simple analog fuel injection

Bruce Plecan nacelp at bright.net
Tue Jun 23 01:58:13 GMT 1998


-----Original Message-----
From: Ron Tyler <dcmckenna at worldnet.att.net>
Subject: Re: simple analog fuel injection


  You will need to have a gain and an offset pot.
>> The gain sets the slope of the pulse-width versus MAP, and the offset
>> pot shifts the whole curve (or rather, straight line) up and down the y
axis.  You can even use the offset pot as a manual 'choke' equivalent.
>> The system won't be as good as a real modern EFI, but I have found that
>> on a small tuned 4 cylinder engine (998cc Hillman Imp) it works better
>> than the old twin 1.25 carbs ever did. (I only suggest you try this on
>> vehicles that aren't subjected to stringent emissions checks.
>>
>  Chris,
>         I'm not a hack, but I am familier with the 555. I believe I
>understand the concept, but I dont know how to build in "gain" for the
>MAP. Can you send me a schematic or mabey a brief verbal summary please?
>Also, how would you build in an "accellerator pump" with a TPS?
>Mucho Thanx
>Ron & Stephanie Tyler


%TPS change per amount of time.  Or change of voltage per amount of time.
Remember you have 70% throttle opening at 20% throttle
travel.  Then cold coolant correction.  Air temp correction.  RPM
Correction, gee gettin complex quick.  I'm not at all trying to rain
on your parade.  Within the last 6-7 months I think this very issue
accleration pump has been talked about.  Think the final thoughts were 5
tables, corrections for it.
  You can minimize these corrections IMHO by using a fuel pressure
regulator referenced to engine vac.  But, still complex, to do right.
Also, intake tract ducting can help (ie real long in lenght).
  If I had to do something along these lines I rack a bunch of 555's
together.  Base Pulse width, then temp correction, then air correction
accleration/TPS, accleration temp, accleration MAP etc etc.  add'em
up and then fire the injector(s).
Just some thoughts
Bruce     One similiar project here at CSH, HQ was a traction
               control device worked really nice then one night temp
               dropped on test drive a couple degrees, and the car
               could not be made to move, disable TCD and drove
               home.  Put device in freezer wouldn't work.  Thaw to
               34+ and it was fine.  Could not be made not temp
               sensitive.  Months of work down the drain...  Tandy
               Corp stock rose $2/share over what I spent at radio
               shack




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