Practical Reflash Tuning: Step 5: Optimising the Tune
Watch This Course
$229 USD $114.50 USD
-OR-
Or
8 easy payments of only $14.31
Instant access. Easy checkout. No fees.
Step 5: Optimising the Tune
42.51
| 00:00 | - The next step of our process is to optimise our calibration using our dyno. |
| 00:04 | And we're moving on from our last step where we've optimised our volumetric efficiency table, it's now time to actually start optimising our air/fuel ratio targets, particularly under power enrichment conditions and then we can start optimising our ignition timing too, trying to see exactly how much power we can safely get out of our new larger cam. |
| 00:25 | Before we get into that though I do want to just spend a little bit of time talking about what is one of the more difficult parts of tuning the GM LS series engine with a large cam, which is getting our idle control dialled in. |
| 00:38 | We've already briefly touched on some of the topics in the build up to actually getting our engine started. |
| 00:44 | However now that we've got our VE table dialled in, it's time to actually look at some of those aspects in a bit more detail and see how we can go about optimising them. |
| 00:53 | It's first of all worth just having an understanding of how our idle speed control strategy works and there are a few moving parts here with the idle control so let's jump into the tuning software and we'll have a quick look. |
| 01:07 | We are here on our idle tab and we've already looked at our RPM tab. |
| 01:13 | We've set some idle set points that are going to be suited to our new cam and we've talked about those. |
| 01:19 | Now those values that we used there, I know from experience these work pretty well with the HS108D. |
| 01:24 | However don't be scared to try tweaking your idle speed targets a little bit. |
| 01:30 | What we really want, particularly with the automatic transmission they are prone to pushing when we are in drive and the car is stationary. |
| 01:38 | So the higher the idle speed in drive in particular then the more the car is going to push which a lot of drivers really don't like. |
| 01:46 | So we really want to be able to get our idle speed as low as we can get it without the engine having trouble or struggling to idle so it's definitely worth trying reducing the idle speed in maybe 50 RPM increments to just see how low you can go while still maintaining good idle quality and making sure the engine isn't going to stall. |
| 02:05 | In our case we're not going to adjust that though. |
| 02:08 | The other aspect here is we do have some settings over here for our adaptive idle. |
| 02:12 | So this is the idle control system. |
| 02:14 | Typically I don't find too much reason to make changes to this, however because a cam does naturally provide a bit of lope to the idle, that lope can actually cause issues with larger cams with the adaptive idle strategy, basically trying to correct the natural increase and decrease in RPM. |
| 02:34 | We'll just have a quick look at the aspects here so first of all, we've got a proportional gain and what we can find here is our airflow adjustment which is basically based on the error, we've got one for normal and one for coast down. |
| 02:48 | So basically the larger these numbers the more adjustment the closed loop control strategy will try and make to the idle in response to an error. |
| 02:56 | With these tables I don't try and get too granular with the adjustments I'm making. |
| 03:00 | What I'll do if I wanted to make an adjustment to this is simply highlight the entire table and normally we would be reducing the power of the adaptive idle so maybe making a change of 0.5 and then using the multiply, that'll halve the effect of the adaptive control. |
| 03:17 | Likewise it's not just our proportional that is working here, we've also got an integral element. |
| 03:23 | And again we've got an airflow tab for that. |
| 03:27 | Very much the same and we can make changes in the same way. |
| 03:30 | The other thing we may want to do here, we've got the error in RPM that basically if we are within 50 RPM here of our target idle speed, the ECU will consider that to be on our target idle speed and won't try and make adjustments so again may find some benefit in increasing these numbers, increasing the threshold also for our integral element a little bit but as I've mentioned personally I don't usually find I need to make adjustments to the adaptive idle, it's just about explaining that that system is there. |
| 04:02 | Before we move onto our airflow tab which is over here, we've again already addressed this lightly, I just want to move out of order a little bit and we'll come over to our spark tab because there is another element that works here for our idle control and that is our idle adaptive spark control. |
| 04:18 | So I prefer to use the term idle ignition control, it's exactly the same though, basically it's using the ignition timing, advancing and retarding the ignition timing in order to help maintain idle speed and this is quite a quick and effective way of getting idle speed control. |
| 04:35 | So the ECU uses this in conjunction with making adjustments to the electronic throttle control throttle opening. |
| 04:41 | So just quickly looking at this, if we look at our overspeed which is simply when we are above our target idle speed. |
| 04:47 | So we've got tables for park and neutral, for gear and for coast so if we just have a quick look at our park and neutral for a moment. |
| 04:55 | So what we can see here is basically this is our RPM error. |
| 04:58 | So when we are for example 112 RPM above our target idle speed, the adaptive ignition system will end up pulling 12° of ignition timing. |
| 05:09 | So if we actually quickly look at our underspeeed, basically this works in the opposite way. |
| 05:15 | Now when we are 112 RPM below our idle target, the ECU will add 14°. |
| 05:22 | So we see this rapid increase and decrease in our ignition timing to help stabilise the idle speed. |
| 05:27 | It works very well but even in a stock cammed engine, what we find is that if the numbers in these tables are quite large, it will actually create almost a lope a little bit like having a larger cam. |
| 05:42 | So we do need to be mindful of this. |
| 05:44 | What I generally find is if the numbers in these tables are too aggressive with a large cam, it creates a very lopey idle, very choppy and can actually be quite uncomfortable sitting in the car because the car will tend to shake. |
| 05:56 | So if you've got that situation, simply going into these tables here, what I try and do, rather than getting granular again with the adjustments, the whole table here and make an adjustment of maybe 0.75 and then use the multiplication function, that will reduce the amount of control available. |
| 06:12 | It's a trial and error system here, I suggest making a reasonably large change like that, 25% or 50% adjustment, do it in both the underspeed and the overspeed tables and then test and see when you've got the sort of idle quality that you want, you will also be able to monitor what the adaptive idle ignition control system is doing in the scanner. |
| 06:32 | Likewise you've got, as I've mentioned tables for in gear and coast as well and I generally will make similar across the board changes to all of those tables when I am changing them. |
| 06:43 | Alright so that's our spark here and that's really the only aspect of that that we need to deal with as part of talking about our idle strategy. |
| 06:51 | We'll now come back across to our idle tab and this time we're going to move across of course here to our airflow tab. |
| 06:58 | And again we've looked at some of these parameters, in particular we've already made some adjustments to our base running airflow table. |
| 07:05 | In particular here our airflow final minimum. |
| 07:09 | So as I've mentioned already, I kind of liken this to a base set point for our electronic throttle control opening. |
| 07:17 | So this is going to get us close to our target idle speed before the adaptive idle controls come into play. |
| 07:25 | We'll open that table again and have a quick look at it. |
| 07:27 | And we do have tables for each gear as well as neutral and park. |
| 07:32 | Generally but not always we find that we'll have similar numbers across all of them and in fact at the moment as you can see, we have exactly that. |
| 07:41 | It's a good idea here just to take note in the idle areas of the sort of numbers we've got in this table. |
| 07:47 | We'll show you in a second how we can use our scanner to figure out what sort of numbers we actually want in that table. |
| 07:52 | We do need to be mindful in the higher RPM areas because if these numbers are too low, we're going to end up with our idle speed potentially dipping as we blip the throttle and come back to idle. |
| 08:05 | Alternatively if they're too high we're going to end up with the idle speed hanging and it won't come back to idle neatly so it is important to make sensible changes to these. |
| 08:15 | What I generally do as we sort of looked at when we were setting up this file is I focus most of my adjustments down here in the idle area and just a gentle extrapolation out into those higher RPM areas without making wholesale changes out there. |
| 08:29 | When we are making changes here, a change of 1-2 grams per second should be sufficient to see the effect of that change. |
| 08:37 | We do also have a baro multiplier for that table which generally shouldn't need to be touched and we've got an engine coolant multiplier as well. |
| 08:47 | So if you've got the base running airflow set up pretty well under normal operating conditions and you're having problems down in the cold start region, then you can make slightly more specific changes using the ECT muliplier table. |
| 09:01 | We do also need to consider as part of our idle control the throttle follower torque table which is this table over here. |
| 09:08 | And this is used to calculate the throttle follower airflow. |
| 09:12 | So basically if we don't have this table set correctly, we're going to struggle to get good control of our idle speed. |
| 09:19 | So these are torque targets in terms of newton metres inside of this table vs our gear and our engine RPM. |
| 09:27 | So what we can see here is we know that our target idle speed's down around here and in this stock file we've got a value there of 8 Nm. |
| 09:36 | What we are going to be able to do here is use our scanner and actually see what the commanded torque is or the engine delivered torque I should say is at 800-900 RPM. |
| 09:46 | And then we can use those numbers and help fill in this table a little bit more accurately. |
| 09:51 | We do also need to be careful with this table so we'll be making changes to our target idle speed, we will need to do a little bit of extrapolation down to the lower RPM region and a little bit out to our higher RPM region. |
| 10:05 | However you'll see we've got negative numbers here which on face value might not make a lot of sense. |
| 10:11 | Obviously our engine isn't really delivering negative torque but this will define how the or help control how the idle speed returns to, sorry the engine RPM returns to idle speed when we get off the throttle. |
| 10:23 | So we make wholesale changes there, we can end up with stalling or the RPM hanging so I generally try and restrain my adjustments to very close to our target idle speed. |
| 10:34 | Alright so some other tables here that we will need to consider. |
| 10:37 | We've got a start up airflow table which as its name implies will control the initial startup. |
| 10:45 | So if we open this up, we can see that what we've got is our engine coolant temperature on the vertical axis and we've got time in seconds since startup on our horizontal axis. |
| 10:55 | So for a given engine coolant temperature, let's say we're at 80°, we can see that initially we have an increase in our idle airflow, 14.64 grams per second and then as the time ticks away we see that drop away so this is used to get our idle speed under control during initial startup and then basically we'll transition to our base running airflow target. |
| 11:19 | So if you've got a situation where the RPM flares on startup then what we'd want to do is reduce the numbers in this table. |
| 11:27 | Conversely if the idle is low initially and then the adaptive idle kicks in and grabs it and pulls it up, then we'd want to adjust this table upwards. |
| 11:36 | The way I make these adjustments is again not too granular just across the board changes at least to get started. |
| 11:44 | If we're going to make adjustments again I'd recommend making adjustments of about 2 grams per second or thereabouts, it should be enough to get a sense of whether you're going in the right direction and getting your desired results. |
| 11:55 | Now of course if you do find that you've got an isolated issue with startup, maybe only when cold, well you can then start looking at more specific areas of that table and adjusting just those. |
| 12:07 | I do try and recommend trying to keep a reasonably smooth shape to this table. |
| 12:13 | This is what we should end up with once we've got that dialled in. |
| 12:18 | Alright we've got a couple more aspects to deal with here as well which is our transmission shift airflow, relevant of course for automatic transmission engines. |
| 12:26 | So this is the control of what happens to our idle speed as we go from park or neutral and we pull the engine into gear. |
| 12:35 | Conversely when we do the opposite and we go from gear and we push the transmission into neutral or pak. |
| 12:41 | for example we've got our drive transition here. |
| 12:45 | So when we go from neutral and we pull the car into gear, the transmission into gear, there's going to be more load on the engine so if we don't do anything about this, the idle speed will drop so if we look at this table here, this is going to be the increase in the airflow that we will be demanding based on our engine RPM and also based on our transmission temperature. |
| 13:08 | When we're making adjustments to this, again I'd probably suggesting making across the board changes initially and around 1 gram per second per step of change should be enough to guide you to whether you're going in the right direction. |
| 13:22 | We've also got, as part of this, a drive hold table. |
| 13:27 | And this, as its name implies is just the amount of time that that increase will be held before we drop back into adaptive idle control. |
| 13:35 | We've also got the complete opposite here which is our park neutral transition. |
| 13:40 | Which is when we're transitioning from a gear into park or neutral. |
| 13:44 | This works the opposite way, this actually removes airflow from our idle control system so drops the airflow which is obviously what we want, we're going from being in a gear where there's a lot more drag on the engine, transitioning into neutral or park, obviously that drag is reduced so if we don't do anything about this the RPM is going to flare. |
| 14:03 | So there is a little bit of tooing and froing with all of these tables. |
| 14:07 | It's not a 2 minute job to get this dialled in. |
| 14:09 | The workflow that I would suggest here is to start with your throttle follower torque and then also getting your base running airflow minimum tables dialled in so you've got good control of your idle speed at a normal operating temperature. |
| 14:26 | Once you've done that then you can start looking at these other aspects such as your startup airflow, getting that dialled in so that you don't have a flare or a drop in your RPM during startup and then we can also start looking at our transmission shift airflow and make sure that that's nice and smooth as we transition into and out of gear. |
| 14:45 | So just to see what that all looks like, let's head over to our scanner and we'll just get our engine up and running. |
| 14:50 | I'm not going to use any throttle to actually get this running, we'll just see exactly what our response is like. |
| 14:56 | And what we may need to do in our tables. |
| 15:05 | OK so the startup there was actually pretty good, we'll just allow this to idle for a few moments and then we'll pause our logger and have a bit of a more in depth look at exactly what's going on here. |
| 15:16 | So let's do that now.. |
| 15:18 | Alright so first of all we can see the RPM trace here in red, so we can see that we get a pretty quick startup, very slight flare here, we've gone out to about 1300 RPM briefly and then it's dropped straight away back to 1000 RPM and then as we click through here we can see that we're settling down to our 850 RPM target. |
| 15:39 | So pretty much doing everything we'd expect there. |
| 15:41 | I've added in this parameter in blue here which is our engine torque. |
| 15:45 | I'll just shut the engine down while we're going through this. |
| 15:48 | We can see that here in our parameter list as well. |
| 15:51 | So this again can be used just to help you fill in that torque table so we can see although I didn't really allow it to settle down, the torque's moving around quite a bit. |
| 16:01 | We're somewhere around about 50 Nm at that particular point, 850 RPM. |
| 16:07 | I'll come back and address that again in a moment. |
| 16:10 | And we can also see here our adaptive spark which is the white function here, or this is actually our spark timing being delivered but we can see how this is all moving around. |
| 16:21 | Now we can use this as a bit of a guide to help us with what's going on with our base running airflow as well. |
| 16:28 | What we ideally should be doing is seeing the ignition timing doing much what it's doing now so we can see, it's all over the place of course because that's exactly how it's responding but the point I've just clicked on here, we've got 5° timing and we're jumping up here to somewhere around about 20° timing so basically if we look at the average of that, we're probably somewhere around about this point, 12° or thereabouts. |
| 16:53 | So that's OK but what we're trying to do is get our timing to be going positive and negative from maybe somewhere between 12 and 18° of ignition advance. |
| 17:04 | So if we're seeing constantly our numbers dropping negative, that means that our base running airflow base position for our electronic throttle control is too high and the ignition timing's been massively retarded in order to control that. |
| 17:17 | And we will quite often see that just after startup which is exactly what we've got here, nothing to be worried about with this, we can see that in this instance we're actually going into the negatives with our timing and we can see during this region here that's exactly what happens. |
| 17:31 | We can often see this for a few seconds after startup but we shouldn't be seeing this during sustained idle speed control. |
| 17:38 | We want to be seeing something that looks a lot more like this. |
| 17:42 | Alright so we know that our torque was 50 Nm or there abouts. |
| 17:47 | Now that's not necessarily going to be an absolute value though. |
| 17:52 | Generally I've actually found that some manipulation of that number will be required. |
| 17:56 | We may also need a different number when we are in neutral or when we are in a gear. |
| 18:02 | So generally I try and set this, initially a little bit more conservative. |
| 18:06 | We are already running with these numbers here which are much much lower than that but let's start by setting that to 40 Nm and then as I've mentioned, little bit of manual interpolation here, I'll interpolate that out and we'll also interpolate from 800 out to 1200 RPM. |
| 18:24 | So that's just putting some numbers into that table there that should get our torque a little bit more accurate to what's actually going on. |
| 18:31 | Another parameter in our logger that is worth monitoring is our actual airflow. |
| 18:35 | So getting some realistic values for what our airflow is so let's get back to our logger, we'll start our engine up again and we'll record some new data and we'll just see what exactly our airflow is doing. |
| 18:52 | Alright so the parameter that I'm looking at here is our volumetric efficiency airflow. |
| 18:56 | We can see that currently that's sitting around about 11 to 13 grams per second. |
| 19:03 | Now the reason we're looking at volumetric efficiency airflow here is because of course we don't have a mass airflow sensor. |
| 19:08 | If we had our mass airflow sensor we would have our mass airflow value right here. |
| 19:13 | Also being demonstrated in grams per second so now that everything's stabilised a little bit more, we can see that we're actually sitting down closer to about 10 grams per second. |
| 19:22 | So we can use this to help us fill in the base running airflow table as well. |
| 19:28 | There's a bit of manipulation here and it is an iterative process, we want to basically get our torque table set up, we want to get our base running airflow table set up and then we want to make sure that our startup airflow is not giving us flares or a drop in RPM and then we'll also have a quick look here at our transition into gear. |
| 19:46 | So I'll just pull the handbrake on here, we're in neutral at the moment so we'll just pull the car into gear. |
| 19:52 | And pretty good there, we saw very very slight drop in our RPM. |
| 19:57 | But absolutely nothing to be worried about there and we can also see our adaptive idle ignition is still doing its job there. |
| 20:05 | We'll just transition back into neutral and see that that goes smoothly. |
| 20:09 | And again everything's looking pretty good there. |
| 20:11 | So now that you understand a little bit better at what those tables are, what they do and where we may need to adjust them, it's just going to be an iterative process for yourself to go through and get a result that's going to work for your cam. |
| 20:25 | Unfortunately there are no numbers I can provide that are going to work in every instance and it is a case of actually testing and seeing how your particular combination responds. |
| 20:35 | We will be providing this file as a base calibration that you can use as a compare file and see what sort of changes we've made and you can model those on your own calibration to get the right results. |
| 20:49 | Now that we've covered our idle speed control which again is really the hardest part of getting our cammed engine running nicely and responding like a factory engine, we can move on with our actual calibration. |
| 21:02 | And we're going to start here by shutting down our engine and we're going to disconnect our scanner and we're going to go through and make a few more changes to our calibration based on where we were at. |
| 21:13 | So the first part of this, we're going to head across to our fuel tab. |
| 21:17 | And we're going to make some changes to our power enrichment. |
| 21:22 | Now you'll remember that during our mass airflow sensor, sorry our volumetric efficiency table scaling I should say, we were running with a flat power enrichment table so we'll open that table up and we can see that it's filled with 1.149 which you'll remember gave us a 0.87 lambda target. |
| 21:40 | Now I don't necessarily want to run that, we could get results that way, it's not dangerous but it's probably a little bit richer particularly at low RPM than we really need so what we're going to do, we've got our calculator up here. |
| 21:52 | I want to start by targeting 0.90 and we'll target that up to about 3000 RPM. |
| 21:58 | So we'll enter 0.90, we'll use our inverse function on our calculator and we see that that gives us an equivalence ratio of 1.111. |
| 22:07 | So let's enter that. |
| 22:09 | We'll just highlight the cells up to 3000 RPM, 1.111. |
| 22:14 | Now as we go higher in the RPM we're going to want to run richer. |
| 22:18 | 0.87 probably actually isn't a bad place to be. |
| 22:21 | I'm going to go a little bit richer at higher RPM and just see how that works for us so we'll bring our calculator back up. |
| 22:29 | Let's try 0.86, now these numbers aren't set in stone. |
| 22:32 | Of course we can always come back and manipulate these to suit once we've actually tested on the dyno but for our purposes, we're going to start with this. |
| 22:40 | So we'll again use our inverse function here, we can see that that gives us a value of 1.162, going to round that to 1.163. |
| 22:49 | So we'll highlight the cells from 6000 RPM and above and enter 1.163. |
| 22:55 | For the sake of simplicity here I'm now going to just click on the cell at 3000 RPM, right arrow across while I'm holding down the shift key to 6000 and then we'll just use the horizontal interpolate function there to give us a nice smooth trend to our power enrichment table and we can view that graphically, that's what we've got there. |
| 23:13 | So that's going to give us at least a good starting point there for our power enrichment. |
| 23:17 | While we're on our fuel tab we also want to now reenable our closed loop control so we can do that by heading across to our oxygen sensors tab. |
| 23:26 | And the easiest way of doing this is to use our compare file here so we'll just bring up our first file that we had, our stage 1 file and basically all of the green tables we want to copy the original information back from so we'll just go through and do that now. |
| 23:48 | Alright so those 2 tables that I've just changed there, this will reenable our short term fuel trims or our closed loop system altogether however we've now got the personal choice to make here, we've got our long term trims. |
| 24:00 | The numbers that I've got in here, we can see will actually disable our long term fuel trims which is my personal preference how I like to run this sort of system when I have gone through and optimised the calibration. |
| 24:10 | So I'm going to rely solely on short term fuel trims alone. |
| 24:14 | If you do want to enable the long term fuel trims it's simply a case of using your base file, copying those numbers from the base file and then pasting those back into your current calibration. |
| 24:26 | Moving on, we'll also head across to our open loop base tab and we also have a few changes to make here so we'll just go ahead and make those now. |
| 24:43 | Alright at this point we've set up our file, we can now save the file and we're going to close down our compare as well just for simplicity. |
| 24:52 | We can flash this into the engine, into the ECU and we'll get ourselves up and running and get ready to perform our first ramp run. |
| 25:06 | Alright we've got the engine up and running, we've allowed the engine's temperatures to stabilise so we're not suffering from any heat soak we can see that our coolant temperature's up to 93°. |
| 25:17 | Our air temperature is 28, it's probably going to climb a little bit because it is a warm day here, once we've done some runs. |
| 25:23 | Let's have a look at just how well everything is tracking as well. |
| 25:25 | So coming down to the bottom we've got our measured lambda vs our commanded. |
| 25:29 | It's moving around a little bit but we can see that for the most part we're pretty close to our target. |
| 25:34 | We can also see our short term fuel trim's now doing a little bit of work and here at idle we can see everything's looking really good, we're basically cycling backwards and forwards across 0 while controlling our air/fuel ratio. |
| 25:46 | So this is a good sign that our volumetric efficiency scaling from our last step has worked. |
| 25:53 | Of course we will also get to see how well that all tracks once we actually perform our ramp run with our new air/fuel ratio target. |
| 26:00 | So let's get that underway now and we'll head across to our dyno and see what this has resulted in. |
| 26:34 | Alright we've got our first run complete there and we can see we've just put down 451 horsepower, 336 kW. |
| 26:42 | We can see our red line here on the dyno for our air/fuel ratio, pretty much tracking what we'd expect, we've still got that reference line in there at 0.87, understandably with our target, 0.90 at low RPM we start above that and then we're tracking a little bit richer than that right at the top of the run. |
| 26:59 | Let's have a look into our scanner and we'll see what's going on in here though. |
| 27:03 | So looking at first of all our lambda, we can see that again we're tracking pretty well, we've got a little rich area down in here but for the most part from the start of the run, 2000 RPM through to 6600 RPM at the end of the run, we're within about 1% of our target. |
| 27:20 | Might have a couple of areas here which we may want to address, 2600 RPM for example, we're sitting at 0.88 with a target of 0.90. |
| 27:30 | If we want to, we could go and address that in our VE table just by taking note of our manifold absolute pressure, 96.5 kPa. |
| 27:37 | Of course our RPM, 2600, 2700, that gives us a guide as to where to make those changes in the VE table and then it's a repeat of what we've already looked at in the last step. |
| 27:48 | The last step should have got us really close but there can always be a little bit of fine tuning, it is also important to be realistic about what you can expect here. |
| 27:57 | You're never going to get an air/fuel ratio that overlays directly on top of your target, it's always going to move around slightly and it's also going to likely always give a bit of a variation from one run to another. |
| 28:09 | Generally if I'm within about 1 or 2% of my target, I'm going to call that good, I'm going to be pretty happy witih that. |
| 28:15 | Generally in this regard also, I'd probably like to see my air/fuel ratio erring on the side of a little richer than my target rather than a little lean but basically you've got the skills and the tools now to make adjustments to your VE table as you see fit to get that as close to your target as you're comfortable with. |
| 28:35 | We're not going to address that any further because it is just a repeat of what we've already looked at but let's look at our spark timing. |
| 28:40 | So the spark timing is our white values here and we can see basically we've got peak values at low RPM about 27.5°. |
| 28:50 | We can see at higher RPM we're down to about 23°. |
| 28:54 | So from my own experience on this fuel with this cam, I'd expect we are a little bit retarded from what the engine will take. |
| 29:02 | You can see we've got just a little bit of noise from our knock retard here. |
| 29:07 | This isn't anything to worry about, we've got a peak value of 0.7 but basically it's just flickering around 0 so how do I know this isn't real knock? Well if we have got reall knock we're going to see a much more pronounced response from our knock sensor, we're going to see a sharp increase which hopefully as we progress through this worked example we will in fact see, we will purposefully go to the point where we do have a little bit of knock and also if you aren't sure whether to trust the knock retard parameter you can always add audio knock detection equipment just so you can audibly listen for knock and see if this is real or it's background noise. |
| 29:46 | Basically with numbers looking like that, I'm not at all worried so we're going to first of all start by adding a little bit of ignition timing. |
| 29:52 | So we need to know where abouts we were running and we can use the spark advance histogram to help us with this. |
| 30:00 | This is actually a default histogram so you're not going to need to create this. |
| 30:05 | Important aspects to understand here, we've got the same break points and load axis, cylinder air mass in this case and engine RPM as our actual ignition table. |
| 30:13 | So what we want to do is have a look at where abouts we're running in this table. |
| 30:17 | And we can see that down at the start of the run here we're around about 0.60 grams per cylinder, whereas we are at higher load here, sitting around about 0.88 grams per second, 0.84 grams per second. |
| 30:34 | So let's go back to our editor, we'll shut down the engine and we'll also disconnect from our scanner. |
| 30:42 | And for our first change here we're just going to make an across the board change. |
| 30:45 | When I'm making changes to my spark timing I like to make a big enough change to actually assess the effect of that change so we'll come across to our high octane table here and what we're going to do is start by making a 2° change. |
| 30:57 | Now you can get a little bit specific on where you are making those changes and as we go, that's probably what will happen but for the start here, what I'm going to do is from 0.60 grams per second and above we're simply going to add 2° here. |
| 31:13 | Now when we are doing this, we do want to be a little bit mindful of creating weird steps in our table and we can actually see graphically, that's exactly what's happened here. |
| 31:24 | So there's a couple of ways of dealing with this. |
| 31:26 | We can do a little bit of hand blending. |
| 31:29 | Or alternatively we can just use the vertical interpolate or vertical smoothing function. |
| 31:35 | So again for simplicity, we'll just do that and we can see that has got rid of that ugly little step that we just created. |
| 31:42 | But as we go through here just a little bit of common sense applies, we want to make sure that we've got relatively smooth changes to our spark timing without creating any big steps from one cell to another. |
| 31:54 | The general trend that we should see in this table is that as we move from low load down the table to higher load, we should see a reasonably smooth progression in our ignition advance numbers, reducing or retarding. |
| 32:05 | If we haven't got that, then we may need to look a little deeper into that. |
| 32:09 | Alright so we've made our first change there, one really isolated change so we're going to now flash that into the engine control module and we'll get ourselves back up and running and we'll see what that's given us in terms of our power. |
| 32:22 | Alright we're back up and running with that change flashed into the engine control module, we've got our last ramp run that's going to stay up on the dyno screen live in purple so we're overlaying with that and of course with our extra 2° what we're hoping for is an increase in power and torque so we'll see how that actually pans out and that'll guide us on our changes. |
| 32:42 | At the same time we're also going to be monitoring our knock retard parameter on our scanner, making sure that we haven't induced any knock as a result of that additional timing so let's get our run underway now. |
| 33:15 | Alright second run up there and we see that we did gain a little bit of power, we're up to 453 horsepower at the rear wheels. |
| 33:23 | Now if you were monitoring that carefully as we went through you would have been able to see that in the lower RPM part of the range we didn't really see a dramatic increase in our power and torque, it wasn't until we got past about 4000, maybe 4500 RPM that we started to see the improvement from that additional timing. |
| 33:40 | So we can see that in a little bit more detail, what we'll do is we'll save this file now and we'll overlay it with our last run. |
| 33:48 | So let's have a look at that in a bit more detail. |
| 33:51 | Alright so what we can see is first of all we've got this little dip here where the blue run which his our first run, it looks like we've actually lost a little bit of power there. |
| 34:01 | That's not actually realistic, this is just an aspect of the automatic transmission, there's a little bit of a slip there in the automatic transmission. |
| 34:10 | We can actually see that if we jump into the laptop tuning software, the scanner, we can see this little blip in our RPM here so this is just an aspect of our automatic transmission so we didn't actually get complete comparable run back to back. |
| 34:24 | That's resulted in what looks like a reduction in our power but I can assure that isn't real, that's an aspect of our transmission alone. |
| 34:31 | So looking at this in a bit more detail we actually can see we have picked up very marginally in our power and torque, almost right the way through. |
| 34:40 | It was a little bit harder to see during the ramp run but yeah right the way through other than that little glitch that I've just explained, we actually have picked up a little bit of power. |
| 34:50 | It's not until we get up to, as I've mentioned probably about 4000 RPM, 4700 and above, we start to see that that additional ignition timing has actually made a reasonable difference. |
| 35:03 | So I'll take back my initial comments, it's a little bit hard to see with the live plot because the lines are a little bit thicker. |
| 35:09 | Sometimes subtle variations like this don't show up but as soon as we go into the analyse screen, we can see that yes in fact we did actually see an improvement from that. |
| 35:18 | Let's just jump back into the scanner and again we're obviously monitoring knock and again we've got no real activity, we've got a little bit of noise back around that 0° retard, our peak ignition advance now up to 30°. |
| 35:32 | I know from previous experience I'm not really expecting any more power as a result of increasing the timing, particularly down low. |
| 35:41 | Peak ignition timing, 25.5, 26° at higher RPM, we're probably also there or there abouts but for the sake of completeness, let's add another couple of degrees and we'll see what we end up with so again just to refresh our memory here, we'll get rid of our chart logger, we will also have a look here at our histogram and we can see that basically from 1600, 1800 RPM and above we are operating here 0.60, our last change we made from 0.56 grams per revolution, grams per cylinder I should say. |
| 36:19 | So this one we will make from 0.60 so we'll highlight that and again I'm going to create, actually we'll go down a little bit just so I don't create that step which I was just about to explain. |
| 36:30 | We can see that if we look at the numbers here, we've got 35 then 34° so if I added 2°, we're definitely going to create a step. |
| 36:37 | If we come down to 0.64 grams per cylinder, we're at 31° in this region so we can add a couple of degrees here, we're not going to create any step, that all looks nice and smooth. |
| 36:47 | We'll head back to our scanner as well and we can just see that that is actually going to give us basically a result from the point we're at about 1600, 1800 RPM and above so, sorry just head back and I'll make sure that I'm, no we're 0.64 I should say so that in fact is going to be from about 2200 RPM and above. |
| 37:08 | So just understanding using the scanner to help us understand where abouts in the ignition table we are so that we can make changes to the relevant spot and as you can see there, I just about managed to confuse myself so we're on top of that now. |
| 37:20 | We'll disconnect from the scanner, we'll flash that change in and get ourselves up and running again. |
| 37:27 | Alright we've got our engine back up and running so let's get our next run underway. |
| 37:58 | Alright our next run complete there and it looks like we actually still continued to gain power just about everywhere so we're up to 459 horsepower at the rear wheels. |
| 38:09 | Let's just save that and again we'll overlay it with our last file just to make sure that we are in fact up everywhere so we'll get rid of our first run. |
| 38:17 | And yep we can see that our yellow run does in fact make more power everywhere so obviously the engine did like the additional timing. |
| 38:25 | Let's have a look back in our scanner and we'll see what's going on here. |
| 38:28 | We can see our peak ignition advance there about 32° so exactly what we'd expect from our added 2°. |
| 38:35 | 27.5 in the top end so again, nothing, no big surprise there, exactly what we'd expect to see. |
| 38:41 | Again we really don't have anything occurring with our knock retard, certainly nothing that is significant enough for me to be worried about. |
| 38:50 | So we're going to do one more run here and we're going to add another 2° timing. |
| 38:54 | Really want to get to a point where we can see that we have actually gone too far and hopefully create a little bit of knock so you can see what that looks like so we'll shut the engine down, and we will head back across to our editor. |
| 39:08 | So we added 2° at that point from 0.64 grams per second so that again pretty much covers our entire running area. |
| 39:17 | And we did gain power everywhere so that does show that the engine did want that additional timing. |
| 39:23 | So what I'm going to do, I just added 1° there at 0.64 grams per cylinder and above, I've just dropped down to 0.60 grams per cylinder and above, we'll add another degree there and just having a quick glance through here, we want to make sure that our timing hasn't really created any steps and we do have a few here so again we've got the ability to do some hand blending or using our interpolate function so let's just go through and we'll do that now. |
| 40:08 | Alright a little bit of hand blending complete there just to make sure we don't have any ugly steps in our ignition table. |
| 40:13 | We can now write that file into the engine control module, get ourselves up and running again. |
| 40:19 | Alright we're back up and running, let's get our next run underway. |
| 40:50 | OK so with that run, 456 horsepower, you could see for the most part we really didn't see any significant improvement from the additional timing then and in some places, we were down. |
| 41:02 | Let's just save that and we'll overlay it with our last run so we can see exactly what that looks like. |
| 41:14 | So again just highlighting the 2 runs that we are interested in, our yellow run, the run before last, the green run, the run that we've just completed and essentially our green run, we can see that we've lost a little bit of power just about everywhere. |
| 41:28 | So the engine definitely hasn't wanted that additional timing. |
| 41:31 | If we jump into our scanner, we can also see, well it's not too significant, we now do have a little bit more significant knock activity here, particularly here up at 6600 RPM, we can see we're pulling 1.3°, we're starting to get that saw tooth pattern as well that we see when we do have real knock. |
| 41:51 | So that coupled with the fact that the engine didn't actually respond by giving us more power, we'd simply go back and reverse that last change we made, taking that 2° out of that area. |
| 42:04 | So this is just an iterative process, we're going to go through basically finding the point we either reached the knock threshold for the engine or we reached MBT and we don't see any further improvements with our additional timing. |
| 42:18 | Generally on a good quality pump fuel with stock compression ratio, I find that the level of modifications that we have on the engine, we will actually be able to either achieve or be very close to MBT right through the wide open throttle operating area which is essentially exactly what we can see here. |
| 42:37 | From here it's a case of now taking our car off the dyno and we can head out into the real world and confirm everything that we saw on the dyno, does stack up under real world conditions. |
