Practical Standalone Tuning: Fuel Configuration and Testing
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Fuel Configuration and Testing
04.22
| 00:00 | Configuring the fuel system means telling the ECU about the size of the injectors fitted as well as how they should be operated. |
| 00:07 | The Motec M150 is quite advanced here, and allows the complete characterization data for the injectors to be entered. |
| 00:14 | This provides very accurate control of the fuel delivery, but also requires detailed information about the injectors fitted to the engine. |
| 00:22 | If we go to the fuel injector sheet in the initial setup workbook, you can see we have a number of settings that need to be configured. |
| 00:29 | Firstly, we have minimum volume, reference flow, and reference pressure for the injectors. |
| 00:35 | The critical part though is the linearization table which is a 4D table that defines injector flow based on pulse width, fuel pressure, and battery voltage. |
| 00:46 | From these parameters the ECU knows exactly what pulse width is required to provide the required fuel flow. |
| 00:53 | The way the M150 deals with the injector setup is quite advanced and still not too common. |
| 00:58 | So we're going to look at the settings in a more conventional Motec Hundred Series ECU too. |
| 01:04 | In the Hundred Series the injector operation mode is defined partially by the trigger mode the engine uses. |
| 01:10 | Where possible we want to use sequential injection where each injector is operated separately, and this requires that the ECU has a sync input to tell it where in the engine cycle it is. |
| 01:22 | When configuring the fuel system, we start by setting the type of injector that we are using either pick and hold, or saturated drive. |
| 01:30 | Motec defined this with the injector current and peak and hold ratio. |
| 01:35 | Be aware that some ECUs are not compatible with low impedance peak and hold injectors without adding a ballast resistor. |
| 01:43 | The next setting we have to adjust is the injector dead time table. |
| 01:47 | This is a simplified version of the injector linearization table in the M150. |
| 01:52 | Motec referred to this table as injector battery compensation while it's also known as injector dead time, or injector latency in other ECUs. |
| 02:02 | This table required some detailed injector data so you can fill it in properly. |
| 02:06 | Fortunately, this data is available with most quality aftermarket injectors. |
| 02:11 | If your ECU uses a millisecond-based main fuel table, you'll need to set a base injector pulse width which basically calibrates the fuel output. |
| 02:20 | This isn't necessary with the M150 since it uses a proper volumetric efficiency-based fuel delivery model. |
| 02:27 | In Motec's Hundred Series ECU, this base pulse width is referred to as injector scaling. |
| 02:33 | The number here refers to the injector pulse width supplied with a number of 100 in the fuel table at 100 kPa manifold pressure before any compensations are applied. |
| 02:45 | We want to select this number to give us good resolution in the main fuel table. |
| 02:49 | The correct number will depend on the size of the injectors, the fuel pressure, and how much power we expect to make. |
| 02:56 | While you can calculate the likely pulse width using an estimate of engine VE, and the calculations we learned in the EFI Fundamentals course. |
| 03:04 | It really isn't necessary since we can tweak this later as we will see. |
| 03:09 | I will normally start with a master pulse width of around 10 to 12, and adjust this later once we have the engine running. |
| 03:16 | Once we have the fuel configuration complete, we can test the injector outputs. |
| 03:21 | Most ECUs provide a test output mode which can be used to drive an output and test it's working correctly. |
| 03:29 | The M150 has a special test mode where the test RPM can be set, and each output can be tested as if it was operating at the test RPM. |
| 03:38 | We can use this to test each output individually. |
| 03:41 | We're going to start by selecting a test RPM of 2000, and we can use the test output to select each injector output. |
| 03:50 | When you do this you want to make sure that the fuel pump is not operating as otherwise you'll end up injecting fuel into the engine. |
| 03:57 | While you're testing the injectors, you should be able to audibly hear the injector operating, and you can isolate and confirm the correct injector is operating. |
| 04:07 | You can confirm this by unplugging the injector. |
| 04:10 | This is a great way to confirm the injectors have been wired in the correct firing order. |
| 04:15 | Now we can move on to the ignition system. |
