Water Injection controller, Any electronics guys out there.
11-07-2014, 05:56 PM
#26
No. That would work in theory, and it's an ok idea, but in practice it would never work well. There would still be a large amount of noise being input into the maf signal since cars are naturally very noisy, and dirty PWM signals are also quite noisy.
It would have to be decoupled using an opamp or something similar to avoid mutilating the MAF signal to the ECU.
It would have to be decoupled using an opamp or something similar to avoid mutilating the MAF signal to the ECU.
First it does already work like this going to the ECU, so it not only works in theory, it works in the real world. And similar measurements works all around in the real world. A MAF sensor is relatively low impedance(resistance), therefore noise will normally not be an big issue.
And of course, you need to buffer, but isn't that whats happening at a voltage- meter that I mention earlier?
Not trying to be cocky here, but since electronics design is my profession, I'd like to get rid of misunderstandings, and be clear in my statement. But if for a reason I'm wrong(definitively happens!), hopefully I should be knowledgeable enough to understand an explanation.
11-07-2014, 06:42 PM
#27
Hmmm...
Isnt MAF voltage simply read by a ADC at ECU input? If so I do not see why jitter should come into the picture...? To my knowledge, jitter does not appear on an analog signal itself, only in the process of making it digital numbers, or after. Jitter - Wikipedia, the free encyclopedia
And there is always an input filter at less than half the sample frequency, so any HF noise should not make a difference, neither find its way through PCB etc.
Or are your concern that the conductors with PWM output to motor will act as an transmitter antenna, maybe? Keep them short. Alternatively an output filter. If they can make it work close to coil and spark plugs, motor control is a walk in the park compared.
Isnt MAF voltage simply read by a ADC at ECU input? If so I do not see why jitter should come into the picture...? To my knowledge, jitter does not appear on an analog signal itself, only in the process of making it digital numbers, or after. Jitter - Wikipedia, the free encyclopedia
And there is always an input filter at less than half the sample frequency, so any HF noise should not make a difference, neither find its way through PCB etc.
Or are your concern that the conductors with PWM output to motor will act as an transmitter antenna, maybe? Keep them short. Alternatively an output filter. If they can make it work close to coil and spark plugs, motor control is a walk in the park compared.
Not trying to be cocky here, but since electronics design is my profession, I'd like to get rid of misunderstandings, and be clear in my statement. But if for a reason I'm wrong(definitively happens!), hopefully I should be knowledgeable enough to understand an explanation.
11-07-2014, 07:26 PM
#28
My reasoning: Normally you will connect a buffer of several Mohm (unity gain opamp) reading MAF sensor voltage. Anything else would be a mistake. Then, MAF sensor is not too many kilo- ohm, say 10kohm. 100M/10k gives me an error of 0.1mV. My MAF table is limited to 10mV steps, so I do not see how this paralleling will influence in to a degree where it has an influence that matters on what voltage ECU read? I would also believe that the extra jitter that occurs in ADC due to the 0.1mV decrease, is negligible.
Anything in this reasoning you would say is wrong?
11-07-2014, 07:34 PM
#29
listen carefully.............................. "I shall zay zis only vonce " ....
A complicated control system for doing this is not only not necessary but not good practice . All you need is a hobbs switch and an rpm signal (VFAD wire does the trick) .
Hobbs switch turns pump on vfad signal opens secondary solenoid for your extra nozzle .
Anything more precise or sophisticated than this is just ..................... silly .
A complicated control system for doing this is not only not necessary but not good practice . All you need is a hobbs switch and an rpm signal (VFAD wire does the trick) .
Hobbs switch turns pump on vfad signal opens secondary solenoid for your extra nozzle .
Anything more precise or sophisticated than this is just ..................... silly .
11-13-2014, 04:03 PM
#31
Or use an arduino with a fuel injector. It will take the maf signal straight with no additional circuitry, and you can use PWM to drive the fuel injector through a logic level mosfet.
I took the MAF voltage, converted it to a number 0-255 then used that number to look up a value from an array. Then write that to a PWM pin and bing bang boom. If anyone wants I can share that section of my code, but it's pretty simple.
It's a bit complicated, but all the hardware is reliable and it give excellent control.
I took the MAF voltage, converted it to a number 0-255 then used that number to look up a value from an array. Then write that to a PWM pin and bing bang boom. If anyone wants I can share that section of my code, but it's pretty simple.
It's a bit complicated, but all the hardware is reliable and it give excellent control.
11-13-2014, 04:22 PM
#32
Here, it should be pretty self explanatory. This is from my boost/WI controller, but it's just a snippet of the whole code and hasn't been tested independently.
I also have a spreadsheet to make editing the arrays easier, i'll find it when I get home from work tomorrow.
It takes a 0-5volt maf and a 0-5 volt map and generates a PWM signal for a boost control solenoid and a water injector.
I also have a spreadsheet to make editing the arrays easier, i'll find it when I get home from work tomorrow.
It takes a 0-5volt maf and a 0-5 volt map and generates a PWM signal for a boost control solenoid and a water injector.
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