[Diy_efi] Making a fake O2

[Marcello A. Belloli]

Hello Everyone,
     I'm having a great time reading these replies.  I can't wait to get
back to the states and work on this project.  I have seen GM ecus
where the blm, and Int were basically forced not to work.  And I've
actually used that for base-line tuning of an engine.  You set the
min/man to 128, and no correction can be made.  The o2 system
(feedback) is basically negated.  I seen this done on many off-road
vehicles using GM computers.  It works really well.  No o2 to worry
about.  And yes, there were no CATS on these vehicles.
     Now, the ecu in the car I'm working on right now is a P28 OBDI ecm in
a 1991 Acura Integra.  It's computer is quite different from the GM
computer I'm use to working on.  I do not see a BLM function being
used on these ecms.  Now just because I don't see it doesn't mean it
isn't there.  There are some software programs out there, notably
"Crome", that allow you to modify the chip and fuel/spark map easily.
 They have much of the computer mapped out.  But not all of it.  If
the o2 sensor is removed while using this style ecm the fuel mixture
goes very rich.  It doesn't seem to force the computer into open
loop.  The computer believes the input from the o2 no matter what! 
There is a diagnostic mode, where the o2 is not used.  But again it
is amazing how rich the vehicle is run.  If you leave an o2 sensor in
there for any length of time while in this mode it will be coated
with nice later of soot.  We've ruined a couple o2s doing this.
     This is why I'm trying to fake the o2.  I'm wondering if there is
something in between diagnostic mode, and closed loop?  Or is the
base map really that rich?  When I get back the first thing we are
going to do is use some WBo2s from Innovate to take a better look at
it.  Put it on the dyno with a four gas on there as well.  What is
really worrying me is the "Pinging".  I was told they had to retard
the timing 10 degrees to get it to stop.  That immediately sounds
like a motor killer to me.  Some of the ecms used on the Acuras used
a knock sensor.  But not this one.  I just hope they don't detonate
it before I return.
     Once again thanks for all the input.  I really liked hearing there
are some other cars out there running open loop all the time with no
problem.  I think we are probably going to try and go this way.  I'm
going to try diagnostic mode.  And play with the spark/fuel maps
while in that mode.  See if we can't make something happen.  I'd
rather not use an o2. They seem to go through them on the track like
crazy.  One goes bad like every third time they go out.

Thanks,

Marcello









>
> ----- Original Message -----
> From: "David Cooley" <n5xmt at bellsouth.net>
> To: <diy_efi at diy-efi.org>
> Sent: Sunday, May 29, 2005 2:49 PM
> Subject: RE: [Diy_efi] Making a fake O2
>
>
>> BUT, I bet there was some serious tuning done to get the A/F just right
>> before putting it to daily driving...
>
> Well, sure, you have to put in the time required to get it right. :)  It's
> the high(er) boost maps that are the critical ones. The rest of the
> mappings
> are pretty straightforward, not different from any other engine.
>
>
>> Different than one wanting to just leave a stock cal in open loop mode
>> all
>> the time...
>
> Ok, but I assumed you were going to modify the open-loop maps (and
> probably
> get rid of the cat, if it was still on there).
>
> -Marc
>
>
>
>>
>>> -----Original Message-----
>>> From: diy_efi-bounces at diy-efi.org
>>> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Marc Reviel
>>> Sent: Saturday, May 28, 2005 2:41 PM
>>> To: diy_efi at diy-efi.org
>>> Subject: Re: [Diy_efi] Making a fake O2
>>>
>>>
>>> ----- Original Message -----
>>> From: "Adam Wade" <espresso_doppio at yahoo.com>
>>> To: <diy_efi at diy-efi.org>
>>> Sent: Saturday, May 28, 2005 9:31 AM
>>> Subject: RE: [Diy_efi] Making a fake O2
>>>
>>>
>>> <snip>
>>>
>>> > People survived an awfully long time with open-loop
>>> > EFI without all their engines self-destructing.  Most
>>> > motorcycles still use only open-loop operation, and
>>> > they don't blow up from EFI faults.
>>>
>>> Absolutely.  We build very high hp turbo Porsche engines and
>>> always run
>>> open-loop, for both street and the track. My 1000hp 3.8L
>>> Porsche engine runs
>>> open-loop all time and I use it for daily driving (in Texas)
>>> as well as
>>> high-speed events. My dual widebands on  the MoTec are used
>>> only for tuning.
>>> If it's tuned right  (ie, conservatively,  thoroughly), there are no
>>> problems.
>>>
>>> -Marc
>
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