[Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?

[Marcello A. Belloli]

Steve,
     With your setup how accurate can you get?  All the scanners I've used
in the past to look at cars gave readings in the x.xx ms range.  At
idle I've seen cars that started running rich, or lean based on the
o2 reading and seen no change in injector pulse width on the scanner.
 I see the computers short term / long term trim values change, and
yet the IPW reading never changed?  I am guessing I need another
order of accuracy like x.xxx ms to see these changes at idle.  Do you
think I could get that out of your circuit.  And how does it handle a
Peak Hold type injector?  This is the most important piece of data
I'm grabbing to try and do what I want to do in the end.  I'm going
to go grab the details to your project right now, and check it out.

Thanks,

Marcello
>
>> -----Original Message-----
>> From: diy_efi-bounces at diy-efi.org
>> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Marcello A. Belloli
>> Sent: Saturday, May 21, 2005 10:31 PM
>> To: diy_efi at diy-efi.org
>> Subject: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?
>>
>> Hello Everyone,
>>      I'm still working on a datalogger project.  Been doing a
>> lot of the
>> software while I've been on vacation in Thailand. I'm still on
>> vacation, but can't keep my mind off of this project.  I'm using a
>> PIC18F452 as the Micro behind my datalogger.  I've got just about
>> everything working.  The one place I'm having problem is the
>> understanding of how to read pulse width of a fuel injector.
>>      Is there a way of looking at all types of injectors,
>> that will allow
>> for an accurate account of timing?  I've been looking at two type of
>
> For the pulse width meter I built (see the diy-efi.org projects page) I
> used an opto-isolator to both insulate the measuring circuit from the
> injector circuit, and make it able to hook up across the injector no
> matter which side of the injector is driven, or what the voltage
> waveform looks like.  This particular opto-isolator has 2 diodes in
> parallel, so the polarity of how it's connected doesn't matter -- if the
> injector fires, then one of the diodes will light up and complete the
> circuit.
>
>> injector firing.  Low resistance injectors, which use a driver that
>> duty cycles the injectors after the main firing to keep the current
>> within limits.  And Higher resistance ones where the resistance alone
>> keeps the current down.  Now how do you look at firing time of an
>> injector when the driver starts to duty cycle it after 1.2ms?
>
> I haven't see all driver circuits out there but I think most of them
> don't duty cycle the injector, they just reduce the voltage applied to
> the injector.
>
> --steve
>
>
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