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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 - The tuning process for injection time based ECUs is very similar to what we've already looked at for the VE based ECU with a subtle difference when it comes to the way we handle the required fuel delivery with changing ethanol content.
00:15 I've broken the tuning process down this time into five steps and we'll go through each in turn here.
00:22 Before we start though you'll need an ethanol content sensor fitted to the engine, wired to your ECU, and correctly configured.
00:30 Step one is to tune the engine for your primary fuel.
00:34 As far as your primary fuel goes, you can choose to make this pump gasoline or your final target blend of ethanol, such as perhaps E85.
00:43 It doesn't really matter which way you choose to do this, but I typically choose the primary fuel to be the fuel I expect the car to run on predominantly.
00:52 For the steps I'll outline here I'm going to assume that our primary fuel is gasoline and our second fuel is E85.
01:01 We also want to start by making sure we have a tank of uncontaminated fuel to begin our tuning with.
01:09 There isn't strictly any specific set up to do here that's any different to how we would deal with a dedicated tune for a single fuel, as this type of ECU won't take the fuel characteristics into account inside the fuel model.
01:24 During this step of the process we also need to optimise all of the cold start and warm up tables too.
01:31 If you need further information on the actual tuning process you can refer to our practical tuning courses for an in depth description.
01:40 With the primary tune complete the second step is to drain the fuel system and refill it with our secondary fuel.
01:47 During this step we want to be careful about contamination of the fuel system from any of the primary fuel that may remain in the tank and the fuel lines.
01:56 You can refer back to the swapping fuels module for a refresher on the techniques and precautions I recommend here.
02:04 Once the fuel system has been refilled with our second fuel the third step of the process is to configure the ECU to suit.
02:12 This is going to require us to start by enabling a flex fuel option or setting in the ECU.
02:19 If the ECU provides a complete second fuel table, then we want to start by copying the table across from our primary fuel table to our second table, and then increasing the values by the required percentage to suit our ethanol blend.
02:35 As we've discussed previously if we were running on E85 then we'd want to increase the fuel table values by approximately 40% and we can achieve this by highlighting the entire table and multiplying it by 1.4 If on the other hand the ECU uses a trim table to make corrections, then we'd start by setting this table to 40%.
02:59 At the bottom of this module you'll find an Excel spreadsheet where you can simply enter your ethanol content and the spreadsheet will give you a multiplication factor that you can use as a starting point.
03:10 It's unlikely that this multiplication factor will be perfect but it should be sufficient to get the engine running well enough to optimise the tune.
03:20 With the ignition tables we're best to begin tuning with a conservative map for our second fuel.
03:26 To do this if we have an error between our desired air fuel ratio and our measured air fuel ratio, we would make these changes directly into either the second fuel table or our fuel trim table.
03:40 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 table, which I know is going to be safe for E85, and I can optimise it from there.
03:54 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.
04:03 The actual warm up and post start tables can normally be left the same as our gasoline maps as we begin our tuning.
04:11 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 boost starting point.
04:22 The last configuration change we need to make is to ensure that the blend tables are correctly configured.
04:28 We want to make sure that the ECU is using 100% of the secondary tables at whatever our final ethanol percentage is.
04:37 Once we've done this I use a linear interpolation back to my gasoline maps when the ethanol content reaches zero.
04:45 With our configuration complete, the fourth step of the process is to complete a full comprehensive tune on our second fuel.
04:53 This includes optimising the second fuel table or trim table, ignition table, boost control, and cold start settings.
05:02 It's important to make sure that when you're tuning on the second fuel that you are making changes to the correct tables.
05:09 It's very for example to make adjustments to the gasoline tables instead of our ethanol tables, which is not only going to have no effect on our tune, it's also going to negatively affect the accuracy of our previously tuned tables.
05:24 With the tuning optimised for our second fuel, the fifth step of the process is to check the calibration at various ethanol blends between our two limits.
05:34 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.
05:43 It's not strictly necessary to check the tune at every possible ethanol content, as this can understandably be very time consuming.
05:52 I'll generally check the tune at at least three different blend percentages in between my two limits.
05:58 For E85 and pure gasoline for example, this may includes tests at 20%, 50%, and 70% ethanol.
06:07 Checking at more blend points can improve the accuracy of your tune but it's going to take you more time.
06:14 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.
06:22 With the blend tables optimised, the tuning process is complete, and you can be confident that regardless of the ethanol content the engine will perform correctly, offering consistent air fuel ratios, good performance, and most importantly good reliability.
06:39 So let's just go back over those steps again briefly.
06:42 The first step is to tune the ECU for your primary fuel.
06:46 Following this we can drain and refill the tank with our secondary fuel.
06:50 Next we can configure the ECU by enabling flex fuel and configuring the various tables for our second fuel.
06:57 Now we can perform a full tune on the second fuel, and finally we can test at various ethanol contents in between our two fuels.

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