[Diy_efi] Making a fake O2

Wed Jun 1 22:17:38 UTC 2005

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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> >>
> >
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