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Practical Standalone Tuning: Steady State Tuning

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Steady State Tuning

14.39

00:00 - When it comes to steady state tuning on a turbocharged engine, the process really is no different to what we've already looked at on a naturally aspirated engine.
00:09 Particularly when you're just getting started with tuning, it can seem a little bit scary holding a turbocharged engine in steady state and positive boost for extended periods of time.
00:20 However, if we're considering the heat management which we've already discussed, there's really no downsides to doing so, and there's no real risk inherent in doing so.
00:30 So we're going to have a look at the process on the Dyno now, with our turbocharged Toyota 86.
00:36 Let's get it running in fourth gear, and we'll have a look at some steady state tuning.
00:40 We want to begin our steady state tuning process with the minimum amount of load and RPM that we can satisfactorily run the engine with and again, the process is exactly the same as what we looked at with a naturally aspirated engine.
00:56 For the purposes of this demonstration, I'm going to be focusing on the fuel tuning.
01:01 The ignition tuning still follows exactly the same process as the naturally aspirated example.
01:08 So just going to look at a few key aspects here, using steady state tuning with our fuel table.
01:15 So currently you can see that we're sitting at 60 kPa and 2,000 RPM.
01:20 If we look down at our time graph, we've got our lambda target as well as our measured air fuel ratio or lambda value.
01:28 Again, just like a naturally aspirated engine, we always want to take note of our target to see how close to the center of the current cell we're operating in before we make any changes.
01:40 Now I'm just going to use the Q key or quick lambda function to make changes to my air fuel ratio, if we're too rich or too lean.
01:51 You can see that I've got that cell now tuned correctly, we're right on our target.
01:56 Now at this point we're still in vacuum so the process here is exactly what we've looked at for our naturally aspirated engine.
02:03 Let's open our throttle a little further now, and we'll come up to 100 kPa.
02:08 And we can see that that's exactly where we are now.
02:13 So remember for our naturally aspirated engine this would be the maximum amount of load that we could achieve and this would be full throttle, this would be where we're running at full throttle.
02:23 In this instance, if we look over at the left hand side of our screen we can see our throttle position reading, which in this case, we're achieving 100 kPa with only 37% throttle opening.
02:35 So the ultimate amount of load being placed on the engine at this point isn't actually particularly great.
02:42 We're nowhere near wide open throttle at this point.
02:45 So again, this process is exactly the same, we're going to simply make adjustments to our fueling based on whether our air fuel ratio is richer or leaner than our target.
02:56 Now I'm going to increase the throttle and we're finally going to move into positive boost pressure.
03:01 And you can see now we are sitting at around about 120 kPa, we're almost in the center of our 120 kPa site.
03:10 Although I'm now at full throttle, as you can see here.
03:15 If we look at our throttle, we can see that we're sitting just on 100%.
03:20 So this is the maximum amount of throttle opening we can achieve.
03:23 If we look at our manifold absolute pressure, you can see that we're sitting at 116 kPa.
03:28 So at 2,000 RPM, this is the maximum amount of boost I can achieve.
03:33 You can see we can't actually quite get to the center of the 120 kPa site.
03:38 However, because I've correctly tuned our 100 kPa site, the ECU's going to be interpolating between the 100 and the 120 kPa site, so even though I'm not quite central in the 120 kPa zone, if I adjust the volumetric efficiency value in this cell until I'm reading on my target, we're still going to have an accurate tune for that particular cell.
04:06 Now the reason we can't get exactly into the 120 kPa site here is because the turbocharger isn't receiving sufficient exhaust gas energy to spool up and produce more boost pressure.
04:20 And this is what we're likely to see when we're running at relatively low RPM before we've actually managed to reach the wastegate boost pressure.
04:29 The wastegate currently is actually closed, so all of the exhaust gas energy is going through the turbine housing, through the turbine wheel and helping to spool the turbocharger.
04:40 So we can see that this cell is tuned, we're sitting on our target of 0.89 lambda.
04:47 Now the key point is, I've now been running the engine for probably close to a minute while I've been talking at wide open throttle, and what is still a relatively low boost pressure, but we have been running in positive boost.
04:59 And there's been no problem with doing so.
05:02 You can see our engine coolant temperature is sitting quite happily at around about 90 degrees centigrade, and likewise, our intake air temperature has been sitting relatively constant at 13 and a half degrees.
05:16 So nothing's particularly outside of the happy region I'd like to see from those temperatures, and I'm quite happy sitting here at wide open throttle while I've been talking.
05:28 Let's now go and raise the engine RPM though, and we'll look at how we can approach our tuning with slightly more RPM and hence, slightly more boost pressure.
05:38 So we'll just come up to, in this case we'll bring our RPM up to 3,500.
05:55 And we're now running the engine at 3,500 RPM and again we're starting with 60 kPa so exactly the same zone we were in at 2,000 RPM.
06:07 So you can see at this point, again, we're in vacuum so nothing different to how we'd approach the tuning on our naturally aspirated engine.
06:16 And all I'm going to do is make sure I'm central in the zone, make sure I'm in the middle of that particular zone before I make any adjustments.
06:24 And then again, I'm just going to use the quick lambda function to correct any error between my measured lambda and my target.
06:34 Let's increase our throttle opening though, and we'll see what happens as we start moving into positive boost pressure.
06:40 So again, we will start at 100 kPa, so again, this is the maximum amount of load we could apply with a naturally aspirated engine.
06:51 And again, if we look at our throttle opening, just like we saw at lower RPM, we're now sitting at 38% throttle, so again, we don't actually have our throttle very far open in order to achieve 100 kPa.
07:06 Let's move up into positive boost pressure now, and we'll go up to 120 kPa to start with.
07:22 So now I'm central in the 120 kPa zone, and you can see that our air fuel ratio is a little bit richer than our target.
07:32 Again, I can simply use the quick lambda function or the page up and page down keys to correct any error there.
07:41 And now you can see that we're sitting on our target.
07:44 So at this point, because we have got the engine producing a little bit more power and torque, I am going to want to monitor my engine coolant temperature and my intake air temperature.
07:55 And if we look at our engine coolant temperature on the left hand side, you can see now we're sitting at about 92 degrees centigrade, and you can see that it is increasing while I'm talking.
08:05 Likewise, our intake air temperature has risen slightly, but I'm certainly not worried about 14 and a half degrees centigrade.
08:13 Let's increase our throttle opening slightly further and we'll see if we can get up into our 140 kPa zone.
08:23 Okay, so we're sitting in our 140 kPa zone now, and you can see that I'm sitting at around about 76% throttle, so we're definitely using a lot more throttle.
08:35 You can see that our air fuel ratio is still richer than our target, we're sitting at around about 0.79 lambda.
08:43 So again, I can use the quick lambda function to just get our lambda back on track.
08:48 And if we look at our engine coolant temperature, you can see now this has risen to 94, 94.5 degrees, likewise our intake air temperature's almost hitting 15 degrees.
09:00 Certainly not worried about these aspects at this point but we do need to keep an eye on these.
09:06 Let's increase our throttle opening and we'll see what we can get to at 100% throttle.
09:10 And you can see that our boost pressure actually hasn't increased.
09:15 We're still sitting at about 140, 141 kPa.
09:19 So that's got our fueling tuned through to our maximum throttle setting at that 3,500 RPM zone.
09:30 So again, at that particular boost pressure that we're seeing, 140 kPa, we're not seeing the engine coolant temperature rise too greatly, we're not seeing our intake air temperature spiraling out of control, so we don't necessarily need to be too worried about holding the engine at wide open throttle.
09:50 Now if you've got an engine that does tend to build temperature quite quickly when you're steady state tuning at higher RPM and positive boost pressure, there's another technique that we'll look at now that we can use to tune our fuel and our ignition tables.
10:07 In this instance what we're going to do is we're going to bring the engine into the zone that we want to tune.
10:13 For our example, we're going to use our 3,500 RPM, 140 kPa site.
10:19 We can bring the engine into that zone, have a look at our fuel, or if we're tuning the ignition timing, have a look at the torque the engine's producing, get an idea of what it's doing, then we can back off, bring the engine back down into vacuum, reduce the amount of load being placed on the engine, and we can make our changes to that particular site, and then increase our throttle again, go back into that site and see if the changes we've made have achieved the right effect.
10:46 So to do this, to demonstrate this, what we're going to do is start by setting the fueling or volumetric efficiency value at 140 kPa, and 3,500 RPM to 110%.
10:59 This is just going to give us a rich value to start with and we can tune from there.
11:04 So let's open the throttle and we'll have a look at our air fuel ratio at 3,500 RPM and 140 kPa.
11:14 So I'm just going into that site, we're central in that site now, and I'm just going to pause our time graph and back off.
11:23 So now, I've backed off back into vacuum.
11:27 So this is going mean there's no stress being placed on the engine and my coolant temperature isn't going to continue to increase.
11:33 Now using our time graph, I'll just full screen that, we can see that our engine RPM was 3,544, our manifold pressure was 138 kPa, and we can see that in this case, our measured lambda was 0.79 against our target here was 0.82, so we're a little bit rich.
11:56 So now let's just have a look at how we can alter, how we can tune our 3,500 RPM, 140 kPa site.
12:05 So I'll bring up our calculator and we're just going to use the correction factor that we've learnt in the course to correct our air fuel ratio.
12:15 So in this case, what we're going to be looking at is the measured air fuel ratio or lambda, in this case, 0.79 and then we're going to divide that by our target or desired air fuel ratio, in this case 0.82 and this gives us a correction factor of 0.96.
12:37 So in essence what it's saying is we need to reduce the fueling by 4%.
12:43 So what we're going to do now is we'll just highlight the cell we want to adjust, and we'll enter a value of 0.96, so our correction factor, and then use the multiply symbol, and that's made that correction to that cell.
12:59 Now what we'll do is we'll unpause our time graph, you can see we're sitting here with our coolant temperature at 89 degrees, because we've been sitting in vacuum, we're sitting quite happily at 68 kPa.
13:12 You can see the engine operating quite happily there.
13:15 Just going to increase my throttle opening again.
13:17 We'll go back into our 3,500 RPM cell, and you can see that as we move into that cell, now our air fuel ratio is pretty well perfect, right on our target.
13:34 So this is a quick way of allowing us to tune a particular cell of our fuel or ignition table without having to sit in that particular cell for extended periods of time.
13:45 Of course, if we go back into that cell, we find there's still a discrepancy between our measured and our target, we can simply make another round of corrections.
13:54 So this is the process we're using to tune our fuel and ignition tables in steady state, no different to our approach to tuning a naturally aspirated engine.
14:05 And my recommendation is to do our tuning in steady state out to around two thirds of our engine rev limiter, so in this case around about 4,500 RPM and then we would extrapolate our results out into the untuned area.
14:20 Again, exactly the same approach we've already looked at for our naturally aspirated engine.