L-jetronic mods

[James Montebello]

Around '80 - '81, the Fiat Spider was sold with a turbo in this
country.  It was, as I recall, an option added by the US importer,
not a factory item.  The same L-Jet was used, albeit recalibrated.
I'd try and scare up some data on this conversion.  I'd guess that
the conversion parts couldn't have been all that expensive or
exotic, given the origin, nor could I imagine extensive 
modifications were done to the L-Jet to get it to work.

james montebello

> -----Original Message-----
> From: owner-diy_efi at esl.eng.ohio-state.edu
> [mailto:owner-diy_efi at esl.eng.ohio-state.edu]On Behalf Of 
> James Seabolt
> Sent: Sunday, May 09, 1999 10:24 PM
> To: diy_efi at efi332.eng.ohio-state.edu
> Subject: L-jetronic mods
> 
> 
> Hello. I'm new to the list (sort of), so forgive me this 
> subject has been
> covered before.
> 
> I installed a custom turbo system on my 1980 Fiat Spider. Building the
> system was a task itself but getting the engine to resist 
> detontation has
> been an uphill battle. If detonation is as destructive as 
> what everybody
> describes, then my engine would have been toast months ago because my
> engine has shown no ill effects. So far anyway.
> 
> I had been running a few band-aid solutions such as water/alcohol
> injection, timing retard, etc. but these are getting old. My 
> real problem
> is fuel enrichment.
> 
> Here's some specs:
> 
> 2 liter/twin cam/hemi design
> C/R: 8.1:1 (factory), current unknown, head was resurfaced 
> during the last
> rebuild.
> Bosch L-jetronic fuel injection system w/lambda sensor
> Turbo: Rayjay 301
> Boost: 7 pounds
> gasoline : 93 octane (of course)
> 
> Fuel enrichement device, rising rate fuel pressure regulator 
> and a 2nd cold
> start valve mounted upstream triggered at around 2 pounds.
> 
> With these specifications, this engine should handle 7 pounds 
> of boost with
> no problems. That is with proper fuel enrichment, but I can't 
> figure out
> how to get more fuel into the engine. 
> 
> The most frustrating thing is, the potentional is there, I 
> just don't know
> how to unlock it.
> 
> The other day, I was able to trick the computer into dumping 
> more fuel into
> the motor than it could handle, to the point the car was 
> smothering and
> belching black smoke out out the exhaust at 7 pounds. The 
> engine seemed to
> handle the extra amount of fuel until the contacts in the 
> throttle position
> switch closed and dumped too much fuel.
> 
> I did this by installing a set of boost switches which adds resistance
> (about 2000 ohms) between the computer and coolant 
> temperature sensor. This
> doesn't work on my car because I've got a rising rate fuel 
> pressure regulator.
> 
> My latest experiment was to splice a Hobbs pressure switch between the
> oxygen sensor and computer. As soon as I hit boost (.1 
> pounds) the control
> loop is disrupted.
> 
> Today the temperature was near 80F and the car seemed to do OK.
> 
> Can someone tell me this:
> 
> I was under the impression that when the engine is under wide open
> throttle, the throttle position switch breaks the control 
> loop. Is this
> correct?
> 
> Or no matter what, the engine is still in the control loop?
> 
> My theory is that any attempts to get more fuel into the 
> engine are being
> overiden by the oxygen sensor even under wide open throttle, but by
> breaking the control loop, now I can get more fuel into the engine.
> 
> Seems like my latest attempt has worked by I would still be more
> comfortable knowing that I am getting the most fuel I can get 
> into my motor
> without causing the car to choke.
> 
> Here's a rundown of my current setup:
> 
> 1) rising rate fuel pressure regulator
> 2) 2nd cold start valve mounted upstream before the throttle 
> body triggered
> at around 2 pounds.
> 3) Oxygen sensor to computer broken at .1 pounds
> 
> I would like to do away with the 2nd cold start valve and use 
> the injectors
> as my sole source for fuel because I know they have the 
> potential when the
> fuel pressure is stepped up.
> 
> Also I want to point out that during the experiment where I 
> got too much
> fuel into the engine was done with the 2nd cold start valve 
> disconnected.
> 
> What could I do to increase the pulse rate of the injectors? 
> My attempt to
> create my own boost switch didn't work. I tried rigging up 
> another pressure
> switch with several rated resistors (600-1000 ohms) in 
> parallel but the CPU
> didn't like this.
> 
> Also is there anything to my latest experiment by breaking the circuit
> between the oxygen sensor and computer under boost?
> 
> If you guys need anymore details, just email me.
> 
> This fuel injection system has been around for 25 years so I 
> am sure there
> is someone on here that knows how to trick this system.
> 
> Should I just have the injectors remapped to flow more fuel 
> and run a lower
> fuel pressure so the engine won't run rich at idle and cruise?
> 
> Great Scott! I'm running out of options here. Someone help me!
> 
> Thanks.
> 
> 
> ----------------------------------------------------------
> 
> James Seabolt -----> mailto:jseabolt at intermediatn.net
> Webpage: http://users.intermediatn.net/jseabolt/
> ICQ # : 7344463
> 
> United States
> 
> 1980 FIAT 2000 TURBO Spider injected (John Deere aspirated)
> 1981 FIAT 2000 Spider (Rest in Pieces)
> 1981 FIAT X 1/9 (Injected)
> 1994 JEEP Wrangler (2.5l )
> 1976 Chevrolet Pickup (454 Big block/7.3 liter) 
>      
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> 
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