This response is from Darrell Boehler, long-time Listmember and originator of the Digitool ecu readout.

      The digifant models go into closed loop much sooner than the 
others which are mostly digijet. The digifant has a heated o2 sensor. 
 So lets talk about digifant  models.  
       The o2 unit is hot and ready to function  before  the engine is heated
and ready  for a lean hot running mixture,  especially when the engine is 
below about 50 degrees.  The temp 2 sensor/ engine coolant temp needs
 to get an output below about 2 volts before the ecu goes into closed loop. 
You probably know the actual voltage better than I.  The engine would do
 a lot of stumbling if you went into closed loop much sooner. I am sure 
if you hit the interstate holding a steady 3k rpm you could go into 
closed loop sooner without adverse stumbling. 
      Digijet models would save fuel with a heated sensor. Especially when 
starting off with a warm engine. The warm engine situation I am referring is 
when you stop for less than 30 minutes like for gas or for groceries. 
  It takes a non heated o2 sensor a long time to get hot enough to function
compared to a heated sensor. 
       Keep in mind on all ecus the mixture leans out using the  temp 2 sensor 
as the engine  warms up and before it  goes into closed loop. This mixture 
should not be excessively rich if the  afm is properly  adjusted. I am not
 trying to be negative about Geza's idea and I am positive there are situations 
where forcing closed loop sooner would save fuel. Like hitting the interstate
early in the warm up cycle. 
     It is a cool 54 degrees down here in southern Illinois this morning. It 
feels  very good  to be cool . 

Darrell
   

.  
                     

Budd Premack wrote: 
Darrell,

This was on the Vanagon List today.  What do you think?

Budd

----- Original Message -----
From: "Geza Polony" <gezapolony@SBCGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, September 06, 2006 7:49 PM
Subject: O2 Sensor Idea (long)

  
OK, so here's the problem. In our vans and probably in other'80s cars as
well, the ECU kicks into closed loop mode on the late side, as the O2
sensors are slow to get to operating temp. That's why on later models, car
companies started incorporating O2 sensor heaters.

What this does is give excellent (rich) running when cold, probably what
    
the
  
engineers were looking for when gas was cheap. But you get worse gas
    
mileage
  
this way. Probably a lot worse, depending on how much around-town driving
you do.

So here's what I'm thinking. Rather than install a heated 02 sensor to
correct  the problem, why not just supply voltage to the ECU in the
    
correct
  
amount to trick it into going into closed-loop mode? This could be done
    
with
  
a transformer, a toggle switch, and a few long pieces of wire.

Start the van in open loop, drive for a few minutes, and instead of
    
waiting
  
for the ECU to decide it's time, toggle it into closed-loop as soon as it
runs smoothly.

I say this because, having installed one of Ken Lewis' monitoring devices
for the O2 sensors, it's painfully obvious that I'm driving open-loop much
of the time, and thereby wasting gas.

Anybody done this? Heard of it being done? Any reasons it wouldn't work?