ECM Tolerances? EEPROM PCM in LT1

[Roger Heflin]

Bruce, 

I  am going to post to this list what I posted to the fourth-gen list for
larrys article. 


The knock sensor filter is in the computer. (I think).   Maybe one of the
filters is broken and the other is working correctly?  There is generally
quite a bit of deviation in analog filter design, it is real hard to get
them exaclty the same, even with components with pretty good tolerances.
So both filters might be mostly working just working differently, and one
is filtering more of the "junk" (false knock) out.
 
In the <94 I believe the knock filter is in the Calpack.  At least that is
what something I read claims is the thing in the rest of the calpack.  So
it would be possible on a 93 to get different results by changing the chip
(and therefore the knock sensor filter) with exactly the same programming
in the chip.  I wonder if anyone adjusts these?
 
                        Roger


On Thu, 20 Aug 1998, Bruce Plecan wrote:

> 
> -----Original Message-----
> From: Kurek, Larry <LKurek at ocfexch2.ocf.anl.gov>
> To: 'diy_efi at efi332.eng.ohio-state.edu' <diy_efi at efi332.eng.ohio-state.edu>
> Date: Thursday, August 20, 1998 2:29 PM
> Subject: RE: ECM Tolerances? EEPROM PCM in LT1
> 
> 
> > Peter wrote:
> > >Hi Larry
> > >Not sure. Please take this with a grain of salt
> > >1.      An 8051 PCM can have different cals.
> > I know this...but we both have 94 LT1's with identical engines,
> >and manual transmissions. The only difference is the PCM I borrowed is
> >from a Pontiac and mine is a Chevrolet. Same part numbers though...
> 
> <snip>
> 
>  The Left and right O2's
> >were actually fairly similiar at WOT, yet the pulse widths were
> >different by a few .1 milliseconds.
> > >later:peter
> > <SNIP>
> > Thanks!
> > Larry
> 
> 
> This is most interesting,  I've talked with a few other folk relative to
> some forms of racing where things must be pure stock, and they
> try an arm load of ecm's to get the most HP.    This is not just a 
> gm issue.   The folks I talked to didn't have the ability to measure 
> the PW, so this was an unknown, but to actually hear that there 
> is, is rather enlightening.
>    Seems like another perfect bench ecm test.  
> Cheers
> Bruce
> 
>