Do FD's use top-feed or side-feed injectors?
 

Anyone also care to explain the difference. Thank you.

Side feed (fuel feed into the side of injector).

The primaries (550cc) are top feed, while the secondaries (850cc) are side feed. Side feed injecotrs have fuel input from the side of the injector body (they fit into the fuel rail instead of the rail at the top). I do not know what other engines have this setup, all the other engines I know use top feed. I imagine it was a space issue when designing the engine.

I believe all four of the RX-7 injectors are side feed, as are many japanese OEM cars..

3SGTE
SR20DET
2JZGTE

to name a few. The side feed design allows the fuel to act as a cooling agent to the injector, immersing the entire unit fuel drops the operating temps. It also allows low-profile installations. However, Some impedances/flow rates are simply not available in the side feed design due to physical limitations.

ALL the stock FD injectors are side feed. Aftermarket fuel rails typically use top feed though.