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Practical Standalone Tuning: Step 7: Steady State Fuel Tuning

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Step 7: Steady State Fuel Tuning

23.29

00:00 - Now that we've got our engine up and running, it's time to begin our steady state fuel tuning.
00:04 And what we're going to do here is use our Mainline chassis dyno to control our engine RPM and this is going to allow us to move very accurately through the volumetric efficiency table in the Link G4 Plus ECU and we'll be able to tune each zone individually.
00:19 What we're going to do is begin our process with very low RPM and very very light throttle opening so there's very little load or stress being placed on the engine, and we're going to gradually increase both our throttle position and our engine RPM and as we do this we're going to see the shape of the fuel or efficiency table start to develop and we're going to be extrapolating that out into the untuned areas.
00:44 And this is going to speed up our tuning process and it's also going to mean that as we move into the untuned areas, our air fuel ratio should already be very close.
00:52 Now I'll point out that at this stage we aren't going to be touching our ignition table.
00:58 When I'm actually tuning an engine rather than presenting a worked example, even while I am tuning the fuel table, I'll still be listening to my audio knock detection equipment to detect any detonation occurring and if our ignition timing does prove to be over advanced, I'm going to go back and retard the timing further.
01:18 With the numbers we've got in our tables at the moment, I know these are going to be safe for our purposes.
01:24 Now before we actually begin our main fuel tuning task though, there is one more job that needs to be undertaken when we're tuning using the Link G4 Plus modelled fuel equation and that is the fuel charge cooling coefficient.
01:40 Now we already looked at this parameter briefly during our initial setup and configuration and we can find this particular parameter here on our fuel main page.
01:51 At the moment it's set to a default recommendation of 10 degrees centigrade.
01:54 What this does, just to reiterate is it equates to how much the injected fuel will help cool the intake charge.
02:04 So what the ECU really is trying to do here is estimate the charge temperature as it enters the cylinder or goes past the intake valves.
02:12 Now if we don't tune the charge cooling coefficient right at the beginning of our tuning process, what that's going to mean is that if we adjust it later on, it's going to affect the accuracy of our entire tune.
02:25 So this is one of the steps we need to do fairly early on.
02:28 Now I will just explain what this does though.
02:32 if the charge cooling coefficient is not correctly tuned, it's not going to be the end of the world.
02:39 We still can achieve a good tune on the engine, we can still reach our air fuel ratio targets but what we will find or may find is that if we go back to our lambda target table and request a different lambda target, the ECU may not correctly track that lambda change.
02:58 So that's why we want to do this fairly early on.
03:01 So we've got a default value of 10 degrees centigrade in here now.
03:05 What we're going to do is just get our engine running and we're going to make some really broad adjustments just so we can tune this particular element.
03:14 And then what we're going to do is come back and go through our steady state fuel tuning process.
03:20 So this is a little bit out of order but it is a peculiarity with the modelled fuel equation.
03:27 Let's get our engine started and we'll see what we need to do.
03:30 Now what I'm going to do here is I'm just going to get our engine running in fourth gear and I need to run the engine at around about 2500 to 3000 RPM to adjust the charge cooling coefficient.
03:41 Now you can see that our numbers at the moment in this area have our engine running too lean and what I'm going to do, I've just highlighted an entire block of values here and I'm just going to increase them all just very very broadly until I can get my air fuel ratio on target.
03:59 So we can see our target at the moment is lambda one.
04:02 Just going to adjust the numbers until we're running on our target.
04:08 Just make sure that our numbers around this area are tuned correctly.
04:12 Just increase our throttle opening slightly up to -40 kPa and tune this site.
04:21 And we'll reduce it slightly, make sure that our -50 kPa site is also correct.
04:29 OK so at the moment you can see that we are now running pretty accurately at lambda one.
04:35 Now in order to tune the charge cooling coefficient, what we need to do is request a change in our target lambda.
04:42 So I'm just going into my target lambda table and what I'm going to do is highlight all of the cells around the area that we're running in at the moment, and I'm going to request a change of lambda, I'm going to request a target of 0.95 lambda.
04:59 And what we're looking for is what we end up with.
05:02 And you can see that the lambda value has dropped richer but it hasn't quite gone rich enough, it's gone to 0.96, 0.965 lambda.
05:13 If we go back to lambda one, you'll see that we're back on our target of lambda one.
05:18 Now when the lambda doesn't quite track as far as we need it to, what we want to do is go back into our fuel main and we want to increase the value of our charge cooling coefficient.
05:34 Let's just take a guess here and increase it by five degrees, so we're going to go to 15 degrees.
05:40 Now when we make a change like this, often this will require us to make a small change to our efficiency value again, just to make sure that we are still tracking on target.
05:51 So I'll just make sure we are on target.
05:54 We'll go back to our AFR lambda target table and we'll make that same change again, we'll just again request a change to 0.95 lambda.
06:08 So we can see that this time we're actually pretty close.
06:13 So this is the process we need to go through there.
06:15 Now I've only made one really quick adjustment there just to show you the process of tuning the charge cooling coefficient.
06:25 It is an iterative process and we may need to make multiple attempts to get that right.
06:31 But what we're looking for there is making an adjustment to that charge cooling coefficient until our lambda tracks our target lambda when we request a change like that.
06:41 Now that we've got our charge cooling coefficient dealt with, we can move on and begin our steady state tuning.
06:47 So let's get our engine up and running again.
06:50 Alright I'm just going to get our car running in fourth gear now and what we'll do is we'll bring our engine RPM down as low as we can, what I'm going to do is try and get us down to 1250 RPM.
07:04 It's always best if we start with minimal RPM when we're doing our steady state tuning and this is going to put the least amount of stress on our engine, as we've already discussed.
07:15 So I'm just bringing our RPM down now to 1250 and we're just sitting at the moment between -40 and -20 kPa.
07:25 Just bring my throttle position down here, see if we can get into the centre of our -40 kPa zone.
07:31 And you do find that there's a limit to how far you can reduce your throttle.
07:36 If we continue to reduce our throttle position, what we are going to find is that the car will simply slow down.
07:42 So what we can see here at - 40 kPa is we're actually a little bit richer than our target, we're sitting at around about 0.92, 0.93, our target's 0.97.
07:54 What I'm going to do is just highlight the entire column above this point, because we're not going to be able to get there.
08:00 If I reduce the throttle further, the engine's simply going to slow down on the dyno.
08:05 And I've just reduced those numbers now and we're sitting, you can see now on our target.
08:10 Now we've got that site tuned, I'm going to open the throttle further and we're going to go up to -20 kPa.
08:21 OK so we're in our -20 kPa zone here and we can see that this time we're quite lean, we're sitting at about 1.14, 1.15 lambda.
08:30 So obviously it's much leaner than we'd like our engine to be running at.
08:33 Now you'll notice at this point though, I'm not really particularly stressed about this, there is no load on the engine so there's absolutely no chance that we're going to do any damage because of this lean mixture.
08:44 I'll just make sure I'm in the centre of our site there and we'll just increase the value in our efficiency table until I get to my target of 0.96.
08:56 And we can see that we're on our target right now with a value of 60%.
09:00 Actually 58.5%, let's increase our throttle and we can move into the 0 kPa zone.
09:09 Before we do that though, you'll notice that now you're going from 58.5% VE at - 20 kPa, as we increase our throttle opening and we go to 0 kPa, you'll see our value now drops to 50%.
09:24 That's not particularly likely.
09:27 As we open our throttle further, we're expecting the air flow into the engine to increase, so we could expect the volumetric efficiency at 0 kPa to be at least 58.5% if not more.
09:40 So what I'm going to do is simply copy that value down into that 0 kPa zone, and this is going to hopefully have me a little bit closer before I increase the throttle and move there.
09:52 Let's have a look and see how that's worked out now.
09:58 So you can see that even by copying that value, we're still lean, we're sitting at 0.13, 0.14 lambda and our target is 0.95.
10:08 So we're way too lean there, we're in the region of about 18% or 19% too lean.
10:17 So let's use some maths there and what I'll do is I'll multiply our value by 1.19 and that should get us pretty close to our value.
10:26 I've gone to 0.97 so we're still a little way away.
10:30 This time what I'm going to do is just use the shift and Q key to make the last little change and get us onto our target of 0.95.
10:41 OK so we've got our 0 kPa zone tuned.
10:45 Now our next zone is 20 kPa.
10:48 At this low RPM it's unlikely that we're going to be able to actually build enough boost, we're not going to be able to supply the turbo with enough exhaust gas energy to reach 20 kPa.
11:00 So we'll go to full throttle now, and it's likely we're just going to start interpolating into that 20 kPa zone.
11:07 But before we do that, what I'm going to do is just take a guess that the values in the 20 kPa zone are probably likely to be somewhere in the region of 80%, and all I'm doing there is looking at the trend that we've got going there for the few sites that I have tuned.
11:24 So we'll go to full throttle and as you can see we haven't managed to make it into that 20 kPa zone.
11:29 And looking at my lambda point in this cell where we're interpolating, we can see that's sitting at 0.91, 0.92.
11:38 Our target's 0.94 so in this case we've gone probably a little far.
11:43 We know that we were correctly tuned at 0 kPa, now we're interpolating so because we've got an error, this means that our 20 kPa site is actually too large.
11:54 So I'm just going to reduce all of the cells that I've just guessed at, until we get down to our target of 0.94, that's where we're at now.
12:04 So now we've got as much of that 1250 RPM column tuned as we can.
12:11 What we're going to do now is I'm going to highlight the entire column and I'm just going to copy that across to the 1500 RPM column.
12:20 Now before we move into the 1500 RPM column though, I'm just going to take a rough guess and I'm going to multiply the 1500 RPM column here by an additional 10%.
12:32 And this is just a pure guess at how much I might expect the efficiency to increase as I move from 1250 to 1500 RRM.
12:40 As we move up in the RPM at this low RPM range we're expecting our engine efficiency to increase.
12:47 And it's always nice if we start a little bit rich and that allows us to lean out the air fuel ratio rather than find as we move into an untuned area that we are in fact too lean and we have to increase the fuelling.
12:59 So let's now increase our set point on our dyno and we'll move up to 1500 RPM.
13:06 Now as we move up to 1500 RPM, I want to reduce my throttle opening as far as I can and I can see we've got down to our - 40 kPa zone.
13:17 And at this point we can see that despite adding 10% fuel, we're actually still around about 4%-5% too lean.
13:26 So what I'm going to do at this stage, before I make individual changes, I'm just going to increase the entire column and the reason I'm doing this is if I'm lean in one zone, there's a very good chance that my efficiency has either increased or decreased overall relatively consistently as I've gone from 1250 to 1500 RPM.
13:45 So If I'm lean in one zone, there's a reasonable chance that I'll be lean in the entire column.
13:50 Now that we've tuned our entire column approximately, we can start tuning individual zones so I'm just going to have a look at our - 20 kPa column now, just get ourselves right in the centre of that site and we can see that we're very slightly too rich there.
14:08 We're at about 0.97 instead of 0.98 so I'll just remove 1% from that cell.
14:14 And you can see that when we use this process, it is easy to tune the engine, because we've guessed ahead, we're already quite close.
14:23 And it gives us a little bit less work to do.
14:26 So now what we'll do is we'll increase our throttle opening and we'll move up to our 0 kPa site.
14:33 So we're in our 0 kPa site now, this time we're actually a little bit too rich.
14:38 You can see we're sitting at 0.88 instead of our target of 0.95.
14:44 So let's reduce our efficiency value until we get to our target there, 0.95.
14:50 We've done that now, we'll increase our throttle further and move up to our 20 kPa zone.
14:56 Again we're at such low RPM that we can't reach 20 kPa.
15:01 So we're just looking at our air fuel ratio.
15:05 Again we're a little bit too rich so what I'm going to do is just remove a little bit of fuel from the entire column below that 20 kPa point.
15:17 So we're sitting at our target, 0.94 now.
15:20 OK so that's our 1500 RPM column tuned or what we can reach.
15:25 What we're going to do now is copy that again across into our 2000 RPM column and I'm simply going to continue the process and you'll be able to watch this, we'll speed it up a little bit.
15:37 This is simply a rinse and repeat of what you've just looked at in the 1250 and 1500 RPM columns.
15:44 Because this engine does make a lot of noise, I'm just going to fit a set of ear defenders now to reduce the amount of noise in the cabin, and we'll tune the fuel in steady state out to 4500 RPM.
16:30 So that's our steady state tuning process complete there out to 4500 RPM, and I just continued to use the techniques that I already discussed in order to make the changes to the map out in those untuned areas.
16:42 Now one thing you do need to be aware of, particularly with a turbocharged engine is that as we start increasing the load and RPM, you do have to keep a very careful eye on your engine coolant temperature and intake air temperatures, in particular the engine coolant temperature can start to become excessive, in which case we just need to bring the RPM and load back down and allow the cooling fan on the dyno to bring the engine temperature back under control.
17:07 But it is very important that you keep an eye on this, otherwise you can end up doing damage to the engine.
17:14 So we've got our process complete there to 4500 RPM but obviously we still have a lot of the map that hasn't been touched.
17:21 So what we're going to do now is address that.
17:24 What I'm going to do for a start is address these low load areas that we haven't been able to properly get to on the dyno.
17:32 Now while on the road or the racetrack, it's unlikely we're going to be able to spend a lot of time operating in these areas, by virtue of the inertia that the car has while rolling out on the road or the track, if we reduce our throttle while we're in a gear, we can move down into these areas which on the dyno simply results in the dyno slowing down.
17:53 Now while at this point we can't get these areas tuned correctly, what we are going to do is just take an educated guess based on the shape of the rest of the fuel map in the areas that we have been able to tune.
18:07 So for example if we look here at our 4500 RPM column, and we have at this stage been able to tune the - 50, the - 40 and the - 20 load zones.
18:19 What we can do is take a look at the kind of magnitude of change.
18:23 So for example as we've gone from - 20 down to - 40 kPa, we've gone from 76% to 82% or 82% to 76%.
18:36 So essentially we've changed our volumetric efficiency by about 4%.
18:42 Now we've gone from - 40 kPa to -50 kPa, it's smaller change of 10 kPa this time, and we've ended up with around about the same magnitude of change there, around about 4% VE.
18:54 So as we go from - 50 to - 60, I'm simply going to take an educated guess that we might see a similar change and we'll reduce our volumetric efficiency here by another 4%.
19:07 Now what I'm going to do is just continue that trend and reduce my volumetric efficiency as I go down.
19:14 And we see that looking at our load break points here we have - 70 and then - 100 so this is quite a large change, so we're going to make a larger change to our - 100 kPa zone.
19:27 We've gone down 30 kPa so what we're going to do is reduce the value by 12% this time instead of 4%.
19:37 So we can do that by entering a number of 52%.
19:42 So that's going to give the volumetric efficiency curves some shape and again we're just estimating the kind of numbers that we might expect to see.
19:51 If we are tuning a road car, we're going to be able to confirm these once we get out on the road for our final step of our process.
19:59 This should get us very close, it's certainly going to be closer than leaving these zones completely untuned.
20:06 We'd continue that same process down into the other areas that we haven't been able to address here, the process is the same.
20:13 Now let's look at how we deal with the areas above 4500 RPM.
20:16 What I'm going to do is copy my 4500 RPM column across to the right, to the 5000 RPM column.
20:23 Again I'm going to assume that my VE at this point would still be increasing.
20:28 And again it's always safe to be a little rich anyway.
20:31 So if we end up with our VE curve actually decreasing, it's not gonna be the end of the world, we'll be able to address this quickly when it comes to our wide open throttle ramp run tuning.
20:41 So what I'm going to do is just multiply these areas out by 1.05 and I'm just going to increase my VE by 5% per column, 'til I get out to 6500 RPM, and I'm just going to copy that across.
20:55 Now our VE obviously is going to drop away at higher RPM.
20:59 So for the moment I'm just going to copy that across all the way to 9000.
21:03 We could choose to put some shape into this curve and start dropping it away.
21:08 I'm going to in this instance simply start doing that once we see what our air fuel ratio does when we run it out to higher RPM on the dyno.
21:16 But because I've copied this directly across to the right here, I know that my VE will be reducing at 8500, 8000 RPM perhaps and hence I'm expecting my air fuel ratio to be rich once we start running out on the dyno to those sort of RPM ranges.
21:35 OK so that leaves us with our low RPM areas and again we can't necessarily drive the car perhaps down here at 60, 40 kPa of boost and 750 or 1000 RPM, we can't really drive the car there and in fact we don't.
21:51 We still want to continue the general shape that we've got in our VE table.
21:56 So in order to do this, what I'm going to do is take note of, first of all my idle areas.
22:01 So at the moment we're idling somewhere around about 1000 RPM and - 40 kPa.
22:05 We see that we've got a value of 44% VE there.
22:09 So what I'm going to do is copy my 1250 RPM column across, and when I do that, what I'm going to do is just reduce the numbers in the VE table until we've got the same values in the idle area.
22:27 And this is obviously going to mean that our engine is still going to idle correctly.
22:32 So I'm just going to simply copy those out and to the left.
22:35 Now again these numbers may not be 100% correct, we'll be able to spend some time fine tuning the idle areas and what we're going to end up with, the only time that the, areas we're not actually in boost, the areas around here, 0 kPa and 0 RPM are going to be used is during the cranking and starting phase.
22:58 So we don't need to be absolutely pinpoint accurate here because there are a lot of interactions going on during cranking including our cranking enrichment and our startup enrichment.
23:10 So this should get us a VE table that's really close and we're going to be able to fine tune any of those areas, as I discussed, once we get out onto the road in our final stage.