Engine Management System / Traction control

[BMEP]

Carsten,

There are many systems out there today. Most EFI falls into one of two types: speed density and mass airflow. Speed density relies largely on tables of data and a "computer model" to calculate the amount of fuel to inject under any given situation. The amount of air entering the engine is never really measured but rather calculated based on various inputs like manifold pressure (vacuum), RPM and temperature.

Mass airflow systems actually measure the amount (mass) of air that's entering the engine at any given time. This makes it much easier for the ECU to calculate the correct amount of fuel to inject at any given moment.

Because it actually measures the amount of air entering an engine, mass airflow is easier to tune and in fact, some systems out there are "self tuning". Speed density systems require manual tuning to "program" the data tables to correctly match the engine's needs. This is what a "tuner" will do when he/she tunes a speed density EFI (plus some other settings like spark advance, sensor calibration, etc.). A good tuner can make a speed density system work just as well as a mass airflow system. However, a poor tune on a speed density system will mean poor running, especially in varying conditions. Of course, it's possible to do a bad tune on a mass airflow system too.

One challenge to mass airflow systems: The mass airflow sensor ("MAF") has to be able to measure the total amount of air entering the engine. For this reason, the multi throttle body systems (like the TWM "stack" system) are all speed density design. In theory this could be done a couple of ways but there aren't any commercially available "stack" type systems that use mass airflow that I'm aware of.

The Racelogic traction control system is largely independent from the ECU. It's wired between the ECU and the injectors. That's why you see the restrictions about what type of injectors (and to some degree, how the ECU works with injectors).

Hope that helps...

Cheers, Rob

[NC427]

Rob,

thanks a lot for the above information - Getting closer and closer to a point where I hope being able to understand at least a small portion of FI-mystery.

What you wrote was definately of great help to me.

Carsten