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Practical Reflash Tuning: Step 3: Configure Base Tune File

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Step 3: Configure Base Tune File

21.46

00:00 - Our next step is to set up any changes that we need to make to our base ROM file.
00:05 Now, again, because this car is 100% stock standard, I'm definitely going to perform my first base run on our Dyno, as delivered with the stock ROM, the stock tune installed in the ECU.
00:19 It's always important to get a really solid baseline so we can have something to judge our modifications to the tune against.
00:27 So we're going to do that before we actually flash anything into the ECU.
00:32 However, this is still a good opportunity to make any changes that we deem necessary so that the first time we flash a tune into the ECU, we're already going to have our base parameters set up and ready to go.
00:45 So, let's have a look at what we need to do now.
00:47 I've got my HP Tuners VCM editor software open, and we've got our new file open, so remember we've already downloaded the stock ROM file out of the ECU, we've saved our base ROM file so we'll always have that factory ROM file to revert to if we need to, but now we've saved this again with the name new, so we can modify this new file.
01:12 Let's start by looking at our engine parameters.
01:16 And we're going to go through and make a few changes here.
01:19 I'm going to actually start with our torque management.
01:23 So, the torque management settings here will depend on the particular car you're tuning.
01:29 It's always a good idea to have a look at these settings and make sure they match your expectations.
01:34 In this case, I am going to make some changes here.
01:37 We're going to start with our maximum torque RPM verus gear table.
01:42 And, you can see that this table, from third gear onwards, is maxed out at the maximum value we can enter in here, which is 8,192.
01:53 However, in first and second gear, and less importantly in reverse gear, this value has been lowered.
02:00 So what I'm going to do now is highlight the entire table and we're going to enter a value of 9,000 and press enter.
02:07 And all that does is it sets it to the maximum value.
02:10 When we close this down, you can see that this particular table now turns red to show that we've made some changes to that table.
02:18 I'm going to go through now, and I'm going to complete the same process in our individual gear tables.
02:24 Now, the actual values that you choose may differ to what I'm doing here, you don't necessarily need to max them out like I'm doing, but this will be 100% certain to ensure that we're not going to have any torque management occur, and that can be frustrating to find later on when we're actually tuning the car, trying to figure out why the engine isn't responding to our tuning changes as we'd expect.
02:52 Alright, so we've now maxed out the first through to sixth gear tables, I'm not going to touch reverse because honestly I'm not too worried about how much torque the engine is producing in reverse.
03:04 I'm also going to max out out trans input max value, and our trans output max value.
03:12 So this is just a good practise to get into to make sure that these values are all where you want them to be.
03:20 The next tab we're going to move to is our Spark tab, and there's a few changes we're going to make here.
03:26 First of all, it's important to understand how these tables are set out and where we actually want to make our changes.
03:33 We see at the top here we have under General, we have a max torque timing table.
03:38 And it can be tempting to make changes in here, however this table represents MBT timing and is used by the ECU's torque calculation strategy so we don't actually want to change this table.
03:52 If we want to make timing changes, these are made in our Main Spark Advance tables, and we have high octane and low octane available there.
04:01 At this point, I'm not going to make any changes to our ignition timing until we actually see what the knock detection system is doing.
04:11 We'll see how our engine is running, whether it's suffering from any knock in the standard form.
04:16 The next thing I'm going to do, is we're going to move to our Retard tab.
04:20 So this is the knock control strategy, and there's a few changes I'm going to make in here.
04:26 In general, my experience with the knock control in the GM ECUs is excellent, it's actually very good at detecting knock, it does a great job, and it is very good at protecting the engine.
04:38 However, the basic strategy, the factory strategy, is also set up for an engine that may be running on various grades of fuel, and the GM engineers may not have a great amount of control over what atmospheric conditions that engine is going to be presented with.
04:56 Right now, we are tuning the engine for the specific fuel it's going to be running on, the specific conditions it's going to be running under, and any modifications performed.
05:08 So we can be a lot more accurate with our tuning to ensure that knock isn't occurring as a normal event.
05:14 And this we can find happens in a stock standard car.
05:18 What this means is we don't need to rely so heavily on the knock control system, and we can make some changes to make it a little bit less overbearing.
05:27 Let's start with our knock retard decay, and this is our decay rate which defines how quickly the knock retard will be removed.
05:38 So, after the ECU detects knock, it will retard the timing and then it will slowly reintroduce that timing if no further knock is noticed.
05:47 From stock, that decay rate is quite slow, so it takes a matter of several seconds for the retard to be removed.
05:54 And what we're going to do is simply start by highlighting this entire table, and I'm going to simply double the values in this table.
06:03 So this is going to mean that the knock retard is reintroduced, or removed I should say, twice as quickly.
06:11 Okay, so we've dealt with that.
06:13 Now, the other thing we're going to look at here is our maximum knock retard values.
06:18 So this is the maximum amount of ignition retard that the ECU can use, and what we're going to do is open this table here and have a look at it, and you can see, particularly at the higher load, higher RPM areas of our map the knock retard maximum value is ten degrees.
06:37 Now, in a stock system, where we may be suffering from a lot of knock, that may be necessary.
06:42 In our instance, again, because we're tuning the engine specifically for our operating conditions and fuel, I certainly don't expect to need ten degrees of retard in order to stop knock.
06:54 So what I've done there is I've multiplied that entire table by 0.75, so simply reduced the table by 25%, and you can see now our maximum values are at eight.
07:05 That's still plenty of knock retard.
07:08 We're still going to be able to adequately control knock.
07:13 The next thing we're going to look at is our burst knock retard.
07:16 And this function is there as a preemptive measure that allows the ECU to remove ignition timing to preempt knock, or to prevent knock occurring.
07:26 So this is a predictive strategy.
07:29 In the stock engine, stock ECU, this does tend to work reasonably well.
07:34 However, we find as we modify the engine that this can become overbearing, and particularly if we are seriously modifying the car, we can find that the burst knock system will make it very difficult to maintain consistent spark timing, and we will find that it's going to hamper our efforts to tune the ignition timing accurately.
07:56 This is a transient function, so this happens during transient periods and what we're going to do here, is simply click on our base verus cylinder air delta, and I'm going to highlight that entire table and I'm simply going to set that to zero.
08:12 So this disables the burst knock table, no, the burst knock function.
08:17 Now, don't be alarmed.
08:19 This doesn't mean that we've just eliminated the knock control strategy, we still have that set up and functioning, this is simply the burst knock system.
08:28 And my advice would be to remove that when you're setting up your base ROM.
08:33 The next thing we're going to look at is our base retard.
08:38 So this is the initial amount of retard that is used in relation to a knock event occurring.
08:45 Now, again, we can reduce this somewhat, and what I'm going to do again is multiple this by .75 to remove 25% from this table.
08:56 So I'm just dulling that initial retard down.
08:59 And what I'm trying to do, again, we've now got a system which we're going to be tuning the ignition timings to suit our particular car and our particular application, so we shouldn't be relying so heavily on our knock control strategy.
09:15 Alright, let's move on, and now we're going to have a look at our Fuel tab.
09:20 Now there's a few things we're going to set up here.
09:23 First of all, we are going to actually move across and we're going to talk about our Cat Overtemp Protection Strategy, and that's found under the COT and Lean Cruise tab.
09:35 Now, the Cat Overtemp Protection Strategy will want to be shut off on cars where the catalytic converters have been removed.
09:43 The Cat Overtemp Strategy is there to dump extra fuel into the engine, if the ECU calculates that the exhaust gas temperature has exceeded what it deems is the safe limits for the catalytic converters.
09:57 So you can see here, we have a max enrichment value of 1.35, and this defines how much additional fuel the ECU is able to include, or add, if the cat temperature is deemed to be excessive.
10:12 Now, in our particular application we do have catalytic converters still fitted to the car, so I am going to leave this enabled.
10:19 However, if we had removed the cats, we would simply select disable from that dropdown menu.
10:26 Now, we're going to move back, and we're going to talk briefly about our power enrichment.
10:31 And this is how the ECU defines our target, or commanded air fuel ratio under wide open throttle applications.
10:39 So, here we don't actually have a full fuel map.
10:42 The ECU is simply defining whether or not it is a closed loop, in which case, it's going to be targeting stoichiometric, or an open loop, in which case, it's going to be looking at the values from our power enrichment tables.
10:58 Now, let's start by defining how the ECU knows if it's in a power enrichment or open loop, or whether it's in closed loop, and that's done through our Power Enrich Throttle Position table here.
11:10 And if we click on this, we have a 2D table which you can see is throttle position relative to engine RPM.
11:19 So, essentially how this works is, if our throttle position exceeds the value in this table, the current engine RPM, then the ECU will transition into open loop mode and use the air fuel ratio targets from our power enrichment tables.
11:36 Now, I'm going to make a change to this table.
11:39 You can see, particularly at lower RPM here, up to about 2,500 RPM, we need to exceed 60% throttle in order to move into power enrichment mode.
11:51 And we can get a better part-throttle power and torque if we transition into power enrichment a little bit earlier.
12:00 Now this will be at the deficit of fuel economy, so we want to make sure that the values we put into this table are realistic.
12:08 We don't want to be entering power enrichment when we're really trying to make the engine cruise.
12:14 So what I'm going to do is I'm going to highlight the values up to 2,500 RPM, and I'm going to set a target of 45% throttle instead of the factory setting of 60.
12:26 Then what I'm going to do is simply highlight from 2,500 RPM out to 5,000, and we'll use the interpolate between horizontal bounds function by clicking here, and that's going to smoothly interpolate between those areas.
12:43 So what we're trying to do here is set up a threshold that's realistic so when the driver is wanting to cruise, that will result in closed loop operation.
12:53 However, when we put the throttle down a little bit further and we're really asking for some more power, it's going to allow the ECU to transition into open loop mode.
13:03 The result of doing this is that the car will feel more powerful at part-throttle settings.
13:08 Let's close that table down.
13:11 And now we need to talk about our power enrichment table.
13:14 Now, in this particular ECU, this particular car, we are only running on gasoline, so we don't need to worry about our alcohol table which you can see here.
13:25 This isn't a flex fuel system.
13:27 If we open our equivalence ratio table, you can see we have another 2D table, and this is our target equivalence ratio verus engine RPM.
13:38 Essentially what this, is actually our commanded air fuel ratio, or target air fuel ratio versus engine RPM when we're in open loop mode.
13:48 However, the values in this table are defined in units of equivalence ratio.
13:54 And I know that this might be a new term for a lot of tuners.
13:58 An equivalence ratio is simply the inverse of Lambda.
14:02 So let's see how this works by bring up our calculator.
14:06 And if we take a value from this equivalence ratio target table, let's look at the value we have here at 3,000 RPM.
14:14 We have an equivalence ratio of 1.13.
14:17 So if we enter this into our calculator here, 1.13, and then we use the inverse function here, which is one over our equivalence ratio, this will give us our Lambda target.
14:31 Which, in this case, you can see is 0.88.
14:34 So this makes a little bit more sense to those of you who are familiar with tuning and units of Lambda.
14:40 If we want to go one step further, if we now multiply this value by the stoichiometric air fuel ratio, which in the case we're going to take as 14.67.
14:52 Let's do that now by clicking multiply, and we'll enter the value of 14.67 and press enter, and this gives us our air fuel ratio target, which you can see in this case is 12.98:1.
15:05 So that's how we can move between the various ways of defining our air fuel ratio target directly in units of AFR, units of Lambda, and then, of course, equivalence ratio.
15:18 So now we know what these values are, we need to enter some new values into this table.
15:23 Now this particular course is not designed to show you how to define the correct air fuel ratio for your particular engine, but rather how to adjust the air fuel ratio, or the tune, in order to achieve your targets.
15:38 So what I'm going to do here is just start by setting up a very simple table.
15:42 What I'm going to do is start with a Lambda target of 0.9, so I'm going to enter that into our calculator, and then I'm going to use the inverse function to turn that into an equivalence ratio.
15:56 So, we're going to start by entering that from zero RPM up to 2,000, so we were 1.111, and we've done that now.
16:06 Let's bring up our calculator now, and our higher RPM, I'm actually going to want to target significantly richer.
16:14 So I'm going to target at 5,500 RPM and above I'm going to target 0.87 Lambda.
16:23 So we'll enter that, 0.87, click our inverse function and we find that that gives us a value of 1.149.
16:30 So let's enter that into our equivalence ratio table here, and you can see that I'm just extrapolating that out to the right.
16:38 In this particular instance, there's no way we're ever going to get out to 7,500 or 8,000 RPM, for the sake of completeness, we're just going to extrapolate that through our table.
16:48 Now, for the sake of simplicity, all I'm going to do is highlight our cells between 2,000 and 5,500 RPM.
16:57 And again, I'm going to use the interpolate function to fill out that table.
17:02 And if we look at it as a 2D chart, and just expand it out, you can see we've got a nice, smooth shape to our power enrichment table.
17:10 So that's set up with something that should be a good starting point.
17:14 We're going to be coming back to this table a little bit later on when we actually start tuning the engine, and we'll be making some adjustments to it.
17:22 Now, let's move into our Open Loop and Closed Loop tab.
17:26 You'll remember form the main body of the course that our long term fuel trims can affect our open loop air fuel ratio, and for this reason, I'm always a fan of disabling our long term fuel trim.
17:39 So I'm going to do exactly that.
17:41 And it's relatively straightforward to do this.
17:43 We can look at our long term fuel trim enable parameters here, and you can see we have a minimum engine coolant temperature, which is the minimum engine coolant temp when long term fuel trims can become active.
17:56 I'm simply going to max that particular value out by setting it to 300.
18:02 When I press tab, that will revert to the maximum value that can be entered in that site, so you can see that changes to 256 degrees.
18:10 The next parameter we have is our maximum engine coolant temperature, and in this case I'm simply going to enter minus 40, which is the minimum value that we can enter.
18:21 So what this is going to do is simply make sure that our closed loop, our long term fuel trims are never going to become active.
18:30 We're still going to have our short term fuel trims active and they're going to do a great job of controlling any minor differences we have from our commanded air fuel ratio, and they're also going to allow the ECU to cycle the actual air fuel ratio back and forth across stoichiometric, in order to get our catalytic converters to function correctly.
18:50 But it's going to prevent any effect on our open loop air fuel ratio.
18:55 Okay, so now that we've covered, okay now that we have covered the closed loop fuel trims and getting rid of our long term fuel trims, let's move on, and I'm going to click on the Air Flow tab.
19:07 Now there's not a lot we're going to do here, it's just important to understand what we have available.
19:13 And here in our General tab, we have our MAF calibration.
19:17 So this is where we'd be making any changes if we need to, to our MAF sensor calibration.
19:23 If we click on that, we can see we have a two dimensional table of MAF frequency versus air flow, mass airflow, and grammes per second.
19:33 You can see we've got a nice, smooth shape to our MAF calibration.
19:38 We also have our speed density coefficients here.
19:43 I'm not going to get too deeply into these right now, we're going to be addressing these in our next worked example where we are going to look at rescaling our MAF and our speed density coefficients, but it's enough to know for now where these coefficients are found.
19:58 Alright, we can close down our Engine tab.
20:01 The next thing we're going to look at is our engine diagnostics.
20:06 So this is where we can go through and we can disable any diagnostic trouble codes that we don't want to be popping up.
20:15 Now in this instance, again because our car is 100% standard there's not really any work that we're going to be doing right here at this particular point.
20:24 To give you an example, though, if we cycle through this list of error codes, one of the common ones that we would be looking at is something like our P0420, and our P0430 errors, which are for our catalyst system efficiency bank one and two.
20:44 So we would need to disable these particular error codes if we were removing the catalytic converters from the exhaust system, and we would also generally be disabling any error codes relating to our rear oxygen sensors.
20:59 Okay, so at this point we have the basic changes made that we want to, to suit this unmodified vehicle.
21:08 Now, I'm going to save the file at this point, and you can see that our file name is still, has the new title in it, so we know exactly what we're referencing there.
21:21 Now, I'm not actually going to flash this map, this ROM file, into the ECU at this point.
21:27 Remember, we've already talked about that fact that is is 100% stock standard, so it's important for us to get a completely stock standard base run on the Dyno, so we have something to compare against.
21:38 So that completes our step.