so you'll be running too rich. A controller is needed to tune the mixtures to your mods.

 

Bigger orifice
Bigger/matched needle "valve" matched to the bigger orifice

Other than that, the solenoid and electromagnetic sections are all the same.



-Ted