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EFI Tuning Fundamentals: Fuel and Ignition Tables

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Fuel and Ignition Tables

02.24

00:00 - Now that we have a better understanding of what inputs and outputs are available to the ECU, let's have a look at how we, as tuners, can actually talk to the ECU and adjust it to get the results we want.
00:11 While every brand of ECU has its own unique software, the principles remain the same so let's have a look at the most common tables.
00:19 While there are a lot of similarities in how we address the tuning in aftermarket standalone ECUs, reflashing an OE ECU can vary a little more and we'll address this in a separate module, shortly.
00:30 The first table we're going to look at is the fuel table.
00:33 This is where we're going to be spending a lot of our time tuning because it tells the ECU how much fuel needs to be injected to achieve the correct air fuel ratio.
00:43 This table is 3-dimensional with engine RPM on one axis and engine load on the other.
00:49 The load signal will depend on the sensor we're using here.
00:52 As we saw in the EFI Components module, options include MAF, MAP or TPS data.
00:58 Now we have a table which represents the full range of the engine's operating envelope, everywhere from cranking and idle through to maximum power and maximum RPM.
01:08 This lets us very accurately adjust the required fuel injection in each zone to get whatever air fuel ratio we have decided on.
01:17 The other table we're going to spend a lot of time tuning is the ignition table.
01:20 This is similar to the main fuel table, but this time it includes the ignition advance angle in crankshaft degrees.
01:27 This represents the point in the engine cycle that the spark plug will fire and initiate combustion.
01:33 We're going to learn more about ignition timing and how to tune this a little later, so you don't need to worry much about it right now.
01:40 The numbers in the ignition table are degrees of crankshaft rotation relative to TDC on the compression stroke.
01:47 Typically, we'd have the ignition event occur before the piston reaches TDC and this is represented by a positive number in the table.
01:55 In some unique situations, we may want to have the ignition event occur after the piston has moved past top dead centre and this would be represented by a negative number.
02:05 So now, you should be familiar with the two tables that you're going to spend the largest portion of your time working on when you're actually tuning the engine.