Ethanol & Flex Fuel Tuning: Ethanol Hold Function - Practical Demonstration
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Ethanol Hold Function - Practical Demonstration
03.39
| 00:00 | - In this module we're going to have a quick look at how an ethanol hold function would typically work in an aftermarket standalone ECU. |
| 00:08 | For our demonstration we are going to be using our custom flex fuel package for the Motec M150 ECU. |
| 00:15 | However the fundamentals of an ethanol hold function remain fairly consistent regardless of the brand. |
| 00:21 | You may find that the actual parameter or channel that's used for the ethanol hold function may vary. |
| 00:28 | In our case we are using engine speed and inlet manifold pressure. |
| 00:32 | Another common channel or parameter is injector duty cycle instead of inlet manifold pressure. |
| 00:39 | So let's have a quick look at the function in the ECU. |
| 00:43 | We can see our ethanol hold function here with our two channels or parameters that we're using for the trigger point. |
| 00:50 | For the hold point we've got our engine speed threshold and we have our inlet manifold pressure threshold. |
| 00:56 | So we can see at the moment we've got an engine speed threshold of 4000 and an inlet manifold pressure threshold of 120 kPa. |
| 01:03 | Now both of these thresholds have a built in hysteresis value attached to them. |
| 01:08 | So what that means for example if we look at our engine speed, we can see in the help that it says that we have a 200 RPM hysteresis. |
| 01:16 | What this means is that as the engine speed exceeds 4000 RPM, as soon as it goes past 4000, the ethanol value will be held at the current live reading. |
| 01:26 | Once the engine speed drops back below 4000 however, it needs to drop back by that hysteresis amount of 200 RPM. |
| 01:34 | In other words it has to reach 3800 RPM before the ECU will start looking at the live value again from the ethanol content sensor. |
| 01:43 | This just avoids the ethanol content jumping around erratically as it goes from holding to not holding, if we're sitting right at that RPM threshold. |
| 01:53 | Likewise if we move down to our inlet manifold pressure we can see that a hysteresis value of 10 kPa is applied to this. |
| 02:01 | With either of these if we set the values to zero this will disable that particular channel and the ECU will ignore it in its hold calculation. |
| 02:10 | What I'm going to do for the moment is I'm just going to set our inlet manifold pressure threshold to zero. |
| 02:16 | We're going to get the engine up and running. |
| 02:18 | What we're going to be looking at here is our ethanol content reading. |
| 02:22 | We can see at the moment that's sitting at about 83%. |
| 02:25 | Once we start the car we will see that this ethanol content reading will move around very slightly. |
| 02:31 | And what I'm going to do is demonstrate the ethanol hold functionality. |
| 02:35 | So let's get the engine running now. |
| 02:37 | OK with our engine up and running we can now see that our ethanol content is moving around a little bit more as I change the engine speed. |
| 02:44 | What I'm going to do is just come across to our engine speed threshold and I'm going to bring this down to 2000. |
| 02:51 | What I'm going to do now, we can see our engine speed over here on the left hand side, just going to increase the throttle opening, and what we're going to do is go past that 2000 RPM threshold, and what we want to do is watch what our ethanol content does as we exceed 2000. |
| 03:05 | We can see at the moment below 2000, it is moving around. |
| 03:08 | I'll just go past 2000 and we can see that our ethanol content is now latched or held at that current reading of 83.3%. |
| 03:17 | I'll just bring the RPM back down below 2000. |
| 03:20 | And as we drop below in this case 1800 RPM, we see the content value starting to update again live from the sensor. |
| 03:28 | It's a relatively simple strategy, a relatively simple function, but it is important to understand and see how that works. |
