123ignition 123-TUNE-4-R-V User Manual page 8

Example 3
GB
This demonstrates how to set the unit in a real-life situation, using the original data from a Bosch-
distributor 0.231.116.051 ( see the picture at the last pages of this manual )
This distributor was kind of special, because it had 'negative vacuum', e.g. the more vacuum the less
advance. This 'trick' was used in two situations :
a. European car-manufacturers were faced with more stringent emission-rules in the USA and Canada.
Retarding the advance around idle was a popular solution to improve emissions.
b. cars with automatic gearboxes ; once set in "neutral" the advance was retarded, thereby keeping the
engine-speed acceptably low.
Back to the 0.231.116.051 : the vacuum-retard starts at say 100 mmHg below atmospheric.
But how can we retard ? Simple as '123' ! In the list you see point no.5 as (99;11,0) ; it is important to
use only 99 kP to achieve this!
The 123\TUNE will now produce 11,0 degrees advance, immediately after starting the engine. That is
why off-course the MAP-start is set here to zero !
The advance then begins to drop around 100 mmHg , point no.4 (85;11,0) to eventually 400 mmHg at
point no.2 (50;0,0)
Example 4
This demonstrates how to use the centrifugal advance to get idle-control ; the engine will tend to stay
in the dip around 1100 rpm. In the vacuum-curve you can see an example of how to achieve so-called
"gear-shift-retard"....if the absolute pressure in the manifold gets below 37 kP, the advance will fall to zero.
The result is, that if you release the throttle ( and the engine begins to produce vacuum ) you either want