[DML] Clarification: DeLorean Spark Advance

["content22207" <brobertson@xxxxxxxxxxxx>]

Before I get flamed out of existence, let me clarify DeLorean spark
advance relative to its Volvo counterpart:

The DeLorean ignition distributor has one centrifugal counterweight
disabled. Otherwise it appears to be identical to Volvo F Series
(mechanical advance spec's are one half Volvo's).

To compensate, DeLo runs full manifold vacuum to the spark advance
diaphragm. Of course this makes the engine extremely difficult to
start and risks predetonation when the throttle plates are closed (max
vacuum), so they stick a microswitch under the throttle plate linkage
to operate a solenoid that cuts off vacuum spark advance when the
plates are closed.

And of course base ignition time is advanced 3 degrees before Volvo.

In contrast, Volvo runs ported vacuum (same port as the purge signal
to the charcoal canister) to the spark advance diaphragm. No
microswitch or solenoid. Not only is this a much cleaner and simpler
installation, but by virtue of having both counterweights active it
actually yields more spark advance at higher RPM's (minimum vacuum),
which is when you need it most.

The whole DeLorean setup appears designed to maximize fuel burn at low
RPM's, such as stuck in California traffic, not yield better performance.

As I understand it the DeLorean distributor does have its missing
counterwight inside -- it just isn't connected to the rotor hub. If
the missing spring were replaced it should perform like a Volvo
distributor (DeLo mechanical spec's are one half Volvo's). In such a
state vacuum advance could then be attached directly to one of the
throttle plate ports rather than the driver's intake rail. Otherwise,
owners are stuck with DMC's rather convoluted setup.

FWIW: I'm running a fully functional distributor and find performance
to be quite invigorating.

Bill Robertson
#5939






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