Author Topic: dwell a function of map pressure?  (Read 6197 times)

Offline multiplex

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dwell a function of map pressure?
« on: October 13, 2009, 08:23:39 pm »
i noticed something interesting in my logs, that was not there under older firmware (1.1.27)

I'm now running 1.1.62

under large MAP pressure, the dwell increases dramatically.  I guess this is a good feature, but where can i set the max? 

this graph shows the peak, but it also follows the map pressure at lower pressures.


Offline multiplex

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Re: dwell a function of map pressure?
« Reply #1 on: October 13, 2009, 08:34:43 pm »
guess i answered my own question after searching the firmware changelog.  Anyways, maybe it will help the next guy

#  config.ign_dwellmap configurable MAP-based dwell scaleup (VBATT based is automatic)

    * 00 no dwell extension at all (neither VBATT nor MAP based): ign_dwell14 is used
    * 01 only VBATT based dwell extension (max *2, when VBATT <= 7V)
    * values 02..FF : VBATT based extension is automatic. Slope of MAP-based dwell-extension is configured with this variable. MAP-based extension is max *1.4 (+40%), while total scaleup (vbattmultiplier * mapmultiplier) is max *2
          o dwell is extended by (map - 70kPa) * ign_dwellmap/4096 but no more than +0.4 (40% extension that is *1.4). Examples:
          o ign_dwellmap=0A (decimal 10) max dwell-extension +40% reached at 234 kPa because (234 kPa - 70 kPa) * 10 /4096 = 0.4
          o ign_dwellmap=14 (decimal 20) max dwell-extension +40% reached at 152 kPa because (152 kPa - 70 kPa) * 20 /4096 = 0.4
          o higher value means higher slope (so max dwell extension reached earlier). Take care not to overload the ignition output or the coil (use lower ign_dwell14 so you only get extended dwell when really necessary).

Currently my ign_dwellmap=0E (decimal 14). 

I'll probably change it to at least 10, or possibly reduce my standard dwell time.  I scoped a stock BMW, and its dwell time is 3.2ms.  Which seems a little long to me, but thought it would be good under boost.  guess vems already has that taken care of for me!