Spark timing,points/Hall effect

[Gary Derian]

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The way I see it, 7.5 BTDC and single diaphragm can is a good spark =
setup for a non emissions engine or a catalyst equipped engine.  These =
settings run better and use the catalyst to clean things up.  5 ATDC and =
dual diaphragm can is typical for a non-catalyst emissions engine.  The =
retarded timing at idle cleans up emissions a little.  What really =
matters for power and economy is the timing at normal driving speeds.

Gary Derian <gderian at cybergate.net>

-----Original Message-----
From:	Mario Tito [SMTP:mario at swingbridge.com]
Sent:	Wednesday, October 01, 1997 12:13 AM
To:	fi discuss 2
Subject:	Re: Spark timing,points/Hall effect

>	You answered your own question.  The California engine has a catalytic
>converter.  The dual diaphragm Bosch distributors used ported vacuum =
for
>the advance but manifold vacuum for the retard.  At idle, the =
distributor
>is in full retard.  At cruise, the retard diaphragm has no effect =
because
>its function is to move the zero vacuum stop in the vacuum can assembly
>towards the retard side.  When there is vacuum pulling some advance, =
the
>position of the stop does not affect the advance.  When there is no =
vacuum
>advance (idle) moving the stop does provide more retard.
>
>	Non catalytic cars had retarded spark and very lean mixture to get low
>emissions.  When a catalyst was added, emissions were even lower and =
the
>engine could be tuned for efficiency.
>
>Gary Derian <gderian at cybergate.net>
>
>----------
>>   Perhaps a discussion will help Tom C. as well.
>>   Thanks
>>=20
>> Mario T.
>> mailto:Freshmar at aol.com-----'76 VW Camper FI A/T,,'79 Fiat X1/9
>


I didn't really answer my own question -the cali version did have the=20
cat, and the dual-chamber vacuum thingy and the idle timing set at 5 deg =

atdc, Hall-Effect ignition.  But, the model before mine did not have =
cat,=20
nor Hall, but was timed similarly to this one. My model has points, a=20
single vacuum advance, but it is set at 7.5 deg btdc at idle. What am I=20
missing? I am thinking of a computer ignition, and I want to understand=20
more of what I need to do- without using a 'advance-till-it-knocks'=20
possibly destructive method. Thanks everybody.

Mario T.
mailto:Freshmar at aol.com-----'76 VW Camper FI A/T,,'79 Fiat X1/9

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