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Ethanol & Flex Fuel Tuning: Tuning Process

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Tuning Process


For a refresher or if you are unfamiliar with optimising the cold start and warm up tables of your Standalone ECU please refer to the Practical Standalone ECU Tuning course.

Ethanol Fuel Blend worksheet - Direct download.

00:00 - There's nothing particularly difficult about tuning flex fuel systems but there is quite a lot of work to do and the tasks need to be completed in the correct order to get the best results in the minimum amount of time.
00:12 For this reason we've broken the tuning process for volumetric efficiency based ECUs into six individual steps that I'll go through in this module.
00:22 Before getting started however you'll need an ethanol content sensor fitted to the engine wired to your ECU and correctly configured.
00:32 Step one is to configure the ECU for your primary fuel.
00:36 What I mean by this is to set up the ECU with all of the information required for the primary fuel you're going to run on.
00:44 How thoroughly the ECU deals with this will depend on the particular brand you're tuning.
00:49 Some may just include the fuel stoichiometric air fuel ratio while others will include aspects such as the fuel density and fuel density temperature coefficient too.
01:00 It's critical to make sure you have these parameters correct as well as all of the other typical settings that are essential for any volumetric efficiency based ECU.
01:11 If any of these basic set up parameters are missed or overlooked then the ECU won't be able to correctly cope with the changes in ethanol content.
01:21 As far as the primary fuel goes, you can choose to make this pump gasoline or your final target blend of ethanol such as perhaps E85.
01:31 It doesn't really matter which way you do this, but I typically choose the primary fuel to be the fuel I expect the car to predominantly run on.
01:40 For the steps I'll outline here I'm going to assume that our primary fuel is gasoline.
01:46 We also want to make sure that we have a tank of uncontaminated fuel to begin our tuning with.
01:52 Once the configuration is complete we can move onto the second step which is to perform a complete thorough tune for our primary fuel.
02:01 At this stage we can actually ignore the fact that we're tuning a flex fuel vehicle, and just tune the engine as if we're performing a dedicated tune for this fuel.
02:11 During this process we also need to optimise all of the cold start and warm up enrichment tables too.
02:18 If you need further information on the actual tuning process you can refer to our Practical Tuning course for an in depth description.
02:26 With the primary tune complete, the third step is to drain the fuel system and refill it with our secondary fuel.
02:33 During this step we want to be very careful about contamination of the fuel system from any of the primary fuel that may remain in the tank and fuel lines.
02:43 You can refer back to the swapping fuels module for a refresher on the techniques and precautions that I recommend.
02:50 Once the fuel system has been refilled with our second fuel, the fourth step of the process is to configure the ECU to suit.
02:57 Usually this will require us to begin by enabling a flex fuel option or setting in the ECU.
03:04 We can then set up the fuel characteristics, as well as copying across the table values for the likes of our ignition, volumetric efficiency, and cold start parameters.
03:16 If the ECU provides a complete second VE table, then we want to start by copying the table across from our primary VE map.
03:24 If on the other hand the ECU uses a trim table to make corrections then we'd start by setting this table to zero.
03:32 With the ignition tables we're best to begin tuning with a conservative map for our second fuel, so I'll begin by using the gasoline ignition map values, which I know is going to be safe, and then I can optimise from there.
03:46 With the cold start tables I'll start by adding some additional cranking enrichment for our ethanol fuel blend as discussed in the body of the course.
03:55 The actual warm up and post start tables can normally be left the same between ethanol and gasoline as we begin tuning.
04:03 If the engine is turbo charged I'll start by copying across the gasoline boost control settings so that we can begin tuning from a safe and conservative starting boost point.
04:15 The last configuration change we need to make is to ensure that the blend tables are correctly configured.
04:21 We want to make sure that the ECU is using 100% of the secondary tables at whatever our final ethanol percentage is.
04:29 Once we've done this I use a linear interpolation back to my gasoline maps when the ethanol content reaches zero.
04:37 With our configuration complete the fifth step of the process is to complete a full and comprehensive tune on our second fuel.
04:45 This includes optimising the second VE table, or fuel trim table, ignition table, boost control, and cold start settings.
04:54 It's important to make sure that when you're tuning on the second fuel that you are making changes to the correct tables as it's very easy to accidentally adjust your gasoline tables which will not only have no effect on the tune while running on the second fuel, it's also going to affect the accuracy of our previously tuned tables.
05:15 With the tuning optimised for our second fuel, the last step of the tuning process is to check the calibration at various ethanol blends between our two limits.
05:26 This step allows the blend tables to be checked and optimised and gives you the confidence to know that the flex fuel system is working as intended.
05:36 It's not strictly essential to check the tune at every ethanol content as this can understandably be a very time consuming process.
05:45 I would generally check the performance of the system at at least three different blend percentages in between my two limits.
05:52 For E85 and pure gasoline this might include tests at 20%, 50%, and 70% ethanol for example.
06:01 Checking at more blend points can improve the accuracy of your tune but it's going to take more time.
06:08 What we want to do with these blend tables is adjust the blend bias between the gasoline and ethanol maps as discussed in the body of the course.