Discussion and questions related to the course **EFI Tuning Fundamentals**

Which ECU are you looking at? Different brands have different ways for representing the data.

With the MoTeC M1, the values in the Engine Efficiency table are Volumetric Efficiency based, this means that they are showing how much of the cylinder is filled in comparison to your reference pressure. So if you have a number of 80, and it is ambient pressure referenced, then this means that the cylinder has 80% of the ambient pressure in it. i.e. ambient of 101.325kPa * 0.80 = 81.06kPa in the cylinder. The M1 then calculates the mass of the air in the cylinder based off of this, and then injects the required mass of fuel to meet the lambda aim.

With the Mx00 family of ECU's, these use a millisecond based fuelling table, where the number in the table is a percentage of the injector pulse width that is configured when you setup the Mx00. So if you have a PW of 10ms, and a value of 80 in the table, then the Mx00 is going to inject 10 * 0.80 = 8ms worth of fuel into the cylinder.

There are other compensations going on in the background for injector dead times, temperatures and pressures as well, but this is the basic premise.

Hi,

No, there is not always a direct relationship between the number in the fuel table and the lambda value., it may be a smaller number needed due to the flow characteristics of the injector used, the manifold pressure and fuel film and other variables.

Regardless of whether the ECU uses a VE based fuel table or an injection time based fuel table, you can apply a simple correction to your fuel table if the measured lambda/AFR isn't your target.

Let's take your example where you have a value of 85 in your fuel table, the measured lambda is 1.05, and you actually want a lambda of 1.00. We can correct this using the equation taught in the body of the course - Correction factor = Measured Lambda / Desired Lambda. In this case the correction factor would be 1.05/1.00 = 1.05 which means we need to multiply the current value in the fuel table by 1.05.

1.05 x 85 = 89.25. This will correct your error and achieve your lambda target of 1.00.