IGNITION TUNING

Perfect Power Articles.

 

The ignition of a car engine can be tuned by a tuning chip or by a piggyback control unit. The piggy-back control unit will result in more flexibility but initially more work. There are many reasons why an ignition should be tuned. Here are a few: increasing engine performance, saving fuel and increasing horsepower. Of course, if you have changed/improved any part of the engine, then ignition tuning is called for.

 

Here are a few reasons why you should not tune the ignition:

  • The car has an active knock-control
  • You can’t guarantee the available fuel quality


If your engine has knock control then any tuning effort you make is countered by the ECU, and you get no results. The fuel quality is not such a big hurdle. If it is acceptable to operate a manual switch for high/low grade fuel, then you can get by.

The fuel quality is measured in OCTANE: The higher the number the better the fuel is. A simple explanation of octane rating is: Lower octane fuel ignites voluntary at lower temperatures than high octane.

We can see that the temperature plays a roll and the octane. The temperature is the temperature in the cylinder and of the piston/spark plug. Any high spots or wrong chosen spark plug may get very hot and ignite the fuel mixture BEFORE the actual ignition point. This can results in power loss, and eventually engine destruction.

However, a very good tuned ignition can increase the engine power and reduce the fuel consumption. A more graphical explanation is: We like to ignite the fuel at a point well before the top dead to center (TDC), so that it reaches its max expansion at TDC and remains in the cylinder as long as possible.

If the manufacturer has chosen safe design criteria for low-grade fuel then ignition tuning is called for. If you have modified your engine, then you may want to ignition tune your car. If you have installed a turbo or supercharger, then you MUST tune the ignition.


 

HOW IS IT DONE?

The piston position (Crank angle) is measured on the flywheel by some sensor. The sensor produces pulses. Somewhere else, or on the flywheel, a marker is produced, which identifies one (or two) complete crank turns. This signal is counted (processed) in the ECU, which will then issue ignition pulse at the correct crank position to the correct cylinder. Sounds complex, but is rather simple.

 

Ignition tuning is INTERCEPTING the crank signal, and modifying it (in time) so that the ECU issues the ignition pulse at the desired time. If the modification is a DELAY, then the ignition pulse is retarded. Advancing is also possible, but a little more complex to understand. How can the unit issue a pulse BEFORE it has happened? Well, it can when it knows the pulse sequence for a complete (or two) turns. The knowing of the pulse sequence is sometimes described as learning, synchronization or locking-on. Once the unit knows the pulse sequence, it takes the pulse, which is just about to happen and outputs it before it actually happens for advancing. In other words, it delays a pulse for 350 degrees in order to achieve 10 degrees advance.

 

Various units can handle ignition tuning in different ways. One of the main differences is CAM tuning. If the engine has a CAM sensor, which provides the cylinder information, then tuning the crank alone may produce an ECU error, because the Crank/CAM relationship is violated and the ECU thinks that the CAM belt has slipped. In this instance the CRANK and the CAM must be tuned together. In some instances an engine may have one crank and four CAM sensors for variable inlet and exhaust CAM’s. Check below on how many ignition signals a unit can modify.

 

 

THE FOLLOWING UNITS TUNE IGNITION :

Unit Crank CAM
     
SMT8 piggyback 1 4
SMT8L piggyback 1 0
SMT8T piggyback 1 0
XMS4A stand alone 1 1
XMS4B stand alone 1 1
XMS4C stand alone 1 1


The tendency of the motor manufacturer is save on the CAM sensor, and to incorporate the position information in the crank signal in the form of a gap. The two popular crank signals are:

  • 36-1: 36 teeth per turn, 10 degrees per tooth, one missing
  • 60-2: 60 teeth per turn, 6 degrees per tooth, two missing


Other related tuning articles:
Lambda Tuning
Extra Injector Tuning