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Practical Standalone Tuning: Step 7: Steady State Fuel Tuning

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Step 7: Steady State Fuel Tuning


00:00 - We're now at a point where we can begin the actual tuning process and running the car on the dyno and we're going to start here with our steady state fuel tuning.
00:08 You'll recall that we've already set our ignition table values to numbers that we should expect will be safe and result in no knock.
00:17 However even when we are concentrating on the fuel tuning, under normal circumstances we would be listening using audio knock detection equipment just to make sure that we don't have any over advanced areas that are resulting in knock.
00:30 If this is the case of course we'd stop running the car and remove some timing from these areas of the ignition table in order to ensure that no knock does occur which we complete filling out our fuel tables.
00:43 Now I'm not going to be using audio knock detection equipment during this particular step so that I can actually present and explain what we're doing.
00:51 Let's jump into our software and we'll have a quick look at a few more details on how we can make changes.
00:57 So at the moment we've got our very basic map developed here, we've got our large chunk of our table which we made coarse adjustments to just to get our engine up and running and we've done some more fine tuning just around the idle areas here however we still haven't got everything perfected.
01:12 What we're going to be doing now is building up our table from low RPM and low load.
01:18 Now we've already looked at a couple of simple ways we can make changes to the numbers in the table and we'll just expand on that a little bit more, so let's just highlight a few numbers out of the area that we're actually modifying.
01:29 So we've looked at the fact that we can use the plus and the minus keys to add or subtract 1% at a time so that's a nice quick and easy way of making changes, particularly if you're already quite close to your target air/fuel ratio.
01:42 If you're a little bit further away we can use the shift and plus or the shift and minus key, that'll add and subtract 5% at a time.
01:50 If you want to make slightly finer adjustments using the alt and plus key will add 0.1% every time we press the plus key and alt and minus will remove 0.1% so this will let you really dial in your tuning to get your VE table accurate.
02:08 Now some other ways that we may want to make changes here, we can use math functions.
02:12 So for example if we wanted to add 5% to this table, we could enter the value five followed by the plus symbol, press enter and that will have that effect, of course five and the minus symbol, will remove 5%.
02:25 And one of the ways I like to use the math functions is for percentage changes, particularly when we are creeping up on our correct fuelling here.
02:33 So let's say we wanted to add 5%, we can enter a value of 1.05 and follow this by the multiplication symbol, press enter and that's made the change.
02:45 Also powerful to keep in mind that the control Z function will undo your last change.
02:51 So if you've made an accidental change that you don't like then you can undo that.
02:55 We've also broadly looked at the interpolate functions which are quite helpful.
02:59 So if we just set our values here to 55, and we can highlight across to the left there.
03:06 The control and H will make a horizontal interpolation just like that.
03:11 Let's just undo those last 2 changes, we can also do a vertical interpolation, let's just highlight our values there and control and L will do a vertical interpolation.
03:25 So there's a few key ways there that we can just make quick and easy changes to our numbers.
03:32 As we go through this particular step you'll see me using a variety of different options and it's just a case of depending how close we are to our target.
03:40 So as I mentioned, we're going to begin here with our tuning at low RPM and as low a load as we can actually achieve to keep the dyno running here, we need to maintain enough load on the engine to actually keep the dyno speed up so as we reduce our throttle position we'll actually find that we get to a point where the RPM slows down and we can't get down to our very low load points down here and maybe around 35 to 50 kPa, just won't quite be possible to get to those areas.
04:11 It's OK though, we're going to be building up our map and you'll see how we can extrapolate the shape of that map out into those areas that we can't get through to.
04:20 So let's get our engine up and running and we can start our tuning.
04:25 Alright we've got ourselves up and running at 1500 RPM on the dyno.
04:28 Before we make any changes we just want to make sure that our coolant temperature and our intake air temperature are in the normal operating range, we don't want to be trying to make our tuning adjustments while the engine is still warming up.
04:40 Now you can see here, because I haven't made any changes straight away, we're running very very lean, we're sitting at about 1.13 lambda.
04:48 The engine isn't running particularly well.
04:50 And I'm not at all worried about this, we're not going to do any damage to the engine because the load is so low here.
04:57 But we do want to obviously correct this.
04:59 So before we make any wholesale changes, or sorry any fine tuning changes here, let's just highlight our entire row here at 1500 RPM and we'll set the values to 65%.
05:11 I'm just taking a broad guess here, don't need to be too accurate.
05:14 But straight away you can see that that's got be pretty well on the mark, we can see that our measured lambda and our target are now sitting very close to being the same.
05:21 So now that we've got our numbers broadly in the target here, let's just reduce our throttle down and we'll see how low we can get into our load.
05:30 And what we're looking for here is our red cross hairs and we want to try and be central to the particular cell that we are tuning and this will avoid the affect of any interpolation.
05:40 Now that's not always going to be possible, particularly at very light load.
05:43 And as we go to wide open throttle, we're not going to necessarily be able to get into the higher load cells either but we'll see how that works as we progress so let's just close down our throttle and we'll see how low we can get down.
05:56 So we'll come through 70 kPa, we can get nicely into the centre of that particular cell, reduce the throttle down further and we should be able to get down into the middle of the 60 kPa cell I would imagine, without too much trouble.
06:08 We'll just continue closing our throttle down.
06:10 So we're nicely in the middle of that particular cell there.
06:14 I'll close the throttle down further and we'll see if we can get into the middle of our 50 kPa cell and you can see at that point our RPM actually slows down.
06:22 So for this particular RPM row, the lowest we can get in our load and be in the centre of a cell is actually 60 kPa.
06:31 So we'll bring ourselves back up to the centre of that cell and we'll begin our tuning.
06:35 So let's just make sure we are in the centre, obviously everything moves around a little bit.
06:40 So can take a little while to just make sure you're established in the centre of the cell.
06:50 Alright so what we can see here is that our measured lambda is sitting at 0.90, 0.91 so we are a little bit rich there, there's a few ways we can make these changes.
07:01 Easy enough to just use our minus key and remove fuel but let's just try removing 10% here because that should get us very close to our ballpark.
07:10 0.9 and the multiplication symbol will have that effect and we can see straight away we're pretty close to our target, still actually undershot just slightly but generally when I'm trying this sort of tuning, I'm looking for being within about 1% of my target and we can see that we're right there now, actually we'll go back a little bit.
07:31 Alright so we've got that particular cell tuned there, let's move across to the right and what we always want to keep in mind is trying to make sure that we're following the trends.
07:40 Hard to build a trend when we've only tuned one cell but we can see we've got a value of 58.5% in our 60 kPa cell.
07:46 We can assume that at 70 kPa as we increase our manifold pressure, the volumetric efficiency will increase.
07:54 So we've gone from 58.5% to our initial guess of 65%, that's probably going to be close enough, let's increase our throttle and we'll come up to 70 kPa.
08:03 So we we move into the centre of our 70 kPa cell we can see that we are very slightly rich, 0.97, 0.96 versus our target of 0.99.
08:12 I'm just going to use the minus key here a couple of times and remove a little bit of fuel, very quick and easy to get us onto our target.
08:19 So we've now got a value of 62%, we'll increase our throttle opening further, come up to 80 kPa.
08:25 It's always a good idea, once we've got a little bit of load on, just to have a recheck of our RPM and make sure that we're pretty close to the centre of that cell.
08:34 The problem is here, particularly as we are developing our first RPM row, if we aren't very close to the centre we can be interpolating to numbers that are very very incorrect.
08:45 For example if we look up here at higher load, we can see that we've got a value of 65% at 1500 RPM, we drop away to 50% either side of that so it is important to make sure that we are quite accurate to the centre of that cell.
09:00 Anyway we're at 80 kPa, we're on our target here without actually making any changes so just good luck and that's basically where we started by making that broad change to that entire row.
09:13 So as we come up to 90 kPa here, we can see that we've got a general trend here, we're increasing our VE by around about 3%, there or thereabouts.
09:22 As we move up 10 kPa steps so we can sort of guess this ahead and we'll enter a value of 68%.
09:29 Now at this light load it's not that critical, if we move from 80 to 90 kPa and we were a little lean, definitely no chance of doing damage, this does become more important as we move higher in the RPM and we start building into the positive boost areas of the map.
09:44 Let's increase our throttle up to 90 kPa and we'll see where we're at.
09:47 And you can see that that guess has actually got us right on target there so this is the power of following those trends.
09:53 So we'll follow that trend again, we'l come up to let's say 71% at 100 kPa, increase our throttle, come up to that cell and have a look at where we're at.
10:02 You can see that we are slightly lean here, we're about 2% lean so we'll just add a couple of percent into our 100 kPa cell and we've got ourselves on target.
10:12 So again we'll just take a broad guess, as we move up to 120 kPa, we'll go up to 78% VE and we can see here I'm now at wide open throttle and we can't quite get into the centre of that cell there.
10:25 So we are interpolating a little bit.
10:27 We are also a little bit lean there so let's take another broad guess at our values there, we can see that our guess of 84% got us pretty close, we'll add another couple of percent there and we're on target.
10:38 Now I am also going to just take a bit of a stab in the dark out here at 140 kPa and above, not super critical, we can't really get there right now and we probably won't be able to get there at all, our turbo can't produce that sort of boost response.
10:51 But we're just going to follow those general trends.
10:54 Alright so we've got most of our 1500 RPM column dialled in there.
10:58 But we haven't been able to do anything with these areas down below here, remember we couldn't get that far down in our load.
11:05 We can't ignore them though and what we want to do is follow the general trend that we've got.
11:10 Remembering that the first cell that we were able to accurately tune was our 60 kPa cell and we're generally seeing a trend of around about 3-4% per 10 kPa.
11:20 So what I'm going to do is just guess this as well so let's take around about 3% off here so we could probably go with a value of about 55% here.
11:32 Not being super accurate here, we're not going to be on target but we're just trying to follow that trend and particularly in these lighter load areas, sometimes we will need to fine tune them out on the road but we want to get them as close as we can before we need to do that.
11:47 Our next cell here, we need to be mindful, we're now dropping down not 10 kPa but 15 so we're looking at about 3%, 4% per 10 kPa, I'm going to extend that out to around about 5% here.
12:01 And it's always better to err on the side of being a little rich than a little lean.
12:05 Again we're coming down to 20 kPa in this particular cell and we're going to remove another 5% here so we'll enter a VE value of 45%.
12:17 So at this point, while we know these numbers won't be absolutely accurate, they're going to be pretty close and allow us to fine tune that once we get out on the road.
12:26 We'll now copy that entire row, we'll use control C, we'll come up to our 2000 RPM row, control V will paste that.
12:34 Now because we are moving from 1500 out to 2000 RPM we can rightly expect our volumetric efficiency being this low in the RPM should increase, it's not always going to, it's always a good idea to just add a little bit of fuel before we venture out to our next row so what we're going to do is enter a value of 1.04% and we're going to multiply that entire row, adding 4%.
12:59 Now we're going to get back up and running and we'll come up to 2000 RPM and see how that guess has worked out.
13:11 So initially we'll just get ourselves set up on the dyno so that we are pretty close to the centre of our 2000 RPM row, you can see we've got ourselves there right now.
13:21 And to start with I'll just come up to 80 kPa, a little bit of load here and we'll just have a quick look at how close our guess was and we can see we're actually right on our lambda target there so that guess of adding 4%, we were pretty close.
13:33 That's not always going to be the case as you'll see as we progress so what we would do before we make individual cell changes, if we're too rich or too lean, we'll raise or lower the VE numbers for that entire row.
13:45 In this case, that's not necessary so I'll start simply by reducing our load back down and we'll see how low we can get, probably not going to be able to get down to 50 kPa, we'll just try though.
13:59 And we can see that as we tip into our 50 kPa cell our RPM slows down so again the lowest we can get in our load there is 60 kPa, we'll get into the centre of that.
14:09 Now looking at our fuelling there we can see that we're a little bit rich, we're 0.95, 0.96 versus our target of lambda 1.0 so this time because we can expect the cells to the left here at lower load to also follow this trend, I'm going to, before I make any changes, highlight all of those cells and here I'll just use the minus key to remove a few percent and get us onto our target.
14:36 We can now come up to 70 kPa, have a look at how we're going there.
14:41 70 kPa, pretty close to our target, probably 1-2% too rich, just use the minus key and remove some fuel there.
14:49 Come up to 80 kPa and we should be pretty good at 80 kPa, that was where we started, you can see we are.
14:56 Bringing the cells up to 90 kPa here and we can see that 90 kPa, again we're pretty much on our target, we're within 1% so we'll leave that for the time being, come up to 100 kPa and again on our target so you can see the benefit of just copying and pasting and extrapolating the shape of these curves out, makes our tuning relatively quick and easy.
15:17 Let's come up to 120 kPa and we'll have a look and see how we're looking there.
15:22 So we can see here at 120 kPa we've actually moved quite rich.
15:27 So before I make a change to that particular cell, this may not necessarily be the case here but I am at 100% throttle so the numbers to the right we can't get to anyway and we're just going to remove a few percent there and get us onto our target which we can see we've done there.
15:42 So that's our 1500 and our 2000 RPM row completed.
15:48 We're now going to simply repeat that process, we'll copy and paste our 2000 RPM row, paste it into our 2500 RPM row and again let's start with a multiplication factor of 1.04 and you'll start building up a bit of an idea as you move from one row to the next and we increase the RPM, you'll get an idea of if your last change was 5% and you overshot or undershot, then you can learn from that when you make your next adjustment and move further into the RPM.
16:19 Now we'll repeat that process, we'll get ourselves up and running at 2500 RPM and we'll have a look at how that row has worked out with our 4% adjustment.
16:43 Again being mindful initially to make sure that our RPM is getting us pretty close to the centre of these particular cells, we're looking pretty good there, and straight away you can see again, our guess of 4% has worked out pretty much on point, at least at 80 kPa, no need to make any broad adjustments to our entire column, we can start getting a little bit more granular.
17:05 We know that we're probably unlikely to get down below 60 kPa so we'll start by going to the centre of that cell and you can see again our lambda is right on our target, again just showing the value of extrapolating these changes out, let's continue up here, 70 kPa, also no need to make any changes.
17:21 Come up to 80 kPa, we already know that's OK, extend out to 90 kPa here.
17:25 We're about 1% rich there so I'll just use the minus key and we can clean that up.
17:31 We'll come out now to 100 kPa, right on our target again.
17:36 120 kPa, starting to move out into the positive boost.
17:40 And we can see again, right on our target, no need to make any changes at this point.
17:45 Let's just creep up to 140 kPa and see what that looks like.
17:50 140 kPa we can't quite get into the centre there, we're at full throttle now and we can see that we're just tipping into 140 kPa but we can see that our lambda's on target so no need to make any changes there, everything's looking pretty good so far.
18:05 Of course a rinse and repeat now, control C and we'll copy that row, control V, paste it up to 3000 RPM.
18:13 So far our guess of 4% has been working out pretty well so no need to really change what we're doing there, we'll add another 4%, let's get back up and running at 3000 RPM and see how we're looking.
18:38 Alright so again at our 80 kPa test site there, we're bang on our target of lambda one so no need to again make a broad overall adjustments, we'll come back down, get ourselves down to 60 kPa, we'll just test and see if we can get down to 50 kPa, we can actually now start to tip into it.
18:56 You can see that we are quite rich there, we're sitting at about 0.90, can actually get right into the centre there.
19:04 So we're about 10 or 11% rich there so instead of just making the change to that one cell, I'm actually going to highlight the cells to the left as well and what we'll do is start by making a change of 11%, 0.89 multiplied by that and we can see we've corrected most of that error, still a little bit of error remaining so I'll just manually fix that using the minus key.
19:26 Now that may also indicate there that our guess for these cells at low load, 2500, 2000, 1500 RPM may not be correct.
19:35 Again we can't get there so it's very difficult for us to be more accurate.
19:39 But we will be able to address these on the road.
19:42 Let's bring our load up to 60 kPa and we'll continue the process there.
19:46 60 kPa we can see we're around about 4% rich there so we'll just use our minus key to correct that, come up to 70 kPa now.
19:55 70 kPa you can see we are pretty close, still a little bit rich, just the minus key a couple of times will correct that.
20:02 80 kPa we already tested that so we know that we're on point there.
20:06 Let's move up to 90 kPa now, you can see no changes necessary there.
20:11 100 kPa, still looking pretty good, we'll creep up to 120 kPa and now we can start to see we're just a touch lean.
20:20 Now I'm not worried about this here, we can just add a couple of percent manually.
20:23 But what I'm going to do is just reduce our load, get back out of boost into vacuum so there's no load on the engine.
20:30 Because we're a touch lean at 120 kPa, I'm going to guess there's a pretty good chance that that trend will continue out to our higher load point.
20:37 So before we go there, what I'm going to do is just highlight the numbers out to the right and just make a manual guess at what that might want to be.
20:44 Let's now increase our throttle position and we'll come back up and we'll test our 140 kPa site.
20:52 So we can see actually I was wrong, we're a little rich but nothing wrong with that so what we'll do is we'll reduce our fuelling there just manually, get ourselves onto our 0.95 target.
21:02 I won't change the 160 kPa but we'll see if we can get out there and we can.
21:05 160 kPa you can see we're pretty close, just a touch rich there so again just manually adjust that and we'll go through to full throttle, we can tip into our 180 kPa.
21:16 You can see we're a touch lean there so again rather than sitting there and making those changes, I'll do this manually.
21:23 So we'll highlight the cells again, 180 kPa and out to the right and we'll just add a couple of percent.
21:29 And I'll extrapolate that change out.
21:30 Unlikely we'll get 200 kPa of boost pressure at 3000 RPM but just for the sake of following that trend we will do that manually.
21:39 Let's just finally test our 180 kPa cell again.
21:44 And we can see yeah we're pretty close to our target, just a touch lean there so add another percent.
21:51 And it's really important, particularly when we are tuning turbocharged engines just to be a little bit sensible with the way we approach the steady state tuning.
21:58 Now if I hold the engine at 3000 or 4000 RPM, wide open throttle for extended periods of time, obviously we're going to start building a lot of heat in the exhaust manifold and turbocharger, this could also result in excessive heat in our cooling system so we need to be mindful of this.
22:14 I don't want to hold the engine out under high load for any longer than I need to.
22:18 So rather than making the changes while we're in that cell, that's why I'm backing off, bringing the engine back into vacuum where there's no stress and no load, make the changes then go back into the throttle, test again.
22:29 So this is the easiest way of making changes without putting any additional stress on the engine.
22:37 So at this point we're starting to get to the position where our turbo is able to start making decent boost pressure and we have established a good fuelling curve now up to 3000 RPM.
22:48 Of course the process now is to just rinse and repeat.
22:51 We'll copy and paste that out.
22:54 Now it's important here to notice that as we move from 3000 to our next cell, we're actually going up 250 RPM.
23:00 I've added a little bit of additional resolution in and around here, just to help with some idiosyncrasies that I know exist in this fuel system.
23:08 So we've got 250 RPM increments here at 3250 also at 3750.
23:14 Now we're going to keep this in mind when we are making our multiplications here.
23:18 So far, 4% additional fuel per 500 RPM has worked out pretty well for us.
23:24 In this case we're going to halve that which would make sense.
23:27 Might not be right but we should be pretty close to the mark.
23:31 So we'll add 1.02%, multiply by 1.02, we're going to now speed this up a little bit, let's go through our continued process of steady state tuning, it's just going to be a rinse and repeat of what you've seen so far.
24:03 Now interestingly this is the first row where we've moved out from 3000 to 3250 RPM and we can actually see our initial look at 80 kPa has shown us that we are quite lean, we're sitting at about 1.08.
24:16 So this is the situation where I will now make an entire row change.
24:22 So we can use our multiplication here so let's start by adding 8% or multiplying by 1.08, that should get us onto our target which you can see that it's done.
24:33 So the idea here is because we were lean at 80 kPa, we should rightly expect that we may be lean just about everywhere else as well.
24:42 So rather than trying to individually tune each cell, this just speeds up the process.
24:46 Now we'll continue by dropping down to our lower load and we'll start cleaning up the individual cells.
25:17 Alright we're up to 3500 RPM and I just want to just stop and just talk about what we're seeing here.
25:22 And you've been seeing me apply the various techniques that we've already talked about.
25:27 The important thing now, 3500 RPM, we are starting to get to a point where we are able to make reasonable boost pressure and we want to be mindful of that.
25:36 What's important to note though here is by following those trends and extrapolating those out then using our multiplication to add a little bit of additional VE, you've seen that as we move into those untuned areas, already our fuelling has been pretty typically within a few percent.
25:54 So very little stress being placed, we're not in a dangerous situation where our engine has been dangerously lean as we move into positive boost.
26:02 And if I do get to an area where I'm not comfortable with the fuelling I'm seeing, as you'll be noticing, I'm just backing out of the throttle so I make those tuning changes, just those techniques that we have talked about.
26:13 The other thing that we do want to be mindful of now is just again keeping an eye on our coolant temperature as we go up in the RPM here and we're seeing more sustained load and more sustained manifold pressure, we do want to just make sure that our engine coolant temperature isn't becoming too high.
26:30 Let's continue now, we'll carry on with our 3750 RPM row.
27:11 Alright so at this point, we have completed the steady state tuning from 1500 up to 4500 RPM and hopefully you could see how quick and easy that was to complete by using the techniques that we've shown you there and extrapolating out the shape of the table.
27:26 Now we aren't quite finished here, first of all we're going to have a quick look and see what this table looks like graphically and this is always a good idea just to get a general idea of the shape and if there's any peculiarities around this.
27:41 We can actually see that we've got exactly that, there is a bit of a weird area in our table at lower RPM down around 3000 RPM and light load.
27:51 This is an aspect of the fuel system, idiosyncracies with this engine though so I know that that's to be expected.
27:59 Typically if you are seeing any idiosyncrasies or weird shapes to your map that don't follow a common trend, this would be a good indication to go back and review those areas before we move on.
28:11 So at this point I'm quite happy with that so what we're going to do now is copy the numbers that we've got at 4500 RPM, use control C there and we're just going to extrapolate these numbers out into the rest of our table, the untuned areas.
28:26 Now we're only taking an approximation here, we can't expect that this is going to be perfect and we always want to be a little bit rich as we move into our untuned areas so what I'm going to do to start with here is just take a bit of a stab in the dark here, we'll highlight the areas from 6000 RPM to 5500 RPM.
28:46 We might add, let's say 2% to that particular area and then we might also want to do the same from 6500 down to 5000 RPM.
28:58 So we'll add another 2% here.
29:00 So just generally following the sort of trends we may expect.
29:03 Likewise at 8000 RPM, we can probably quite happily expect that the VE will be dropping away so we'll multiply that by 0.98.
29:13 We'll extrapolate that change down here to 7500 and then finally to 7000 RPM as well.
29:20 Now we don't need to be too accurate here, we're not expecting these numbers to be perfect, we're just giving a little bit of shape to this table that's hopefully going to be close to the mark as we move into our wide open throttle ramp run tuning, then we're going to be able to fine tune those areas of the table once we get to that step.
29:37 We've also obviously got this ugly area down at low RPM which we haven't been able to get to, we haven't been able to access that so we need to address this as well.
29:46 Again what we're going to do is just follow the general shape, the general trends in our table here and extrapolate those down and it's also worth taking a look here, we know that we're idling here about 900 RPM with a number of 45% VE so obviously we need to expect to have that VE value there as well.
30:09 So what we'll do is we'll copy our 1500 RPM row here and we're just going to start by pasting that down into our lower load rows.
30:19 So we've done that now, we've got our table sort of smoothed out but of course we have resulted in numbers now that are going to give us a excessively rich idle which is exactly what's happened.
30:31 So what we're going to do is just highlight that particular cell here, we know that we're around about 10% rich there so we'll just enter 10, sorry 10% too high in our VE compared to where we were, so we'll enter 10 and minus.
30:44 We can also extrapolate that into our next cells there, 10 and minus and then what we can do here, there's a variety of different options but what I'm going to do is just highlight the cells across that 1250 RPM column and we will do a vertical interplation there, so control and L will make that change there.
31:07 So it's not necessarily going to be perfect, it's not going to be right but it's going to be pretty close, we can see our lambda at idle is back on target.
31:15 We've got a reasonably smooth trend to that table.