Oxygen sensor and high speed stumble UPDATE

Greg Hermann bearbvd at sni.net
Sun Nov 1 15:41:38 GMT 1998


>But from the below convertsation  the question I have is...what affect does the
>capability of doing the block learn tables over driving time have o
>this...seems
>that the BLC would correct for any built in errors due to the changes....?
>rite? rong?   GENE

Hi Gene--

First, let me say that my assumption in writing the stuff below was that
the mfgrs would program their ecu's in a manner which would maximize
mileage and minimize emissions, so as to do the best job possible of
conforming to their CAFE and EPA restraints, no matter how foolish some of
those restraints might be. Perhaps this is a faulty assumption, but I would
be very surprised if it is--mostly because mfgr sales and profits depend
very heavily on meeting those rules!

Second, I will admit freely to the fact that I am groping for an answer
about the BLC's--I know about enough about them to be dangerous. My
perception of the BLC stuff is that it provides enough "self-learned"
variability in the ecu's tuning tables so that the ecu can compensate for
things like changes in leak-down rate as the mileage on an engine adds up
and natural variations in flow, crank indexing, cam timing and lobe
variation, compression, etc., between (non-blueprinted) production engines
in a given series. I THINK that the variability provided by the BLC stuff
extends over much too limited a range for it to be able to compensate for
such a drastic variation in conditions as turning off the EGR. I think that
you get a trouble code posted when something takes the BLC's to their outer
limits, unless a chip twiddler has turned that feature off.

Third, I believe that it would be fair to assume that the mfgrs did not
provide the BLC stuff out of the goodness of their hearts or to help out
the occasional hot-rodder. Far more likely, it was determined that is was
cheaper to provide them than it was to tighten up engine production
tolerances, or to build enough durability into their (also now required to
be built at a higher level of precision) engines to meet the (EPA required)
extended emission warranties without any need for manual tuning
adjustments! The automatic tuning adjustments provided by the BLC's is OK
per the terms of the EPA rules on the warranty, I do not believe that any
other approach would be.

 'Twould be fascinating to hear the level of mfgr squalling (and see the
hardware) that would result if the CAFE regs were changed to require a
warranty of the required fuel mileage over an extended period!!! Too bad
that bureaucrats' hunger for power is never matched by greater quantities
of wisdom or intelligence!!--Could it be that an increase in the latter two
qualities will always cause the first thing to grow smaller???!! (One could
point to Hitler as an example of one extreme, and Einstein as an example of
the opposite extreme!!)

(Never could understand why so many people are convinced that I have a very
dirty, sarcastic mind!!)

Regards, Greg


>
>Greg Hermann wrote:
>>
>> Hi--
>>
>> Good accurate info, in general.
>>
>> >The knock you are detecting at part throttle with the aftermarket chip is
>> >from lack of EGR... Guaranteed that the chip people only removed the EGR
>> >and didn't fix the EGR timing and fuel tables to make it run right without
>> >the EGR...
>>
>> Yep.
>>
>>  GM adds timing and leans the fuel during EGR so there is no loss
>> >of power from the EGR.
>>
>> As to this one, I have a bridge in Brooklyn you can buy!!
>>
>> Yes, they lean it so that CO and HC do not go up, on account of less total
>> air, and yes, they advance it so that they get back some of the response
>> and mileage screwed up by EGR (mixture diluents are a knock resister, so
>> they CAN get away with more advance when EGR is on), but NO WAY you do not
>> lose power at equal MAP levels with EGR on vs. off!!
>>
>>  Take away the EGR, and now the timing is way too
>> >high, and the fuel is too lean because the part of the combustion air that
>> >was recirculated exhaust is now air and it needs fuel.
>>
>> Yep.
>>
>> >This is why a lot of chip makers charge a fortune hoping no one knows what
>> >the tables contain... it shows they have no clue as to what they are doing.
>>
>> What?!?--people involved in the automotive aftermarket who would screw
>> their customers?? Where on earth did they learn such tricks--working for
>> auto manufacturers before they went into making aftermarket stuff??!??
>>
>> Regards, Greg
>
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>
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