fuel injector theory

[89z51l98]

Lets say I've got stock 21 lb injectors... and i replace them with 28 lb-ers. At say 50% throttle, will the bigger injectors put out more fuel (ie. more fuel at any given throttle than the stockers) or do they only move more fuel at WOT?

Thanks

 

[Ken]

The computer will still control the pulse width and duty cycle time. You'll have to modify its thinking.

 

[89z51l98]

Ok... thats kinda what I thought.

I have another problem that I'm trying to research... does anyone have a writeup of how to check for leaking fuel injectors?

 

[Ken]

Checking an injector on the vehicle has changed through the years. Some of the tools and procedures from yesterday are not the tools and procedures of choice today. It is also important to have a good understanding of the type of fuel system and the PCM strategy for the system you are working on.

Check this out: Fuel Injector Operation Confirmation - How to Check an Injector's Performance

 

[WhalePirot]

Along with what Ken said, (a wonderful researcher and font of knowledge) the ECM will try to trim the injectors' fuel output to achieve an optimum fuel burn. Ken spoke of the methodology employed; essentially, varying solenoid open time.

The ECM has limited authority to 'take fuel out' which is why many modded engines run rich. The 'zero trim' values in the fuel tables can be changed with PROM burning, allowing the ECM to stay within its authority in optimizing the fuel/air ratio.

Some tuners vary fuel pressure, using less pressure behind larger injectors, while other express concerns over proper spray patterns with too-low pressure. Others use higher pressure and smaller injectors. Mine runs very, very well with stock pressure and injectors sized for my expected power output.

 

[89z51l98]

Thanks for the info!