why do we have primary and secondary injectors. what is the use of the secondarys and why when i look in super street every1 always upgrade the secondaries.
i got an 88gxl any1 know how big the injectors are stock.

 

primary injectors fire all the time, sec don't come on until about 3800 rpm, for higher air intake ratio
more air requires more fuel
upgrade secondarys because at higher RPMs is when you need LOTS more fuel
i believe stock NA injectors are 550 cc?
correct me if wrong
on NA, i wouldn't worry too much about upgrading injectors, unless you've got some serious porting in mind

 

460cc

eljefe62 is right about not needing to upgrade them. Unless you're going bridgeport in the near future.

 

good deal i was gonna do some porting but not like really insane porting where i can start to see the needle on the fuel gauge actually drop. but im new to rotary club and the fuel system was the only thing i didnt understand that much.


thanks guys

 

skool is spelled school and super street isn't something i'd use as a good reference.

 

It's because of the large amount of fuel each rotor requires. A single 13B rotor needs a similar amount of fuel as a 1.3L piston engine. You need at least one injector per rotor, so a single injector would need to be very big to adequately fuel each rotor. For example the 12A Turbo only made ~140hp, but had one huge 800cc/min injector per rotor. Two injectors on a 255hp FD would need to be massive, and the bigger the injector, the worse it's accuracy is at short pulsewidths.
So by having two injectors per rotor they can be smaller, and only two of them need to be used at low rpm. Because of their accuracy, smaller injectors improve idle quality, economy, and emissions.
If you need to upgrade the injectors, leaving the primaries stock means not losing any of these benefits, while the larger secondaries allow more power to be made (as long as they're controlled properly).
NA FC's have four 460cc/min injectors, which are big enough to support ~250hp. Without at least a bridgeport, they're fine.