Practical Standalone Tuning: Step 7: Steady State Fuel Tuning
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Step 7: Steady State Fuel Tuning
39.27
| 00:00 | - Now that we've got our engine running, we're comfortable that it's mechanically sound and we're comfortable that our ECU is able to do its task properly, it's time to actually start doing some tuning, on our dyno. |
| 00:12 | And we're going to start by look at steady state fuel tuning. |
| 00:16 | Particularly, when we're just learning to tune, it's always easiest if we can concentrate on one task at a time. |
| 00:23 | And I'm going to start with the fuel. |
| 00:25 | Once we're a little bit more comfortable, we'll generally be steady state tuning and swapping backwards and forwards between fuel and ignition, tuning both simultaneously. |
| 00:35 | But for now, remember, we started with some base safe numbers that we know are likely to be very retarded for our ignition timing, so we can concentrate solely on tuning our fuel. |
| 00:46 | Now, even when we are tuning our fuel, it's always advisable to use audio knock detection equipment, so if we do happen to be over-advanced in our ignition table at some point, we're going to hear the engines begin knocking and we can stop and address that. |
| 01:03 | I'm not going to be using audio knock detection here because I am presenting this worked example to you. |
| 01:09 | But in the real world, we would always be listening for knock. |
| 01:14 | OK, so the process of tuning in steady state is to use the dyno to control the engine RPM. |
| 01:21 | So we're going to set the dyno to control a constant engine RPM, and then we're going to use our throttle to adjust the load point, so we can move accurately through our three-dimensional volumetric efficiency table. |
| 01:34 | And what we're going to be doing at each point is adjusting the VE until our air-fuel ratio matches our target. |
| 01:40 | Let's have a look at our laptop screen. |
| 01:43 | And the main feedback we're going to be using are these two parameters here. |
| 01:47 | We have our wide-band O2, which is our air-fuel ratio being measured in the exhaust. |
| 01:51 | And of course, with have our target Lambda, which you remember, simply comes from our target Lambda table here, which we look at during the base table configuration. |
| 02:02 | Again, I'll stress it’s important that to make sure that these target Lambda values are what we actually want to be tuning for. |
| 02:10 | So we've got our VE table set up here, and I've made some small adjustments here so that our idle area where we're operating at our target of Lambda 1.0. |
| 02:22 | Now before we actually start tuning, you'll notice that, at the moment, we're sitting at -71 kPa. |
| 02:29 | And that puts us in this awkward area where we're actually operating in the middle of these two zones, or these cells. |
| 02:37 | We're operating between our -80 column and our -60 kPa column. |
| 02:42 | So before I do anything else, what I'm going to do is I'm going to click on our axis setup icon, and I'm going to simply add in another column by clicking the insert column icon. |
| 02:55 | And I'm going to add a column at -70 kPa. |
| 02:59 | Now, if we click OK, that column will be entered in. |
| 03:04 | Now this has no, at this stage, on our actual tuning. |
| 03:07 | What the ECU will do is interpolate the surrounding cells. |
| 03:11 | But this is gives us a column now that is exactly centered on our idle load, and this makes it much easier to be very accurate with our idle tuning. |
| 03:23 | Likewise, there's a good chance we're going to be accessing this particular load column when we start doing our cruise area tuning. |
| 03:32 | Okay, so we've already got our idle setup, what we're going to do is start by getting our engine running in fourth gear at a 1,000 RPM, and we'll have a look at how we can make adjustments to this VE table. |
| 03:45 | So let's do that now. |
| 03:47 | Now particularly, when you're just starting like this with a completely untuned VE table, it is quite likely that when you start trying to run the engine and you bring out the load and the RPM, like I'm doing now, you may find that the engine will stutter, it'll be hesitant and it won't run correctly because it's too lean. |
| 04:06 | In that case, it's as easy as simply highlighting the cells that the ECU is trying to access and we can make an across the board change to our VE just for the purposes of getting our engine up and running. |
| 04:21 | Once we've got the engine running, we can then come back and fine tune these cells. |
| 04:25 | So, we don't need to be too accurate when we're first starting our steady state tuning. |
| 04:31 | Alright, so now what I'm going to do, you can see, I've just brought my throttle back, and we're sitting comfortably right now at -60 kPa at 1,000 RPM. |
| 04:42 | And the little cursor, square cursor showing us where we're accessing in the table. |
| 04:47 | Now one handy feature with the Haltech is, if we press the Spacebar, the current cell will be highlighted. |
| 04:53 | So the cell the ECU is accessing, the cursor will jump to that so we can make changes to the correct site. |
| 05:01 | Another key factor to look at here is on the left hand side of our table, we have this little target. |
| 05:06 | You can see at the moment, we've got a little green square sitting in there. |
| 05:10 | And it shows us where exactly the ECU is accessing relative to our current cell that the cursor is in. |
| 05:21 | So I'll just change our RPM slightly on the dyno there. |
| 05:25 | And you can see, when we're right in the middle of that cell, the square goes green. |
| 05:31 | If I increase my throttle opening slightly, and we'll move out of that, you can see the cursor goes away, the green square goes away and we end up with a little red circle showing that we're outside of that particular cell. |
| 05:43 | It's very important, when we're making any changes with our tuning to make sure that the engine is as close as possible to the center of the current cell before we make these changes. |
| 05:55 | Otherwise, we're going to be having our accuracy reduced because of interpolation with surrounding cells. |
| 06:02 | So that target is useful for showing us how close to the center of the cell we are. |
| 06:07 | And while I've been talking, you'll notice that our wide-band Lambda is showing that we're sitting in around 1.09, 1.08 Lambda, so we're quite lean. |
| 06:17 | And you can see that it isn't concerning me in the slightest. |
| 06:21 | Despite the engine being, what we would consider quite lean, at the moment, we're sitting there with very little RPM onboard. |
| 06:28 | The engine is only sitting at 1,000 RPM and if we look at our throttle position here, you can see that our throttle position is at 8.5, 8.6% that's barely open. |
| 06:40 | So there's very little air, very little load on the engine. |
| 06:44 | And this means that there's no chance of us doing any damage due to a lean mixture. |
| 06:49 | And this is really why we want to start with as little load and RPM on the engine as we can. |
| 06:55 | And progressively increase both the RPM and the load. |
| 06:59 | This allows us to begin building up a picture or a trend for the shape of the VE curve. |
| 07:06 | And if we keep following that trend and copying ahead, what that means is, as we increase our load in RPM, we're already going to be very close to our target Lambda before we get to a untuned cell. |
| 07:19 | And that's what you'll see me doing. |
| 07:22 | OK, it's time to actually make some changes, and there's a variety of ways we can do that, and we're going to look at a few of the common techniques now. |
| 07:30 | So you can see that we're lean, so we need to increase the number in our VE table in order to correct that lean condition. |
| 07:39 | And we can do that. |
| 07:40 | First way we'll look at is simply by entering a larger number into our VE table. |
| 07:47 | So let's take a guess and enter a number of 80. |
| 07:50 | So we've typed in 80 using the keypad, we press enter, that change is locked in. |
| 07:57 | Now, you can see instantly we see our wide-band Lambda move richer. |
| 08:03 | Now, in this case, we've actually gone a little bit too far. |
| 08:07 | You can see that our wide-band Lambda is now showing 0.97, 0.96. |
| 08:12 | So it's a little bit richer, we've gone a little bit too far. |
| 08:15 | It's a little bit richer than what we really want and a little bit richer than our target. |
| 08:20 | So we can try taking a guess at a smaller number. |
| 08:23 | Let's try perhaps 75, so we'll lock that in and see what happens. |
| 08:27 | Now we're really close. |
| 08:30 | Now we're sitting at 1.01 to 1.02, so we're still a touch lean. |
| 08:35 | So we started out too lean, then we went too rich, now we're a little bit lean again. |
| 08:39 | Let's try 77 and see if that works. |
| 08:43 | Okay, 77 has got us right on to our target of Lambda 1, well 0.99. |
| 08:49 | You'll notice that when we're talking about Lambda values, the air-fuel ratio being measured and the exhaust always moves around slightly, it's never really a constant fixed number. |
| 08:59 | And for that reason, when I'm talking about a target of, let's say, Lambda 1, I'm always talking about a range that I'm going to be happy with. |
| 09:09 | So when I say Lambda 1, I'm generally going to be shooting for a range of plus or -0.01. |
| 09:16 | So, I'll accept perhaps 0.98, 0.99 through to 1.01. |
| 09:22 | So the technique that we've just looked at is what I call the trial and error method. |
| 09:28 | We simply take a guess at the number that we might need to put in the VE table and we keep adjusting that number until we reach our target. |
| 09:37 | There's nothing specifically wrong with it and this is how many tuners around the world operate. |
| 09:43 | However, what we're going to look at is some ways that we can speed up the process and be a little bit more accurate with our tuning. |
| 09:52 | Before we increase the load, let's look here at our table. |
| 09:55 | And you can, what might seem strange, is that I've actually started at -60 kPa. |
| 10:02 | Now, that leave us with these three zones out here to the left that are untuned. |
| 10:07 | Now obviously, we'd like to tune the entire table, so why haven't we started at -100 kPa? Well the simple reason is because we can't access this area. |
| 10:17 | This would be known as the overrun area. |
| 10:19 | and in fact, -100 is an absolute vacuum. |
| 10:22 | The engine's never ever going to get quite that far down. |
| 10:27 | What we need is a certain amount of torque to keep the dyno moving. |
| 10:31 | And what you'll find is, if I close my foot down on the throttle, watch what happens to our little cursor here. |
| 10:37 | And it starts moving down the towards the -70 kPA site, which is great, that's the next site down. |
| 10:45 | But as we continue to close the throttle, you'll see the engine RPM actually drops. |
| 10:50 | So that means that we can't, quite, access in this case. |
| 10:54 | Can get very very close but we can't, quite, access the -70 kPa site. |
| 11:00 | So when we started our tuning at 1,000 RPM, the -60 kPa site, is the lowest zone that we can actually operate right in the middle of. |
| 11:10 | Now, remember when we're making changes, we always want to be in the center of the cell. |
| 11:15 | So this makes it very difficult for us to accurately tune this -70 kPa site. |
| 11:20 | Cause you can't quite get to the center of the site. |
| 11:23 | However, we can look at what's going on here. |
| 11:27 | And based on the fact that we know -60 kPa was tuned correctly. |
| 11:32 | At the moment we're interpolating very slightly between the two. |
| 11:36 | We're sitting at -67 kPa. |
| 11:39 | So we're closer to the -70 kPa site, than we are to the -60. |
| 11:44 | You can see that for the most part we're sitting a little bit lean here. |
| 11:48 | So I'm just gonna take an educated guess here, and I'm going to enter a value of 72, in that site. |
| 11:55 | That's going to correct our Lambda. |
| 11:57 | And I'm going to be happy enough with this for the moment. |
| 12:01 | I'm going to completely ignore, for the moment, our -80, and our -100 kPa sites. |
| 12:08 | Once we finish this entire row, we'll come back and I'll tell you how I'm going to address those. |
| 12:14 | Okay, so now we've tuned our -70, our -60 kPA, we've taken an educated guess at what our -60 kPa site should be. |
| 12:23 | Let's look at out -50 kPa site. |
| 12:26 | So we'll just increase our throttle opening now. |
| 12:28 | And we'll bring ourselves up into that -50 kPa site. |
| 12:33 | Now you'll notice that as I'm moving to the -50 kPa site. |
| 12:39 | Again, our Lambda moves very lean. |
| 12:43 | This is completely to be expected. |
| 12:45 | We've now gone to 1.13 Lambda, so we're very lean. |
| 12:49 | Also simply because as we increase our load, we increase the air flow on, into the engine, we rightly expect that the VE will probably increase. |
| 13:00 | So we've gone from a tuned zone at 77% VE. |
| 13:04 | Now we've gone into this untuned zone that still has our broad guess of 70% in it. |
| 13:10 | So, in reality I wouldn't do that. |
| 13:13 | What I would have done, before we moved from 60 kPa to -50, I would have copied that value across. |
| 13:21 | So, let's enter a value of -77. |
| 13:24 | Now, when we increase our throttle opening, we're probably still going to be a little lean. |
| 13:30 | You can see this time, we're already very very close to our target. |
| 13:34 | We're sitting at 1.03 already. |
| 13:37 | So this is just using common sense, and, applying what we think the engine should do, as we increase our load. |
| 13:48 | So that we're already closer to our target. |
| 13:50 | Okay, so now we're going to look at another way of making changes to our cells. |
| 13:54 | This time we're going to use a little bit of math. |
| 13:56 | Don't get scared off though, it's really easy. |
| 13:59 | So I'm going to bring up my calculator. |
| 14:02 | And I'm going to use the correction factor that we looked at in our EFI tuning fundamentals course. |
| 14:08 | So in order to do this, what we need to do is take our measured Lambda or air-fuel ratio. |
| 14:13 | In this case 1.03. |
| 14:15 | And we wanna divide this by our target air-fuel ratio, or Lambda, in this case one. |
| 14:22 | So this gives a multiplicational correction factor of 1.03. |
| 14:26 | So what this means is, if we multiply our current VE value, in this case 77, by 1.03, this should give us a new VE value that will correct the error. |
| 14:40 | Let's look at that. |
| 14:41 | So we're going to multiply our 1.03 correction, by the value in our VE table, 77%. |
| 14:48 | So that gives us a value of 79.3 I'll close down our calculator cause we're not gonna need that anymore. |
| 14:56 | So let's enter 79.3. |
| 14:58 | And we'll see how that effects our Lambda. |
| 15:03 | Straight away you can see in one adjustment we're right absolutely bang on our target Lambda. |
| 15:09 | So we've made that correction now with no guesswork. |
| 15:12 | We've calculated what the value needed to be. |
| 15:14 | That's corrected our error and air-fuel ratio, in one single adjustment. |
| 15:20 | So that's a really quick way of making that adjustment. |
| 15:24 | Okay, we're going to look at now how we can do that without needing to bring up the calculator every time we wanna make a change. |
| 15:31 | So we're going to increase our throttle opening again. |
| 15:33 | And we're going to move across to -40 kPa site. |
| 15:37 | This time I'm going to extrapolate that shape that we've got, to, our VE table. |
| 15:44 | Even though we've only tuned a few cells, you can see that, particularly between -60 and -50, the VE's increased by about 2%. |
| 15:54 | So let's just take a guess that, that's probably going to increase about 2%, when we go up to -40 So let's enter a value of 81. |
| 16:04 | So that's our 79% from our tune site, plus another 2%, as a broad guess. |
| 16:10 | Let's increase our throttle opening now, now we'll move into that particular site and we'll see how that's worked out for us. |
| 16:18 | So you can see that, it's a very powerful technique once we start getting a feel for how to follow the trend that we're seeing in our VE table. |
| 16:28 | We've moved into that untuned site. |
| 16:30 | I haven't needed to make any adjustments and we're already absolutely bang on our Lambda target. |
| 16:35 | So that's worked out really nicely for us. |
| 16:37 | Let's move further forward. |
| 16:39 | And this time I'm going to look at the -30 site. |
| 16:42 | This time I actually want a little bit of an error so we can make some adjustments. |
| 16:46 | So let's enter a value of 80. |
| 16:48 | And, I'm going to expect that that will have us a little bit lean when we move into that site. |
| 16:53 | Move our throttle open. |
| 16:56 | And as expected, you can see now, we have got a little bit of an error. |
| 17:00 | We're sitting at 0.99 Lambda, our target is, 0.97. |
| 17:07 | Okay, so you've seen how we can use the calculator. |
| 17:10 | Let's do it now without the calculator. |
| 17:12 | Now if we look at this the difference between 0.99 and 0.97, is 0.02. |
| 17:18 | What that suggest is that we're about 2% too lean. |
| 17:24 | This means that we need to add 2% to the VE table in order to correct that error. |
| 17:29 | And we can do that simply pressing the P key. |
| 17:33 | This brings up the percentage change box. |
| 17:36 | And this is one we're going to be using a lot. |
| 17:39 | Now we can simply enter our desired percentage change. |
| 17:42 | In this I'm going to enter a value of two. |
| 17:44 | Press Enter to lock in the change. |
| 17:46 | You can see that it has the same effect, as us manually calculating. |
| 17:50 | And now our Lambda is tracking our target beautifully. |
| 17:54 | This is a very fast way of making adjustments. |
| 17:57 | Okay, let's move further forward, and we'll take another guess at our -20 kPa site. |
| 18:03 | And we'll increase the throttle opening again, to get up to there. |
| 18:08 | Okay, another way we can make changes, particularly when we're really close to our target, which you can see we are now. |
| 18:14 | We're only around about 1 to 2%, rich. |
| 18:18 | Instead of using a calculation or making a percentage change, of course we can always just make small adjustments to the current cell. |
| 18:26 | So the Page Up and Page Down keys will do this. |
| 18:29 | If I press the Page Down key, that will remove 1% from the current cell. |
| 18:33 | So I press Page Down and you see, that reduces the value to 82%. |
| 18:39 | If I want to make a larger change, we can hold down the Shift key. |
| 18:43 | If I press Shift and Page up, that'll add 10% to the current cell. |
| 18:48 | And we don't want to do that, I'll hold down Shift and Page Down to remove that 10% and get us back where we were. |
| 18:54 | We can also make finer changes by holding down the Ctrl key, and pressing the Page Up and Page Down, to make 0.2% adjustments. |
| 19:04 | So particularly, if I'm already very close to my desired Lambda, this a technique I'll use quite frequently. |
| 19:12 | Okay so we're on our target now. |
| 19:14 | Now we're going to open our throttle, and we're going to tune our 0 kPa, or our wide open throttle area. |
| 19:23 | Let's do that now. |
| 19:24 | I've again made a guess. |
| 19:26 | And you can see that, my guess is already, almost perfect. |
| 19:30 | And we're very very close to our target, I'll just remove a little bit of fuel, and, get us back to where we want to be. |
| 19:38 | Actually I'm adding fuel, which is never the right way to go when you're already too rich. |
| 19:44 | And, we're on our target now. |
| 19:47 | So that's given us one complete row of our VE table that we've now got tuned. |
| 19:53 | And we've looked at, a few different ways of adjusting the cells. |
| 19:56 | We've looked at the trial and error method. |
| 19:59 | We've looked at how we can calculate a correction factor. |
| 20:01 | And we've also looked at how we can simply make an adjustment to the current cell directly, using the Page Up Page Down keys. |
| 20:11 | Okay so now remember I said we were going to look at these cells down here. |
| 20:17 | I'll bring the engine back to idle while we're doing this. |
| 20:19 | So these are the areas that we couldn't tune. |
| 20:22 | Now, again we know that within reason, as we reduce the load on the engine, we're going to see the engine's volumetric efficiency most likely decrease. |
| 20:33 | So it's unlikely that we're going to want to leave these two cells completely flat at 70%. |
| 20:40 | And what I'm going to do is just make it guess. |
| 20:42 | Again, based on the trend that I'm seeing, with the rest of the VE table across that 1,000 RPM row. |
| 20:50 | And, I'm going to reduce the values in the VE table, as we move further to the left. |
| 20:57 | So in this case what I'm going to do is take a guess that, our value at -80 kPa might want to be 68%. |
| 21:07 | And I'm going to guess that our value at -100 kPa, might want to be 62% Now, there's every chance that that's not going to be quite right. |
| 21:17 | And this is an area we're going to be looking at when we finally get off the dyno, and get to adjust and optimize our tune on the road or racetrack. |
| 21:25 | Now, bear in mind that this isn't an area that we're going to be driving the car in, under normal conditions. |
| 21:32 | The dyno does a really good job of showing us where we're actually likely to be operating when we're out on the road. |
| 21:38 | So we can't get to these areas on the dyno, but there is the chance that, under certain conditions on the road, we may be able to get into these cells occasionally. |
| 21:47 | So we still want them to be as close as possible. |
| 21:50 | That's why I'm extrapolating the shape of that VE table, and taking an educated guess at what these might want to be. |
| 21:57 | The type of area will be operating in this region, the type of operation of the vehicle, we might get into these regions of the table. |
| 22:05 | This is the sort of area where we might be coming up to a stop, and we're on overrun, and we're just barely touching the throttle. |
| 22:13 | Or likewise perhaps coming down a slight hill, and again we've got the car in gear and we're just barely touching the throttle. |
| 22:20 | So these areas can be accessed under those conditions. |
| 22:23 | And of course we want them to be as close as possible. |
| 22:27 | So we've taken an educated guess. |
| 22:28 | We've got that entire row tuned now. |
| 22:32 | And we're going to move up to 1,250 RPM. |
| 22:34 | However, before we do that, in order to speed up the process, we're going to copy our 1,000 RPM column. |
| 22:42 | Now I did that by simply holding down the Shift key, using the arrow keys to highlight that row. |
| 22:49 | And then I pressed Ctrl C to copy. |
| 22:52 | Use the up arrow key to move into the new 1250 RPM row. |
| 22:56 | And then Ctrl V will copy and paste those values across. |
| 23:01 | Now again, the reason we're doing this is because, as our RPM increases, particularly from such low RPM, we're generally expecting that the VE curve will increase. |
| 23:12 | So as we go from 1,000 to 1,250 RPM, we're expecting at least the same VE numbers, if not more. |
| 23:19 | And I'm going to actually take that a step further, by pressing P. |
| 23:23 | And I'm going to add 5% to that next 1,250 RPM row, before I get started tuning. |
| 23:30 | And again that's just estimating, that we're probably going to see a higher VE number at 1,250 RPM, then what we've just seen at 1,000. |
| 23:39 | So let's get our engine running now. |
| 23:40 | And we'll use the dyno to bring our RPM up to 1,250. |
| 23:47 | And we'll make some changes. |
| 23:48 | Now, before we make changes to individual cells, at 1,250 RPM, what I'm going to do is, I'm going to actually make my first change, across the entire range, the entire row. |
| 24:07 | So what I mean by this is if we move into our 1,250 RPM row, and we find that, we're a little bit rich, or a little bit lean for that matter. |
| 24:17 | And in this case you can see that, we're 1.04 Lambda, at -60 kPa. |
| 24:22 | So we're about 4% lean. |
| 24:24 | My first change will be to add 4%, to, the entire row. |
| 24:28 | And the reason for that is, again, we would expect generally, the entire row to have the same general shape. |
| 24:37 | So if we are lean, or rich in one spot, there's a pretty good chance that we will be lean or rich throughout that entire row. |
| 24:47 | So it's all about trying to speed up the process. |
| 24:50 | Once we've tuned our, entire column, or our entire row there, overall, we've made a coarse adjustment, we can start making adjustments to our individual cells. |
| 25:00 | So, we've just tuned the -60 kPa site there. |
| 25:04 | And, we're still actually, a little bit too rich there. |
| 25:08 | So I'll just take 2% out. |
| 25:11 | Let's now open our throttle, and we'll move through to -50 kPa. |
| 25:17 | And, as we do this, you can see now, we're already very very close, in fact I don't need to make a change, to that particular site. |
| 25:25 | So this is, the advantage of doing this is, often we'll find that we don't need to make any adjustments. |
| 25:31 | Likewise you can see our -40 kPa site, is also perfect. |
| 25:36 | We'll move across to our -30 kPa site. |
| 25:39 | Now you can see we're a little bit rich, so we'll take 3% fuel out there, by pressing P and -3. |
| 25:47 | That's got us correct there. |
| 25:49 | And we'll move across to the right, to our -20 kPa site. |
| 25:56 | Again, you can see we're a little bit rich here. |
| 26:00 | So we'll make another change. |
| 26:01 | We'll take 4% fuel out. |
| 26:06 | Still a little bit rich. |
| 26:07 | So now instead of using the P function again, I'll just take one more percent out, using the Page Down key. |
| 26:13 | And you can see we're on target. |
| 26:15 | Now we can open the throttle to wide open, and we can tune our 0 kPa zone. |
| 26:23 | Again you can see we're a little bit too rich there, so I'll just take 4% out. |
| 26:28 | So you can see that, before we moved into that, new row, our 1,250 RPM row. |
| 26:34 | We're already very very close to our target. |
| 26:38 | Now I just wanna make a point here. |
| 26:39 | You can see that I've got, I'm at wide open throttle. |
| 26:43 | You see me my throttle sitting, while we're at 99% throttle essentially. |
| 26:47 | And you can see that we're sitting at -3 kPa. |
| 26:50 | So we're not actually quite in our 0 kPa site. |
| 26:54 | And that's due to, at the moment, our atmospheric conditions, we're at relatively high altitudes. |
| 26:59 | So we're not actually reaching 0 kPa. |
| 27:02 | So when we're making changes here, we need to be a little bit careful, because you can see that the ECU is, very slightly, accessing the -20 kPa site, as well. |
| 27:17 | Now, particularly at higher RPM, what we're going to find is that the restriction of the air filter, the intake and the throttle body, will actually result in the manifold pressure dropping very slightly, as we go higher in the rev. |
| 27:31 | So we're going to get a trend, where we move through our VE table. |
| 27:35 | That's exaggerated, but it's going to look something like this. |
| 27:39 | Now in order to allow us to make more accurate adjustments, particularly in those wide open throttle areas, what I'm going to do before we continue is, I'm going to add another site, or another column to our load there. |
| 27:53 | And I'm going to add one at -10. |
| 27:56 | And again this just helps us be a little bit more precise, around that wide open throttle area. |
| 28:02 | Just because we are interpolating. |
| 28:04 | Okay so, we're going to continue the process now. |
| 28:07 | I'm going to tune the VE table out to 4,500 RPM. |
| 28:12 | You're going to be able to watch along, as we do this. |
| 28:16 | And, I'll be applying the techniques that I've just shown you. |
| 34:45 | Okay, so we've tuned the volumetric efficiency table there in steady state, out to 4,500 RPM. |
| 34:52 | And you've seen me use a variety of techniques while I've been doing that. |
| 34:55 | Just based on the magnitude of change I need to make, and also how much load applied to the engine. |
| 35:02 | Particularly once I start getting up to the higher RPM, and higher load areas of the table. |
| 35:07 | If I move into a higher load area and find that's it lean, I don't really want to sit there for a long period of time, with a lean air-fuel ratio, while I adjust that. |
| 35:16 | So I'll be using the technique of tuning ahead. |
| 35:19 | So if I find a particular cell as I move, I cross and increase the load. |
| 35:23 | Starts becoming leaner. |
| 35:25 | I'm quite likely going to highlight the entire row out to the right, to the higher load areas, and make a change to that entire area. |
| 35:34 | Likewise if I do move into an area, at a higher load, find it's too lean. |
| 35:38 | Rather than sit there for an extended period of time making the change, it's always easiest just to back off the throttle a little bit. |
| 35:45 | Make the change to that area that was too lean. |
| 35:48 | Then increase the throttle again and make sure that you've got it right. |
| 35:51 | Now it's not going to be damaging on our low powered 350Z. |
| 35:54 | But on a high powered turbo-charged car, that can be dangerous if we sit with a very lean mixture for an extended period of time. |
| 36:03 | Okay, so that's tuned the majority of our map. |
| 36:06 | But we've obviously got some quite large chunks of the VE table that aren't tuned, and we're going to look at what to do with those now. |
| 36:13 | First of all, in this higher RPM area here. |
| 36:17 | What we're going to do is, we're going to simply copy the 4,500 RPM row. |
| 36:25 | And we're going to paste that through the rest of our table. |
| 36:29 | Now, simply again, we are assuming that, as we increase our engine RPM, we're going to see our VE increase, peak, and then drop away. |
| 36:38 | Also, I'm happy to be starting with, a VE number that's too high. |
| 36:44 | And hence an air-fuel ratio that's too rich. |
| 36:47 | And then I can just simply remove numbers from the VE table. |
| 36:50 | Rather than moving into those untuned areas and finding that I'm too lean. |
| 36:55 | Now I'm going to go a little bit further, and I'm going to highlight the 6,000 and 5,500 RPM rows. |
| 37:02 | And I'm going to add 4% fuel to those. |
| 37:06 | And I'm going to extend that range out to 5,000 and 6,500, and add another 4%. |
| 37:13 | So what I'm doing there is just adding a little bit of shape to that VE curve, that I'd like to think is going to be somewhat realistic of what I may see once we get out there. |
| 37:24 | Now you can see we've got a VE table that's showing, a relatively smooth and sensible shape to the curve. |
| 37:33 | This is important to look at, because if we are seeing areas where we've got really erratic shapes to that VE curve, it could indicate that we've got a problem with that area of our VE table. |
| 37:46 | Or perhaps there's something else going on that we need to address. |
| 37:51 | The last area before we move on. |
| 37:52 | You can see that we also couldn't tune these low RPM areas. |
| 37:57 | And that's simply because we can't, load the engine up at 0, 500, and 750 RPM on our dyno. |
| 38:05 | Now strictly speaking, it doesn't matter either, because we can't drive the car there. |
| 38:10 | And we really want to make sure that we are, optimizing the engine, and the areas that the engine will actually operate in. |
| 38:17 | What I am going to do though, is just copy the general shape of our VE table, down into these untuned areas. |
| 38:24 | So I'm gonna take our tuned row, of 1,000 RPM. |
| 38:28 | I'm gonna copy that, and I'm going to paste that down into these lower areas. |
| 38:35 | Now, you can see that, our, Lambda is now, richer than our target, which again is to be expected. |
| 38:42 | As our RPM drops, we would expect the VE to also drop. |
| 38:47 | So what I'm going to do is highlight those lower three rows. |
| 38:50 | The 0, 500, and 750 RPM rows. |
| 38:53 | And I'm going to take 8% out of those, to correct our Lambda. |
| 38:58 | And you can see now, we're operating on our target idle. |
| 39:03 | So we've now got a VE table that's fully tuned. |
| 39:07 | We're going to obviously be looking at the wider, wide throttle, wide open throttle areas of operation shortly. |
| 39:14 | And then we're going to also look at how we're to address those higher RPM, low load areas as well. |
| 39:20 | We're finished with our steady state fuel tuning, and it's time to move on to the next step. |
