RE: Injectors?
My wife was hanging over my shoulder last night, "reminding" me about a restaurant reservation...
I'm not sure how clear I was.
First of all, keep in mind that those "on" times are in relation to a second, so move the decimals over and you've got a HYPOTHETICAL duty cycle. See how (comparatively) short on is to off? The physical limitations of fuel flow through an open (100% duty cycle) injector are hardly an issue under most circumstances.
Hypothetical?
Please, you must understand that those numbers in my previous post were what I have seen in my day-to-day work. At best, they are simply figures in a very large ballpark.
You'll be hard-pressed to find documentation anywhere as to what "correct" or "normal" pulse times are, and if you do, be highly suspicious. There are just too many variables used by the PCM to make its delivery calculations.
-Open or Closed Loop?
-ECT
-IAT
-MAF
-TP
-O2s/Catalyst Monitors(OBDII)
-What's the trans doing?
-How far has the PCM advanced injector timing at the moment being discussed?
-Where has it put ignition timing?
-Is the stereo pumping? The PCM even accounts for things as minor as electrical/alternator load at any given time.
-A/C on?
Etc..etc..etc..
So why would you ever want bigger injectors?
WOT Open Loop.
Let's talk those hypothetical numbers:
Somewhere, a programmer, working with the driveline engineers, decided that,...say... a 24lb injector opening at...I don't know, let's say... 500mS would provide exactly the correct amount of fuel to an engine at WOT. He's a programming engineer, which means he's better than God. He knows he can't be wrong, so why would the PCM need O2 feedback to correct him? WOT only occurs in short bursts, right? Hence WOT Open Loop. (There's many other reasons, too, but bear with me).
You now take your car and change cams, or add a blower, whatever, but it's something so radical that the pre-programmed "24lb at 500mS" cannot supply your new requirements. Even tuning a chip to increase WOT pulse width can't do it. Only now do you have no choice but to push the fuel through a bigger hole.
If high flow injectors are not really required, the PCM might be able to correct with negative fuel trims in Closed Loop, but at WOT, fuel is delivered at a preprogrammed pulse. If the hole is bigger, the system goes too rich, loses power, and you've caused more harm than good.
You may be able to compensate for your mistake with chip programming and a different MAF calibrated to the new injectors, but what's the point?
The end result? You've put a half-dozen apples in a bag and taken six back out!