[Diy_efi] Low tech fuel injection system

[James Seabolt]

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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