Author Topic: Injectors pwm signal  (Read 361 times)

Offline Ainis

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Injectors pwm signal
« on: July 05, 2017, 10:43:51 pm »
Hello all,

I have a question: I want to use vems with DBW and low z injectors. As far as i understand, DBW and low z uses same PWM signal, so only one of them can be used (DBW or low z). Looking at the schematic, it seems that PWM signal pulls PREINJ signal via resistor to vcc or gnd, which enables injector pwm'ing. As far as I understand, in such case, PREINJ signal from atmega should have 3 states:
High, which would be used to open injector with no pwm
Floating (?) which would be used for PWM
Low, which would pull pwm signal to the gnd and mosfet would close.

Question is:
if I made some auxilary generator to generate PWM signal for low z, would it work? For this, I would need to set "Injector PWM peak time" to some sensible value (not 25,5, which dissables it). Injector PWM DC could stay 100%, which dissables it. Would such thing work in a software? Or these setings would interfere with DBW pwm? Im not sure what "Injector PWM peak time" seting do. Does it has some influence to PWM timer, or it is just the time constant to change in between 3 output states?

here is vems schematic:
http://www.vems.hu/files/genboardv3/v3.8/genboardv3.8_sch.pdf
and some info about low z pwm:
http://www.vems.hu/wiki/index.php?page=GenBoard%2FVerThree%2FLowZInjectors

Thank you.

Offline Sprocket

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Re: Injectors pwm signal
« Reply #1 on: July 07, 2017, 12:30:37 am »
What about another option?................. Peak and hold driver board?

Offline Ainis

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Re: Injectors pwm signal
« Reply #2 on: July 07, 2017, 12:40:59 am »
Can be. I planed to make one for 8channels with LM1949 and mount into the vems case, but it takes lots of space and adds up complexity.

What about using resistors? What might be the drawbacks? Injectors are Delphi 1000cc low z, engine V8 5.0 + T on E85.

Offline Sprocket

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Re: Injectors pwm signal
« Reply #3 on: July 07, 2017, 03:02:45 am »
Resistors work ok. OEM's used resistors from time to time, so you can find a resistor pack from an OEM application, but don't ask me where to find them  ::) They slow injector response, simply because they reduce the current.

Offline mr_g

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Re: Injectors pwm signal
« Reply #4 on: August 05, 2017, 08:58:52 pm »
What about oc1a and oc1b outputs? Those are pwm outputs. Can they be used for dbw?

Offline Kamuto

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Re: Injectors pwm signal
« Reply #5 on: August 07, 2017, 01:54:44 am »
What about oc1a and oc1b outputs? Those are pwm outputs. Can they be used for dbw?
I believe they are used for something allready
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