Practical Reflash Tuning: Step 5: Optimising the Tune
Watch This Course
$229 USD $114.50 USD
-OR-
Or
8 easy payments of only $14.31
Instant access. Easy checkout. No fees.
Step 5: Optimising the Tune
54.53
| 00:00 | - Now that we've got our MAF scaling dialled in, we can actually begin the process of optimising our tune. |
| 00:05 | Before we get stuck in though, there are a few aspects to the Cobb Accessport that it's worth touching on so that you've got a better understanding of how the Accessport works as well as how the basic Subaru ECU structure and logic works. |
| 00:19 | We're going to start by talking about how the ignition control in the Subaru ECU works and particularly if you are new to the Subaru ECU, this is quite unusual, if you don't understand how it works, it can be really confusing and you can easily come unstuck here. |
| 00:37 | Rather than just running off one base ignition table, there are several ignition tables and they interact depending on feedback from the knock control strategy. |
| 00:46 | And this is part of Subaru's dynamic advance multiplier system. |
| 00:52 | So let's talk about how that works. |
| 00:55 | Let's have a look at the software for a start and if we go into our real time tables, the main table that we're going to be doing our ignition tuning on is found here. |
| 01:03 | This is the primary ignition table, TGV's open main. |
| 01:08 | So let's have a look at that. |
| 01:10 | So this is our table here, we can see three dimensions, nothing particularly surprising here. |
| 01:15 | We've got our load in grams per revolution on the horizontal axis and we've got our engine RPM on the vertical axis. |
| 01:24 | It's important here because we are dealing with grams per revolution, which is a channel or parameter that's calculated based off the mass airflow and engine RPM. |
| 01:34 | It's important to log this parameter so that we know exactly where we are operating inside of this table. |
| 01:40 | Now we also have a graphical representation of this table of course down here at the bottom and just like any ignition table, we should expect in a properly tuned table, for this to look relatively smooth. |
| 01:52 | However you may notice, particularly in the higher load areas of the table where we're likely to be running under wide open throttle, full boost, that there is very low ignition timing, particularly through the peak torque area we've got negative ignition timing values, the ignition starting after top dead centre. |
| 02:10 | Now the reason for this is that this table works in conjunction with a couple of other tables which can add timing based on the knock control strategy. |
| 02:20 | So let's have a look at those. |
| 02:22 | In order to get to those we're going to need to come down in our menu structure to the ignition tables, let's open up the ignition tables here. |
| 02:30 | And what we're looking for here is advance dynamic. |
| 02:34 | So if we open up the advance dynamic, there are two options of adding timing here. |
| 02:40 | There's the dynamic advance adder tables. |
| 02:43 | Now in stock form, with the base calibration from Cobb, these are actually zeroed out just to make things a little bit easier to understand so we know where abouts our timing is coming from. |
| 02:55 | Instead the Cobb calibration will work on these tables here which are our dynamic advance base tables. |
| 03:03 | So let's have a look at the dynamic advance base TGVs open table. |
| 03:08 | So we've got exactly the same table structure here as our base ignition table, our primary ignition table. |
| 03:14 | We've got the same load axis, the same RPM axis and the numbers in this table essentially can be added over on top of those primary ignition timing table values. |
| 03:25 | So if for example we take a value here, 6400 RPM, 2.46 grams per revolution, you can see that this table has the ability to add 5.27 degrees of ignition timing. |
| 03:38 | So to see what that means, let's go back to our primary ignition table. |
| 03:41 | We'll find the same point here at 6400 RPM and 2.46 grams per revolution. |
| 03:47 | You can see that we've got 3.5. |
| 03:50 | So what this means is that if the ECU is adding all of our dynamic advance base table over on top of our primary table, we'd actually end up with a final ignition advance being delivered of about 8.8 degrees at that point. |
| 04:05 | So the next obvious question is how does the ECU decide how much of our dynamic advance base table to add on top of our primary ignition timing? And this comes down to another parameter inside of the ECU called the dynamic advance multiplier D.A.M. or DAM depending on how you want to pronounce it. |
| 04:23 | Now the dynamic advance multiplier is a number between zero and 1.0 that's based on the feedback from the knock control system. |
| 04:32 | Essentially depends on how much activity the knock sensor is seeing. |
| 04:37 | And if there is no knock occurring, that number is going to increment up to 1.0 And if it's at 1.0, it's a simple multiplier so it means that all of our dynamic advance base table is added in. |
| 04:52 | If we come back to our dynamic advance base table here, the unit or the cell that we were looking at before, that would mean 5.27 degrees multiplied by 1.0 and of course is 5.27 degrees. |
| 05:06 | All of that table value is going to be added on top of our primary ignition table. |
| 05:12 | Now if on the other hand some knock activity is occurring, let's say for example the ignition timing is overadvanced causing knock or the fuel that the car is running on is a lower octane that's leading to knock then what's going to happen is that over time that dynamic advance multiplier is going to decrement down from 1.0. |
| 05:31 | Let's say it gets to a point where the dynamic advance multiplier is sitting at 0.5, again this is a multiplier for our dynamic advance base table so if we take our multiplier, our DAM value at 0.5, and we use that same value of 5.27 degrees, of course we're going to be adding half of that, 0.5 multiplied by 5.27, we're looking at about 2.6, 2.7 degrees added in. |
| 05:58 | So this is how the ignition system works. |
| 06:01 | And it's important to understand that, and it's also important to understand as we'll see as we go through this part of the worked example, what parameters we need to log so that we can really understand how the ignition system is working and what that dynamic advance multiplier is sitting at. |
| 06:19 | Now since we've just been talking about the dynamic advance multiplier, it's also worth just having a look at the parameter for the dynamic advance multiplier starting points. |
| 06:29 | So that's down here, let's click on that and we can see that in the Cobb base map, that's set to 1.0. |
| 06:35 | So in a stock calibration we'll actually find that that's set to 0.7. |
| 06:39 | Meaning that when we first start the car, the dynamic advance multiplier is not going to be adding all of the available ignition timing in, meaning that we're actually going to start with a slightly detuned engine over the first few minutes of running, provided no knock is occurring, that dynamic advance multiplier is going to increment back up to 1.0, adding in some additional timing. |
| 07:01 | So by setting this to a starting point of 1.0 we're actually starting with a slightly more aggressive tune immediately after startup. |
| 07:09 | Now the activity from the knock control system is going to constantly be changing that dynamic advance multiplier so it's a really good parameter to have a look at in our logging to give you a quick snapshot of what's happening, whether the engine is suffering from knock. |
| 07:25 | And essentially any time we're seeing the dynamic advance multiplier sitting anywhere but 1.0, this should be a bit of a red flag that perhaps the ignition timing is a little bit aggressive. |
| 07:37 | Now working in conjunction with the ignition control system of course is the knock control strategy and again we need to understand how that works and which parameters we need to be looking at. |
| 07:47 | Now there are two parameters here that we need to be logging. |
| 07:51 | If we look at our gauge list here, we've got those two listed over here. |
| 07:55 | We've got our feedback knock correction and our fine knock learning. |
| 07:59 | And essentially the feedback knock correction is an immediate response to a knock event. |
| 08:04 | So if we're doing a ramp run on the dyno or we're running in steady state and the engine starts to suffer from knock, we're going to immediately see that feedback knock correction value drop into the negatives. |
| 08:14 | Meaning that the ECU is retarding timing in response to a knock event. |
| 08:18 | So we obviously want to be logging that and take note of where abouts that's occurring, that's an indication that we're potentially running a little bit too much timing in that particular area of our primary ignition timing table. |
| 08:31 | Now this also works in conjunction though with the fine knock learning parameter and as its name implies this is a knock learning strategy where if knock is occurring, there is a table inside of the ECU where the learned knock value or knock retard required to prevent detonation is stored. |
| 08:49 | What this means is that the next time the ECU runs through the same area of the map, the ignition timing will automatically be retarded as a preemptive measure to stop knock from occurring. |
| 09:01 | Now over time, if no knock is occurring then the numbers in the fine knock learning table will be reduced back to zero, basically adding timing back in. |
| 09:10 | So this is a fluid strategy where the timing is constantly changing in response to knock in order to try and prevent knock occurring. |
| 09:19 | Now in the Cobb Accesstuner software, we do have the ability to see what's going on in our fine knock learning table, we can see that here under our real time tables. |
| 09:29 | If we open up the fine knock learning table, we can see we've got a relatively small three dimensional table there, we've got load in grams per revolution versus engine RPM. |
| 09:39 | You can see at the moment this table is all zeroed out which is what we hope to see. |
| 09:44 | This means there is no fine knock learning going on while we've been running the car. |
| 09:47 | The reason it's important to take note of this table is that if you are performing ramp runs and you're a little bit aggressive with the ignition timing causing some knock, we can end up with that knock retard coming through into the fine knock learning table. |
| 10:00 | If you're not aware of this it can cause a little bit of run to run variation because the engine may not be receiving as much ignition timing as you're expecting. |
| 10:09 | Another aspect that's worth touching on before we get into the tuning is the boost control strategy in the Subaru ECU. |
| 10:16 | And we're going to do some basic boost tuning through this particular worked example. |
| 10:21 | As I've already mentioned here, because we have got a three port solenoid fitted, the existing boost control duty cycle tables are going to need some manipulation to get our boost onto our target. |
| 10:33 | But let's have a look at how that all works. |
| 10:35 | First of all if we go to our boost targets under our real time tuning table, we can see the existing boost targets, these are displayed in bar however you can display them in imperial units if you prefer. |
| 10:48 | We've got our load axis as requested torque here and this is an important aspect to note here because we do want to be logging our requested torque parameter so that we know exactly where abouts in the table the ECU is referencing. |
| 11:04 | It happens that for this particular calibration under wide open throttle operation, we're constantly referencing the 350 newton metre row here, or column here. |
| 11:14 | We've obviously also got our RPM axis there on our vertical axis. |
| 11:18 | So it's important to make sure that these boost targets obviously are realistic and safe as our first starting point. |
| 11:26 | We've also got our boost limits here so we can make sure that the boost limit is set to something that's going to be safe. |
| 11:34 | Now in order to get us onto our boost targets we've got two tables here, our wastegate duty cycles high and low. |
| 11:41 | We'll just talk about how these interact. |
| 11:43 | Let's bring up our high duty cycle table. |
| 11:45 | We've got the same axis as our boost control table with requested torque on the horizontal axis, RPM on the vertical axis. |
| 11:53 | And this is simply the maximum duty cycle that can be delivered to the wastegate solenoid. |
| 11:59 | So regardless of the proportional and integral gains, as part of the closed loop control strategy, nothing can ever exceed the numbers in this particular table. |
| 12:08 | So for our solenoid we need to start by essentially doubling the numbers in this table. |
| 12:15 | We'll get onto that a little bit later though. |
| 12:16 | Now we've also got a second table here, replicates that first table, this is our wastegate duty cycle low table. |
| 12:23 | And the idea with this table is that it should be set somewhere around about 8% duty cycle lower than our high duty cycle table. |
| 12:32 | How this works is that if we perform a ramp run and we come up onto boost, the ECU will use the high duty cycle table as an open loop duty cycle table or a feed forward table for the starting position before it begins closed loop control. |
| 12:48 | However if we were only working off that high duty cycle table, on a transient or a gear shift we're very likely to see an overboost. |
| 12:55 | So in this situation the Subaru ECU on a gearshift will revert to the low duty cycle table, once the engine is stable again and back at full throttle, it will then instigate closed loop control to get back onto the targets. |
| 13:09 | This helps prevent that overboost. |
| 13:11 | And the suggestion here is to keep about an 8% duty cycle difference between high and low. |
| 13:16 | Now this also works in conjunction with the proportional and integral gains system. |
| 13:24 | We're going to see how that works as we go through the tuning. |
| 13:27 | And another aspect that's important to note here, if we cycle down to our boost control tables which we'll see in our menu structure here, let's open that up. |
| 13:35 | And if we look at our wastegate duty cycle here or wastegate duty and open that up, we're also going to have the ability to adjust our wastegate solenoid frequency. |
| 13:45 | You'll see that in the stock calibration for the factory Subaru boost control solenoid this is set to 10 hertz. |
| 13:52 | Now this is quite low for a lot of the three port solenoids that we use in the aftermarket. |
| 13:57 | Typically I'd be running somewhere between about 20 and 30 hertz for the typical MAC three port solenoid. |
| 14:04 | Now a little trick with the Subaru ECU is it appears the maximum duty cycle, it's able to use here is 15 hertz. |
| 14:12 | So we're going to set that to 15 hertz and if you do try and set this high, you're going to run into problems where you're going to end up with very poor or no boost control. |
| 14:22 | So make sure that you're aware of that and keep your boost control frequency at 15 hertz maximum. |
| 14:28 | The next topic to talk about here is Cobb's MAF simple mode. |
| 14:32 | And this is a little bit complex to explain in really simple terms but the Subaru ECU while it primarily uses the mass airflow sensor as its load input, deciding on fuel and ignition based on the MAF signal, under transient conditions, sharp throttle inputs or gear changes, the MAF sensor can lag a little bit. |
| 14:53 | So the stock Subaru ECU logic actually uses a volumetric efficiency or speed density subsystem that it can revert to on these throttle transients. |
| 15:03 | Now in stock form, Cobb believe that there can be as many as 200 different parameters that can affect the final calculation during these transients. |
| 15:12 | They've highlighted the two key ones and if we cycle down to sensor calibrations, we can see we've got MAF corrected volumetric efficiency input, TGVs open and closed, let's have a look at one of those tables and this is essentially a volumetric efficiency table where we've got manifold absolute pressure on the load axis this time. |
| 15:33 | Now the problem for us as tuners is that there's no easy way for us to make the Subaru ECU run continuously on the volumetric efficiency tables so that we can calibrate these accurately. |
| 15:45 | So this makes it really tricky for us to tune these tables and get good results. |
| 15:48 | So as an alternative Cobb have instigated their MAF simple mode which basically eliminates the volumetric efficiency subsystem and runs continuously off the mass airflow sensor. |
| 16:01 | And in simple terms, it does work really well. |
| 16:03 | So it's a good idea to understand that that option is available. |
| 16:07 | We'll close down our sensor calibrations and we will find the MAF simple mode functionality under our Cobb custom features and we can see that under the MAF simple structure here. |
| 16:19 | Now we don't really need to make too many adjustments to this, what we do want to do though is activate it here so if we click on our MAF simple mode activation threshold, we can see that at the moment this is set to 1.5 grams per revolution. |
| 16:30 | In the base calibration you're likely to find that this is set to 3.2 grams per revolution which is a little high for it to really do any good. |
| 16:40 | So Cobb's recommendation is to set this activation point between about 1.5 and 1.7 grams per revolution. |
| 16:47 | We do need to be wary, if you set this too low, you're likely to run into drivability problems. |
| 16:53 | It seems that the ECU does work best if we set this around about that 1.5 to 1.7 grams per revolution mark. |
| 17:01 | So that's going to give you a really simple way of eliminating that subsystem which can be problematic for us to tune in the aftermarket. |
| 17:08 | Another aspect I want to touch on here is some of the compensations available inside of the Subaru ECU. |
| 17:15 | In particular we'll focus here on our ignition trim for intake air temperature. |
| 17:19 | So let's have a look at that, we're going to find that under our ignition tables and then if we move down to compensation and then finally to intake temp. |
| 17:28 | Now there are two tables here that interact so we'll start here with our ignition timing compensation. |
| 17:35 | Now this is a simple two dimensional table based on our intake air temperature. |
| 17:40 | Now it is possible here to choose either the intake air temperature sensor pre turbocharger or in the inlet manifold based on your own personal preferences here. |
| 17:50 | And we can see we've got our trim here and you can see that does look like it might be a little bit excessive, particularly at 70 and 80°C, we've got -6.5 and -7.5 degrees of ignition retard. |
| 18:05 | It's important to understand that this does work in conjunction with our activation table below. |
| 18:11 | And essentially this is a three dimensional table with our load in grams per revolution on the horizontal axis and RPM on our vertical axis of course. |
| 18:21 | Now the way this table works is that it gives the ability to control the magnitude or weighting of how much of that trim will be applied. |
| 18:30 | So we can see that in particular down in the idle areas we've got -100% so essentially there's going to be no trim applied down in those idle areas. |
| 18:39 | However under high load here and high RPM, we're applying about 50% of that trim so instead of the full magnitude of the trim from our table here, we can see that we're only applying half of that so for example if we were at 70°C with a trim of 0%, we would see all of that applied, so 6.5 degrees of trim minus 50%, we would only see half of that, so 3.25 degrees applied. |
| 19:07 | So you are able to manipulate that as you see fit based on the intake air temperatures you're seeing and how sensitive to knock your particular engine is. |
| 19:16 | Next we can take a look at the injection timing control. |
| 19:21 | Now being that this 2015 WRX does run a direct injected engine, the engine timing tends to be a little bit more sensitive than on a port injected engine, but it's still worth having a look at how this is controlled. |
| 19:35 | So we can find this under our fuel tables and then if we cycle down to injectors and finally injector timing. |
| 19:42 | The table that we're going to primarily be using here is our fuel injector, start of injection, homogenous main beta table. |
| 19:51 | We can see here we've got our three dimensional table of our injection timing values. |
| 19:57 | Now this is a stock table, doesn't actually really benefit from modification where we're running on pump gas here. |
| 20:04 | But it is important to just point out where you'll find that if you do want to make some adjustments to this and see the effect of those changes. |
| 20:13 | Because it is a real time tuning table you can make these adjustments while the engine is running and see the effects instantly. |
| 20:20 | Now that we've had a tour of the software, we've talked about the interaction of some of the more important tables, let's get started and lay down a base run here on our Dynajet dyno so we can see what our starting point is before we start making adjustments to any of those tables. |
| 21:00 | Alright we've got our baseline run laid down and we've actually got a slightly lower figure there than we were working with after our MAF scaling at 248.9 horsepower at the wheels. |
| 21:12 | Now I am not too worried about that at this point, we're going to be making some pretty dramatic changes from here anyway and we are also on the dyno on a different day than when we finished our MAF scaling so we're likely to have some day to day variations creep in there. |
| 21:26 | Let's see how we progress as we begin optimising that tune. |
| 21:30 | Before we make any changes though, let's jump into our MegaLogViewer HD software and we'll have a look at what's going on in the software, what happened during that ramp run. |
| 21:39 | So for a start, let's have a quick look at our MAF scaling just to confirm that that's still on point. |
| 21:45 | So we can see that as I click through, we are within about 1% or 2% positive and negative of our zero so we know our trims are pretty good there, we know that our MAF scaling is still good from when we finished that up exactly as we'd expect. |
| 22:02 | What we want to do now is we'll get rid of that particular graph, just so we've got a little bit less going on because we shouldn't need to worry about our MAF scaling from here on in. |
| 22:12 | What we're going to do is start by looking at our boost control. |
| 22:15 | So we've got some parameters set up here that we're going to be looking at, we've got our wastegate duty cycle, we've got our manifold relative pressure and then we've got a parameter called turbo dynamics boost error extended. |
| 22:28 | Essentially this is just showing us how far away we are from our boost target. |
| 22:33 | So our yellow line there in this plot is our boost pressure that we're actually achieving in the manifold. |
| 22:39 | So we can see that our peak there, sitting around about 0.95 so remembering that our boost targets were sitting at about 1.43, 1.45, we're a little way off that and that is shown by our turbo dynamics boost error showing at the moment 0.522. |
| 22:57 | So we're a little bit lower, the reason for this is our red line here that we can see in our plot is our wastegate duty cycle and we can see that that is basically flatlined at 32% so remember this comes from our wastegate max duty cycle. |
| 23:12 | So the first thing we're going to do is head back into our Accesstuner software and we're going to double our wastegate duty cycle tables. |
| 23:22 | Before we do that though, one other aspect that we always want to be looking at here is our knock control. |
| 23:28 | So on this set of graphs here, we've got our ignition timing, we've got our feedback knock correction and our fine knock learning as well as our dynamic advance multiplier. |
| 23:38 | So really what we want to always see is both our feedback knock correction and our final knock learning sitting at zero, exactly what we've got, as well as our dynamic advance multiplier sitting at 1.0 so we know that currently we've got no knock, exactly where we'd expect to be. |
| 23:53 | So let's head back to our Accesstuner software and what we'll do is we'll start with a really simply modification here, doubling our wastegate duty cycle. |
| 24:01 | We can do that quickly by holding down the shift key and the ctrl key, right arrow will highlight an entire row, down arrow will highlight an entire column, we'll press the M key for multiply and we're simply going to double that table. |
| 24:15 | Now what I'm going to do is press ctrl C, that will copy that table to the clipboard, we can now head across to our low duty cycle table, ctrl V will copy that onto our low duty cycle but remember we need a spread here, we want to reduce this so what I'm going to do is hold down the shift and minus key and we're going to reduce that so we've got about a eight degree spread from our high table to our low table. |
| 24:40 | So that's a very basic change there. |
| 24:43 | Obviously when we are making changes like this, we do want to monitor our boost and make sure that it's not becoming excessive. |
| 24:49 | So with that simple change done there, let's do another run and see the effect of that result. |
| 25:16 | So we can see with that one simple change to our boost control we've definitely got a healthier result there on the dyno with a jump up to 288 horsepower, 321 pound foot of torque. |
| 25:28 | Let's have a look at our logging through and we'll see how all of that panned out. |
| 25:32 | Now of course the first thing we always want to check is our knock strategy and we can see in this group of graphs here, we've still got our dynamic advance multiplier sitting at one, we've got no knock feedback, no knock correction, no knock learning, so that's good. |
| 25:50 | We've got no knock occurring so we know that the engine is safe. |
| 25:53 | Let's have a look at our boost control though and see how that panned out. |
| 25:57 | So if we head down and we have a look at our yellow plot for our manifold pressure, we can see that our peak number now looks about here, 1.53 bar so we're actually a little bit above our target there, 1.43 bar. |
| 26:10 | And we can see what our boost control system is doing. |
| 26:15 | So looking at our group with our turbo dynamics integral and our turbo dynamics proportional, what we're looking for here is what the proportional gain is doing. |
| 26:26 | So we can see that at the start of our ramp run here as the turbo is coming up onto boost our proportional gain is essentially maxed out at positive 10%. |
| 26:37 | So the problem with this is we get what's referred to as integral wind up which can result in overboost as the turbo comes up on boost. |
| 26:45 | We can see that that's exactly what's happened here. |
| 26:48 | At this point here where we've hit 1.53 bar, we've still got a positive integral there of about 5.5%. |
| 26:55 | So what this generally means is that we're targeting a boost pressure down at low RPM, that the engine can't really quite achieve. |
| 27:04 | So we're seeing 3000 to maybe 3500 RPM our boost targets are a little bit optimistic. |
| 27:10 | Once we're actually up on boost though, we can see that our control is not too bad, our integral gain here is moving around a little bit, we want to try and get our integral gain through the ramp run to be within sort of 1-2% of zero ideally, giving it a little bit of head room to add or subtract to our boost control system. |
| 27:34 | We can see that particularly at higher RPM, the integral gain is pulling quite a lot of duty cycle out so we want to address that here. |
| 27:43 | So we're going to make two changes here, first of all what we're going to do is below around about 3500 RPM, we're going to reduce our boost targets to something a little bit more realistic. |
| 27:56 | And then above around about 6000 RPM, we're going to start reducing our wastegate duty cycle so let's head across and do that now. |
| 28:04 | So first of all let's head up to our boost target table. |
| 28:09 | And we know that we are running at a target here of 350 newton metres of requested torque, let's just quickly head back and we'll see where we can find that value. |
| 28:20 | So I've got our requested torque added into our top set of graphs in white and we can see, or you can't actually see it doing anything because we're at full throttle right through this ramp run, but we can see that that value there is sitting constantly wherever I click at 350 newton metres. |
| 28:38 | So that's our requested torque so we'll head back across to our Accesstuner. |
| 28:42 | So what we want to do is below around about 3600 RPM, we're going to reduce our boost target. |
| 28:51 | So I'm actually going to extend that down a little bit down to 300 newton metres and we'll take it down to in this case 2000 RPM. |
| 29:00 | So what we can do now is just reduce our boost targets a little bit, make them just a little bit more realistic. |
| 29:06 | We do always want to make sure that our boost targets are relatively smooth so that the ECU can track them. |
| 29:12 | So what we're going to do here is highlight the cells that I've just adjusted here and we can press V for vertical interpolation and this will just smooth those values across. |
| 29:21 | Alright so that's our first change there, we've reduced our boost targets, hopefully that's going to be a little bit more realistic. |
| 29:27 | Now we'll head across to our wastegate duty cycle high table here and just heading back to have another look at our data here. |
| 29:35 | It's around about 6000 RPM and above that we want to make that change to our duty cycle so let's head to that zone there. |
| 29:44 | So again we'll just extend the change that we're making down here all the way to 300 newton metres and I'm highlighting 6400 RPM and above and what we'll do is just shift and minus a couple of times just to remove a little bit of duty cycle there, I'm also going to make a further change at 6800 RPM. |
| 30:06 | Once we've done that we can simply copy and paste that table back across to our low duty cycle rather than making the same change, I just find this a little bit easier. |
| 30:18 | And then again we're going to just reduce that to make sure that we've got around about that 6% spread. |
| 30:24 | So now that we're ready for another run, let's check that out and see what our results are. |
| 30:50 | Alright looking at our results from that particular run we can see we've picked up a little bit of peak power there, we're up to 293.9 horsepower. |
| 30:57 | We've got 322 pound foot of torque at the wheels. |
| 31:02 | More interesting though is our data so let's have a look at that. |
| 31:05 | And we can see if we look at our boost, we've still got this spike here in our boost and that's coming up to a peak of 1.54 bar. |
| 31:14 | However we have got better control there. |
| 31:16 | What we want to do is again have a look at our integral gains. |
| 31:20 | So we can see that we're still probably requesting a little bit much boost and in the early part of that ramp run we've got the integral basically tapped out at positive 10%. |
| 31:30 | Now that's causing that overboost here because where we see that overboost we're still, we've got a positive integral there of about 7.5%. |
| 31:39 | So we've got a little bit more work to do there in terms of our duty cycle as well as our boost aims, just getting those in line with what the engine can actually produce. |
| 31:49 | Now this is a common problem with boost control where tuners try and achieve a boost set point that's simply unachievable. |
| 31:58 | This causes havoc with the closed loop control strategy, trying to drive the turbo harder to achieve a boost that it simply can't get to and once the turbo gets to a point where it can produce boost, it then creates this overboost which is exactly what we're seeing. |
| 32:10 | However you'll also recall that we reduced our wastegate duty cycles at higher RPM and that's worked pretty well, we can see at high RPM now we've got a integral of -2.5, which is pretty close to where I'd want it to be. |
| 32:25 | So this is an iterative process just like our MAF scaling so you can simply go through this process, adjusting your boost targets and adjusting your wastegate duty cycle until you've got something where your integral is under control and you've got nice smooth control. |
| 32:41 | So let's jump ahead and we'll perform another ramp run with our final boost control strategy dialled in and see what that looks like. |
| 33:09 | With our third run up on the dyno screen now, we can see that we've picked up a little bit of peak torque up to 330 pound foot of torque. |
| 33:18 | We've actually lost very slightly in terms of peak power but that's more to do with a very slight spike that we were having in our boost in our previous runs. |
| 33:27 | So by actually smoothing out that boost control and getting it where it should be, we've actually sacrificed a little bit of peak power that is genuinely just across a very very small RPM range. |
| 33:39 | We're not too worried about that right now because we've still got some timing to add into this. |
| 33:44 | More importantly though, let's jump into our log file and we'll have a look at what's going on. |
| 33:48 | So what we can see here is our peak boost here, we're sitting at about 1.5 bar so slightly above our target and we can see that from that point on, about 4000 RPM and to the right there, all the way through to the rev limit, we can see that our red trace here for our turbo dymanics integral is moving around reasonably close to our zero point. |
| 34:12 | We've got positive integral in that from that point onwards. |
| 34:15 | But as I've mentioned we're trying to get that so it's relatively close to zero, we don't want it maxed out and that's what it's doing. |
| 34:22 | Now what we've actually ended up doing here is artificially limiting the maxixmum duty cycle as we're coming up onto boost. |
| 34:30 | And this can be beneficial in some ways to just prevent overboost. |
| 34:33 | So what we're doing is just limiting that maximum duty cycle in the max duty cycle table up to a point where we've reached peak boost and then we're bringing that max duty cycle to a point where the integral and proportional gains can take over. |
| 34:47 | So at this point I'm comfortable with the amount of boost that we're running, I'm comfortable with our boost control, so what we're going to do now is move on and we're going to try adding some timing. |
| 34:57 | So let's have a look at how we can go about doing that. |
| 35:00 | Before we head back to our Accesstuner software, it's a good idea to take note of what maximum load we are actually seeing, so in other words where abouts we're actually operating within that ignition table. |
| 35:12 | So we've got our calculated load channel in red up here in our top set of graphs. |
| 35:16 | And what we can see is that our peak values here are sitting around about 3.1, 3.2 grams per revolution. |
| 35:25 | At higher RPM as we get up towards our rev limiter, we're dropping back down to about 2.3 grams per revolution. |
| 35:32 | So let's head across and have a look at our ignition table. |
| 35:36 | Now the first thing we can see here, straight away is we've got a bit of an issue in that the maximum load site in this ignition table at the moment from the base file is 2.84 grams per revolution. |
| 35:47 | So straight away even with the base file and the boost pressure targets that we're achieving we're exceeding that limit. |
| 35:53 | Now that's not necessarily to say that it's a problem however what will happen is that our ignition timing is going to essentially remain stagnant from 2.84 grams per revolution and above. |
| 36:06 | Not necessarily what we want and it's generally considered best practice to at least make sure that we're spanning out our load cells so that we're always operating within the map. |
| 36:16 | So what we're going to need to do here is rejig our break points for our load axis so that we're spanning that out for the full range. |
| 36:24 | So I'm going to go out to 3.3 grams per revolution out here in our far right cell. |
| 36:29 | Now because we have got a limited number of break points in this particular table, we do want to be a little mindful of the difference or gap between these sites. |
| 36:40 | So what we don't want to do for example is just take our last cell here at 2.84 grams per revolution and change that to 3.3. |
| 36:48 | That's going to give us a really big jump between 2.59 and 3.3. |
| 36:53 | So what I'm going to do here is sort of split the difference, we're going to start by copying our 2.59 gram per revolution column here, we're going to copy those values there, or ctrl C and we're going to move those across to the left. |
| 37:08 | So that's now moved them across to the 2.46 gram per revolution break point site. |
| 37:14 | So of course I'm going to now change that to 2.59. |
| 37:18 | Now what this means is I know that my values there are going to be acccurate when I get to 2.59 grams per revolution. |
| 37:25 | We're going to now repeat that process, we'll ctrl C for our 2.84 gram per revolution column, copy that across and again we'll change our break point here to 2.84. |
| 37:37 | Lastly what we're going to do is change our final break point here to 3.3. |
| 37:42 | Now we've got the same numbers here that we were previously running. |
| 37:47 | So we already know that we were seeing no knock with those numbers so at the moment I'm going to leave them as they are. |
| 37:54 | You can get a little bit more fussy with these break points if you want and start interpolating between these, we've got 2.59, 2.84 and then quite a large jump up there to 3.3. |
| 38:07 | So what we could do there is choose to split the difference, if we highlight those and use the horizontal interpolate, that's going to give us a nice even set of break points. |
| 38:16 | So this should give us essentially the same ignition timing that we were seeing previously. |
| 38:21 | What I'm going to do to start with for our next run is we're just going to highlight essentially the entire area that we're operating in under wide open throttle and we're going to go from 2000 RPM, 2.07 grams per revolution and above and what I'm going to do is simply add two degrees to all of those sites. |
| 38:40 | So this is just going to give us a good starting point, we're going to see what the effect of that two degree change to our timing is. |
| 38:47 | So let's get another run underway and we'll see what our results are. |
| 39:11 | Alright so we've got our run up there on the dyno and we can see that we've got a nice little gain there, we've picked up to 303 horsepower at the wheels, 346 pound foot of torque at the wheels. |
| 39:24 | So that's a good gain for just two degrees of ignition advance. |
| 39:26 | However to get the full picture of what's going on, let's jump in and we'll have a look at our log file. |
| 39:32 | So first of all, we obviously want to be mindful of any level of knock that's occurring so the first thing we want to check is our feedback knock correction and our fine knock learning, along with our dynamic advance multiplier. |
| 39:44 | Good news there, no activity from our knock control system which means that we've got no detonation occurring so our tune is still nice and safe. |
| 39:52 | It's a good point to mention here that during the ramp runs we obviously want to be mindful any time we're advancing the timing of knock. |
| 39:59 | So it's a good idea while we are ramping the car up, if you're not audibly listening for detonation using audio knock detection, check out your gauges while you're ramping the car up and keep an eye on your knock control feedback, just making sure that if any knock is occurring, you can abort that run, get out of the throttle and address that particular issue. |
| 40:20 | Now one thing we have seen here though is now that we've changed our timing a little bit, we've actually got a slight overboost here that's occurring at about 4300 RPM. |
| 40:29 | So this is just going to require a little bit of fettling to our closed loop boost control tables and this is an iterative process because as we progress through the tune, we may find that the ignition timing, because it effects the amount of energy in terms of exhaust gas heat delivered to the turbocharger, it can affect our boost control strategy as well so this can be a back and forth process between changing our timing and coming back and affecting our boost control strategy as well. |
| 40:57 | So that spike there to 1.57 bar, is probably the main reason why we've seen that increase in our peak torque. |
| 41:06 | Not to worry though, what we'll do is go back to our boost control tables and I'm simply going to make a change to our maximum duty cycle at that point so that we can ride that maximum duty cycle table and bring down that peak spike. |
| 41:19 | However what we're going to do now is make a further change to our ignition table. |
| 41:24 | So because we've got a gain in power and torque everywhere with that change that we've made, we'll head back to our Accesstuner software, head back to our primary ignition table and what we're going to do is make a further change. |
| 41:37 | So I'm going to smooth this change that I'm making down further into the load. |
| 41:42 | So we'll go down to 1.8 grams per revolution now and we're going to make that change from 2400 RPM and up. |
| 41:52 | So at this point again because we've got no knock, we're going to try another two degrees, it may prove that this is a little bit optimistic but we'll see what the effect of that change is. |
| 42:03 | When we're making these sort of block changes, we do want to be a little bit mindful of making sure that we keep a smooth trace or smooth shape to the curve and in particular here we can see that at 1.55 grams per revolution, we've now got a little bit of a step in our ignition timing. |
| 42:19 | We move from 6.5 degrees to 1.5 and then back up to two. |
| 42:23 | Likewise we move from eight degrees to three degrees and then back up to 3.5. |
| 42:27 | Now we can address this quite easily just by selecting the cells that we're interested in there and we can use the horizontal interpolate there just making sure that we've got a nice smooth shape to the curve. |
| 42:39 | Obviously when we are doing this, we want to be a little mindful of how far we extend our timing changes beyond the area that we're actually operating in. |
| 42:47 | In the perfect world what we'd actually do is creep up on this, starting at low boost, optimising our timing at that particular load area and then we'd increase the boost and work just solely in the area that we're operating in. |
| 42:59 | So for our demonstration today I'm cheating this a little bit and just speeding up the process. |
| 43:04 | Let's get another run underway and we'll check out the results of that additional timing. |
| 43:28 | With our last run complete there we can see we've picked up another good improvement in our power, we're up to 313 horsepower at the wheels. |
| 43:36 | Maximum torque there of 355 pound foot at the wheels. |
| 43:41 | Now we can see we've got a good gain everywhere over our last run and I've just removed a few of the other runs just to make it a little bit clearer where we're going there on the dyno. |
| 43:50 | Let's jump into our data and we'll have a look at our datalog. |
| 43:53 | Now straight away what we can see here though is we are now seeing a little bit of knock creep in. |
| 44:00 | And in particular we've got around about 1.5 degrees of feedback knock correction and that's occurring at around about 4200 RPM and around about 3.2 grams per revolution. |
| 44:15 | So we're right on the limit there obviously of knock. |
| 44:17 | That is only some fairly light knock so I'm not going to necessarily want to remove all of that timing that we just added in because we did see a good gain there. |
| 44:27 | So what we can do is make a specific change to just that area of that map. |
| 44:32 | So taking into account 3.2 grams per revolution, 4200 RPM, let's head back and we'll have a look at our ignition table. |
| 44:39 | So we are spanned out not to 3.3 so this is why it's important now, we can make quite specific changes to just the area that we are having problems with. |
| 44:48 | So what I'll do is we don't obviously have a break point at 4200 so what I'm going to do is remove some timing at 4000 and 4400 and just to safeguard the engine as well I'm going to bring this change back a little bit down in the load, down to 2.59 grams per revolution as well. |
| 45:07 | So what we'll do there is we'll just start by taking 1.5 degrees out. |
| 45:11 | And I'm just going to smooth that change as well. |
| 45:14 | So at 3200 RPM I'm going to remove one degree and then again at 4800 RPM, I'm going to remove one degree. |
| 45:24 | So this just gives a nice smooth shape to the curve. |
| 45:27 | Now despite that little bit of knock that we had there at 4200 RPM, at higher RPM once the knock retard had gone away we can see that we didn't have any knock occurring and we've got rid of that knock retard by around about 5600 RPM. |
| 45:44 | You can see the jagged shape there as the knock retard basically increments back up to zero. |
| 45:51 | So what we can do there, I know we're probably pretty close to the limit, is we can try adding a little bit of timing, both below and above that point. |
| 45:59 | So let's look at 5600 RPM and we're at 2.6 grams per revolution and we do drop down to 2.3 so let's have a look at that area there. |
| 46:09 | So from 5000, I'm going to make it from 6000 RPM there just to get us a little further away from that area of peak cylinder pressure. |
| 46:19 | And we're going to make this change down to 2.07 grams per revolution and above so I'm just going to add this time, one more degree so I'm just going to be a little bit more gentle with the amount of timing that I'm adding in. |
| 46:33 | Let's have a look at our low RPM range, and our knock didn't occur until 4000 RPM, we know we've removed a little bit of timing below that. |
| 46:41 | So from about 3400 RPM and below we've got no knock occurring and we're operating between 1.69 grams per revolution and 3.1 so let's have a look at that area of our curve. |
| 46:54 | So what we'll do is we'll choose to add a little bit of timing here, from 2400, let's add that from, let's go from 1.8 grams per revolution there and we'll make it up to 3200 RPM. |
| 47:09 | So again I'm just going to add one degree there, just a small change to our timing. |
| 47:14 | So let's get another run underway and see the effect of that small change and hopefully we've got rid of that knock in the mid range. |
| 47:43 | Alright with our last run complete there, we can see that our peak power's actually reading very slightly lower, 312.66 but essentially it's there or thereabouts compared to our last run. |
| 47:55 | What we can actually see though if we compare the two runs is we have picked up or smoothed our power very slightly above that peak power level. |
| 48:03 | And we've seen another small boost variation which has affected our peak torque so that's why we're down to 334 pound foot compared to our last run at 355. |
| 48:13 | So essentially the small gain that we've made in timing there at low RPM and high RPM, has shown us a very small improvement, although in the lower RPM that's been masked by the boost moving around. |
| 48:25 | So this again is why it's so important to make iterative changes to your timing, your fuelling, as well as your boost, making sure that when you're comparing two runs that you are actually comparing apples with apples and that the boost in particular was the same from one run to the next. |
| 48:39 | Let's have a look at our logged data though and we'll see how our knock worked out. |
| 48:45 | So straight away we can see that our knock samples now, our knock logging is nice and clean, we've got no activity there through that run. |
| 48:53 | So at this point we're probably pretty close to where we're going to want our timing. |
| 48:58 | We could do another run there, creep in another degree through the rev range and just see how that affects everything, although given the very very small change that we've just seen there from that last run and the fact that we know that we're right on the brink of detonation or knock right through that mid range around peak torque, I'd say there's little to be gained and we also end up risking having a much more on edge tune. |
| 49:24 | So personally I would prefer to err on the side of caution here and leave the timing where it is. |
| 49:30 | There's one last aspect we want to look at here with our tune optimisation and that is our air/fuel ratio. |
| 49:36 | So far through our tune we've simply left our air/fuel ratio targets exactly where they were from the Cobb base file and as I've already noted, this is quite rich, particularly in the top end, however it's been found that this particular FA20 DIT engine does like to run a little bit richer than what we'd conventionally see. |
| 49:54 | However for the sake of experimentation, let's test and see how the engine responds if we lean that air/fuel ratio out a little bit. |
| 50:02 | So let's head back to our Accesstuner software and what we'll do is we'll go to our closed loop fuelling target base table and we know that we are running up around this area of our table. |
| 50:16 | And in this instance I'm not going to change our break points for our load axis. |
| 50:20 | The reason for this is there's no need for me to change our air/fuel ratio targets as we move to higher load than 2.84 so we can make all of our changes in this area of the table. |
| 50:32 | Now what I'm going to do is just make this change all the way down to 2.08 grams per revolution. |
| 50:39 | The reason for this is that we are running down to that area at higher RPM. |
| 50:43 | So what I'm going to do is just try for our first test, leaning out our air/fuel ratio targets. |
| 50:50 | What I'll actually do here is make that change from 2000 RPM and above. |
| 50:53 | What we'll do is lean out our lambda target there by 0.02. |
| 50:57 | Let's do another run and see the effect of that change. |
| 51:00 | Now while we are doing this, because we've leaned out the air/fuel ratio we don't have the benefit of some additional fuelling for combustion cooling there. |
| 51:07 | We would want to be very mindful of knock during this next run. |
| 51:11 | Let's get our run underway and see the effect of that change. |
| 51:35 | So with our run complete there we can see that essentially our power hasn't been affected at all. |
| 51:41 | We're sitting at 311.5 so we've actually lost a touch of power but obviously we've got some run to run variation in there. |
| 51:46 | Likewise our torque, we've picked up a little bit to 338 but again that's within our expectations of run to run variation. |
| 51:54 | Let's have a look at our datalogging though for a full picture of what was going on. |
| 51:57 | So what I've done here is I've added in our measured air/fuel ratio and our closed loop target and while we can't compare these directly now to our previous runs, we know that we have leaned out that target by 0.02 lambda so we can see through the low RPM area we're sitting with a target of 0.80 lambda, at higher RPM that's sitting at 0.75 where we were at 0.74 thereabouts. |
| 52:24 | So we haven't really seen any major difference in our power. |
| 52:28 | What we are interested in of course is our knock and we can see from our group of data there on our knock control, that we haven't actually ended up with any knock feedback so still no detonation occurring with that leaner mixture. |
| 52:41 | However in this instance I would tend to err again on the side of caution. |
| 52:47 | I'd probably leave my lambda targets a little bit rich. |
| 52:50 | We haven't seen any dramatic improvement in power as I've leaned that lambda target out and it's a benefit here with this particular engine, particularly when we are pushing that turbo very hard, out on the street I'd prefer to have the benefit of that additional fuel to help cool that combustion charge and protect us. |
| 53:08 | We're obviously only doing short ramp runs here on the dyno and what we may see out on the road is the benefit of that richer air/fuel ratio is going to actually help protect our engine when we're running the car through the gears and we're under sustained high load at high RPM and high speed. |
| 53:25 | Now we've got our new calibration flashed into the ECU, it's also saved onto our laptop as well as to our Accessport, so our job of tuning is complete. |
| 53:34 | Normally at this point we would move onto step six of our six step process which is to confirm our calibration out on the road or the racetrack. |
| 53:42 | Unfortunately due to our restrictions here, relying on Cobb's facility and their own cars, we're not able to do that. |
| 53:50 | However the process is exactly as you've seen in the body of our course, you're simply going to take the car out onto the road. |
| 53:56 | Using our datalogging we're going to confirm first of all under cruise conditions that our closed loop trims are under control, meaning that our mass airflow sensor calibration is still sound. |
| 54:07 | We're also going to be checking to make sure that we're not seeing any knock under cruise or transient conditions. |
| 54:13 | Once we're comfortable with that, we can also test under some wide open throttle pulls through the gears, again datalogging to confirm that our boost is under control, our air/fuel ratio and our closed loop trims are under control and most importantly making sure that we're not seeing any knock activity. |
| 54:29 | If we are seeing any knock activity in particular, we can use our datalog to then highlight exactly where in the calibration that's occurring so we can pinpoint that area and remove timing just from the areas where it's necessary. |
| 54:42 | So this brings us to the end of our worked example and if you do have any questions on this worked example, please ask them in the forum and I'll be happy to answer them there. |
