Date: Tue, 13 Feb 2007 14:39:11 -0800
Reply-To: jon <jon@KENNEKE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: jon <jon@KENNEKE.COM>
Subject: Re: ECU reset, O2 voltage stability
In-Reply-To: <bfb5ccc40702131411i499897p3ffa87954ba852c3@mail.gmail.com>
Content-Type: TEXT/PLAIN; charset=US-ASCII
What I'd like to know is *what* settings the Digifant retains between
cycles. Figuring that out would require disassembly of the EPROM, and
lots of head scratching. The Bosch information I have doesn't mention
any good technical details like that.
I used to own a POS Neon. After disconnecting and reconnecting the
battery, it would run like crap until the ECU "learned" the correct
settings. I wonder if Digifant is like this after a reset, and before
learning.
I do know the "map" in the Digifant has 65536 data points. They use a
table ookup system, since the 6803 does not have the horsepower to compute
these values on the fly. It uses 16 bit values for "load" and RPM. I think
the load value is combination of AFM, temp, and O2 data. RPM, is, well,
RPM (hall sensor).
If I remember correctly, the Megaquirt actually calculates values instead
of using a table look up system. Thus, you have finer control. I would
imagine all modern FI systems would not use a table lookup.
Jon
On Tue, 13 Feb 2007, Old Volks Home wrote:
> Based on my experience, the Digijet ECU appears to re-set itself when turned
> off and then on (it's possible some settings are retained, but not much, if
> at all). On a cross country trip last year, I had ECU issues half way back
> to So Cal. As I was driving, I would momentarily turn the key off, then
> back on to re-set the ECU and it would run fine for about 2 to 3 minutes,
> then act up (surging, hesitation at freeway speeds, etc.,). After putting
> up with this nonsense for around 20 miles, I finally stopped outside
> Amarillo, TX and swapped ECUs (always a spare in the bed/seatbox) and voila,
> no more ECU issues. When the Digijet vehicle first starts, it runs in "Open
> Loop", disregarding the O2 signal. After about 2 to 3 minutes, it reverts
> to "Closed Loop", thus depending on the signal the O2 sensor is giving it.
> However (and as jon states), the Digifant retains some settings when turned
> off.
>
> The O2 signal is not constant and does flucuate/swing between 0 to .5 volts
> when operating.
> --
> Jim Thompson
> 84 GL 1.9 "Gloria"
> 84 Westfalia 2.1 "Ole Putt"
> 73 K Ghia Coupe "Denise"
> 72 411 Station Wagon "Pug"
> oldvolkshome@gmail.com
> http://www.oldvolkshome.com
> ***********************************
> On 2/13/07, Mike Frost <wasserleaker@gmail.com> wrote:
> >
> > Greetings all,
> >
> > It's time for smog testing on my 86 2.1L and I am failing for HC and CO.
> > So
> > I am looking closely at the O2 sensor which was very recently replaced.
> >
> > My first question is about the Digifant I ECU. I have read many differing
> > statements about resetting or clearing the memory of the ECU. Does the ECU
> > have any kind of static RAM (memory that does not lose its contents on
> > power-down)? Does the computer reset completely when the ignition is
> > turned
> > off? Some things I have read talk about entering 'service mode' by
> > disconnecting the temp II sensor and then 'blip' the throttle 3 times up
> > to
> > 3000RPM (or 4 times up to 2500). I can believe that there is a service
> > mode,
> > but I'm having trouble believing that the ECU can 'remember' the state of
> > the ignition system after the engine is shut down.
> >
> > Second question involves the voltage from the O2 sensor. Under idle
> > conditions (no change in RPM) I am seeing the voltage swing down to zero
> > and
> > then back up again to some value above 0.5V when the O2 is connected to
> > the
> > ECU. Is this normal? I'm guessing that I should see a fairly stable
> > voltage
> > unless the speed of the engine changes.
> >
> > Thanks in advance,
> >
> > Mike
> > wasserleaker@gmail.com
>
| 
