Timing Retard w/o knock & MAF oscillations

[Mike Rolica]

Yep, I agree of this intake valve opening theory.  Since this is only a
"snapshot" at a specific point in time high point are due to valve being
open or closed when this snapshot occurs.  Seems the average is around 225.
Same thing happened on dyno with fuel flow, I got a/f ratios that bounced
from 21:1 to 8.7:1.  Would depend on if injectors were open or closed.
Mike Rolica
EXT. 260
 :-)


-----Original Message-----
From:	David Cooley [SMTP:n5xmt at bellsouth.net]
Sent:	Friday, September 24, 1999 10:58 AM
To:	gmecm at efi332.eng.ohio-state.edu
Subject:	Re: Timing Retard w/o knock  &  MAF oscillations

At 10:45 AM 9/24/1999 -0400, you wrote:
>In trying to understand some Diacom data. I'm seeing "knock retard" being
>introduced, but No "spark control counts" being sensed..  Will the ECM
>retard the timing when the table jumps from LV8 column to LV8 column and
>the requested advance decreases in this column jump?
>
>(IE, if the EPROM table has spark advance for 3600 rpm at LV8=176 set to
>         22 deg and the LV8 goes above 192 and into the next column of
>         the spark advance table where 3600rpm has a 20 deg advance
request,
>         will the ECM apply retard of 2 deg to get there?


Nope... Would just show as a different value in the timing advance data... 
retard is when it pulls timing due to knock and it's modifying whatever 
value is in the timing table.


>(BTW, while I'm sending this email, I'll ask...  Would anyone know why my
>  air flow thru my MAF would oscilliate at high load/flow?  I have a PDF
>  graph of what I mean at:
>                 http://www.eecis.udel.edu/~davis/z28/ecm_swap/165chart.pdf

It appears it may be due to being sampled during an intake valve opening, 
or between openings...  The air flow will pulse.
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