Re: quattro-digest V3 #813

[Robert Houk - SMCC Bos Desktop Hardware <rdh@UrQ.East.Sun.COM>]

   >I also "fixed" the ECU to smooth out the warm-up open-loop
   >mixture shenanigans . . . )
   I would be interested in hearing how .....please.

In the MAC-02, the static/openloop mixture (FreqValve duty cycle) is con-
trolled via the table(s):

  ; Block temperature => Index-8 map, used to determine cold engine open
  ; loop warmup mixture (Pg 24 -- warmup frequency valve duty cycle ).
  ;
  ;	Values are A/D converted:
  ;
  ;	    0xE0  =  TBD
  ;	    0xC4  = -20C  /  -4F (by the book; empirically ~ +10F)
  ;	    0xA7  = -10C  /  14F (by the book; empirically ~ +25/30F)
  ;	    0x89  =   0C  /  32F
  ;	    0x7A  =  10C  /  50F
  ;	    0x6C  =  20C  /  68F
  ;	    0x5C  ~  25C  /  77F
  ;	    0x53  ~  32C  /  90F
  ;	    0x40  ~  38C  / 100F
  ;	    0x1D  ~  60C  / 140F

  BlockTempMap8:
  F190:	C4=196	A8=168	89=137	7A=122	6C=108	67=103	5A=090	55=085

  ; Table of cold engine open-loop FreqValve duty cycle values, indexed by
  ; BlockTempMap8 index, with last entry also doubling as a general-purpose
  ; "open-loop" default.
  ;
  ; 	Values (8-bit) percentage (duty cycle):
  ;
  ;	    0x41  =  65%
  ;	    0x3C  =  60%
  ;	    0x37  =  55%
  ;	    0x32  =  50%
  ;	    0x2A  =  42%

  ColdOpenLoopFQV:
  F198:	50=080	41=065	3C=060	37=055	32=050	25=037	25=037	32=050

Right around 70-80F block temp, the map dips way *WAY* down to 37% duty
cycle (way lean), before jumping back up to 50% (nominal), just before
going closed-loop (at around 95F block temp, O2 sensor willing).

My observations are two-fold: one -- exactly at the 37% dip the engine
starts running like cold lumpy s**t (easy to watch with your trusty
duty-cycle meter (CP7678???) hooked up), and smooths out again as the
mixture goes back up to 50%; two -- when the system goes closed-loop
the ECU seems to like to run a little rich (typically around 52-55% duty
cycle, in my observations) for awhile till it finishes warming up.

Running a Schrick cam exacerbates the problem; the Schrick definitely
likes a richer cold mixture!

Thus, I made two changes to the map -- I stretched the temp range a little
to run out to 120F or so before permitting closed-loop, and I didn't drop
the duty cycle below 50%.

(Also note that the trailing 50% entry is also the "test point" value for
closed idle and WOT switches simultaneously, so you want it to be 50 al-
ways)

Note: the above is the "F" ROM decoding; the "B" (earlier) ROM is similar
but different.

					-RDH