Using LABVIEW To Read and generate pressure for fuel injection

[jamran]

ok thanks for your reply. but my project is also due for march. final yer project. so if ucan fit some time in pls. like you said it seems quite straight forward. i dont even no how to read the signals from the hardware n what tools to use

[jamran]

Hi. I had another question. what is the minimumvoltage required for the fuel pump in order for it to work/ orperate? for the injector its around 250V what about the pump? is it the same? also is there a certain sequence that needs to be followed if we were to just put voltage onto the VCV and PCV without going via the ecu jus to check if it generates pressure? if so does anyone whATS the sequence?  e.g do we open the PCV first then the VCV or vice versa or do all the same time?

thanks

Message Edited by jamran on 02-10-2009 05:35 AM

[TechWiz]

The fuel pump PCV & VCV normally require 0 to 5 V DC to operate. (They are typically and almost always solenoid valves). A common procedure followed in the industry is to keep a fixed opening of the VCV (~20 to 30%) and control the PCV to change the pressure. You could apply a fixed 1 to 2V on the VCV and then apply voltage to the PCV.  These action can be done simultaneously but ensure that the VCV is always open.

A word of caution: Depending on the pump specs and the manufacturer,  for the PCV, 0V can mean minimum pressure or the highest pressure. So make sure you know the specs and that all the pump connections are secure and safety gear is worn.

Recommended:  the pump should not be in the same room as the person handling the control. 

Hope this helps

Cheers!!

[TechWiz]

Please discard my last post.

The PCV and the VCV are pulse width (or duty cycle) modulated controls where the duty cycle of the pulse train determines the opening of the valve.

The frequency of the digital pulse train will depend on the manufacturer but a freqency of 200 to 300Hz for the VCV and about 1 to 1.2 kHz for the PCV. So you generate a TTL compatible pulsetrain (0 to 5 V typically) and use the duty cycle to adjust the opening.

The operation can still be performed as I said in the earlier post. Keep a fixed opening of the VCV (20 to 30%) and then change the CV to adjust the pressure.

You cannot use a DC Voltage directly.

Hope this helps

Cheers!!!

Message Edited by Mani's World on 02-10-2009 04:28 PM

[jamran]

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Mani's World wrote:

Please discard my last post.

The PCV and the VCV are pulse width (or duty cycle) modulated controls where the duty cycle of the pulse train determines the opening of the valve.

The frequency of the digital pulse train will depend on the manufacturer but a freqency of 200 to 300Hz for the VCV and about 1 to 1.2 kHz for the PCV. So you generate a TTL compatible pulsetrain (0 to 5 V typically) and use the duty cycle to adjust the opening.

The operation can still be performed as I said in the earlier post. Keep a fixed opening of the VCV (20 to 30%) and then change the CV to adjust the pressure.

You cannot use a DC Voltage directly.

Hope this helps

Cheers!!!

Message Edited by Mani's World on 02-10-2009 04:28 PM

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hi thanks but i dont understand what you are saying mate. Please could you explain in laymen's terms. Y cant we use a direct DC voltage? thanks

[TechWiz]

Pulse-width modulation uses a square wave whose pulse width is modulated resulting in the variation of the average value of the waveform. For a waveform with a time period T (frequency = 1/T), the DC can vary from 0 to 100 % (0<=DC<=T) 

See the following link.

http://en.wikipedia.org/wiki/Duty_cycle

You cannot use a DC Voltage directly since the pumps are manufactured to use PWM control. This is a neater way of controlling the amount of power sent to a load.

Cheers!!

[jamran]

could you please elaborate exactly what the VCV and PCV do.

Message Edited by jamran on 02-16-2009 09:52 AM

[TechWiz]

The fuel injection pump has a low pressure supply line which is connected to the fuel tank. There is also a return line and a high pressure output which goes to the common rail.

The pump needs the fuel to flow through it even if the injector is not opening since the pump is also cooled by the fuel. 

The VCV controls the amount of fuel that is made available to the pressurizing elements and the rest of the fuel is returned back to the tank through the return line. To be more exact, the volume flow control valve is used for demand-dependent setting of the volume flow of the high-pressure pump. At higher engine loads/speeds, the VCV is opennig more to allow more quantity of fuel to be pressurized.

The PCV regulates the pressure generated by varying the opening of the valve. The smaller the valve opening, the higher the pressure that is generated.

Cheers!!

[jamran]

so we will control both the volume and pressure using the pid controller? what is the best language to use?

[TechWiz]

As I mentioned in one of my earlier messages, you can keep a fixed opening of the VCV ~20 to 30% to simplify the control. Then you can use a PID controller for managing the PCV only.

Cheers