Getting an electronic fuel injector to only open partially

[bdunham7]

The intake cycle doesnt take 720 degrees of crankshaft rotation to complete, instead it's more around 1/4 of that, 180 degrees. furthermore the injector is PWM'd to control the volume of fuel injected. so it's way faster than 2ms

Having an idea is nice, but you keep mistating the fundamentals of what you are discussing.  Assuming we are talking about a conventional-ish multiport electronic fuel injection system with typical pintle-valve injectors, not a single-point, central, mechanical, direct injection or a MPI/GDI hybrid (all of which exist) then you should observe the following:

The 'intake cycle' is not really relevant to the discussion. During normal cruise, a typical MPI gasoline engine often turns the injectors on during the exhaust stroke.   This may vary widely with temperature, load and engine design.

During high-load high-RPM operation, the duty cycle of the injectors may exceed 80%, or 576 degrees. 

Typical PWM injector drives use an inital current to open the injector and then a PWM current to control the current and keep the injector open, not pulse it or hold it partially open. 

There have been a huge number of variations tried and produced over the years, so if you want specific answers you have to be discussing a specific system.  Finding a solution to your issue would most likely be realized by tracking down the right injector(s).  Using two different injectors also might be something to think about.  If you want to 'out-engineer the engineers', start by learning what they've already tried and done. 

I'll just go and convert my engine to gas vapors because liquid fuel is lower efficiency... you know.. smaller droplets that evaporate faster always mean higher efficiency right 

To an extent the statement is actually true--evaporating the fuel before it gets in the cylinder (using waste heat) improves the overall thermal efficiency of the engine.  This may come at the price of reduction in power density, emissions issues and other things I can't think of right now. 

[ELS122]

Having an idea is nice, but you keep mistating the fundamentals of what you are discussing.  Assuming we are talking about a conventional-ish multiport electronic fuel injection system with typical pintle-valve injectors, not a single-point, central, mechanical, direct injection or a MPI/GDI hybrid (all of which exist) then you should observe the following:

The 'intake cycle' is not really relevant to the discussion. During normal cruise, a typical MPI gasoline engine often turns the injectors on during the exhaust stroke.   This may vary widely with temperature, load and engine design.

During high-load high-RPM operation, the duty cycle of the injectors may exceed 80%, or 576 degrees. 

Typical PWM injector drives use an inital current to open the injector and then a PWM current to control the current and keep the injector open, not pulse it or hold it partially open. 

There have been a huge number of variations tried and produced over the years, so if you want specific answers you have to be discussing a specific system.  Finding a solution to your issue would most likely be realized by tracking down the right injector(s).  Using two different injectors also might be something to think about.  If you want to 'out-engineer the engineers', start by learning what they've already tried and done. 

Ok thanks for the "help"

To an extent the statement is actually true--evaporating the fuel before it gets in the cylinder (using waste heat) improves the overall thermal efficiency of the engine.  This may come at the price of reduction in power density, emissions issues and other things I can't think of right now.

You got my point... bravo

[CaptDon]

After working on engine ECU's for the last 10 years, and having experience with many types of injectors including 'one-off' trial designs from big boys like Bosch the 'partially open' type only work (as another poster clearly stated) in the older style throttle body low pressure injection scheme. In the medium high pressure systems (60 to 100psi) a partially open injector produces poor atomization NOT BETTER. As another poster already stated RAISING THE FUEL PRESSURE and shortening the duty cycle is the correct answer and is why you now see injection systems running very high pressure which leads to some spectacular fires from the mist created by very tiny pinhole leaks or loose fittings. Injection systems today can produce such a fine mist in the intake manifold that it looks like fog. B.T.W., you never 'polish' intake runners and ports thus causing 'wet flow' issues where the particles come out of suspension and wet flow along the runners. The best designs look like they are 'parkerized' with a dull finish and often acid is used to obtain the dull finish appearance. There was a design study done about 40 years ago with carbuereted engines where a 4" diameter piezo ultrasonic driven disc was built into the floor of the intake manifold directly under the carb. It worked so well that when activated the engine ran excessively rich and the air fuel mixture had to be leaned out. The BSHP vs. the fuel consumption increased by about 20%. No 'drivable' control system was ever developed for street use sadly. Also as stated, to get enough fuel injected during high horsepower output the injection cycle starts long before the intake valve opens for port injected engines and easily can go to 80% of the 720 degree engine cycle.

[HighVoltage]

 There was a design study done about 40 years ago with carbuereted engines where a 4" diameter piezo ultrasonic driven disc was built into the floor of the intake manifold directly under the carb. It worked so well that when activated the engine ran excessively rich and the air fuel mixture had to be leaned out. The BSHP vs. the fuel consumption increased by about 20%.

No 'drivable' control system was ever developed for street use sadly.

Actually BOSCH Germany did develop such system for the OEM and promoted it at a conference in the 1980s. I had the luxury to drive such a prototype car but the automotive world did not implemented it for production.

This ultra sonic system was the best fuel atomization at the time. But today's high pressure fuel injectors are much better.