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

MERLINS RALLIART & EVOLUTION-X TUNING GUIDE4.06-FUEL TUNING – LAMBDA CONTROL THRESHOLDSWhen the engine temperature is low (below a preset value), the ECU does not usethe (front) LAMBDA sensor to control the stociometric 14.7:1 fueling as shown inthe fuel maps. Instead, it calculates the required AFR from the air-flow and thenapplies the warm-up enrichment.This LAMBDA TEMP THRESHOLD parameter sets the engine temperature abovewhich the ECU starts CLOSED LOOP operation, by using the front LAMBDA to trimfueling to the desired 14.7:1 AFR as shown in the fuel maps. The value shownbelow (40°C) has been altered from the 20°C factory ADM spec switch on point.Figure 18:FUEL TUNING – tuned LAMBDA TEMP THRESHOLDEngines with 264 degree or bigger cams may benefit from setting this value at 30-40 degrees centigrade so the engine can get more consistent fueling during warmup.To do this however would require the injector SCALING and LATENCY values tobe right, but you always need to do that anyway.There are also four tables based on LOAD v RPM and TPS v RPM that control thetransition from CLOSED LOOP to OPEN LOOP operation, once the enginetemperature is above the switch threshold. When the value in the table is exceeded,the ECU ceases trying to operate in closed loop (adjusting fuel via O2).Note that when the ECU is in OPEN LOOP, the LONG TERM FUEL TRIM (LTFT) %that was applied in CLOSED LOOP is applied to the whole map. This is a greatfeature, but does mean you should try and get your trims close to zero by gettingthe scaling and injector latency set correctly. These should be very close to zerotrim if using 98-100 octane fuel and stock injectors.The ECU has a short term fuel trim range of ±25%, so it has plenty of adjustmentrange to work with.REV: 0.K merlin@three.com.au Page 41 of 134