[Diy_efi] Low tech fuel injection system

[Daniel Nicoson]

My suggestion would be to use a LM556 chip (dual timer).  Pull down the data
sheet from Digi-Key.  You can use one for the timer's to create a variable
(or fixed) frequency pulse signal, the second timer can be made to vary the
pulse width.  You could vary the pulse width just by throttle position
(LOAD) and frequency could vary by the spark primary circuit frequency.  Use
the output of this LM556 circuit to drive one or more Darlington transistors
to turn on-off any number/style of fuel injectors.

Your parts cost of the above approaches $5.00 from Digi-Key or Radio Shack.
You will have to spend some time learning how to make that paragraph work
but it isn't as hard as it sounds.

Functionality of this system would be crude at best, but with a few
additional opamps, a $4.00 map sensor and possibly some other items you
might make a pretty functional analog FI system.

Keep us appraised, sounds like fun!

Dan Nicoson


-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of James Seabolt
Sent: Thursday, January 13, 2005 4:21 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] Low tech fuel injection system


It's been awhile since I've frequented the list. Maybe 7 years but I'm back
again. I'm glad to see the list is still active.

Last episode I was turbocharging a Bosch L-jetronic Fiat Spider which I
still have to this day. I had a lean fuel mixture under boost and was
trying to figure out what was going on. Well I figured it out although my
approach was very low tech. After wiring in a pressure switch to the oxygen
sensor which breaks the signal to the ECU under boost fixed the problem.
The car has been running great with the turbo for the past seven years.
This is actually the second system I've built for this car.

Here's the whole story if your interested.

http://users.chartertn.net/jseabolt/80spider.htm

Now I'm chasing a new project. I've turbocharged a 1987 Yugo and have been
trying to make the carburetor accept the turbo and so far I haven't been
all that successful. I won't start asking questions about carburetors since
this mailing list is for DIY fuel injection. So that's why I'm here.

I'm curious if it's possible to build a low tech fuel injection system
without using an ECU. Sort of like a cross between the old Bosch CIS and GM
throttle body systems.

Instead of having four pulsed injectors use one or two continuous injectors
and have the amount of fuel controlled by fuel pressure based on engine
vacuum instead of pulses.

I'd like install a throttle body from a Saab 900. But the 8 valve engines
that uses the throttle position "switch". Same part number as the one used
on my Fiat Spider. The 16 valve Saabs used a throttle positioning "sensor".

I'm wondering if it's possible to build a functioning fuel injection system
by controlling the injectors in stages which would be mounted below the
throttle body with the throttle positioning switch. Basically like a
carburetor but without a fuel bowl. Such as have one control the idle, one
for midrange and one for WOT and Boost. Who knows one single injector may
be all I need.

I haven't determine a proper injector. Whether it be a cold start valve
(easier to mount) and injector from an L-jet system (harder to mount) or an
injector from a GM throttle body. Like an old Chevy Cavalier.

I thought I could adjust the initial fuel flow using a needle valve.

I'd also like to know how the injector on a GM throttle body works. Is it
on or off like a pulsed system or is it continuous and is controlled by
fuel pressure or some other means.






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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