OEM algorithms (DSM)

Jim Conforti jec at us.dynix.com
Thu Nov 10 17:38:31 GMT 1994




On Thu, 10 Nov 1994, Todd Day wrote:

 Todd, this is Jim C. ... from BMW/Bosch land .. long time no talk ..

 Saw your talon stuff, here's what I can figure out

> 2) In another part of the code, the ECU is trying to decide whether
> 	or not to even run oxy feedback at all.  It takes a look
> 	at the amount of air and compares it against two tables that
> 	are indexed by RPM.  It ends up with three bands of air flow
> 	vs. RPM (split by the two tables).  In the low air band, it
> 	will run oxy feedback.  In the mid air band, it will run
> 	oxy feedback for 20 secs before going open loop.  In the high
> 	air band, it won't run oxy feedback at all.  Now, I can under-
> 	stand what the ECU is trying to accomplish at low and high
> 	air amounts.  But I can't see what it is trying to avoid in
> 	the mid air band.  I was thinking it might be due to oxy
> 	sensor overheating or something, but my friend tells me
> 	they actually enjoy operating at high exhaust temps.

     I has to do with the FTP (Federal Test Procedure) for EPA emissions
     testing and the CARB tests ...

     While in the tests, the car is mostly operating in region #1 ..
     under certain parts of the test, probably during accel, we make
     brief forays into region #2 ... hence, if we're there for less than
     20 sec and return to #1, the EGO control is never disturbed and we
     meet the emissions spec ...

     Region #2 is probably not run in very much under constant throttle
     but if it is, you lose EGO contol and go towards max power  ...

     Of course, Region #3 is the "full bore" non-emissions region ..

     BMW/Bosch handle it slightly differently ...

     As an example ... (E30 M3) ..

     There is a region of speed/load that EGO is active .. if you are
     under the magic load number and 4800 rpms, the EGO is active ..

     If you venture out of the "emissions" region, for longer than 3 sec.
     the EGO goes inactive .. the 3 sec delay is for brief forays into
     the "non-emissions"  region during the official tests ...

     Jim Conforti
     <jec at us.dynix.com>




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