555 EFI

[Bruce Plecan]

-----Original Message-----
From: thergen at svn.net <thergen at svn.net>
To: DIY_EFI <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, January 15, 1999 9:22 PM
Subject: Re: 555 EFI


>Bruce,
>
>Are you thinking of a string of one-shots and using a varying
>voltage on
>the control pins to vary the output pulse width? 

Exactly

 If you're already going
>to be using op-amps to scale the output of the sensors, you could probably
>add/subtract the outputs of multiple op-amps together through resistors
>and run that into the control voltage pin of a smaller number of 555s.

Well this is for kinda 332 for Dummies.  Just a see you can do it
operation.  Skill level requarded, knowing which end of soldering iron
gets hot.
>
>Since there's not 'learning' ability, the circuit might be very
>engine/sensor specific.  Trying to apply it to an engine with a slightly
>different offset in the TPS or MAP sensors compared to the original
>engine/sensor combo it was tuned to might not work very well (without
>retuning that is). The same could probably be said for other fi
>controllers without feedback. 

In this case, that is just fine, since it's meant to be a grow your own.
>
>Use capacitors with good temperature coefficients.  X7R caps would be
>preferable to Z5U caps.

Geez I almost made it all day with just one 3x5 card of notes.
Dang, grin 
Thanks
Bruce
>
>Good Luck! (meant in an encouraging way)
>Tom
>
>On Fri, 15 Jan 1999, Bruce Plecan wrote:
>
>> I've been thinking about a simple EFI using a string of 555s.
>> Just like the "Normal" math would be, ie first 555, base pulse,
>> second Coolant temp correction, third MAP, and so on for like
>> 6+ 555 all in series.  Trouble is this gets me, an addition of
>> correction factors, instead of multipling them, is this a major
>> problem?.  I realize this ain't gonna be as good as a oem,
>> ecm, but would like to get fairly close.
>>   I'm looking to keep this as much as an entry level thing, meaning
>> nothing but 555s, op-amps, and a final drive.  
>>   On a related note, does anyone know if the gm ecms use a 
>> standard "pinout" for the resistors in the netres?.  Is the netres
>> only for full limp home mode, meaning it goes to fixed timing?.
>> Any thoughts appreciated.
>> Cheers
>> Bruce  
>> 
>