Merlins Ralliart and EvoX TUNING GUIDE Version K.pdf - EvoScan

MERLINS RALLIART & EVOLUTION-X TUNING GUIDESECTION 4 – FUEL TUNING4.01-INTRODUCTION TO RALLIART & EVOX FUEL METERINGThe basic function of the ECU is to calculate the correct amount of fuel and ignitionadvance required by the engine at any rpm and load, within it’s normal designoperating range. To make these calculations it needs an accurate measure of howmuch load the engine is under.The RALLIART’s primary load sensor is the Mass Air Flow Meter (MAF). It is theECUs biggest asset, but it can be a limiting factor to the engines ultimateperformance when attempting to tune beyond the factory parameters. TheMITSUBISHI RALLIART and EVO X use a HOTWIRE type MAF, which has a varyingDC output voltage, proportional to air-flow. The mass of the air is calculated byusing the diameter of the intake tube the sensor is mounted on.The MAF makes a measurement of the mass of air entering the engine. At this pointthe measurement is un-corrected and requires manipulation from the followingtables:1. MAF SIZE.2. AIR TEMP.3. BAROMETRIC PRESSURE.At this point load is calculated and is applied to lookup the fuel and ignition maps.Note that not all the compensations have been factored-in yet. The ECU nowdetermines the mass of fuel required for a specific Air Fuel Ratio by checking:4. MAF SMOOTHING.5. BARO + TEMP v RMP.6. FUEL MAP.7. INJECTOR SCALING.8. INJECTOR LATENCY.Now the conditional parameters can be included, such as:9. ACCEL ENRICHMENT.10. WARMUP ENRICHMENT.11. CLOSED LOOP.12. LEAN SPOOL.Because of this, injectors and even the MAF itself can be up-graded to a larger sizewithout requiring a major re-tune, as would be the case with a manifold absolutepressure (MAP) based load sensing, aka speed-density. The characteristics of theinjectors are defined in ROM as the INJECTOR SCALING and INJECTOR LATENCY.Scaling defines the flow capacity of the injector in cc/min, while the latencyparameter is the time in milli-seconds for the injector to turn on. This parametermay be variously referred to as ‘dead-time’ or ‘void blast-off time’.REV: 0.K merlin@three.com.au Page 33 of 134