Engine Map – What is it? What do they do?
2 min read
An engine map is a map for the engine. It tells the engine where to go when the engine conditions are X, Y, Z…….
There “where” being (on a petrol engine) at what angle of ignition rotation to fire the spark plug and how much fuel to inject.
The “conditions” being RPM, crank angle, engine load, coolant temp, intake air temp, engine knock, EGT and so on.
The maps can be basic 3D tables with 8×8 cells (RPM vs Load) for example, with 64 “wheres” (cells) in the ignition map and fuel map.
To ECUs that have 2D tables to add an extra dimension to the basic 3D tables.
Up to “series” based 3D maps which can have tens of thousands of “wheres” (cells) which cover every imaginable engine condition. Conditions which take into consideration all of the sensors mounted on the engine. Instead of being a basic 3D map, these maps can have tens of dimensions with every destination (ignition angle and fuel amount) being based on data from all of the sensors.
Quick Example of a Multi-Dimensional Engine Map
At X coolant temp, at X RPM, at X engine load, at X TPS rate of change, at X rpm rate of change, at X wheel speed, at X gear, at X steering angle, at X intake air temp, at X EGT, at X knock intensity, at X coolant temp, at X oil temp, we will use Y ignition advance and Z fuel amount.
The more dimensions the engine map has the more sensor data it can use to base it’s choice of ignition angle and fuel quantity on. The only limit is the imagination of the engineer and the resources they have to build/make the engine map.
The more dimensions the engine map has, the more testing will need to be done to find the optimum ignition and fuelling settings for each location/”where”/cell.
