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

MERLINS RALLIART & EVOLUTION-X TUNING GUIDEAFR refers to how many parts of air are mixed with how many parts of fuel. So an11:1 AFR means that 11 parts of air are being mixed with 1 part of fuel to createthe air/fuel mixture. When your EVO is at idle or when your EVO is at cruisingspeeds your AFR is around 14.5-14.7:1. This is known as stoichometric or stoich forshort.It has been found that the 14.7:1 mixture produces the least amount of emissions.And since city cars spend 90% of their time at idle, or in cruise, then that is thenumber that the manufacturers use to reduce the emissions on their car.It is worth noting that the 14.7:1 AFR does not produce the best gas mileage. Thebest gas mileage is produced at approximately 15.2:1 AFR.What AFR produces the best power for gasoline? Gasoline gives the best powerwhen it burns at an AFR of 12.5:1. This is regardless of whether the car is normallyaspirated, turbocharged, or supercharged.The following summary shows the story – for gasoline:AFRCOMMENT06:1 Rich run limit.09:1 Low power with black haze.11.5:1 Rich best torque at WOT.12.5:1 Safe best power at WOT.13.2:1 Lean best torque at WOT.14.7:1 Stociometric ideal burn AFR for gasoline.15.5:1 Lean light load, cruise/part throttle.16.2:1 Best economy, cruise/part throttle.18:1 Lean run limit.The RALLIART ECUs all have one HI-OCTANE fuel map and one LO-OCTANE fuelmap, where the values in the 3D maps are shown as desired final AFRs.So what does the AFR look like on a completely stock RALLIART? The stock HI-OCTANE fuel map clearly shows the Mitsubishi engineers intentions and what the4B11 engine needs to run well. Large portions of the 3D map are set to an AFR of14.7:1 and the closed loop control will happily track this fairly well. This yields goodfuel economy and drivability.But then comes the boost and the short answer is PIG RICH at high boost levels! Itis tuned that way to maintain thermal management of the head, turbo and catalyticconverter with sustained WOT operating conditions, and thus not incur warrantyreturns.REV: 0.K merlin@three.com.au Page 34 of 134