[Diy_efi] 555 timers

Tue Jan 18 15:40:17 GMT 2005

The circuit we used to run a 2.3L OHC Ford engine for Oil Qualifications on
the dyno used a 4538 Dual Monostable multivibrator.  The RPM signal would
clock a 4013 Flip flop and the 4538 would change the pulse width to the
injectors (A/F ratio). If you use a TPS in place of the RX pot on pin 2 or
pin 14 of the 4538 the pulse width will vary on pin 6 or 10. I'll see if I
can find the circuit for you.   

-----Original Message-----
From: James Seabolt [mailto:turbofiat at hotpop.com]
Sent: Tuesday, January 18, 2005 7:01 AM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] 555 timers

You guys got me thinking over the weekend and I think I'm going to give 
this 555 timer a shot.
I've had some experience with this chip. I built a timer that would turn an 
LED on and off and when I was looking through an old shoe box, found the 
circuit still hooked up to the breadboard. That was almost 15 years ago!

It's been so long since my Tech School days so I'm hoping someone will 
refresh my memory. If I can put anything to use from my Digital Circuits 
class, I'm hoping this will be it. Since I was unable to use my computer 
degree. I ended up working at a chemical plant instead after school.

What I want to do is take the tach signal from the - side of the coil which 
will be the trigger, feed that into the 555 chip which will pulse the 
injector. And use a potentiometer to adjust the pulse rate.

I want to start out using a Bosch cold start valve since it would be easier 
to mount. Perhaps use the throttle position switch to trigger a second 
injector under wide open throttle and boost.

I downloaded some pages on the 555 timer but can't figure out what size 
capacitors I need. And what range the potentiometer needs to be.

The timer chip I have is stamped NE555N. Is this the chip that will 
tolerate 5 to 18 volts? Or do I need a different chip?

Also I'm a bit confused on the reset (pin #4). One schematic shows it tied 
to pin #8 (Vcc). Another one shows something else.

If someone could draw me up a schematic with what components I need that 
would be really cool!

I'm off for the next three days (I work 12 hour shifts) and would like to 
spend time on my Yugo since it's too cold to do anything else this time of 
year.

Is it possible to build a working fuel injection system by simply 
controlling the injector using just a tach signal? I know it probably 
wouldn't be able to adapt any better to temperature and altitude changes 
than a carburetor but I'm thinking it just might work.

I'm having my doubts whether I am going to successful at getting my Yugo to 
accept blowing through a carburetor so I'm looking toward fuel injection.

James Seabolt
Tennessee, United States
Homepage --->>> http://users.chartertn.net/jseabolt/

2003 Subaru Baja
1987 Yugo GV
1980 FIAT 2000 "TURBO" Spider
1968 Ford Fairlane 500 (Not a Ford Galaxie!!)

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