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Variable Cam Control Tuning: Step 4 Steady State Tuning

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Step 4 Steady State Tuning

30.46

00:00 - The next step of our process is to optimise our intake and our exhaust cam targets under steady state conditions on our dyno.
00:06 We're really going to follow the same process that you saw demonstrated in the body of the course.
00:12 Here what we're really aiming to do is optimise our torque so as part of this on the dyno we are going to be using our time graph of torque which you can see over here on the bottom right hand side of the screen.
00:25 Now this does require a little bit of mental smoothing which you'll see as we go through, naturally that torque is always going to move around but this is a much faster process when we're trying to optimise a range of cells in the table compared to using the torque optimisation function that we demonstrated during the body of the course.
00:44 The other aspect that we will be keeping our eye on here in the tuning software, we've got our short term fuel trim.
00:50 So while we're optimising here our torque, we also want to be mindful of our short term fuel trims, we may get a situation where we can essentially achieve the same amount of torque with different amounts of fuel, in this case obviously we want to go with the smallest amount of fuel possible in order to get ourselves an economy gain.
01:10 Let's just talk about broadly what we're going to be doing here and this is very similar to the 10 step tuning process where we steady state tune the fuel and the ignition.
01:19 Generally I'm going to try here to get out to about 2/3 of the engine rev limiter under steady state conditions so in this case we'll go out to about 4000 maybe 4500 RPM.
01:29 So the area that we're sort of going to be dealing with in this case is, we've only got a break point at 4000 so that would make sense and we're going to be coming up to around about 125 kPa.
01:40 The other thing to be mindful of is the minimum RPM and load that we can realistically achieve.
01:47 Because of the oil pressure driving the control system, generally I don't try and target cam angles much below about 1000 RPM in fact generally I'll step this up to 1500 so we're not going to be tuning down to 1000 RPM, might do some smoothing once we see the general trend of this table.
02:06 Likewise we're unlikely to be able to get down below about maybe -50 kPa here in terms of load.
02:12 We're going to be using some general trends to our table and smoothing into those or extrapolating into those areas that we can't achieve.
02:21 Alright so let's get our engine up and running on our dyno now and we'll get started with the tuning.
02:27 We're up and running here and I've chosen to start here at 2000 RPM.
02:30 You could elect to use 1500 RPM, I mean again we're getting into that area where cam control could be a little bit marginal and it can also be quite tricky with our dyno to actually get good torque readings so 2000 RPM we should be at a point where we can start to get reasonable torque readings and we can always extrapolate as we discussed, the cam targets back into those lower RPM regions later on.
02:54 Now what we're looking at here is our target on the left hand side, it's really important that when we are making these steady state changes that we do stay as close to the centre of the cell as possible, otherwise that's going to influence our torque results.
03:08 And at the moment we are in the -50 kPa, 2000 RPM cell, this is about as low as I can get in terms of load on the dyno before the dyno's going to simply slow down and we're not going to get a reading on our torque.
03:21 Looking at that torque, if we head over to the dyno we can see on our time graph, our torque line is sitting there at around about 75-80 pound foot and it is oscillating around a little bit which we're going to struggle a little bit at very light load to get a really stable torque reading so this is pretty typical, that oscillation.
03:40 We do need to do a little bit of mental smoothing with that.
03:43 However as we get up in the load and the RPM, you're going to find that it is a lot easier to read so often if we're getting inconclusive results here we can simply step ahead, look at our higher load higher RPM cells, get those optimised nicely and then extrapolate the trends that we start to see but let's see if we can get a good read here at 2000 RPM.
04:03 So what I'll do is enter a value of 10°, I like to step in 10° increments here so we can really assess the affect of that change.
04:10 Wait for our torque to stabilise, press enter and really no there is actually a small change, we took a little bit of time there before that actually came in but we can see that our torque line has jumped up there so we do see a change from that 10°, it's pretty small, again as we get up in the load and the RPM this is going to become a little bit more obvious but let's try another 10°, again we'll make sure we're stable in the centre of that cell, make sure that we aren't moving when we press enter and again we do see our red torque line jump up.
04:44 Still a little bit of oscillation there but definitely a clear advantage there so let's go another 10°, we'll go to 30, we'll press enter, again make sure that we're staying in the centre of that cell.
04:54 This time, really no change between 20 and 30° and what we can do here as well is just take note of our short term fuel trims and just see what happens there so obviously with 30° cam angle, sitting at about -2.5 to -3%, let's go back down to 20°, press enter there.
05:17 What we can see there is the short term fuel trim has become less negative.
05:21 So what this means is the ECU isn't pulling as much fuel so this is the other metric that we do want to be mindful of.
05:27 We really saw no effect on our torque, we'll just go back down to 30° and just check our torque graph again and again nothing really that we can see there, we're splitting hairs if there is a torque change but we've got about a 2.5-3% variation in our fuelling so if we can have exactly the same amount of torque with less fuel required we're going to do that.
05:51 So for the purposes of this demonstration here, we're going to choose 20° as our cam target for our intake.
05:58 But we've still got our exhaust to deal with here so let's jump across to our exhaust and we'll have a look at how we can dial that in so come back to the same cell, again we're looking at our torque graph, doing some mental smoothing there with our torque graph, we'll enter a value of -10° and we'll see what happens with our torque.
06:18 Small but noticeable improvement with our torque there.
06:21 So we're going in the right direction here so let's go another 10° here, we'll go to -20, again making sure that we are in the centre of the cell, enter -20.
06:31 Still making sure we're in the centre of the cell and again, very small but noticeable improvement.
06:36 You can see that at the same time, our short term fuel trim has actually become more negative so we're actually now getting a torque gain for less fuel so we're making better use of the fuel that is being injected so this is all good stuff.
06:48 Alright let's go a little bit further, let's try -30°, we'll press enter, see what we get there.
06:55 No noticeable change there and in fact if I get back into the centre of that cell because it crept a little bit, we will actually see that we've dropped.
07:05 So let's come back here to -20 which looked like it gave us the best all around result.
07:10 Now I am making reasonably coarse changes here, you can get a little bit more granular with it, it just depends purely how accurate you want to be and how much time you want to spend.
07:20 Alright let's jump back now to our intake cam because we've made a 20° change to our exhaust cam tuning so we could expect rightly that there may be some advantage in a further change to our intake cam tuning, so we're at 20° at the moment.
07:34 Let's just try a change to 10° again, so we'lll pull 10° out of our cam timing, press enter.
07:43 Making sure that we are staying stationary.
07:46 If anything, a small decrease in our torque there, although it is hard at the moment with that oscillation again, don't be too worried about this, everything will become a little bit clearer once we get higher in our load.
07:58 Let's try 30° here.
08:01 And we do actually see a noticeable improvement with 30° and we can see that our short term fuel trim now, we're pulling almost -9% so that's really good, again a torque gain for less fuel.
08:14 Let's try another 10°, we'll go to 40° here, making sure that again we stay in the centre of that cell and we've just crept a little bit there so we'll get back into the centre of that cell.
08:26 OK so massive reduction there in our torque so we'll go back down to 30°, again just make sure that we do gain, we get back into the centre of that cell.
08:36 30° for our intake, -20 for our exhaust looks like it's going to be a pretty clear winner for our -50 kPa cell.
08:47 Let's come up now to our -25 kPa cell, we'll head back over to our intake and we're going to repeat that process.
08:55 Now I can already be guided a little bit here by the sort of numbers that we've found just for that 1 cell.
09:01 So 30°, I'm probably expecting that I'm going to be either at or further advanced from 30° for this cell but let's go through the process anyway, so we'll look at our torque graph.
09:13 Make sure that we're central in our cell, press enter and yes we do see a gain in our torque despite the oscillation, I actually have dropped back out of that cell a little bit so you can see once I'm back in the centre of the cell, we get a further improvement, let's go again, another 10°.
09:29 And again we see a small but noticeable improvement.
09:33 And just again being mindful that I do need to manipulate the throttle just to stay in the centre of that cell.
09:38 So this is all stacking up with what I'd expect, I definitely wouldn't expect my timing here, target to be less than 30° so let's step up another 10° here, making sure again we're central in the cell.
09:50 Another small but noticeable improvement here, let's go another 10° and we'll see that our torque graph on our dyno has just rescaled there, given that we were right up the top of the graph so we'll just allow that to get a pretty stable line there.
10:04 Let's enter 40° here and we'll see what happens.
10:10 Really no change there, in fact if anything we've seen a small reduction so let's come back down to 30°.
10:18 We see there is a noticeable change here in our short term fuel trims as well, 6% with 30° and if we go back to 40°, about 2.5, 3% so there's a 3, 3.5% difference there but we have seen a small but noticeable difference in the torque so we will go for peak torque here, so we'll come back to 30°, just head over to our exhaust cam angle target table and again -20° at 50 kPa, I wouldn't expect to be higher than that, or less than that I should say, at -25 so again for the sake of completeness, let's step to -10, looking at our torque.
10:59 -10 we do see a small improvement in our torque, not significant but definitely an improvement, let's go another 10° here.
11:07 See another improvement there, -20.
11:10 Let's go another 10° here, -30.
11:13 -30, we do see a small improvement, not particularly significant there.
11:18 Going to split the difference there and we'll come back to -25.
11:21 Let's head back to our intake cam and we'll see again if we do need a change.
11:26 I'll make 5° changes this time just for the same of speeding this process up so let's come back down to 25°, so I'm expecting here the torque will reduce but let's see if that does pan out to be true, press enter.
11:40 And we have seen our torque reduce.
11:42 Let's go to 35° here.
11:45 And should see our torque increase.
11:49 Actually haven't seen much of a change so for that cell I'm actually going to leave our intake cam timing at 30°, seems to be pretty well there or thereabouts what we want so let's step up again to 10° here.
12:03 Back on our intake cam still so let's just make sure we're central in the cell, allowing our torque to stabilise.
12:10 So again expecting to be at or above 30° but we'll start with 10.
12:16 Good solid increase in our torque and you see how much easier it is to read the torque graph now that we are up a little bit further in the load so that makes our life a little bit easier.
12:26 Let's step up to 20° here, again making sure that we're in the centre of the cell.
12:30 An improvement, not quite as significant as our first improvement.
12:33 I suggest that we are getting towards our optimal timing, let's go to 30° here.
12:40 And again an improvement, small but noticeable.
12:44 Let's try 40° here, just waiting for our torque to stabilise.
12:48 Hit enter there.
12:51 And we saw that our torque did actually decrease a little bit there so we'll come back to 30°.
12:58 Let's head over to our exhaust cam timing and we'll repeat that process.
13:06 Alright so let's start by pressing -10, entering -10 in there.
13:11 OK so noticeable improvement in our torque there.
13:14 Let's try -20.
13:18 Another noticeable improvement in our torque, quite significant there, let's try -30 this time, making sure again we're central in that cell, Another improvement so this does follow the trend that I was expecting.
13:34 Let's try -40°, I think we're pretty much at the limit of the cam timing movement at this point, let's try that, -40°.
13:44 Another small improvement there, we can see that we're actually able to track about -39 so we're pretty much on our target there.
13:55 We can try -50 just to see the extent of the available travel and we can only get to 43 so let's go back to -40 and we'll leave that there.
14:06 We'll come back across to our intake cam target.
14:09 It's also important just to calibrate your ideas on what your maximum values should be to avoid the chances of any integral windup.
14:18 Alright so we're at 30° here, let's try, we'll try a 10° increment just so we can see the effect of that change, so we'll come back down to 20.
14:28 OK you'll see our torque fall, we'll go back to 30, back to where we were, torque comes back up to where we'd expect and we'll try 40.
14:37 See the effect of that, press enter.
14:41 And we see our torque drop away again so looks like 30° for our intake cam is where we do want to be.
14:48 Let's step up one more time, we'll come up to our 25 kPa if we can get to it.
14:53 And in this instance we can't so I'm actually at wide open throttle now and we can see that the maximum load we can get is around about 13 kPa so pretty typical with a larger turbocharger.
15:04 That's not a problem, what I'm going to do is just come back to stop and we'll just talk about what we can do here.
15:10 So the cells here out to the right, the higher load cells at the moment, we obviously can't tune.
15:17 But what we're going to do is just simply extrapolate the results that we've got here from the cells that we have tuned.
15:24 So basically following that trend, 30° in our intake and we'll go back to our exhaust.
15:29 -40 here for our exhaust cam and we do want to be a little bit mindful here as well, so we were seeing a noticeable improvement but because we've got this quite large step here, quite often what I'll do is I'll sacrifice a little bit of potential torque, and we were really splitting hairs here for a smoother trend in this table.
15:52 And the reason for this is it just makes the cam tracking a little bit easier.
15:56 So what I can do here is just use the linear interpolate function and that will just give us some smooth numbers here so we've gone from -40 at 0 kPa to -32.5.
16:08 There might be a few pound foot of torque in this but the drivability and response of the cam control system will make up for that, it's definitely going to be an advantage to have smooth cam targets.
16:19 This also begs the question of what are we going to do out in the low load area and what are we going to do down in the lower RPM region? For now we're going to do nothing, we're going to complete our tuning here following the same process out to in this case 4000 RPM and we'll come back and talk about our results so let's go ahead and do this now.
16:38 We'll speed this process up a little bit.
16:40 It's just a rinse and repeat of exactly what you've watched so far.
16:54 What we're going to do now is step up to our next zone which is 2500 RPM, our next row.
17:00 And before we do this, what I'm going to do here is just copy the values that we've already found here and we're going to paste those up to our next 2500 RPM column, do that with the exhaust and we'll repeat that process here with the intake.
17:17 And the reason we're going to do this is that we do expect to see a relatively smooth trend to the shape of these curves.
17:25 So what we've learned here at 2000 RPM, we're likely to see similar numbers at 2500 RPM so we can save ourselves a bit of time here just by extrapolating the results that we've found out into the untuned zones and then rather than starting from scratch what we can do is start bracketing our results, plus to minus 10° on our intake followed by plus or minus 10° on our exhaust and just see if we can get an improvement by advancing or retarding those cams based on what we saw at 2000 RPM.
17:52 So we're going to speed this process up a little bit from here and we're going to go through to 4000 RPM so let's go ahead and get that done now.
19:57 Alright just want to stop for a moment and just highlight one of the cells that we've just gone through here.
20:03 Which is this particular cell here at 0 kPa and 3000 RPM.
20:09 So we can see we've got a funny trend here which is straight away reason for an alarm bell.
20:13 We've got value to the left at lower load of 40°.
20:18 Then we step to 35° in the cell we're interested in and then 45° at 25 kPa.
20:24 Now because obviously here we are making small adjustments that we do need to be quite sensitive on our throttle positon to make sure we're central in the target and also the way we read that torque graph, it does open us up for some potential errors.
20:38 That's OK though, the sort of errors we're talking about with 5° of cam timing are generally going to be in the vicinity of maybe a percent or even less in terms of torque so there's no point beating yourself up here trying to get the absolute perfect result but when we do have an inconsistency across the cells like this, where the trend doesn't follow what we'd expect, this is where we would be mindful of going back and revisiting that particular site.
21:04 Anything that gives us a trend that just doesn't make sense or doesn't stack up.
21:09 In this case, considering we are so close here, what I'm going to do again is just highlight the surrounding cells and use that linear interpolation function.
21:17 We've gone from 35° to 42.5, we were literally battling over a handful of pound foot of torque so it's really going to be neither here nor there in terms of our results but again it's just going to give our cam control functionality the ability to do a better job of tracking that target.
21:34 Alright we'll continue now and do our 3500 and 4000 RPM rows.
23:14 Alright we'll just take a moment here, the engine coolant temperature as we can see, has just crept up to 100° so just like the rest of our tuning we do need to be mindful of our engine coolant temperature.
23:25 Particularly with the steady state tuning as we get higher in the load and higher in the RPM.
23:29 This is a good opportunity just to assess what we've found so far and have a look through our table.
23:34 So we can start to see the sort of trends that we would expect.
23:38 Obviously we haven't got past 3500 RPM right now, sorry 4000 RPM right now but we can see the shape is what we'd expect here.
23:48 We start with our values, our exhaust cam in this case, our maximum values of retard in this case will occur usually somewhere around about peak torque which we'd expect to be somewhere around about 3500, maybe 4000 RPM so that's in line with that.
24:06 We can also see the general trend is that the retard, the exhaust cam retard gets greater as our load increases so everything's stacking up with what we would expect.
24:17 What we can sort of see now is that the values that we've got around about 2500 and 3000 RPM seem to be peak and while we haven't really got too far into this, it seems that as we've increased our RPM here we're starting to advance that exhaust cam back towards 0.
24:33 Again exactly what I'd expect.
24:35 If we look at our intake cam target table, again showing the general trends that I would expect, we've got that taper off in the advance that we see at lower load just like our exhaust cam and we've got our peak value occurring in line with what we would expect so everything at the moment is in line with our normal trends, no reason for concern here.
24:59 What we have been doing here, as we've gotten going here is we've been bracketing the cam timing by 10° increments so basically allowing us to reach equilibrium, steady state, looking at our torque value, regarding the cam 10°, taking a snapshot of what happens to the torque, advancing it 10° beyond our initial starting point and that gives us a pretty good idea of we're in the ballpark or if there is some potential torque to be gained.
25:25 Always a good idea just to back that up with your short term fuel trims, see if you can get a reduction in fuel consumption for the same amount of torque.
25:33 If the cam timing itself is not giving you a torque gain.
25:37 Now because we are already in the ballpark in terms of copying and extrapolating those values across, this does step up the process as well because we don't need to do so much iterative adjustment, essentially we're only making usually adjustments of 5 or at the most maybe 10° to our cam timing as we move from 1 RPM column to the next, row to the next I should say and likewise we shouldn't expect then when we optimise our exhaust cam timing that that's going to have a huge knock on effect with our intake cam timing so this just allows us to speed up the process, again absolutely up to the individual.
26:10 There is the potential for very small improvements beyond this if you do want to go though 1 or 2 iterations of intake followed by exhaust, followed by intake.
26:20 Our coolant temperature's back down under control now so let's continue with the process.
26:40 Alright so that completes our steady state tuning there out to in our case 4000 RPM.
26:45 What we'll do before we'll carry on with the final step of our process is just see what we can do to be a little bit more complete with this table and we've already addressed the fact that for example, let's start with our intake cam target table, we haven't been able to get out to the lower load, -75 kPa and 100 kPa.
27:06 Now the fact that we can't get it on the dyno doesn't necessarily mean that we'll never be able to get there out on the road and what we want to do is just extrapolate approximately the trend that we've already got going here so we can see that as we've been moving from high load down to low load, from the right of this table to the left, we see that our camshaft, our intake cam in this case is being retarded so we're just going to essentially follow this process and we can even go as far, if you want, as just simply leaving the -100 kPa site at 0 and moving across here and using the linear interpolate function.
27:41 This is going to be close enough in most instances to get us there or there abouts in terms of being in the ballpark.
27:49 If we can't quite get into these zones on the dyno, chances are we're going to struggle to really get fully into them out on the road so we're not going to be spending a lot of time there and of course it's a case of there's no point trying to be too precise here.
28:04 We're likely to get with this technique here, at least within the last few percent of torque so again I don't believe there's any point beating yourself up.
28:15 The alternative is you can do some hand smoothing here, look at the trends which in this case we can see in the areas that we have tuned, we've got around about a 5, maybe 7% change per 25 kPa so we could approximate this as well, in this case we've got 25° at -50 kPa, we could end up being more likely around about 17.5° instead of the 12.5 that we ended up with from our interpolation.
28:46 But see the difference there, it's 5° in terms of the actual effect on our torque, it's going to be relatively meaningless.
28:53 Likewise we could apply the same sort of change here, we're probably going to be somewhere in the region of about 12.5-15° here at 4000 RPM so I'm just going to go ahead now and do some hand smoothing with the remaining cells.
29:15 Alright so we've got a reasonable trend to that table there and that's showing up in something that's relatively smooth on our graph over here, always a good way of getting a bit of an approximation of is our timing in the ballpark there? We've got a relatively smooth trend to that table.
29:34 The other thing we're going to do here while we're on our intake cam map is what we're going to do at 1500 RPM.
29:41 Now as I've discussed here, at 1000 RPM, generally I won't have any cam targets because of our oil pressure, we don't however want to ramp straight at 1500 RPM to 2000 RPM.
29:52 In this case, if we look at this particular cell here, between 0 and 30°, that's not going to end that well.
30:00 So what I do like to do here is just use that linear interpolate function and basically just give us a nice smooth trend.
30:07 So we're going to ramp into our cam target timing values in a sensible way.
30:12 I'm now going to go ahead and apply exactly the same techniques we just looked at to our exhaust targets so let's do that.
30:25 So that completes our steady state tuning and at this stage you may be well wondering what we're going to do with these lower load regions at higher RPM.
30:33 Don't worry, once we've dialled in our wide open throttle full power cam targets, we're going to be able to come back and address those.