Secondary Injectors? Who's Got 'Em?

[Boomer420s]

When I searched this(by the way, I like the way "related topics" comes up when I enter in title.) I got three threads. Two referring to 420A, which I have no recognition in, and a thread about mounting. In the mounting thread, all that came about was the arguement whether or not to run said injectors. "Why not run a larger injector?"

Well, I just watched my "instructors" install a second set on an "equivilent" 4G63 motor out of a Dodge Avenger. Correct me if I'm wrong on that assumption. A turbo was being added as well. The injectors came with their own module, mounting bracket, and a new intake manifold was also purchased. The secondary set fires roughly 50% throttle. Not quite sure on the exact specs. Was a little busy myself.

So, my question is this: Where is the benefit there? I understand the install is rather basic, yet time consuming. Where does the second fire of fuel outweigh the larger injectors besides detonation and maybe fuel economy?

 

[Jeff_Ciesielski]

Idle and cruise. Your car will always idle like stock , and if you use staged injection, either via a boost activated switch(which is better IMO), or by rpm/load, you can have massive potential up top, while still getting stock highway fuel economy.

 

[Boomer420s]

So bigger injectors or secondary injectors? I think bigger for the track, secondary for the grocery getter. Considering a trigger set by boost or rpm.

 

[steve]

The trade off is that bigger injectors are harder to match and be consistent at low injector pulse widths.
Think about trying to turn a fire hose on and off quickly. At idle and cruise the engine really doesn't need much fuel so the big injectors are challenged to not provide too much fuel and to feed each cylinder the same.

Running secondary injectors allows you to phase in the extra fuel. The drawback is that the ECU doesn't support them so there will be secondary effects you have to tune around.

At the strip you really don't care too much how the car idles so big injectors work fine and in the grocery getter you usually don't need huge injectors and it's not hard to find good performing injectors in reasonable sizes.

 

[Black99gst]

running 950cc FICs and idle is on the money at 14.7:1 @ 850rpms (FP2's) i vote bigger injectors FTW, secondary is just one more thing to go wrong with the car, and we all know it will.... so why not just have 1 set? p.s. i'm making good power, and still gettting over 21 mpg every day!

 

[2gGSX]

running 950cc FICs and idle is on the money at 14.7:1 @ 850rpms (FP2's) i vote bigger injectors FTW, secondary is just one more thing to go wrong with the car, and we all know it will.... so why not just have 1 set? p.s. i'm making good power, and still gettting over 21 mpg every day!

They're talking about 1600's or larger (e.g. Magnus 2200's). Those do not like to idle like the 1000cc injectors.