Ignition MAP Override This works in the same manner as the fuel map override but the correction occurs on the ignition table.
Normally the ignition MAP override values are all 0 (zero) but there are circumstances where they may need adjusting.
One situation where these values may need changing is for a Nissan GTR RB26 with multiple throttle bodies. The main load source might be TPS, but turbo boost also needs to be sensed. The fuel override will remain untouched as this keeps the variable resolution constant. The ignition, on the other hand, becomes complex and cannot be adjusted via TPS load map alone. This is because at 4500 RPM light cruising the TPS may be at 5% and the engine is pulling a high vacuum that is sensed by the MAP sensor. The driver may then request full 100% TPS. At this point the MAP sensor will read 0 (zero) Kpa (atmospheric) as the turbos are still spinning at cruising speed. The engine, at this point, may require 30 Deg BTDC ignition timing. Within a second the turbo will have spooled up to maybe 200 Kpa (28 Psi) while the engine is still at 4500 RPM, TPS is still at 100% but the manifold pressure has increased considerably. The timing at this pressure must be reduced to a more retarded timing value of about 10 Deg BTDC, a reduction of 20 Deg.
To achieve this tuning scenario you would put 30 Deg BTDC timing in the 4500 RPM / 100% TPS load cell. The ignition MAP override will have 0% (zero percent) in the 0 Kpa (zero) cell and –66% in the +200 Kpa cell. This will reduce the 30 Deg BTDC ignition timing by 66% bringing the actual ignition timing to around 10 Deg BTDC. To achieve a smooth retard curve you must also adjust all of the cells between 0 Kpa and +200 Kpa of the ignition MAP override table. See the table below as an example.
Stinger 4 instruction manual version 2.0