Variable Cam Control Tuning: Optimising Dual Variable Cam Timing
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Optimising Dual Variable Cam Timing
42.31
| 00:00 | - In this module, we're going to have a look at the process we can use when we are dealing with an engine that has dual variable cam control, so variable intake and exhaust cams. |
| 00:08 | And I know that this is something that a lot of tuners, both experienced and novice are a little bit afraid of but given that there is a lot of work to do, having a solid approach to dealing with this sort of engine is important if you want to be able to get the right results. |
| 00:24 | We'll show you here during this module that really it's not that tricky and as long as we do understand the process that we're going to demonstrate, it's pretty easy to apply, irrespective of the engine that you're personally dealing with. |
| 00:36 | The car that we are using for our demonstration of course is our Toyota GT86, it's fitted with the Subaru FA20 engine that is also turbocharged. |
| 00:44 | So technically this is a quad variable cam control engine, given that the FA20 is a boxer engine, we've got an inlet and exhaust cam with variable control on both banks of cylinders but we're going to be dealing with it here just looking at an individual camshaft. |
| 00:59 | Let's jump into the software and just familiarise ourselves with what we're looking at here so we can understand what we're going to be doing. |
| 01:06 | So we're starting here on the camshaft tuning worksheet which is where we're going to be doing most of our tuning when it comes to the cam control system and we've got the ability here to select our exhaust cam aim and our inlet camshaft aim target tables. |
| 01:22 | We are currently on our inlet camshaft aim table. |
| 01:25 | Nothing particularly unusual here, we've got the table displayed here on the left hand side numerically and then of course out to the right hand side, a graphical representation of the table. |
| 01:36 | We've already got a table shape that is probably fairly representative of what I would expect but we're going to be going through the process here that will be applicable irrespective if you're starting from scratch with absolutely no numbers in this table. |
| 01:51 | One thing that I do just want to point out here, just so we don't end up with any confusion creeping in is the load axis for our camshaft aim table. |
| 01:59 | You see that it is listed as engine load normalise which is MoTeC terminology. |
| 02:06 | On face value doesn't maybe give you too much of an explanation on what that is. |
| 02:10 | Conventionally in a MoTeC M1 this would simply be manifold absolute pressure or potentially throttle position, depending how you've got the ECU set up. |
| 02:19 | Our one is a little unique in that we are running pressure ratio as this axis so this is simply inlet manifold pressure divided by exhaust manifold pressure and that's why we see these numbers ranging from 0.2 out to 1.2. |
| 02:34 | Now while I understand that chances are this won't line up with the numbers you're seeing in your own maps, regardless of what ECU you're tuning, the process is exactly the same, we're just going to be looking at a different point in that load axis so don't let that put you off. |
| 02:50 | Just to demonstrate the load axis though, let's just jump across to our fuel tuning worksheet here and we'll see our main VE table which we've got displayed now, we've got exactly the same load axis being demonstrated there so again irrespective of you using manifold pressure, throttle position or in our case pressure ratio, the process of the actual tuning is identical. |
| 03:13 | Down the bottom of the screen here we can see that we do have our fuel closed loop control for bank one so bank one we've only got 1 lambda sensor here. |
| 03:22 | Basically this is an overall closed loop fuel trim and again we're just going to be using this to help pick up the pieces and correct any errors that we've got between our target air/fuel ratio and our measured air/fuel ratio, meaning that we've got one less thing to concentrate on. |
| 03:38 | Our air/fuel ratio that the engine's going to be running during our testing is always going to stay consistent. |
| 03:44 | Alright so let's just head over to our exhaust camshaft aim table and to start with what I've done is I've just completely set this table to zero so obviously this is where you'd be starting if you had a freshly installed ECU with no base map. |
| 03:59 | So we're going to leave that exhaust cam target table set to zero for the moment. |
| 04:03 | Remembering of course that we already understand the engine performance, both torque, power are going to be much more sensitive to our inlet cam timing than our exhaust cam timing so the process we're going to go through here is we're going to start by optimising our intake cam timing for a given situation. |
| 04:21 | Once we've got our intake cam timing optimised for that particular cell, we're then going to switch across to our exhaust cam. |
| 04:29 | We're going to optimise the exhaust cam timing for that same cell. |
| 04:33 | Now this is where things do get a little bit iterative because as we change the exhaust cam timing, we may find that there's a knock on effect that our intake cam timing then needs a further adjustment so we'll see how that all pans out. |
| 04:47 | Before we get started though, let's just switch back to our inlet cam timing table and what we're going to do here is we're just going to highlight a set of cells here, come from 2600 RPM out to 3500 RPM and we're going to set that entire set of cells to zero. |
| 05:03 | This just means that while I'm going through this process, we're going to eliminate any chances of interpolation. |
| 05:08 | And for our demonstration, we are just going to concentrate on a single cell so we've got enough load and RPM on board to get a really good demonstration of this, I'm going to start at 3000 RPM and 0.5 pressure ratio. |
| 05:21 | This will demonstrate the process of course when you're actually starting to build up these maps, we're always going to be starting from our lowest load and RPM that we can maintain on the dyno and start building up our map from there, working up in our load then increasing our RPM and repeating the process, allowing us to build up the shape and trends in that table which is also going to speed up our tuning. |
| 05:43 | Alright let's get ourselves up and running on the dyno and we'll have a look at the process. |
| 05:47 | Alright we're up and running now at 3000 RPM and 0.5 pressure ratio so we can see exactly where we are sitting in the table there. |
| 05:56 | It's really important when we are going through this process to make sure that we stay exactly in the centre of that cell. |
| 06:03 | If we aren't in the centre of that cell of course that's going to affect our results because of interpolation around surrounding cells as well as the fact that as we vary the load on the engine, naturally the engine power and torque will vary. |
| 06:16 | To help me out with this, I have brought up the little target on the right hand side so as I go through the optimisation process, I'm going to be referencing that little target and just adjusting my throttle position if required to make sure that I do maintain a consistent pressure ratio. |
| 06:31 | Let's jump over to our dyno and we'll have a look at what is being displayed there. |
| 06:36 | So we're looking at a torque optimisation test on the dyno screen. |
| 06:39 | On the vertical axis here we have our engine torque being measured by the dyno and on our horizontal axis we do have our inlet camshaft position. |
| 06:48 | I just need to mention that there is a little scaling issue here. |
| 06:51 | The information being sent out from the MoTeC is actually being essentially multiplied by -1 so what we can see is we've scaled this between -50 and +10°. |
| 07:03 | You just need to mentally flip those so it's actually +50° and -10° so we'll talk about that as we go anyway. |
| 07:13 | Let's just jump back into our software and the ECU and the inlet camshaft position on the FA20 is a little unique in that we actually can advance and retard the camshaft from the natural resting position. |
| 07:28 | So we have the ability to go to approximately +50° and we'll see exactly how that pans out and we can retard the cam a further 10 so what I'll actually do, instead of starting with our values at 0, we will start from -10°. |
| 07:41 | And that'll give us the full swing of what's going on there. |
| 07:46 | So what we'll do before we get started is we'll clear our results on the dyno screen, I'll make sure that I am right in the middle of the cell, as close as I can and now what we're going to do is just advance the cam timing at about a degree every second and we'll plot that relationship between engine torque and our camshaft position. |
| 08:07 | So let's go ahead and do that now. |
| 08:23 | Alright we've completed our test there from -10 out to 50°. |
| 08:27 | Let's start by having a quick look at the dyno screen and see what we can take away from what that test has shown us. |
| 08:34 | Alright so at the start of the test, again remembering we just need to reverse those numbers, the positives are negatives, negatives are positive so starting at -10°, we ended up beginning with around about maybe 160 pound foot of torque. |
| 08:48 | We can see as we've moved to the left of this graph and we've advanced that cam timing, the torque has increased and in this case the dyno has shown us that we've ended up with peak torque which is 212 pound foot with a cam timing of 19°. |
| 09:04 | Remembering again this is +19°. |
| 09:06 | Now we can see though realistically there is a reasonable plateau so we're not seeing much in the way of difference from about maybe 28, 29° through to probably about 18 or 19°. |
| 09:19 | So we're pretty flat through that region. |
| 09:22 | Here we are really trying to solve our cam timing for optimum torque. |
| 09:26 | But of course if you're looking at fuel economy or emissions across that range where we're really seeing no change in our torque we could also monitor the fuel delivery and our emissions and see if we can get essentially the same amount of torque with a little bit less fuel being delivered. |
| 09:42 | As we've continued to advance the cam timing past 30° we do start to set that trend where the torque tapers off so we know for our condition there, 19° is our optimal cam timing. |
| 09:54 | Before we lock that in though, let's just jump into our laptop software and we'll have a look at what's going on there. |
| 09:59 | So what we'll do is we'll full screen our time graph here and just get a better understanding of what actually happened during that test. |
| 10:07 | So the first thing we really want to look at here is was our cam timing following our target and we can see at least for the most part yes, from the start of our test at -10 we can see that everything tracked really nicely, in this case our inlet camshaft aim is the red trace, our bank one and bank two are in blue and yellow. |
| 10:29 | But we can see that once we get up to about this point here where we've got about 36° cam advance we actually see that we don't have enough advanced movement, enough mechanical movement so our red trace has continued as I've advanced the cam timing but we can see that our two bank cylinders, bank cams there actually tap out at about 38, in one case 36.5°. |
| 10:53 | So that's important information to understand, obviously our test's shown us we don't want to be there but we know here to avoid the chances of integral windup we would want to make sure that our cam targets are 35°, 36° or less so we're staying within the range of motion that the cams actually provide. |
| 11:12 | At the same time, we're just checking that our exhaust cam was doing what it was told. |
| 11:16 | We can see that it's sitting on our zero target so nothing too exciting going on there. |
| 11:20 | The trace that is worth looking at though is this bottom one which is our closed loop fuel trim so this is what the ECU is doing in the background to get our fuelling on track. |
| 11:31 | And this can be a good guide as to where our peak volumetric efficiency is. |
| 11:36 | Of course as we increase volumetric efficiency we're increasing cylinder fill. |
| 11:41 | In turn, we're going to need more fuel so we can see at the start of this test at -10° cam timing we've got almost -10% trim so we're pulling 10% fuel out to get our fuelling on track. |
| 11:55 | We can see that that nice and smoothly increases here and we can see we've got a bit of a plateau from about this point here which we are at 12° through to about this point here where we are at 23°. |
| 12:09 | So coincides nicely with our torque curve and we can see probably around this point here we've got our peak trim, +2.1%, that coincides with a cam target of 21° which is pretty close to the 19° that the dyno has shown us. |
| 12:27 | So in this area we really are starting to split hairs, the closed loop trims show us around 21°, the dyno's shown us 19° but we're going to close this down and we will set our cam timing for that particular cell to 19°. |
| 12:42 | Now actually before we move on and look at our exhaust cam, just for the sake of completeness, what I will do is also complete the surrounding cells and set those to 19° and this is just going to be helpful because now when we go through the same process looking at our exhaust cam, if we do move around a little bit, our intake cam target is always going to remain at 19°. |
| 13:02 | Let's switch over to our exhaust cam timing table now and we're going to be tuning the exact same cell here, 3000 RPM and 0.5 pressure ratio and we're going to go through exactly the same process with a torque optimisation test. |
| 13:16 | Let's get up and running and go through that now. |
| 13:19 | Alright if we head over to our dyno we can see we've changed the setup for our torque optimisation test. |
| 13:26 | Essentially very much the same although this time we've got our exhaust cam aim on our horizontal axis, 0-50°, this time the numbers do coincide with the numbers in our table. |
| 13:35 | So I'm simply going to repeat the process here, we'll make sure we're in the centre of our cell, we'll stop our current test, clear the results, we'll click begin and now we're going to go through and advance the exhaust cam timing from 0 up to 50° Alright we've got our test complete there and if we have a look at our results we can see as we'd expect here, much less difference in our exhaust cam timing in terms of our torque. |
| 14:16 | We can see that we've got a bit of a plateau really starting from 0 through to about 20° but there is a distinct trend here and we can see that we've seen a small gain in our torque with the cam timing in this case of 17°, 16.9, let's not split hairs. |
| 14:32 | That's given us 215 pound foot of torque so we're up about 3 pound foot so it's definitely not significant but worth taking any advantage we can get. |
| 14:42 | We can see once we get past about 20° the torque really starts to fall off a cliff and realistically if we were doing this test, once we got to 25° and saw that trend, we'd simply stop but for the sake of completeness I've gone through to 50°. |
| 14:57 | So let's jump into our laptop tuning software and we'll analyse what we've got there. |
| 15:03 | Looking at our whole run here, first of all looking at what our exhaust cam has done and essentially both cams have tracked that target pretty nicely. |
| 15:11 | The engine really wasn't very happy running our around 45-50° so we can see that it's not really that comfortable, everything's moving around a little bit and it was a struggle to stay in the middle of that cell which is why we're starting to see these jumps in our cam timing because we were moving around and starting to interpolate to the surrounding cells but again, I've done that for the sake of completeness. |
| 15:34 | There was obviously no advantage in being anywhere near 40°+ of cam timing. |
| 15:39 | In this case though we can see at least we have been able to get all the way to the extremes of 50° of cam advance, giving us a good indication that we are within the range of mechanical travel. |
| 15:51 | Looking at our closed loop fuel trim which is again just a bit of a sanity check on the torque results, we can see as we'd pretty much expect from the start of that test there, sitting at about 2% trim, we see probably around about this area here, 2.4% trim that is around about our peak value but again we are splitting hairs. |
| 16:14 | We're seeing around about 7° of cam advance so a little bit different to the 17° that we actually see in the dyno screen. |
| 16:23 | But again here what we can take advantage of is the fact that if we are making peak torque, if we come out to the actual 16.9, 17° where we did see the peak torque number, we've actually dropped our fuelling delivery slightly which is obviously an advantage, we've gone from 2.4% trim to 1% trim so again any time we can get the same or in this case slighty more torque with less fuel being delivered, that's definitely an economy boost. |
| 16:52 | Alright so that's what we've learned so far, we know that for that particular cell in our exhaust table, the optimal timing, at least as far as our dyno is concerned, is 17° so we're going to go ahead and set that cell to 17° and again for the sake of avoiding any interpolation, I'm going to also set the surrounding cells to 17°. |
| 17:12 | Now this is where we start getting into our iterative process because when we move the exhaust cam in this case 17°, it's a very good chance that that will have a knock on effect of where our optimal intake cam timing will be. |
| 17:27 | The amount of movement we can expect with our intake cam is really going to be dependent on how much movement we see with our exhaust cam. |
| 17:36 | So 17°, it's a reasonable amount of movement, I wouldn't be surprised if we need to now move our intake cam maybe as much as 5° or so. |
| 17:44 | So let's repeat this test back on our intake cam, we'll get up and running and we'll go through the same process again. |
| 17:51 | Alright we're back in the centre of our cell here so we're already at 19° which is where we left our intake cam timing. |
| 17:57 | Now we don't strictly need to repeat our full test, we are very unlikely to need to be at either extreme of our travel so instead of repeating the entire test, what I'm going to try and do here is go maybe about 15° either side of that target so in this case just to split hairs let's set our starting point at 5° and we'll clear our results over on our dyno screen, make sure again we are in the centre of our test point and we'll click on begin and we'll advance our timing through to let's say 35°. |
| 18:32 | So let's go ahead and do that now. |
| 18:42 | Aright so we've completed our test there for our intake cam and we can see that there's a definite trend, a definite shape to that table, we can see the dyno showing this time that the optimal timing is 18° so we've actually only moved by a degree and that's not too unusual. |
| 18:59 | I will just point out here that this time our dyno has shown us a peak torque of 213 pound foot, obviously from the end of our last test, we were at 215. |
| 19:08 | So if you are wondering about this, there is always going to be a little bit of variation run to run in terms of the torque output so this does still indicate a peak torque value here and obviously a degree of cam timing change. |
| 19:22 | So what can we learn from this, well first of all we've made a change to our intake, our exhaust cam timing there and that has shown a knock on effect where our optimal intake cam timing has also needed to shift. |
| 19:35 | Although not dramatic and again this is not too unusual. |
| 19:39 | The magnitude of change we can expect on the intake cam timing is going to be a result of how much change we made on our exhaust cam timing and if you remember back to our exhaust cam torque optimisation test, we really did see that plateau essentially from 0 through to about 20° so none of this is particularly surprising. |
| 19:58 | Sometimes when you do this test you will find that you do need to move the intake cam maybe 3-5°, perhaps even more. |
| 20:05 | It all really comes down to the magnitude of the change that we use on our exhaust cam. |
| 20:10 | So we've gone through one iteration of changes here, we will come back into our cam timing table for our intake cam and set the position there to 18° which we've just found. |
| 20:20 | I'm not going to worry about the surrounding cells for now, we are just solely focusing on our 0.5 pressure ratio, 3000 RPM cell. |
| 20:28 | Now we've gone through one iteration so the next question is, should we go through a second iteration? Right now, going through one iteration, intake followed by exhaust and coming back and revisiting our intake, that's already more work than most tuners are going to put in. |
| 20:44 | Most tuners, even with a few ideas about how to do the cam tuning, will simply optimise the intake cam, go and optimise the exhaust cam and never revisit the intake cam so we've already gone one step further. |
| 20:57 | Given that we only ended up varying the intake cam on our second look by 1°, it's fair to expect that there's not going to be any real need to further adjust our exhaust cam timing. |
| 21:09 | It's really down to the magnitude of that change, if on the other hand I'd made a change to our intake cam timing of 5° well yes under those circumstances there could be benefit in coming back and revisiting the exhaust cam timing. |
| 21:21 | You're getting to a point of smaller and smaller improvements in power and torque with each iteration of change though and it's a personal preference here, how fussy do you want to be, how much time do you want to spend on the dyno because of course time does equal money so the process is what we've just looked at, how many times you choose to rinse and repeat that process is purely up to you. |
| 21:45 | Now of course we have selected to just optimise that one cell there, 3000 RPM and 0.5. |
| 21:52 | As I mentioned, under normal conditions we'd start from low load and low RPM and start building up the intake and exhaust cam timing maps using that same process but irrespective of where you start it's the process that is important. |
| 22:05 | Now that we've looked at the process of optimising our part throttle cam timing for intake and exhaust, we're now going to move on and have a look at the process when we're under wide open throttle ramp run conditions. |
| 22:17 | And what we're going to do is assume there that you've already got your intake cam timing optimised with your exhaust cam at 0. |
| 22:25 | This is essentially the same process we've already discussed and looked at for a single variable cam control engine so we'll assume that we're already at that point, we've optimised our intake cam timing which is really exactly the same as what we just looked at, we start with our intake cam timing, get that optimised and then we move on and look at our exhaust cam timing. |
| 22:45 | So let's jump back into our software and just refresh our memory here and we can see we've got our cam timing map, albeit with the big hole in it that we've just created. |
| 22:54 | That's OK, we're not going to be running in that area. |
| 22:56 | It is important to mention here that with our pressure ratio axis, we're running between about 0.8 and 1.2 maybe 1.3 pressure ratio during a wide open throttle ramp run so that's the area of this table we're going to be operating in. |
| 23:11 | And again we've got numbers in this table that are at least representative of optimal intake cam timing with our exhaust cam set to 0. |
| 23:20 | Let's switch over to our exhaust cam timing table and again we've got this big bump in the table that we've just gone through and optimised but everything else, particularly in the 0.8 and above pressure ratio area, set to 0. |
| 23:33 | So what we're going to do now is perform a range of ramp runs, we're going to do our ramp runs in 10° increments and then build up a composite map. |
| 23:42 | So let's get our engine up and running on the dyno and we'll perform our first ramp run there with our exhaust cam timing set to 0. |
| 23:50 | Before we do make any runs, while we're doing this it's always a good idea just to check our starting parameters in terms of coolant temperature, air temperature, make sure that we are trying to be as consistent as we can, that's going to give us the best results when we are looking potentially for small changes. |
| 24:06 | Let's get our run underway now. |
| 24:25 | Our first run complete there, 361 horsepower, really not too interested in the power at this stage, what we're going to do is simply repeat that run and we will save this run and what we're going to do is call that 0° just so we've got a reference so now we're going to step through in 10° increments, let's jump back into our tuning software, we'll highlight in this case from 1250 RPM, 1.2 down to 0.8 pressure ratio and we'll set our cam advance or retard for our exhaust cam to 10°. |
| 24:59 | Let's go through and repeat this process all the way up to 50°. |
| 25:28 | Alright we've got all 6 of our ramp runs complete there and while we were overlaying these in real time with a previous run, can be a little bit difficult to see some of the subtle differences and also compare all of the runs while we're doing that. |
| 25:41 | So we've got all of the runs up together at the same time on the screen and we'll see what we can learn from this now. |
| 25:48 | So we can see each of those runs and individually where they are showing their strengths and weaknesses. |
| 25:55 | So just to clean things up, straight away we can see this light blue run here which is our 0°, that's not giving us an advantage anywhere at all so we'll get rid of that run just so it's not cluttering up our screen, we know that because there's no advantage there we definitely don't want to ever have the exhaust cam timing at 0°. |
| 26:12 | Let's look at the start of our run where we were down at 2000 RPM and while there's subtle differences there we can actually see that the red run is giving us our most power, with 55.43 horsepower and we can see that essentially that stays the same up to around about 2500 RPM so we want our timing up to 2500 RPM to be at 10° so let's go back into our map and we'll apply what we've learned. |
| 26:40 | So I'm going to leave our cam timing down at 1000 RPM and below set to 0 just because we will struggle with oil pressure potentially and we're going to go in this case 1500 RPM and 2500 RPM to 10°. |
| 26:56 | Now between 1000 and 1500 RPM I do have this zone here at 1250 and what I'm going to do is just interpolate that which gives us a value of 5, just to give us a smooth ramp in. |
| 27:07 | Again we're in the area where oil pressure is going to be low, probably not going to be really too focused on what our cam targets are at 1250 RPM and higher load anyway, we're simply not going to be there and we're just trying to get a smooth ramp in. |
| 27:20 | Alright so we're up to 2500 RPM, let's head back to our dyno screen and if we have a look at our 10° line we can see that it doesn't play any significant role from there on in, right at the top of the run we can see that we're getting very close but our yellow line does give us more power so again just for simplicity and to clear things up we'll get rid of our red run. |
| 27:42 | So from 2.5 which was where we were, we can see that our purple run starts to take over so our purple run is the strongest up to in this case about 4000 RPM. |
| 27:52 | Our purple run of course there is 50° so what we're ging to do is leave our target there up to 4500 RPM where we already have it at 50°. |
| 28:03 | Now this is going to create some steps, don't worry too much, we'll come back and talk about those in a moment. |
| 28:08 | Alright so again our purple run doesn't play any more part in the proceedings so we'll get rid of that off the screen. |
| 28:15 | We're really starting to split hairs now between our white run, our yellow run and our green run but for simplicity of our cam targets, we're going to step now to our 40° map which is our white run and that goes out to in this case about 5400, 5500 RPM, we want to be at 40°. |
| 28:40 | So let's make those changes now, we'll go 5000 and 5500 and set the targets to 40°. |
| 28:49 | Again our white run doesn't play any part from here on in so we'll get rid of it and what we can see here is that our yellow run 20° actually is strongest for the rest of our run. |
| 29:02 | It's a very close thing between our 20° and our 30° map here. |
| 29:07 | So we could go either way, particularly above 6200 RPM, our 20° is a clear winner so what we're going to do is just take note of this because in that mid range that we've just looked at, it's just a run to run variation essentially between those 2 lines. |
| 29:25 | What we're going to do is take note of that. |
| 29:29 | So at 6000 RPM we'll jump down to 30°, again there's not really much of a power variation, and then from 7000 RPM and above we are going to be at 20°. |
| 29:40 | Now it may be that we actually want to shift that to the left a little bit, given that at 6000 if we come back to our table there, 6000 RPM, yeah we really are just splitting hairs between those two. |
| 29:54 | So with our base numbers into our map now we have got these steps so we'll have a quick look at this from the side and we can see in particular here, we've got this big ugly step and we're not going to do anything about that now but that is going to cause some issues with the accuracy of our cam timing tracking that but let's get a composite run on the dyno now and we'll just see how well we're laying over the top of those previous 6 runs. |
| 30:42 | Alright we've got our composite, first composite run out of the way there, we can see 382 horsepower at the wheels and you can see that particularly in the higher RPM range we picked up massively over our previous run, given that that was the 50° map though it's not really a true indication so what we'll do now is we'll save that run and we'll overlay it with our individual ramp runs. |
| 31:01 | Alright so looking at our runs here, our purple run up here, this is the composite run that we've just completed and you can see that it does do a really good job of skirting across the top of all of those individual runs, let's just get rid of some of our other runs just to make things a little bit clearer. |
| 31:18 | Obviously as I get rid of some of these runs, we do lose some of that value but we can see that it's done a really good job of tracking everything. |
| 31:25 | So our composite map has done essentially what we'd expect, we've got the best results from all of our individual runs. |
| 31:32 | Let's just jump back into our tuning software and we'll just see how well our exhaust cam actually tracked that target. |
| 31:38 | Alright looking at our exhaust cam aim here it's actually done a pretty stand up job. |
| 31:42 | However we can see that this big jump in our cam timing right here has, as we'd probably expect, resulted in a bit of an overshoot we've sort of gone up to about 55° here before our closed loop has sort of come back in and kind of gathered things up. |
| 31:58 | We've also got these steps here which while it is tracking quite well, we can probably go ahead and do some smoothing so let's see how we can do that. |
| 32:07 | What we want to do here is just happy a little bit of common sense. |
| 32:11 | Now this is the case where again we may actually get a benefit in terms of smoothness, drivability and our cam control tracking by sacrificing a little bit of ultimate torque in terms of actually getting cam targets that the mechanical system can track a little bit more accurately so let's have a look and see what we can do in here. |
| 32:30 | And the first big problem obviously is this step here that we've got between 2500 and 2750 RPM so we're stepping 40° cam timing in just 250 RPM. |
| 32:40 | And frankly the cam control system probably doesn't have much chance of doing a good job of tracking that so what I'm going to do here is I'm just going to go to 3000 RPM and we're going to pull the cam timing target down a little bit there, we'll go 40° and then what we'll do is we'll also interpolate between 2500 and 3000 RPM there so we'll just use our interpolate horizontally. |
| 33:05 | And that gives us a nice smooth trend to that table there. |
| 33:09 | We can do a little bit of the same here with these steps that we've created. |
| 33:14 | Again we're probably unlikely to see a massive affect on this in terms of our actual power and torque but we can end up getting a much smoother control so we'll just go ahead and make some of these changes now and you can see now I've already got something that is quite nice and smooth. |
| 33:31 | Now the other thing that's worth mentioning here is we are only going out on our dyno to 7500 RPM. |
| 33:36 | We've got a break point here at 8000. |
| 33:38 | It may be beneficial if we're going to run the dyno harder just if we look at the trend that we've got in that table there, I'd expect if that trend continued we'd probably want to drop down to 10° but in our case we're only running to 7500 RPM, we've got pretty well optimal results so we're going to leave that there. |
| 33:56 | With our hand smoothing done now let's just perform another ramp run on the dyno and just see first of all if the hand smoothing has in fact given away any power and how well the cam control is tracking now. |
| 34:27 | Alright so we've got exactly the same peak power values, let's just have a look at that and analyse it over the top of our first composite map. |
| 34:34 | Alright looking at our results we can see that once the engine is up on boost from about 3800 RPM and above, the two runs are essentially overlaid directly on top of each other. |
| 34:43 | We do interestingly see that our composite 2 map's given us a few more horsepower here at about 6600 RPM. |
| 34:51 | Whether or not that's a run to run variation, we could check by repeating the process. |
| 34:56 | We can see that it does look at first glance like our current change to our cam timing has actually resulted in a loss of power through this spool up area. |
| 35:06 | This is simply a case of the way we're running the car here and heat in the exhaust manifold resulting in slightly slower spool so that's not actually real, that's a run to run variation so essentially what we've found here is that the smoothing that we've just done, no real effect, negative effect at least on our power and torque and that's often what we'll find. |
| 35:26 | What we want to do as well is just dive into our tuning software and see, has that change actually given us an improvement in our cam tracking? And we can see if we look at our exhaust cam target vs our cam positions, yes in fact that's exactly what it's done, we've got a really nice trend there, nice shape, it's following really really nicely so we're happy with that. |
| 35:45 | So this essentially gives us our first iteration, we've gone through, started with intake cam timing that was optimised for 0 exhaust cam timing, we've then gone through and optimised our exhaust cam timing for the set intake cam timing but we now want to see if the change we've made to our exhaust cam timing then results in a need for us to change our intake cam timing and we're going to use our bracketing technique to do this where we're going to advance and retard in one block the intake cam position so let's head over to our intake cam targets and we'll have a look at our table. |
| 36:20 | So what we can do here, it's really up to the individual which way we want to go whether we advance the cam timing to start with or whether we try retarding it. |
| 36:30 | We already know that the general rule of thumb as we advance the cam timing we should improve the power in the bottom end, retarding the cam timing should help our top end but let's have a look at our values through here and we can see up at 7000, 8000 RPM, we're already back to pretty well 0, we've got about 30° through our mid range here so what we'll do is we'll highlight the numbers in this table from 1.2 down to 0.8 pressure ratio, 1500 RPM all the way out to 8000 and let's start by adding 5° to the entire map. |
| 37:05 | What we're going to do now is another ramp run and we'll analyse this compared to our composite 2 results to see if there's been any improvement. |
| 37:33 | Alright our first change there, advancing the cam timing, on face value it seems like we've actually lost a little bit of power but let's dive in a little bit deeper and we'll see what the actual results are so what we'll do is we'll save this run and what we'll do is reference this with intake plus 5 just so we can see what we've done. |
| 37:53 | Let's have a look and see how those 2 overlay. |
| 37:56 | Alright so while it is very close and admittedly it was only a 5° change, we can see that right from the start here we've picked up around about 1.5 horsepower, there's an area through this mid range through that spool area where we've really seen no effect and then there is a small but noticeable improvement almost the whole way through that run right up to this point here, 7000 RPM where we definitely wanted that cam retarded so that's actually been pretty positive, what that suggests is that our cam timing for our intake was a little bit too retarded and we can learn from that so let's just jump back into our intake cam timing map. |
| 38:32 | So first of all what we know is 7000 RPM and above, definitely did not like that additional 5° so what we can do is take that 5° out. |
| 38:41 | Now any time we see an effect like this where we've gone one way and we've actually lost power. |
| 38:46 | The natural tendency would be that we'll want to try going the opposite way and see if maybe we're already out of the ballpark so we could retard the timing there 5°. |
| 38:54 | Now obviously that gives us a problem because we can see we're only at 2.6 and then 1.7° so no real room for a 5° change there, we'll try retarding it back to 0 though, I'm not expecting much of a difference with only 2.5° of cam timing change but we'll see what that gives us. |
| 39:12 | On the other hand the change that we did see there through the mid range was positive when we added 5° so of course when we've got that sort of a result, we'd simply go further in the same direction and see if there's any further gain to be had. |
| 39:26 | So given that that change was essentially everywhere, we'll just have a look back on our dyno graph. |
| 39:34 | Essentially the only place where we didn't really see much of a difference was 5300 and then through this spool area. |
| 39:40 | For the sake of simplicity though, let's just highlight the entire area again and we'll come back and make another 5° positive change, advance the timing 5°. |
| 39:52 | Now this does give us one problem here. |
| 39:54 | We've already highlighted that the maximum amount of advance on our intake was around about 36, 37°. |
| 40:02 | So we do need to be mindful when we are doing this, we can see now what we've done is we've created this area in the table where our cam targets are 38, 39, almost 40° and obviously we can't track to that so just be mindful when you are advancing or retarding the cam beyond the limit and make some sensible changes there so we've got a situation like this, what I'm going to do is simply come back in and set the cam targets to the maximum value I know that we can track. |
| 40:27 | Alright our second change made there, let's go ahead and perform another ramp run. |
| 40:51 | Alright so our peak power is back up to where we were prior to that last run. |
| 40:54 | We can see that it was very close during that ramp run but let's go and save that run, we'll overlay it again and we'll see what our results are. |
| 41:03 | Now again as we look at the overlays here, very very close everywhere, essentially there hasn't really been any gain, if we look between our yellow run which is our +5° and the last run we did our green run which is +10°, through the mid range there we've seen no advantage and if anything, and we are really splitting hairs, there is actually a benefit from our last run so we've actually gone too far here. |
| 41:29 | At the top end we can see that if we look compared to our first composite run, 381.9 horsepower, our green run, we're back there so 0° or 2.5° as we expected didn't really see any gain there so we could go back to what we found from our composite map. |
| 41:47 | So the bracketing technique we've seen there, we're just going to rinse and repeat that, basically advancing and retarding the cam timing in 5 or 10° increments until we've found the optimal point for our intake cam timing with our optimised exhaust cam timing. |
| 42:03 | Once we've done this, again we're in a situation where we could rightly go back and make a further bracketing change to our exhaust cam timing and there may be some small incremental gains to be had, it really again comes down to how much time you want to put into this process and how particular you want to be about your results but the process we've just looked at is going to get you probably within about 1 or 2% of the peak power and torque that the cam timing is going to provide. |
