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Ethanol & Flex Fuel Tuning: 4. Configure for Secondary Fuel

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4. Configure for Secondary Fuel

20.59

00:00 - The next step in our tuning process is to configure the G4 Plus ECU to suit our secondary fuel, or in this case essentially we're enabling our modelled multi fuel mode.
00:10 Now we're going to need to do this before we even try and start the car with E85 in the tank.
00:17 Otherwise it'll simply be too lean, it won't even start idle, or run.
00:21 So let's jump back into our Link G4 Plus software.
00:25 And we've gone to our fuel main menu.
00:27 And you'll remember initially we set our fuel equation mode to modelled.
00:33 Now we've got our first tune complete, we can go ahead and select modelled multi fuel.
00:39 What that's going to do is enable some other options inside the menu structure.
00:44 First place we're going to go is into our fuel menu, and we're going to go into our multi fuel menu.
00:52 Now this is some of the settings we need to configure for our secondary fuel.
00:57 In particular you can see we've got our injector flow, and we've also got some characteristics for our secondary fuel.
01:05 It's important before we actually go and configure these, to understand what we're trying to do here.
01:11 In this particular case we've got a car where we know that the ethanol content may vary.
01:17 So we know that we're not going to be running at a fixed E85 and I'm expecting that the actual ethanol content that the car may see when it's in competition use could vary between probably 75% and maybe as high as 90%.
01:32 So for this reason what we're going to do is actually use the specifications for E100 as our secondary fuel even though we're not actually tuning on this.
01:43 The important point here is that this will set the characteristics for the fuel itself in terms of the density and the stoichiometric air fuel ratio.
01:53 Now we'll see shortly that the ECU will interpolate these.
01:57 So the stoichiometric air fuel ratio and the density characteristics will still be correct regardless of what our actual ethanol content is.
02:07 So in terms of our injector flow, as we've found in the body of the course, the actual injector flow may vary or drop off slightly on ethanol or E85 due to the viscosity difference between ethanol and pump fuel.
02:23 We don't have specifications for this, so there's no point trying to take a guess, at this point I'm leaving the injector flow data exactly the same as what we used for pump.
02:32 We know that this may involve some slight discrepancies in our tuning and we're going to account for this shortly by enabling a second volumetric efficiency table.
02:43 Moving down we've got our fuel density and our fuel density temperature coefficient as well as our stoichiometric air fuel ratio.
02:51 Again as we already saw, if we press F1, we can get to the help file, and this will give us the correct values to enter.
02:58 What you can see is that I'm using a value of 9:1 for example for my stoichiometric air fuel ratio, and that is for pure ethanol, not E85, as I've already mentioned.
03:11 Moving down we've also got our charge cooling coefficient and again this may vary between E85 and pump gas so this is one of the aspects that we do need to tune or adjust.
03:22 Lastly we have our multi fuel blend ratio table.
03:27 Now the way we need to set this up is going to depend on our application.
03:31 In this case because we are using E0 as one of our fuels, our primary fuel, and E100 as our secondary fuel, what this table is going to do is define how those fuel properties vary as the ethanol content varies.
03:48 So you can see here that the axis set up for this table, for our multi fuel blend table is in ethanol percent.
03:56 So in this case what we want to do is simply set this as a linear interpolation.
04:01 At 0% ethanol we have a 0% blend, and at 100% ethanol of course we have 100% blend.
04:09 So the parameters that this table is going to control will be the fuel characteristics, so obviously we want these to vary in a linear fashion between E0 and E100.
04:22 This is also going to define how the ECU will move between the two warm up enrichment tables, which we're going to look at shortly.
04:31 We can then choose to use this multi fuel blend value as an input for the blends on our other tables, but we'll talk about that more shortly.
04:43 So at this point we've actually got the ECU set up to a point we could start and run the engine.
04:50 However to take advantage of the ethanol fuel, we're going to normally want to make some changes to our ignition and our boost.
04:59 And also it's very likely that we will see some discrepancies creep in that can't be accounted for purely with the changing fuel characteristics.
05:10 So we're also going to want to enable our second volumetric efficiency table.
05:15 And of course we need to deal with our cold start changes that we're going to require on ethanol.
05:21 So let's have a look at how we can do that now.
05:23 There's a range of changes that we're going to go through to do that.
05:27 First of all what we're going to do is look at our cold start, we can get to that in our menu.
05:31 Here we've got essentially the three tables that we're going to be focusing on are our crank enrichment, our post start enrichment, and our warm up enrichment.
05:41 These are currently all configured for a single fuel.
05:44 What we want to do is go through to each of these tables.
05:47 And you can see that we have a parameter here for three dimensional cranking enrichment.
05:53 So what we can do is simply enable this, and now when we go to this table we can see that a load axis has been enabled.
06:01 Now if that doesn't currently say ethanol percent we can simply adjust that by pressing the x key, and we can enable the y axis here, and by clicking we can then select the ethanol percentage as our axis.
06:18 So that's pretty straight forward to set up, and all we've done is set up axis break points there at every 20%.
06:27 Once we click OK the ECU will ask if we want to interpolate here.
06:31 Now at this point what we should have is a configuration or calibration that is accurate at E0, remembering that we have just done a full calibration on pump fuel.
06:44 What we can do if we don't know any better, is simply take the values that we have at E0, and I'm going to simply copy those through to start.
06:55 Now at around about E85 we can expect to require somewhere in the vicinity of around about 50% more fuelling.
07:04 So what I'm going to do is just highlight the entire row at 80% ethanol, that's as close at the moment as we've got as a break point.
07:12 And what I'm going to do is just multiply that by 1.5 What we can do then is highlight the table downwards, and we can use the control I function to interpolate that back to our values that we've already tuned at 0%.
07:29 So let's just go through and complete that now.
07:48 Once we've completed that interpolation, and we've only gone out at this point to 80%, what we want to do is just extrapolate our results out a little bit further as well to our E100 row.
08:02 So we're going to follow a similar process through for our other warm up or cold start corrections.
08:07 Let's go through that now.
08:09 So we've looked at our cranking enrichment, we're also going to look at our post start enrichment.
08:14 And the process is exactly the same there, we're simply going to enable our three dimensional table.
08:20 When we've done that we'll be able to see our post start enrichment table represented in three dimensions.
08:27 What we generally find here is that our biggest change or biggest required change is in our cranking enrichment.
08:34 And the required changes that we need for both our post start and our warm up enrichment tend to be a little bit less large in their magnitude.
08:42 So we've set up our ethanol content axis for our post start enrichment and we've taken a guess at this point by adding just a small amount more fuel at the higher ethanol contents over what we found worked well on pure pump fuel.
09:00 Moving down we'll also look at our warm up enrichment.
09:02 And in this case we actually have two completely separate tables when we're using multi fuel.
09:09 So in this case you can see our warm up enrichment table is set to single.
09:13 What we're going to do here is select multi fuel.
09:16 This will enable two separate warm up enrichment tables.
09:20 Warm up enrichment one will be for our primary fuel, warm up enrichment table two will be for our secondary fuel.
09:28 And the ECU uses the multi fuel blend table value in order to decide how it's referencing betwen these two tables.
09:38 What I mean by this is if the multi fuel blend value is zero this means we're running on our primary fuel, then the ECU will be focusing solely on the warm up enrichment table one.
09:49 If on the other hand our multi fuel blend value was sitting at 100%, in this case it would mean we're running on E100, the ECU would be focusing solely on the warm up enrichment table two, and of course a value for our multi fuel blend of 50% would mean that the ECU would be interpolating half way between whatever's in those two warm up enrichment tables.
10:12 So we can't actually tune these tables right now.
10:16 This is something we need to come back and do, just like we would on pump fuel, after we've completed our tune.
10:22 However at this point we have set up our ECU to enable the amount of adjustment we need for our multi fuel, our ethanol content.
10:33 Moving on we're also going to go down to our fuel corrections menu.
10:38 And if we go down to dual fuel table we're going to go to our dual fuel table mode, and we're going to enable our second volumetric efficiency table.
10:48 Now the important point when we are using the modelled multi fuel mode, is for all of these tables which is going to include our ignition table as well and maybe boost if we want to use this technique.
11:00 We want to select interpolate between.
11:03 And this is going to allow the ECU to interpolate between the two volumetric efficiency tables based on our multi fuel blend or our ethanol content.
11:13 Once we've enabled our interpolate between, you'll see that the selection or option for fuel table ratio table is now visible.
11:23 Now this is what's defining how the ECU will move between one and the other of those two volumetric efficiency tables.
11:32 Let's look at that table.
11:34 Now by default this table will actually use the axis multi fuel blend.
11:40 However I prefer when I'm tuning on flex fuel with ethanol to use ethanol content for that multi fuel blend table.
11:49 So what we're going to do at the moment is set our values between 80% and 100% all to 100.
11:56 What this is going to mean is that any time the ethanol content is above 80%, we're going to be using all of the second volumetric efficiency table.
12:07 For the moment all i'm going to do is linearly interpolate these values back down to zero.
12:14 What this means is that when we have 0% ethanol, we'll be focusing solely on our VE table one, the table that we've already completely and correctly tuned for pump fuel.
12:26 So we know at that point that all of our air fuel ratio lambda data should be absolutely accurate.
12:32 Now it's quite likely that this table will not want to be a linear interpolation, and we're going to come back and revisit this in that last step where we start looking at some other blends of ethanol between 0% and 85%.
12:48 But for now we know that we're going to be operating solely on that second VE table that's going to allow us to make our changes there.
12:56 Now the other thing we will want to do to start with is copy the data from out first VE table into our second VE table.
13:05 So we can access our fuel tables by pressing the F key.
13:09 And what we're going to do now is make sure we're copying the right data from the right table.
13:15 You can see at the top it says fuel table two, that's our second VE table so this is our VE table that is really focused on our ethanol tuning.
13:26 What we can do is press F again, that'll take us to our fuel table one.
13:30 And what we can do is right click here and we want to click on export to clipboard.
13:37 This will export the contents of our fuel table one, or VE table one to the clipboard.
13:42 We can press F again, that'll take us to our second VE table and if we right click again and we click on import from clipboard this will import the data from the clipboard.
13:54 So now our two VE tables will be identical.
13:58 Now obviously this should get us pretty close.
14:01 We can then make any adjustments to our second VE table that we find are necessary.
14:08 If you decide that you want to tune for a different lambda or air fuel ratio target when running on the secondary fuel then you can use the dual air fuel ratio lambda target table functions.
14:20 If we look at our air fuel ratio target tables, we can see that we have two tables with the modelled multi fuel equation enabled.
14:28 AIr fuel ratio lambda target table one is the target table that we conventionally use for our primary fuel.
14:35 When we're running multi fuel we also end up with our lambda target table two enabled.
14:42 And the ECU will interpolate between these two tables using the multi fuel blend ratio table.
14:49 In this instance I am going to be targeting the same lambda or air fuel ratio values between pump fuel and E85.
14:57 So in this case it's important to just make sure that the values in both tables are the same.
15:03 So that's dealt with our fuel table, we're set up ready to start making adjustments when we get into our tuning.
15:09 However we do need to also deal with our ignition timing.
15:13 Remember with flex fuel or ethanol content, we have the advantage due to the higher octane rating and the knock resistance of the fuel to add timing.
15:23 We already found out when we tuned this engine on pump fuel that it was quite heavily knock limited as we raised the boost.
15:29 So this is one of the places we're going to expect to see a lot of power come into our tune from adding some additional timing at higher boost levels, being able to tune to MBT.
15:39 So in order to do that we want to go into our ignition setup and what we're going to do is go into ignition corrections.
15:48 And just like we did with our fuel, we're going to go into dual ignition table.
15:53 Again by default this dual table mode is off.
15:57 Again we're going to select interpolate between and this will also bring up our ignition table ratio table which will define how the ECU will move between ignition table one for pump fuel and ignition table two for E85.
16:12 If we click on this let's see how that's set up.
16:15 Now again by default the axis input for this table will be multi fuel blend and I've changed this here to ethanol content, ethanol percent, for the same reason that we've just discussed as our fuel tables.
16:30 Now the way this is going to work, it's going to define how the ECU will move between the two tables or what proportion of the ignition table one or ignition table two values will be used.
16:43 How we want to set this table up is really going to depend on our use.
16:47 And in this case as we've already discussed, the car is really going to be running either on pump fuel or E85, and not typically anywhere in between.
16:57 So what I've done with this table is I've set it up so that any time we're above E70, we're 100% focusing on our second ignition table.
17:07 This will be our advanced ignition table to take benefit of the properties of the fuel.
17:12 So we know that any time we're above about E40 percent thereabouts, that this is going to give us the maximum benefit or most advantage from the fuel's properties in terms of knock suppression.
17:25 So we know any time we're above E70 we should be relatively safe with this configuration.
17:30 And that's going to give us some room for that ethanol content to move around a little bit without dropping out of that advanced ignition table.
17:39 Likewise at the bottom end you can see up to E20 I've actually set this blend table to zero.
17:45 So what this means is all the way up to 20% ethanol, the ECU will be using solely the pump fuel ignition map.
17:54 And this is really just a safety aspect.
17:56 If we've got a little bit of ethanol in the tank, maybe 5% or 10% the ECU is still going to be using the pump ignition table and we know that this is going to be very safe.
18:06 In between these values we've just got a linear interpolation there.
18:11 But of course you can do what you want with this particular table.
18:15 Particularly if you're trying to get absolutely optimal performance at every ethanol content, you're definitely going to want to focus, in the last step of our tuning process, down at the lower ethanol contents, down around 20%, 30%, and 40%, and you can focus on this table, make some changes, and potentially ramp in that timing a little bit more aggressively than what we're doing here to really optimise your results.
18:43 So at this point we've dealt with our cold start enrichment corrections, we've dealt with our fuel corrections and we've dealt with our ignition corrections.
18:52 We've got one more step that we're going to look at here and that is with our boost setup.
18:58 Now there's various ways we can do this.
19:00 We can use a close loop boost control system where the ECU can be set up to interpolate between boost set points much like we've already seen with our fuel and ignition.
19:12 In this particular installation we are using an open loop boost control system.
19:17 And all I've done here, if we go down to our boost control, is I've set up two wastegate duty cycle tables, we can see these here.
19:27 And we're going to be switching between these two wastegate duty cycle tables depending on whether we have pump fuel in the tank or E85.
19:37 So it's a relatively straightforward system.
19:39 If we go into our multiple boost table setting you can see I've selected two tables.
19:46 And we're actually switching between these tables based on the output from virtual auxiliary output two.
19:54 This is not the only way we can configure this.
19:57 There's a lot of flexibility here, this is just a really simple way that I've gone through to get seamless boost control change as the ethanol content changes.
20:07 To see exactly what's going on let's have a look at how that virtual auxiliary output two is set up.
20:14 And we can see that it is currently switching based on a single condition which is condition one only.
20:21 That condition is the ethanol content has to be greater than a certain percentage, which in this case I've set to 60%.
20:30 So what this is going to do is any time the ethanol content is greater than 60%, the virtual auxiliary two output will be true, and that will switch to our second wastegate duty cycle table.
20:44 So it's a very straightforward system.
20:46 At this point we've got all of the configuration of our multi fuel blend system done.