Oxygen sensor and high speed stumble UPDATE

Bruce Plecan nacelp at bright.net
Sun Nov 1 15:41:31 GMT 1998


-----Original Message-----
From: Scot Sealander <Sealand at clarityconnect.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Saturday, October 31, 1998 11:43 PM
Subject: Re: Oxygen sensor and high speed stumble UPDATE


>David A. Cooley wrote:
>
>> The knock you are detecting at part throttle with the aftermarket >>chip
is from lack of EGR...
>>That could be true.  But maybe the 'part throttle' changes that the >>chip
maker claims to have made include more advance.
>> 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...


>Not a very good gaurantee.  This statement I doubt is true.  Just >because
of the algorithm used in the code.

Is this to say you have read all the algorithms, and understand them
all?.  Since noone here has seen the code, that may be in as much of an
error as anyone's guess fo far.
>
>> GM adds timing and leans the fuel during EGR so there is no >>loss of
power from the EGR.
>
>It can stand more timing with EGR, assuming you are not knock >limited.
Just less power lost.  The fuel is not really 'leaned'.

Then what does Block Learn reference to?.

> The 14.7 to one (stoich) is still met for the air that is in the cylinder.

If the above statement is meant to be applied to 3 way cat converter
equipped cars, then it is wrong.  They have to hunt between two ratios for
them to work.

> The job of the ECM is to measure (or calculate) the amount of air
>in the cylinder, then add the required amount of fuel at the desired
>AFR.  The measured amount of air in the cylinder does not include the EGR.
>
>
>> 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.
>
>This is only true (in this case) if your assumptions on how things are
>done are accurate, but they aren't.  The main table may have too >much
timing on purpose, or maybe it has been added.  One would >have to see the
file to know.
>
>
>> This is why a lot of chip makers charge a fortune hoping no one knows
what
>> the tables contain...
>
>Possibly.  After figuring this particular code out, I bought a used
aftermarket
>chip for this app.  I'm sure that they have to sell that one as "off-road"
>only.  The "part throttle" changes do not meet emission specs, and the WOT
>changes may actually result in lower gas mileage.  I haven't actually
>tried it to see.
>
>
>> it shows they have no clue as to what they are doing.
>
>Not unusual.  But do YOU know what the chip does?   It is easy to call them
>incompetent.  You have made some assumptions that just aren't true.

I think your carring things too the nenth degree.  Does one need to
know the exact chemical process that an egg goes thru to be cooked and taste
good??, NO.   Knowing how much fuel needs to be where, and the right amount
of timing are what matters.
>
>Scot Sealander   Sealand at clarityconnect.com
>
>
>> If you want a chip that will make the car run better, try a reputable
name
>> like Z Industries... Ron Zimmer has friends in the automotive
manufacturer
>> industry that supply info and his chips are actual dyno tested units...
>
>I trust this kind the least!  I trust people who reverse the code, forcing
>them to understand how things get accomplished.  Having a "friend" means
>that you really don't understand what the code does.  Would WOT dyno
testing
>find the part throttle ping?

Can also be said that I've seen several of the really good guys make
a booboo, in what they saw.

What counts is what's in the car.  If you want to reverse engineer it
fine, if you want to pic it apart fine.  But, the only true test is when you
use it in a car.
Bruce
>




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