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EFI Tuning Fundamentals: 2d vs 3d Injector Deadtime Compensation

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2d vs 3d Injector Deadtime Compensation


00:00 - In the last module, we learned about injector deadtime and how it can affect our tuning.
00:04 We also learned that the deadtime is affected by both differential fuel pressure and the battery voltage.
00:10 This is important because it affects how we would set up deadtime table in the ECU.
00:15 Let me explain this a little more thoroughly.
00:17 In a fuel system equipped with a manifold pressure-referenced fuel pressure regulator, the differential fuel pressure should always be more or less the same.
00:26 It's the fuel pressure regulator's job to maintain a consistant differential pressure.
00:31 This means that we don't need to worry about the differential pressure varying, and we can use a simple, two-dimensional deadtime table that's relative just to battery voltage.
00:41 We simply choose the data from our injector supplier's deadtime data sheet, for the differential fuel pressure we have chosen to run, and enter this into our two-dimensional table.
00:52 This is a little more complex with a returnless fuel system though, where the fuel pressure is fixed.
00:58 In this case, as I mentioned in the previous module the differential pressure changes any time the manifold pressure changes.
01:06 If we want to properly account for deadtime with this sort of fuel system, we really want to use a three-dimensional deadtime table that's relative to both battery voltage and differential fuel pressure.
01:17 Some ECUs may not give us the option for a 3D deadtime compensation table, and in that case we need to accept that the results are going to be slightly compromised.
01:28 If you're faced with this situation, I prefer to use the deadtime data that closest matches the differential fuel pressure you're seeing at idle, as this is the area where deadtime compensation will have the greatest effect.