6.8.2.1 Main Jet Setting
The base line fuel is calculated by the ECU and not mapped in a look-up table like matrix systems.
Calculations alone cannot compensate for all deviations in and engine. The ECU uses correction
graphs to compensate for all kinds of deviations. The Main Jet adjusts global fuel supply to the
injectors much like the main jet in a carburetor would. This is a constant dependant on fuel
pressure and injector size. If all the maps are zero, you can use this setting to adjust the base line
fueling for the ECU. A standard to use is normal load on the freeway at normal cruising speed for
instance 120Km/h. Your total vacuum range can be divided into two and use this setting if you are
on a Dino. Drag the slider up or down to increase or decrease fuel till the desired air/fuel mixture is
obtained. Normally around 14.7 or 0.45Volt on the lambda slide bar. Now stop, put the car in park
and adjust the Idle jet till it idles smoothly and the desired air/fuel mixture is obtained. Now
memorize the digital value above the slider and always go back to that value if you use the slider
for tuning. If you change this value, all the other settings will change accordingly. That is why it is
the first to adjust.
If starting for the first time you may adjust the slider slowly up while cranking, until the car starts.
As the engine warm up to normal temperature, lower the slider to keep the engine running
smoothly. Start with an idle setting of 70.
To adjust this slider you can click on the slider button with the mouse and use the up and down
arrow to adjust one increment at a time. The page up and page down can be used to adjust 10
increments up or down. Alternatively you can use the hot keys Q and A for 1 increment
adjustments and W and S for 10 increments at a time.
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