What is the frequency of typical injector pulse width?

[Dust]

I know that this isn't an electronics board, but I know that tuning and circuits aren't mutually exclusive.

Looking to convert a 0-5v signal into PWM, and although I don't know how I will get there, I do know that one of the parameters will be the frequency of the pulse. Not looking for direct injection, just normal injector frequency. Need it to signal a controller.

[joecar]

For gasoline engine:

sequentially fired injectors: each injector is fired once every 2 crank revolutions, so frequency [Hz] = rpm/60/2 = rpm/120

batch fired injectors: each injector is fired twice every 2 crank revolution, so frequency [Hz] = rpm/60


in each case the injector pulse width is proportional to cylinder fill airmass and commanded EQR.

[Dust]

Two more please

What duration ?
What ratio of high to low ?

[joecar]

The duration is the injector pulse width IPW, this varies with engine load and commanded fuel.

[ IPW is the time the PCM connects an injector to ground to turn it on ]


The duty cycle is the ratio of IPW to one cycle period; DC varies with IPW and RPM (typically from 3% to 85%); DC is expressed as percentage;

one cycle period (in seconds) is as follows:
sequentially fired: T [s] = time for 2 crank revolutions = 120/rpm (e.g. at 6000 rpm, T = 0.020 seconds, this is the upper limit on IPW)
batch fired: T [s] = time for 1 crank revolution = 60/rpm


high:low ratio is not normally used, but is the ratio of DC% to (100% - DC%).

[Dust]

I am trying to mimic a fuel injector, so I was just trying to figure out what info I would need to get it done. THe duration gets longer as load increases, but what would we be talking about here?

[joecar]

The sequentially fired 4 stroke cycle period = T = 120/RPM;
the duration (IPW) can range from zero up to T;

so the IPW gets longer as load increases, but it is limited by T;

if the injectors are too small, the PCM may calculate an IPW longer than T, but physically when IPW is equal to T the injector is now being held statically open (DC is 100%);

T gets smaller as rpm increases:
- 600 rpm: T = 120/600 = 0.200 [s] = 200 [ms]
- 1200 rpm: T = 120/1200 = 0.100 [s] = 100 [ms]
- 3000 rpm: T = 120/3000 = 0.040 [s] = 40 [ms]
- 6000 rpm: T = 120/6000 = 0.020 [s] = 20 [ms]

[joecar]

At low speed, low load, IPW may be 4ms; IPW will increase as load increases, typically to around 10ms, and at 6000 rpm IPW may reach 15ms (representing DC 75%).


If you take some logs of IBPW, TPS, RPM you will see the behaviour.