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Practical Standalone Tuning: Step 7: Steady State Fuel Tuning

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Step 7: Steady State Fuel Tuning

22.48

00:00 - At this point, we're ready to actually begin using the dyno to help us with our tuning and we're going to break this down into two sections of steady state tuning, we're going to start here with our fuel tuning.
00:11 Now you'll remember at this point we've got our nice conservative ignition timing table.
00:16 We know or should expect that for this particular engine with 15 degrees of advance across the board, this shouldn't result in any problems with detonation or knock occurring.
00:27 However we can't guarantee that's going to be the case.
00:29 As usual, any time we are tuning our engines, we want to make sure that we are actively monitoring for knock and while we are concentrating on our fuel tuning to start with, if we do notice that any knock is occurring, we can easily stop, retard the timing further in our ignition table.
00:46 Here we're not trying to optimise the ignition table but rather just take a reasonable amount out of it to prevent that knock and we're going to come through after we've got our fuel tuning sorted out and we're going to dial in that ignition table a lot more accurately.
01:00 So let's get ourselves up and running here on the dyno.
01:03 For this particular section of the tuning, I'm going to be using here our tuning and dyno views tab and we've got the information relevant to this particular process being displayed here.
01:16 Obviously out on the right hand side, we've got our VE table and this is where we're going to be making our tuning changes.
01:22 Down below you can see we've got the graphical representation and right now you can see that we've skewed this table slightly just with our basic adjustments we've made to get our air/fuel ratio in the idle region, about where we want it.
01:35 Now the parameters that we're most interested in here are being displayed.
01:39 We've got our engine speed on the left graph, we've got our target lambda on the middle graph and on the right hand side we've got our measure air/fuel ratio, you can see right now at idle, the two are pretty well matched around about 0.95.
01:53 We've also got a little crosshairs or target that shows us where abouts we are currently operating in this table so we can be quite specific with our tuning changes.
02:03 And this little target here shows us exactly how close we are to the centre of the current cell that we're going to be making changes to.
02:10 And this helps us reduce the chance of any interpolation affecting our results.
02:15 So right now what we're going to do is get ourselves up and running on the dyno, we're going to be using fourth gear on the dyno and what we're going to be doing is trying to get ourselves down as low in the rev range as we can and I'm going to start here by tuning our 1400 RPM column.
02:32 You'll generally struggle to get much lower than that and in fact even with 1400 RPM we may struggle to get our engine to run perfectly smoothly.
02:41 So let's get ourselves running on the dyno and we'll get our fan going.
02:45 Alright we're up and running now on the dyno and we can see that we're basically right in the centre of our 1400 RPM, 40 kPa cell and this is about as low down in the load as I can go.
02:57 If I reduce my throttle opening further then the engine RPM is just going to slow down, we don't have enough torque to actually keep the dyno running.
03:05 So this is the lowest cell we're going to be able to make our changes to right here on the dyno.
03:11 So what we want to do is have a look at our measured lambda and in this case you can see our measured lambda is almost exactly on our target already.
03:17 We've got our target here of lambda one, we're sitting between 0.98 and 0.99.
03:22 So we want to talk about some of the ways we can make changes to the numbers in our MegaSquirt software, in the TunerStudio software.
03:29 And there are a multitude, depending on exactly how you want to make your changes and the magnitude of the required change.
03:37 Considering we're so close to our target right now I would simply use the comma and full stop key as we've already seen, the comma key will reduce our VE number by 0.1 and as I bring that down we can see that we move closer to our target.
03:51 We'll get down to 61.4, we're pretty much on our target of lambda one there.
03:58 You can see we've just been swinging backwards and forwards across lambda one so that's a way of making small changes if you're already very close to your target.
04:05 Likewise if I press the full stop key, we'll add a little bit to that VE table.
04:09 Now if we want to make larger changes, we can use the control key plus the comma and full stop and as we've already seen, that'll make changes of half a percent at a time.
04:19 Now this is useful as I said when we're close to our target, however we can also use math functions as well.
04:25 So if we just come into a cell where we currently are operating, let's come up to 60 kPa, 1400 RPM.
04:31 You can see at the moment we've got a value of 79.6% in that value, in that cell.
04:37 We can directly enter a number by pressing the enter key and then we can change that to let's say 85%.
04:44 So that will direclty enter a number.
04:46 We can also highlight multiple cells in order to do this.
04:49 However if we want to make a percentage change, in that case what we can do is hold down the shift key, press the asterisk key or the multiply symbol and now we can enter a multiplication.
05:02 So in this case a value of 1.0 will make no change so if we want to reduce the number in that cell by 5%, what we would do is enter 0.95 and that will make that particular change.
05:14 So we can manipulate the sort of changes or sort of functions we're using depending on exactly where we are with our fuelling.
05:22 Alright so what we're going to do for the moment is just come up to our next cell which is 45 kPa, we'll get into the centre of that particular cell and we'll see what our fuelling is like there.
05:35 Let's just get into the cell for the moment.
05:37 Again using our target here just to make sure that before we make our changes, we are operating as close as we can get to the centre of the cell, we can see that the cell's turned red there.
05:47 This time we've got a little bit of work to do, you can see that our measured lambda is sitting at 0.95 to 0.96 and of course our target is still the same.
05:55 So again we can just use the control and comma key to reduce that number until we get down onto our target.
06:04 And with 61.7% in that particular cell we can see that our air/fuel ratio's right on our target.
06:09 So I'm just going to continue tuning this particular column now all the way up to 100% throttle, wide open throttle, using exactly the same process, let's go ahead and do that now.
06:34 OK so what we can see is we've come up to 60% or 60 kPa I should say of manifold pressure, we're starting to see that the numbers that we need in the cells are quite dramatically different to the ones we've already got from our VE table that was generated.
06:49 So we can continue the way we're going there but we're just going to find that we're going to need to make larger and larger changes.
06:55 What I'm going to do here is just guess ahead here and I'm going to highlight the rest of the column that I haven't tuned here and we're going to start by taking, let's say 10% out, that's probably going to get us a little bit closer.
07:08 So we can use the multiply sign and we enter a value of 0.9 and that's going to take 10% out of those remaining cells.
07:16 Let's increase our throttle and we'll continue with our tuning process.
07:22 So we can see that we are still a little bit rich here.
07:25 As we've moved into that cell where we've just made that multiplication change, we're now sitting at 0.93 versus our target of 0.99 so we're around about 7% rich still.
07:39 Now we could choose to make a further multiplication change there to our remaining cells and this is just all about speeding up the process.
07:46 What we've tried to do is guess ahead, meaning that we've got less work to do once we increase our load.
07:52 So what we're going to do here is take a further 7% out, so we can multiply by 0.93 in order to do that.
07:59 And we can see we're not quite there but we're pretty close, so now we're going to continue making our smaller changes to get onto our target.
08:07 Let's continue with the process.
08:21 Again we can see we're starting to get a little bit away from our target so we know that our generated VE table unfortunately isn't very good.
08:28 Pretty typical there.
08:30 So we can continue with the multiplication change that I'm making.
08:32 In this case because we're seeing quite small variations in our VE from one cell to the next, what I'm going to do this time is just highlight the remaining cells and I'm just going to enter a value of 70%, we can do this by using the equals sign and enter a value of 70.
08:47 So straight away you can see that that gets us pretty close to our target.
08:50 This time we're actually a little bit leaner than our target, 0.97 versus 0.95.
08:57 So what we'll do is we'll just make sure we're back in the centre of that cell before we make our change here and we're just going to add a small amount of fuel to that cell.
09:09 Now when we do this, now we've got a situation where the cell we're curently in sitting at 71%, as you can see because of that change I made above, we're now a little bit smaller than that, we've gone from 71 down to 70 as we increase our load so just to preempt that, what I'll do is enter a value of 71 in those other remaining cells.
09:29 So we'll highlight those, use the equals symbol and enter 71.
09:32 So again just we are trying here to preempt the sort of change we're going to need, speeding up our process.
09:39 We can increase our load again, come up to our 90 kPa cell and we can see 90 kPa now we're pretty close, just a little bit lean so we'll make a small change to the fuelling in that particular cell which should get us on track pretty easily.
09:52 Making sure again we are in the centre of the cell so that we do see the effect and no interpolation.
10:00 Again just following that change through, we'll make a similar change to our 95 kPa cell increase our throttle up to that point.
10:11 You can see we're pretty close there, we'll just add another 1% fuel.
10:15 Another percent on top of that, we're on our target now of 0.92.
10:19 We'll go to full throttle and we can see that at this stage we actually , because of our barometric air pressure can't quite get up to 100 kPa.
10:25 So what I'm going to do there is just extrapolate the sort of values that I am seeing there in the table to date.
10:35 So we'll enter a value of 78% in that particular cell and we can see that's got us pretty close to our target there, we're right on our target.
10:42 So at this point we have got our first column tuned.
10:47 Now there are a couple of caveates here.
10:49 Obviously at this point we haven't been able to do anything with our area below 40 kPa, remember we couldn't get there on the dyno.
10:57 We can't just ignore this so what we're going to do here is just follow the trend down and we can see that we've got a relatively flat shape here, we're moving probably on average around about 1% every 10 kPa in this area, maybe 2%.
11:11 So what I'm going to do is I'm just going to highlight these particular cells and we don't have to be perfect here.
11:18 Remembering if we can't get to them on the dyno, we're probably not going to be spending a lot of time actually running in these cells on the road so we don't have to be perfect but we would like to be at least close.
11:29 So I'm going to just bring those cells up, taking a bit of an educated guess as to where they're going to be.
11:36 Later on when we get the car out on the road or the racetrack, we're going to be able to gather some data from those cells, so at the moment all we're trying to do is get them pretty close to where we need to be.
11:46 Now as we've mentioned, we can't get to our 1000 RPM column or below so we can't ignore that, or we don't want to ignore that.
11:54 For the sake of completeness, what I'm going to do, using the shift and the down arrow key I'm going to highlight that entire column, I'm going to press control C to copy it, and what I'm going to do is then move across to the 1000 RPM column and I'm going to paste that in.
12:09 Before we do that though, we know that at the moment our target air/fuel ratio at idle is pretty close, actually looking at it, we're just a little bit rich there so what we're going to do is take note of the VE number in the idle areas around 30-35 kPa and we're just going to paste the column back in using control V and we can see that we were at about 50% VE at 30 kPa, 1000 RPM, we've now jumped up to 57 so we've actually added a bunch of fuel in there.
12:44 So what we're going to do is reduce that number down, again we're going to this time start by highlighting the entire column, basically what we're expecting here is there's going to be a consistent trend in the table, so if we need to reduce our VE at 30 kPa and 1000 RPM, we're probably likely to need to reduce the VE, the entire column, so again using our control and comma key we're going to remove some fuel until we're down around about the VE at idle that we were.
13:12 Again using control and C we can copy that down to our 800 RPM column.
13:18 Again we'll just bring that column down until this time we're getting our target idle speed where we want it to be, our target idle air/fuel ratio where we want it to be, so we're going to actually reduce our fuelling a little bit further.
13:31 And then what we can do is copy the 800 RPM column and paste that into our 600 RPM column.
13:38 So it's all about just getting some consistent values across that area, following that trend down and we can sort of start seeing that take shape here in our VE table.
13:47 Again for the sake of consistency, we're likely to see our VE at 600 RPM be a little bit less than what we had at 800 RPM.
13:56 So at this point we've got some numbers into those areas that we can't really reach on the dyno, they're not likely to be perfect but they're going to be there or thereabouts.
14:06 We're also not going to be accessing those cells except for the engine passing through them during startup.
14:12 What we're going to do now again is copy our 1400 RPM column, so the column that we have tuned at the moment, we're going to move across and we're going to paste that into the 1800 RPM column.
14:22 Now as we move from 1400 RPM to 1800 RPM, we could expect at this point that our VE should increase.
14:29 So before we start tuning at 1800 RPM, we're just going to take an educated guess here and we're going to use our multiplication symbol and we're going to add 5% to our 1800 RPM column and we might not be quite right there but that should get us up and running.
14:47 So again we'll get running in fourth gear and we'll bring the RPM on the dyno up to 1800 and to start with before we start making any specific changes, we're going to apply a little bit of load, get ourselves about the middle of this table and we're going to see how close we are to our target.
15:04 So at this point we're running at around about 50 kPa and we're actually looking pretty good.
15:10 So this might not hold true for the entire column but we see that we're sitting at around about 0.98, 0.99 lambda.
15:17 That's not enough for me to want to make an overall change here so instead what we're going to do is drop our load back down here by closing the throttle, we should be able to get down to at least our 40 kPa cell, and we can.
15:30 And what we're going to do now is start making smaller changes.
15:34 Now again what I'm going to do for this first change, because I can't get down below 40 kPa, I'm going to highlight the 40 kPa cell and everything below that and what I'm going to do is just reduce the numbers in those cells until we're on our target.
15:50 So we'll just take a couple of percent out of those cells, get ourselves right on our target, 0.99, we're close enough there.
15:57 Now what we're going to do is start increasing our load and we're going to continue tuning, so let's go through that process now.
16:28 Alright so we've finished our 1800 RPM column there.
16:31 So I'm using a variety of techniques as I go there just depending on my own judgement of the magnitude of the change.
16:38 So as we first moved into the 1800 RPM column, what I did was I started by using a little bit of load just to see how close my guess of adding an additional 5% of fuel was.
16:48 It turned out it wasn't too bad.
16:50 If on the other hand I'd moved up to 1800 RPM and I'd found that we were way too rich or way too lean in the middle of the load zones, what I would do is start by either increasing or decreasing that entire column in fuelling numbers or VE numbers to get us close.
17:06 Now what I'm trying to do here is get ourselves in the ballpark so it's cutting down the magnitude of changes I need to make in each individual cell.
17:14 As I said, that wasn't too bad so there wasn't a lot of work to do there.
17:17 Starting again at our lowest load and the changes we we're making there, we're extrapolating down into those sites we can't get to.
17:24 Again trying to get us at least as close to the ballpark as we can.
17:28 As we moved up I saw that the mid range fuelling was actually pretty much close to my target.
17:35 As I started increasing the load more and more though, we started drifting away a little bit and here I took the move of highlighting the column above the load point I was operating at and making a change to the entire column above that point just to again cut down on the work, meaning that as I moved into those higher load areas, I was already close to my target and you can see that by doing this, using these different techniques that we have in our toolbox, it does cut down on the work, you get your result faster, and as a result also the engine isn't going to be running excessively rich or excessively lean.
18:06 So from here it's a rinse and repeat of that process, we're going to take our 1800 RPM column, we're going to copy that, move it across, paste it into our 2300 RPM column.
18:17 Again I'm just going to at this stage expect my VE to rise so we'll add another 5% to that.
18:24 So from here you can watch the process being repeated.
18:27 We're going to tune here in steady state up to 4500 RPM and you'll see me potentially use all of those techniques to make the changes that we've already talked about.
18:36 Let's go ahead and get the rest of our table tuned in steady state.
19:37 So at this point we've got our fuel table tuned out to 4500 RPM under steady state conditions.
19:43 Now hopefully you could see that that process that I'm using there really does speed up the tuning.
19:48 Particularly when we got into the higher load areas in both the 4000 and 4500 RPM ranges there was almost no work to do for a lot of those cells, they were basically within 1% of my target as soon as I moved into the cells so this is the ideal situation.
20:03 It limits the amount of work we've got to do, it limits the amount of time it's going to take and just as importantly it limits how long the engine's going to need to be held under high load and high RPM on the dyno.
20:15 And on that note as well, we do need to pay attention here ot our coolant temperature while we are running the car here.
20:23 You can see currently that's sitting at 96 degrees and we do need to pay attention to that because we may need to back off the throttle as we start moving to higher RPM ranges and just allow some time for that engine coolant to come back down to a safe level before we proceed with our tuning.
20:40 The other aspect that's worth taking note of here is the shape to our VE table that we're starting to develop.
20:47 So obviously we can see the areas that we have made our tuning changes to so far.
20:51 And what we've got is a relatively smooth, relatively consistent shape to that table.
20:57 We're not trying to get a perfectly smooth table, we're trying to give the engine what it wants.
21:02 But if I've got one particular cell or maybe a few cells in that table that are completely different to the surrounding cells, I'd want to go back and revisit those particular cells and just be 100% certain that my tuning is actually where it needs to be.
21:16 In this case that consistent shape is what I'd expect to see.
21:19 We've got a little bit of variation up and down as we move through the rev range, particularly at lighter load which is quite typical of a naturally aspirated motor.
21:28 What we're going to do before we finish off this step is we're going to take the numbers that we've tuned here at 4500 RPM, that column that we've just finished off, we're going to copy that and we're going to extrapolate that or paste that out through the remaining untuned areas.
21:45 Now at this stage we're only taking an approximate guess as to what the VE numbers are going to be out in this untuned area, we're just trying to get closer to the ballpark before we move into our wide open throttle ramp run tuning.
21:58 Now as part of that as well, I'm actually going to add a little bit more shape to the untuned areas, so what I'm going to do is highlight between 5000 and 7000 RPM and we're going to multiply those zones there, those cells by 3%.
22:15 Likewise I'm then going to multiply the columns between 5500 and 6500, I'll multiply those by 2% just again adding a little bit of shape into the area that we haven't got to with our steady state tuning.
22:32 Meaning that we're going to be closer as we move out and perform our ramp run tuning.