[Diy_efi] Making a fake O2

Thu Jun 2 02:07:39 UTC 2005

But even that's a rather sweeping statement.  You must have some particular
computer's in mind with a specific experience?

I run my 1994 Mustang computer Open Loop whenever I want, no problem.  I do
have the luxury of changing any maps but with stock parts, that computer
would run just fine if only forced open loop, all other settings left alone.

Dan Nicoson

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of David Cooley
> Sent: Wednesday, June 01, 2005 6:18 PM
> To: diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Making a fake O2
>
>
> I never said that ANY open loop maps would destroy an engine...
> My comment was that a computer DESIGNED FOR CLOSED LOOP WITH AN
> O2 SENSOR if
> run in open loop only with the O2 disabled will cause damage.
> Geez people, learn to READ
>
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Marcello A. Belloli
> > Sent: Tuesday, May 31, 2005 11:28 PM
> > To: diy_efi at diy-efi.org
> > Subject: RE: [Diy_efi] Making a fake O2
> >
> > Dan,
> >     Yes, that is exactly where I am.  The stock computers
> > mapping is in no way set up for the engine that is now
> > connected to it.  Everything you said is right on.  We have a
> > mismatch.  The stock ecm and its mapping isn't going to work.
> >      I have kept reading hoping the bickering would stop.  I
> > agree with both sides of the debate.  GM computers are
> > terrible when their O2s fail.  And run so rich I'm couldn't
> > understand why anyone would drive it.  Now the ECM I'm
> > running in my Landcruiser is a GM with TBI setup out of 1989
> > C series 5.7l GM truck.  And it will actually use data
> > gathered during closed loop to effect WOT.  And it can do damage.
> > Now, the Honda/Acura setup we're working on right now will
> > run so rich with the o2 disconnected it will barely idle.
> > Now these are two cars.  I have also seen setups where you
> > could remove half the sensors on the car, and the computer
> > will keep it running like nothing ever changed.  And it won't
> > set a light.  Dodge Caravan OBDII.  And the emissions will be
> > perfect.  I believe it is smart enough to use other data to
> > make a good guess (kinda like
> > Speed-density) at what the sensor should be reading.  You
> > would be hard pressed to get one of these engines to hurt
> > itself.  And if there was misfire that could cause damage it
> > will kill cylinders to wake the driver up (Thats if they
> > don't see the flashing MIL lamp) and protect the engine.
> >      There are many computers out there, and many different
> > approaches used.  Now I have never personally seen a motor go
> > boom because of a bad o2 sensor, but I have seen a lot of
> > damage done.  The o2 goes bad.  The cat plugs up, the exhuast
> > is restricted, and the temps at the engine exhuast go
> > steadily upward.  Exhuast valves damaged, seals damaged,
> > exhuast manifolds damaged, cylinder heads damaged.  etc,..
> > I believe that it all depends on the computer you are using.
> > There are computers that go both ways....  I also don't see
> > the problem with an open loop car.  The Carburetor analogy is
> > a good one.  I've run vehicles 100,000 of miles with a
> > carburetor without any problem.
> > And I can think of one setup or two aftermarket setups that don't use
> > o2 sensors unless you add them.  Both Eldebrock, and Holley
> > have aftermarket EFI setups that don't intially use an O2.  I
> > think Accel has one two.  And these things have been used in
> > many cars, and trucks without any problems.
> >     And this all started with a simple question about faking
> > out the o2...
> >
> > Marcello
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > > I've been watching this thread over the last few days.  People are
> > > debating the safety of the stock maps with 02 faulty but no one has
> > > mentioned that the engine in question is no longer stock.  Marcello
> > > mentioned that his friend "only made a few changes"
> > (eye-roll) meaning
> > > to me that probably the friend put together a parts combination far
> > > from stock.  Most likely higher compression and a more
> > aggressive cam.
> > > Those two possibilities alone probably would make the stock maps
> > > irrelevant or at least "not safe".
> > > Considering how much $$ most people typically throw at a motor when
> > > they "make a few changes" I would proceed slowly and work
> > to develop new maps.
> > > I
> > > think Marcello realizes this and hopes his friend will keep
> > his foot
> > > out of it until he gets home to work at the problem logically.
> > >
> > > My experience is with Ford EEC's.  I know when I "made a
> > few changes"
> > > the EEC was totally confused because my parts changes had taken the
> > > range of operation well beyond the stock limits of compensation.
> > >
> > > Good discussion.
> > >
> > > Dan Nicoson
> > >
> > >
> > >> -----Original Message-----
> > >> From: diy_efi-bounces at diy-efi.org
> > >> [mailto:diy_efi-bounces at diy-efi.org]On
> > >> Behalf Of Steve Ravet
> > >> Sent: Tuesday, May 31, 2005 12:36 PM
> > >> To: diy_efi at diy-efi.org
> > >> Subject: RE: [Diy_efi] Making a fake O2
> > >>
> > >>
> > >> I was going to refer to the EFI testbench that Bruce built.  My
> > >> recollection is that he used a 555 type circuit to generate an O2
> > >> signal.  There's not really any mention of it in the
> > article, but I'm
> > >> sure the details are in the archive.  I think for some
> > computers this
> > >> worked OK, for others that expected to see more
> > correlation between
> > >> pulsewidth and O2, it didn't.  Anyway, go to the gmecm page,
> > >> projects, then ECM testbench for the ascii version of the
> > article.
> > >> The MS word version is probably gone for good.
> > >>
> > >> --steve
> > >>
> > >>
> > >> ________________________________
> > >>
> > >> 	From: diy_efi-bounces at diy-efi.org
> > >> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Bret Levandowski
> > >> 	Sent: Sunday, May 29, 2005 11:16 AM
> > >> 	To: diy_efi at diy-efi.org
> > >> 	Subject: Re: [Diy_efi] Making a fake O2
> > >>
> > >>
> > >> 	Actually, it is not 'impossible to fool an ECU with a
> > constant or
> > >> switching voltage source'. There are two companies I know
> > of (in the
> > >> states) that have developed a plug-in replacement for the
> > O2 sensor
> > >> on numerous vehicles (mostly OBD II) that generates a
> > 'proper' signal.
> > >> These are used in instances where inj size was increased
> > or a turbo
> > >> or screw-charger was installed. Some also did require a
> > flash of the ecu.
> > >>
> > >> _______________________________________________
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> > >> Diy_efi at diy-efi.org
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> > >>
> > >
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