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

MERLINS RALLIART & EVOLUTION-X TUNING GUIDEThe timer mentioned above seems to be set at 500mSeconds on the Evo ECU.In the short term, the timing will be reduced directly, based on the KNOCKSUM.Disassembly of the code has revealed that each knock count will reduce the timingby approximately 0.35 of a degree, thus a knock count of three will result in 1° oftiming pulled from the ignition map. . The exact formula describing exactly howKNOCKSUM imparts a spark timing reduction is:Knock Spark Retard = KNOCKSUM * 90 / 256Thus a KNOCKSUM of 3 yields a spark retard of -1.05 degrees.It has been reported that the octane number recovers to normal or near normal,quite quickly if the engine experiences knock-free operation above the KNOCKTRHESHOLD, which is a LOAD v RPM table. If it sees no knock, it will adjust theoctane number back quickly. If the knock levels are only 1 or 2, it will adjust theoctane number back slowly.This is good news, as it allows for rapid recovery by adding some better fuel oroctane enhancer product if a dud batch of fuel has been supplied.The ECU holds the current OCTANE NUMBER in non-volatile random access memorywhen the ignition is switched off. If for example, a dyno session produced a numberof knocks and you want to get the OCTANE NUMBER quickly back to 100%, the ECUwill have to be disconnected if it an Evo7-8. For an Evo9, a re-flash will reset theOCTANE NUMBER.Additionally, an OCTANE NUMBER of 154 or lower will affect the boost controlsetting, the net result being to reduce boost.When the OCTANE NUMBER = 0, the ECU use 100% of the low octane spark andfuel maps.However, your timing will be less than the LO-OCTANE map, as the ECU is stillpulling timing if knock continues. In the short term, knock control is still pulling 1°of timing per 3 knock counts. So, if you have maxed your KNOCKSUM out to 36counts of knock, you will be running 12° less timing than the ignition maps specify.Thus the LO-OCTANE map acts as a long-term timing adjustment.If false knock has reduced your OCTANE NUMBER to zero, KNOCKSUM can continueto pull timing to the MAXIMUM RETARD value. This has been set on most ECUs to-10º. This parameter is starting to appear on some definition files.So, to sum-up, you want to end-up with a tune that works with the knock sensorand gives 0-2 knock counts to prevent timing being pulled and running 100% onyour HI-OCTANE ignition map.REV: 0.K merlin@three.com.au Page 54 of 134