Date:         Tue, 7 Apr 2009 22:25:09 -0400
Reply-To:     Allan Streib <streib@CS.INDIANA.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Allan Streib <streib@CS.INDIANA.EDU>
Subject:      Re: [WetWesties] 1.9 loss of 1/3 power- Boggy Please HELP!!!
Comments: To: David Kao <dtkao0205@YAHOO.COM>
In-Reply-To:  <271992.26423.qm@web82702.mail.mud.yahoo.com> (David Kao's
              message of "Tue\, 7 Apr 2009 18\:32\:10 -0700")
Content-Type: text/plain; charset=us-ascii

David Kao <dtkao0205@YAHOO.COM> writes:

> It does have a 8088 (or Z-80) microprocessor and an EEPROM (or ROM) in
> it. It's an 8 bit microprocessor. The analog circuit and devices are
> for signal conditioning and possibly for A-D conversion before the
> processor can deal with the signals. The program in the EEPROM should
> have some intelligence or algorithms in making decisions in how much
> fuel to inject into the intake, when to shut off, when to enrich and
> when to lean the fuel, based on the input from AFM, thermo sensors,
> engine RPM, etc.

It's actually not even that sophisticated, as I've discovered.  The CPU
is I believe a motorola microcontroller (not certain about that though),
and it really does not have any "smart" logic it is just doing table
lookups based on inputs.  There are basically 16 rough indexes for
intake air volume (from the AFM) and 16 for speed, giving 256 primary
values which are then combined with input values from the coolant
temperature sensor, intake air temp, O2 sensor, voltage, and throttle
position, to provide 65,000 possible injector cycle durations.  That's
it.  A table lookup in 64K of ram.

> It also should have some unexpected fault recovery (fast recovery)
> routines that will keep it from running out of control. It is a
> computer technically.

It's a very simple, single-purpose computer.  I doubt it has any "error
recovery" logic other than some hard-coded defaults to use if it ever
encounters any "nonsensical" inputs.

Allan
--
1991 Vanagon GL