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Big emissions problems on my '90 Geo Metro
Topic Started: Jun 16 2010, 09:21 AM (4,795 Views)
mwebb
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FOG

Woodie
Jun 21 2010, 05:58 AM
crankcase
Jun 20 2010, 08:01 PM
I would think more advanced valve systems would be the big factor in less soot in the exhaust.
Do Metros uses base timing for idle/low RPM/low load conditions (grasping for proper terms here)
and don’t affect advancing done by the ECU? Please correct my understanding that the advance
set around 8 as opposed to 5 gives better fuel economy, more power, but dirtier emissions. Did
earlier Metros and their G10s use the 10 degree advance before the clean emission drive?



Advancing the ignition timing (up to a point) increases efficiency and performance in every way, including decreasing emissions in every way but one. The sole exception is NOx. Retarding the timing reduces NOx, but increases all other emissions.
Woodie may be able to trick his system into advancing the timing ... some
by
lowering supply voltage to the MAP sensor , from 5 volts to a little less .

which would
lower the MAP value , which would , decrease Engine load and injector pulse width
the feedback system with the 02 sensor would correct for IPW and maintain mixture at stoich , using FT correction s.

but
decreased engine load would also result in slightly greater ignition timing advance.
so
Woodie could trick his system into advancing the ign timing , as long as he did not reduce MAP supply so low that the system exceeded + 25% LTFT

then
we could see if advancing ignition timing on the 1998 G13 has a positive effect on FE ....
it would reduce MAX power unless a 5 pin relay were used to only reduce MAP supply when the EGR was active ....

or the same relay could be used to apply reduced voltage to MAP at anything other than WOT , using the TPS for a control signal

hint hint,wink wink
Edited by mwebb, Jun 21 2010, 11:58 PM.
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