Additional Injector Controller

[Ian Habicher]

>Hi,
>     Check out national semicondutor's LM1949 chip.  Basically,
>you give it a duty cycle signal (5 volt amplitude) and it controls
>the injector.

That's the easy part, what I want to know is how to generate the duty cycle 
signal.

  To do this, I think, the best way would be to use
>some sort of PIC or microcontroller to read RPM, boost, and
>some potentiometers to set up parameters (when to come on,
>and how much to increase etc..).

Hehehe sounds easy unless you have no clue how to do it.  To me a simple 
analog controller would be enough, doesn't have to be fancy or 
'programmable', I've heard that it can be done with a 555 or other chip set 
up to provide a variable duty cycle based on boost sensor (MAP) voltage.  
Reading and factoring in RPM isn't important, the injector just fires once 
every half-revolution, based on the stock injector signal, and the pulse 
width is determined by MAP sensor.

That way it'll work kind of like a rising rate fuel pressure regulator, but 
will be more controllable, less crude and will not be so hard on the rest of 
the system.

  Probably best to have the
>injector fire based on the RPM signal - since you might want to fire
>the injector when the intake valves are open.

Mazda RX-7, Wankel rotary engine--no valves :)  Anyway I figure I'd use a 
signal from another injector to fire the injector, and base the duty cycle 
on the signal from the MAP sensor.

I want the unit to be relatively simple and I don't want to get involved in 
wiring any microprocessors.  Even if I knew how, programming them alone 
would be a bugger.  That's why I want to use a simple analog controller to 
avoid getting in over my head.  It just has to work, not pass emissions 
tests or get maximum fuel economy :)

I need to talk to someone that's done it.

Ian
1987 RX-7 Turbo II
_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org