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XMS5 - First Time Tuning Application | Application Note : AN 3


Perfect Power Application Notes.


Application Note - AN 3

This note describes a shortcut to get the engine running with the minimum of set up and wiring. No attempt is made to produce a perfect map; instead the engine should be drive-able as fast as possible.



  • Install unit in passenger compartment away from heat sources.
  • Wire ground and supply relays, fuel pump in accordance with GENERAL WIRING.
  • Wire pickup(s). Use shielded wire!
  • Wire up ignition. If you have another ignition going, then leave it for now.
  • Wire up injectors. Batch wiring is the easiest and requires no cam signal input
  • Connect up a vacuum pipe to the manifold sensor. You need to calibrate the XMS5 to your application N/A or turbo charged.
  • Wire in the throttle position sensor (TPS). You need to calibrate it. There is a calibration table; the cursor must be in the left bottom corner (right hand bottom corner (WOT) will result in no injection).
  • Turn ignition key on, and observe that the relays "click" in, and that the XMS5 gets power (unplug the USB).



Setting the XMS5

  • Connect a laptop or PC via the USB communications cable to the unit
  • Use the Shift F1 key to access PARAMETERS map. Correct the settings to suit your installation.
  • Use the Shift F9 key to access the OPS mode, correct the trigger pattern to your application
  • Use the F6 key to access the SETPOINT map, to allocate the wire for the fuel pump relay.


Here are the most important ones :


 XMS5 Stand Alone Unit - ShiftF1 - Parameters


XMS5 Stand Alone Unit - ShiftF9 - Ops Mode


XMS5 Stand Alone Unit - F6 - Setpoints

Starting the Engine

  • Turn the key of and on, and observe that the fuel pump runs for entered start seconds.
  • Observe that the injectors are activated just after switch on. This is done via the PRIME (F3) circuit.
  • Turn the key and crank the engine. It may be advisable to do this without the plugs in, and without the fuel pump running. Observe that the PC displays a stable RPM at approx 200-300 RPM. If you have no RPM, then the pickup(s) are wrong. Check the distance on magnetic pickups of the "pull-up" on a hall sensor/optical pickup. If you have some RPM, stable, but the wrong value then you may have the wrong set-up information.
  • Put some plugs into the plug wires so that you can see the spark. Crank the engine and observe single and consistent sparks.
  • If everything seems fine, then re-connect the fuel pump and install the plugs. Start your engine. If it fires and dies, then it needs more fuel. Change the (Shift F1) fuel range number until the engine runs.
  • You need a CO meter, or a wide band LAMBDA probe connected to the XMS5B. This is needed to tune the fuel map.
  • Read the section on tuning and proceed along these lines.
  • Confirm the ignition settings with a timing light. The TDC 0° mark must line up when the software ignition point is 0°, to line them up alter the value in the IGNITION REF of the Shift F1 map.


Tuning The Engine

  • You need to have the throttle deflection calibrated (Shift F8). Check that the cursor stands in the left column at idle, and moves to the next position up once the rpm increases by 150-200 RPM on a running engine. Stop engine, and confirm that the cursor moves to the right column at full throttle.
  • You need to confirm the Absolute Manifold Pressure (AMP) calibration (Shift F4). With the engine switched off, confirm that the sensor indicates 1.0 bar (14.2 psi) at sea level. Then confirm that the cursor moves down to 0.3 bar (4psi) when idling with a normal cam.
  • The map you have has some ignition settings. Leave them as they are, unless some special circumstances dictate otherwise. We are not tuning for max power, but rather to get the car drivable.
  • Repeat the fuel number from idle through ALL columns, increasing them so that the full throttle column is 10-30% higher.
  • You need to set the AMP scale (GRADIENT). This is the amount by which each higher step INCREASES.
  • Drive the car by SLOWLY increasing the load. Observe the AFR indication. If it turns LEAN, then increase the gradient.
  • Repeat this process until the AFR goes to 13.5 at full load for a N/A car.
  • That's it! The car is drive-able.



What Next

  • Acceleration is the single item, which frustrates the tuning process. DO NOT tune it to overcome bad mapping. Leave it to last! If used during tuning, the AFR readings are wrong, and you make the wrong fuel map entries.
  • Tune the NO-LOAD line.
  • Tune the values just after the idle position. These fuel numbers are very important for slow traffic (and acceleration).
  • Tune prime injection.
  • Tune ignition. Establish max timing advance on a dyno with the fuel you are using normally. Establish a different reading (map) for racing fuel or very low-grade fuel.
  • Tune the engine temperature compensation when the engine is cold. Confirm the temperature calibration!
  • Tune the acceleration last. You may find that you need very little or no acceleration enrichment.




It is very easy to tune a racing engine, because you are only concerned with power. It is more difficult to tune a road engine, because it has to work over a wide power, temperature and RPM range. The tuning challenge gets bigger, once you increase the AFR to 15-16, because you need to be very precis with the tuning. In short, rich engines are easy to tune, lean engines are difficult.