[Diy_efi] Making a fake O2
Daniel R. Nicoson
A6intruder
Fri Jun 3 01:24:25 UTC 2005
I'm saying that if my engine was stock (I've got different heads, cam, MAF
and manifold now) that the stock tune would run very nicely without the 02
sensors. That's not a guess, it's very logical. The Ford EEC pops in and
out of Closed Loop very easily in its stock configuration. The fuel maps
and spark maps are very smooth running and conservative. Of course the
spark maps aren't affected by CL/OL or 02 sensors at all. The fuel maps are
very conservative, around stoich at low LOAD levels, quite rich at high
power levels. The 02 sensor affected operation is actually the exception
when considering the full range of operation. I actually pull fuel out at
high power in my modified usage.
Keep in mind that stock 02 sensors serve one purpose only, to keep the fuel
mixture as close to 14.7 AFR as possible. The MAF meters (more expensive
than MAP) take that chore one step better. The MAF meters do such a nice
job correctly metering the air that the engine is able to nail AFR as
commanded all the time, the 02 sensors merely sweeten the process.
I don't mean to be rude but I'm not sure why you feel the 02 sensors have so
much to do with engine longevity? The actual tune (tables), especially at
high power, is what is important for engine livelihood. O2 sensors only
contribute to the operation in very specific conditions. Thank Gosh the EPA
driving cycle is as limited as it is!
I have posted the fuel and spark tables for a stock 1994 Mustang GT:
BASE_SPARK_TABLE # Base Spark Table.(deg BTDC) (Load vs RPM)
35 35 35 28 28 28 28 28 28
28 28
35 35 35 32 35 40 40 40 40
40 40
35 35 35 35 35 36 38 39 40
40 40
17 20 21 26 31 34 36 37 38
40 40
14 17 19 25 30 30 30 30 30
32 32
12 14 15 19 21 22 25 27 28
30 30
10 12 12 18 19 20 23 25 26
28 28
9 10 10 11 15 18 21 23 24
26 26
9 9 9 11 13 17 19 21 22
24 25
STABILIZED_FUEL_TABLE # Stabilized open loop air/fuel ratio.
13.9537 13.9537 13.9537 13.9537 13.9537 13.9537 13.9537 13.9537
13.9537 13.9537
14.1825 14.1825 14.1825 14.1825 14.1825 14.1825 14.1825 14.1825
14.1825 14.1825
14.1825 14.1825 14.1825 14.1825 14.1825 14.1825 14.1825 14.1825
14.1825 14.1825
14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969
14.2969 14.2969
14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969
14.2969 14.2969
14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969 14.2969
14.2969 12.5812
12.3525 12.3525 12.4669 12.1237 12.1237 12.1237 12.1237 12.0094
12.1237 12.3525
12.3525 12.3525 12.4669 12.1237 12.1237 12.1237 12.1237 12.0094
12.1237 12.3525
I imagine the format will not survive the email re-format.
Units are RPM horizontally, left side low RPM, right side high RPM
Vertically, top row is low LOAD, bottom row is high LOAD.
My point is that if the 02 sensors go out of the loop for any reason, the
engine will run off these tables. Data log with a wide band shows that the
engine will consistantly hit the commanded AFR. The process is very
reliable. Not to knock carbs but Mr. Holly would LOVE to have the full
range of control that a modern EFI system provides. Think how many engines
lasted for how many years with factory carburators and no feedback from an
02 sensor?
Loosing an 02 on a stock Ford tune won't ruin your day. If the sensor has
been slowly going bad it could actually have driven the "accumulated tune"
(Ford's adaptive stategy) out of whack. Currently when I use my 02 sensors,
one bank runs more than 1 AFR point more rich than the other. I'm sure one
of my 02 sensors is going bad. Car runs great when I tell the EEC to ignore
the 02's and I have cleared the "accumulated tune".
All of the above is based on my experience with Ford EEC's. Obviously other
brands have different specific strategies. Most of them are similar in the
basic strategy. I find it hard to believe that any manufacturer would allow
a faulty 02 sensor to cause enough havoc to actually damage the engine
itself.
Take care,
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: Thursday, June 02, 2005 7:08 PM
> To: diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Making a fake O2
>
>
> Forced open loop, but on TUNED maps, not the factory provided maps without
> the benefit of learning trims from an O2??
> Or are you comparing apples to oranges again?
>
>
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Daniel R. Nicoson
> > Sent: Wednesday, June 01, 2005 10:08 PM
> > To: diy_efi at diy-efi.org
> > Subject: RE: [Diy_efi] Making a fake O2
> >
> > 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.
> > > > >>
> > > > >> _______________________________________________
> > > > >> Diy_efi mailing list
> > > > >> Diy_efi at diy-efi.org
> > > > >> http://lists.diy-efi.org/mailman/listinfo/diy_efi
> > > > >>
> > > > >
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