EFI duty cycles

WOT = acceleration (i.e., pedal to the floor)? Or is that when you cruising at highway speeds? If it is acceleration how do you propose to accelerate for one full hour, using a dynomometer perhaps?

snipped-for-privacy@optonline.net skrev:

I'm designing an aftermarket injector controller and at WOT = Wide open throttle, pedal to the floor, the vehicle that the prototype box is installed in, is getting a warning from the software that injector dutycycle is 100% above 4000rpm/WOT. In other words, system running out of injectortime. My question is generally, if there are any problems for injectors coming into continous operation, (100% duty cycle), like overheat etc etc? Of course the 100% duty cycle applies only to a few seconds or so.

Regards

Educated Guess Time: For a few seconds at a time it shouldn't hurt anything. I would be more worried about running it that hard because if it needs even more fuel and you "ain't got no more", you could start running lean. And too lean at WOT could start eating valves or doing other nasty things.

Why you are triggering the warning in the first place - do you have any control of the fuel pressure regulator? Or can you stick a VSV on the fuel pressure controller line to trick it into going higher on command? Pump up the injector rail pressure, and you can drop the duty cycle on the injectors a proportional amount and keep the mixture where you need it, and then you won't be flirting with a lean condition anymore.

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You and I have gone through this before.... when you talk about 100% duty cycle, do you mean the injector is on all the time? This could present a problem during compression power and exhaust strokes, right?

FWIW... and of course YOU are right and I am wrong.... Injectors are NOT duty cycled.... They open once per stroke cycle and are left open for a perscribed period of time decided by the PCM. Then, amazingly, they close for three full strokes....

Factoid.... Ford does not list injector duty cycle in ANY of their current service literature. Grasping an example, the Mustang GT500 lists max injector on time as less than 10 ms.... Years ago, I already did the math to find out how far the piston travels at various rpms in regards to spark line time... typically about 1.5 ms, much less than 10ms. Over to you to figure out how far the piston will travel in 10ms at say 4000 rpm...

Trying to apply duty cycle computations to a changing frequency must be somewhat frustrating.... especially when we consider that stock fuel injectors live quite well at WOT and even better when we consider mechanical limitations.... like, leaving the injector open all the time is going to leave you with puddles of fuel sitting behind the intake valve waiting to send your mixture pig rich and your power curve in the toilet...

Feel free to comment on my "mistaken" ideas.... I'm not the one that can't make this thing work... Mostly because I have no misconcneptions about applying duty cycle to an event that needs to PWM...

If you are running out of injector "on" time, is there a chance that you need to make a change to injector flow? If you are writing a program that adjusts the fuel curve, simply adding more "on" time may not cut the mustard. There is a need to understand the events that occur both in the intake tract as well as the combustion chamber.

To some extent, brake mean specific horsepower computations performed through dyno testing have been replaced by mass fuel desired computations that the PCM applies to fuel delivery. Simpy adding fuel to the point that the injector has no more "on" time isn't going to accomplish much other than to make someone, eventually, realize that fuel will precipitate out of the intake charge and stratification is likely going to happen along with it....

wrote

No help, just a related question: Port injection (1 injector per cylinder), or throttle body (central shared injector(s))?

Let's face it... the guy is either totally off his nut or he's researching for a different application.

Since he insists on the 100% duty cycle, I suspect it's as a continuous valve/injection source, like a furnace burner or turbine etc

Jim Warman skrev:

Hi Jim, I appreciate your input, and respect your knowledge, no doubt, but it seems like you didn't exactly understand my question, or maybe didn't read it properly. Anyway, I lower my sight and try once more: Is there any possibillity for a high-impedance (voltage driven) fuel-injector to get damaged of continous operation. That means on all of the time (didn't say 100% duty-cycle...) for a couple of seconds? That's it.