Is it possible to run too much injector? Say you put 42# injectors on a mild setup like mine (see specs in sig). I know that big injectors like that on my mild setup would have a very low duty cycle, but would that cause a problem? Is there an optimal duty cycle that injectors should run at? I'm sure that it won't cause any harm to the injectors themselves, but could the small duty cycle have any affect on performance, or fuel atomization, or the air/fuel mixture or anything like that? I know that guys have run big injectors temporarily before they did the mods that warranted the big injectors, but I'm not sure if anyone has done it permanently for whatever reason.

Thanks in Advance!
Billy

 

i've heard you want to be around 80% IDC...

BTW you'd probably be around 60% with the marine injectors.

 

don't think it's an issue with the 42/43lb injectors but the larger ones have a lower "resolution"

 

What do you mean by resolution?

 

Too large of injectors make idle harder to control also.

 

For example:

In very general terms, the ECM commands a certain length of time for the injector to stay open. The ECM knows the flowrate (lbs/min) and commands an amount of time for the injector to deliver the desired volume or mass.

If your injector are 10lbs/min and there are 10 steps in time you get:
Time.....1..2..3..4..5..6..7..8..9..10
Volume..1..2..3..4..5..6..7..8..9..10

If your injector are 20lbs/min and you are still limited to those same 10 steps you get:
Time.....1..2..3..4...5...6....7....8....9..10
Volume..2..4..6..8..10..12..14..16..18..20

With the larger injector, what does the ECM do when it desires 11 units of fuel? It delivers the wrong amount, (either 10 or 12) because it lost "resolution."

 

You can adjust the pulse width of the injectors to compensate for size, but what Bill is referring to is the injectors ability to atomize the fuel. The less pulse width you command, the shorter duration the injector fires and you're atomization isn't as great. Having a huge injector doing a small amount of work (in a small motor) isn't a great idea. This is where your idle quality and low engine speed operation suffer.

 

100% agree.

 

Agree as well... And from what ive learned IDC should be between 75%-85%

 

Mine's in the 60s with 42lb marines