Variable Cam Control Tuning: Base Table Configuration
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Base Table Configuration
17.37
| 00:00 | - In this module we're going to have a look at some of the considerations around our base table configuration and this is important to cover off before we actually get started with our tuning so that we know we're starting from a solid starting point and all of our axes and outputs are set up and configured as we'd expect. |
| 00:17 | The options here, of course are going to depend on whether we're running a continuously variable cam control system or a more simple switched cam control style. |
| 00:25 | For our demonstration we will be using the Ecumaster EMU Black software however of course there will be significant variations from one software manufacturer to another. |
| 00:34 | Despite this the general principles that we're going to cover off should still be applicable. |
| 00:40 | Let's start with our switched cam control system which actually in this way with our setup is a little bit more complex, there's a little bit more going on here. |
| 00:48 | So we'll start here in our menu structure off to the left hand side here and we can see that we've got the VVT or variable valve timing menu structure, we open that up and we see right at the top here, we have our option for VTEC control so this will give us all of our VTEC parameters. |
| 01:05 | We'll double click on that and that brings up our parameters up here on the right hand side. |
| 01:10 | So the first thing we need to do of course is set up our VTEC output and how that's going to function. |
| 01:16 | Now conventionally this would actually be done as part of our ECU setup however we'll quickly cover that off here, simply a case of selecting a suitable unused output, in this case we have selected half bridge output 2. |
| 01:29 | We can also select to invert that output depending on how exactly our solenoid is being actuated or driven, in this case we are switching to ground so we'll leave that as it is. |
| 01:41 | Now the Ecumaster offers windowing for our VTEC changeover point and it does it in a reasonably unique way so we'll cover off how that works here. |
| 01:48 | So we can see we've got 2 colour coded selections, we've got the green selection that I'm just highlighting now so this is our switch point 1. |
| 01:57 | And then below we've got exactly the same parameters replicated in pink which is our switched point 2. |
| 02:05 | So we can use as many or as few of these as we want. |
| 02:08 | Let's start by just dealing with a simple switching option which would be our switch point 1 here so lt's say we're not using windowing here, we've got a conventional VTEC system that we want to switch solely on RPM alone so we're not worried about manifold pressure, throttle position or our vehicle speed. |
| 02:25 | So in this case let's say we want to switch our VTEC mechanism on at 4500 RPM so that would be our RPM minimum 1. |
| 02:34 | Now the RPM max 1, this is the switch off point so with a VTEC style system, unlike perhaps Nissan's VTC system, we're not going to switch it on and then back off as we move through the rev range so we're simply going to select an RPM for RPM max 1 that's outside of the engine operating range or above and beyond the RPM limiter, in this case 10,000 RPM. |
| 02:56 | This would have the effect of switching on when the RPM exceeds 4500 and it won't switch off again until we drop below 4500 so this would be a conventional VTEC style switchover point. |
| 03:08 | We do have the RPM hysteresis to consider here and in this case I've selected an RPM hysteresis of 100. |
| 03:17 | Typically 50 to 100 RPM is fine for this, we just want to give enough hysteresis that we're not going to have the system switching on and off repeatedly if we happen to be at that RPM point. |
| 03:27 | So that's as simple as this needs to be but if you do want to just switch purely on RPM, we've got a few other considerations here. |
| 03:35 | First of all we've got the ability to bring manifold absolute pressure into the equation. |
| 03:39 | So at this point you can see here our minimum MAP value is 80 kPa so not only would we have to be above 4500 RPM, we'd also need to be above 80 kPa and we need to be below 300. |
| 03:52 | So if we want to switch irrespective of our manifold absolute pressure, we'd need to set this to a minimum value, something that we're always going to exceed, something in the region of about 10-20 kPa there is actually a hard coded limit in here so that would eliminate our manifold absolute pressure. |
| 04:08 | We've got the ability if we do want to switch using MAP as a value, to bring in a hysteresis for that as well, works in exactly the same way as our RPM hysteresis. |
| 04:18 | Third option we've got here is to use throttle position so as you can see here, our minimum and maximum set to 0 and 100 so essentially this will eliminate throttle position as a switching parameter but of course you could use this instead of manifold absolute pressure or as well as if you really want to get complex and finally we've also got the ability to bring in our vehicle speed for this as well so this is actually used in the conventional factory Honda system where the VTEC won't switch if the vehicle isn't actually moving. |
| 04:50 | So that's our parameters one however let's say we want to bring in windowing. |
| 04:55 | So in this case we would probably want to do something similar to this, we've got our switch on point at 4500 RPM and our switch off point obviously outside of our rev limiter so nothing too different there. |
| 05:09 | What we'd want to do though now is address our manifold absolute pressure so for our high load switch on point here, 4500 RPM, we might want to set our minimum manifold pressure to something like 80 or maybe 90 kPa so now the system won't actually switch until the manifold absolute pressure has exceeded that point, 80 kPa. |
| 05:32 | Now what we can do, we can still leave our maximum pressure at 300 kPa so essentially once we're above 80 kPa and 4500 RPM it's switched, it's going to stay switched. |
| 05:43 | We can then bring in our RPM point 2 here so let's say if we are at lower load we might want to switch at perhaps 5000 RPM so we can set that up. |
| 05:55 | Again our maximum value there, 10,000 once it's switched it's staying switched and we want to set our RPM hysteresis, conventionally probably something pretty similar. |
| 06:05 | This time we might want to set our MAP minimum 2 to something a little bit lower, maybe 30 or 40 kPa, our max MAP 2, we're going to set that to the same point here so we're going to be switching between one point and the other. |
| 06:19 | So this would achieve our aim of a windowed system. |
| 06:21 | It's a little clunky in that it doesn't nicely interpolate between those points like a lot of ECUs do however it does give you the benefit of knowing exactly between those points whether you are in the VTEC active or inactive state. |
| 06:34 | So pretty straightforward there. |
| 06:37 | We do also have a couple of other options down the bottom here, we've got the ability to engage the VTEC all the time irrespective of these table values or output parameters if our RPM is above a certain point in this case 15,000 RPM it's obviously set to basically not function and we've got a delay time available as well. |
| 06:56 | Another way of getting a hysteresis into the system so this really comes down to personal preference there. |
| 07:02 | So that's our basic setup there and obviously we're going to manipulate the VTEC changeover points as we see fit once we actually start tuning. |
| 07:09 | So that's got our control strategy structured. |
| 07:13 | Let's jump back over to our fuel or VE table though and we'll have a quick look at how all of this functions so at the moment we've got a single VE table and this is probably how most people will set this up. |
| 07:26 | So what we can see is we've got our break points on our RPM axis and at the moment I've got a break point at 4000, 4500 and then 5000 RPM, pretty conventional. |
| 07:38 | What we may want to do here is add a little bit of high resolution around the VTEC switchover point. |
| 07:44 | Now this doesn't strictly need to be done now because realistically at this point, we're not going to necessarily know exactly what the VTEC changeover point is so there's nothing wrong with leaving this at the moment but just having it in the back of your mind that you will be coming back to it and you may want to add break point resolution maybe every 50 RPM, either side of the VTEC changeover point just to give yourself a little bit of better resolution. |
| 08:08 | Generally if you have optimised the VTEC changeover point there shouldn't be a large jump in volumetric efficiency across that point anyway so whether or not you need that extra resolution is something you're going to find as you go but just bear in mind that it's something you may want to consider. |
| 08:23 | Now at this point we have talked about a conventional VTEC system where we're switching on and we're leaving the system switched on and that may not be the only way we want to do this. |
| 08:32 | As we've discussed in the body of the course, systems such as the likes of the Nissan VTC, generally they'll switch on at a low RPM point and then switch off again, then they may switch on later in the RPM so if we just go back to our VTEC parameters here, it's another way we can use this so here we've got our switch on point, 4500 RPM and our switch off point at 10,000 RPM so let's say we want to switch this system on at 1800 and we find that we actually get best performance by switching that off again at 3800. |
| 09:05 | Then what we might find is that above 6500 RPM it wants to be switched back on so we can do exactly that. |
| 09:12 | Now obviously now we want to change these minimum and maximum manifold pressure parameters so that basically irrespective of our manifold absolute pressure, in this case the system is going to stay active. |
| 09:26 | So just depends on the style of system you're switching and what you actually find the system needs once you actually run it on the dyno. |
| 09:33 | It doesn't really matter, we don't need to finalise this now, we can always come back and manipulate these once we're actually doing some ramp runs on the dyno and we see what our particular system wants. |
| 09:44 | Alright so we've looked at the single VE table but most ECUs, the likes of the Ecumaster here do give us multiple VE tables so let's have a quick look at this and we can see here we've got, under our fuel tables, VE table 1 and table 2, plus we've got 2 target lambda tables. |
| 10:02 | Likewise if we come down to our ignition we see we've got exactly the same here. |
| 10:06 | So we can set up multiple tables and switch these on the VTEC changeover point so let's have a look at that. |
| 10:15 | That's done through a separate parameter, we'll come down here to our other drop down menu or menu structure and down the bottom of this we'll find tables switch so let's open that up and at the moment it's set up to not switch tables. |
| 10:28 | We can drop down that menu and we can see we can switch with our VTEC switch which is nice and easy. |
| 10:36 | Obviously automatically going to switch when our VTEC system is active. |
| 10:39 | So here we can choose what we're going to do with this. |
| 10:42 | The most common here would be simply to switch the VE table and we can do this with a tick box here. |
| 10:50 | You can choose to also switch ignition tables. |
| 10:53 | In my opinion most often that's going to be overkill, we don't generally need a dramatic change in our ignition timing across that switchover point so if we're just coping with windowing then it's not absolutely strictly necessary so we're just going to set up that VE table. |
| 11:09 | Now once we've done this, it does bring us to the point here, if we switch back to our fuel table. |
| 11:15 | So we've got a fuel table or VE table here that has been configured. |
| 11:19 | And now if we come back up to our fuel table menu structure, if we click on VE table 2 and bring that up, you can see at the moment we've essentially got a blank table so that's not going to run particularly well and a good place to get started here is to just copy the values from our existing map so we can do this by saving those values here and we'll call this VE 1 just for the sake of argument, we'll come back down here and we can open that same VE table 1 and what that's going to do is at least start by copying our break points. |
| 11:54 | So if we pull this down now we can see that our break point, so let's move it over here so we can see them side by side, our break points are exactly the same now what we can do here is simply copy and paste the data from this VE table and we'll paste it into our second VE table so that's going to at least give us something where as we switch between tables, we've got the same values, now a case of obviously optimising the individual VE tables for the 2 styles of cam operation, whether it's switched or unswitched and once we've done this, we should essentially have seamless operation between those 2 tables. |
| 12:29 | So that covers the setup for a switched style cam control system. |
| 12:33 | We'll move on now and have a look at our variable valve timing style of operation and this is actually a lot easier, we've already gone through the process of setting up our variable valve time system itself. |
| 12:44 | We'll just look at the tables that are associated with this and we can do this by coming over to a setup that I've got here for our VVT, this is a specific tab here and we've got our cam angle 1 table. |
| 12:58 | Now that covers our intake cam target, we'll just come down here to our VTEC and we'll have a quick look over what is available, we've got cam angle 1 and we've got 2 tables available for this in case we do want to switch our cam targets. |
| 13:14 | Not a lot of reason why I'd want to do that so I'm going to generally be operating off a single table and then we've got our cam 2, we've got the same parameters here however when we are operating two intake cams here, they are operated off individual outputs but of course we want them to be tracking the same target and we can find that here if we come down through our parameters we have got this little tick box here for use angle table from cam 1 so this is important, just making sure that both cams are tracking. |
| 13:45 | That being said, we now need to consider our break points here and this is an area where we can come unstuck, it's really important to make sure that we are using the same load axis in particular as our VE table so we can see here we've got manifold absolute pressure for the load axis for our cam table and if we come back over to our fuel table, our VE table here, we've got that same load axis. |
| 14:10 | Now this is how we should have it and normally it's going to be pretty self explanatory, in most instances we will be using manifold absolute pressure for our VE or fuel table and this would be the default axis for our cam table in most instances as well. |
| 14:26 | There can be some situations though, particularly if you are running a individual throttle body turbo setup where your VE table would be configured with throttle positon as the load axis and if we've got that situation we can get into an area or situation where the relationship between throttle position and our cam position are not the same and this means that we've got essentially a variation in our volumetric efficiency for the same point in our VE table as the relationship between throttle position and cam or manifold pressure changes so what I'm meaning by this, we could for example be at 100% throttle, so that's one individual cell in our VE table but of course as the manifold pressure changes, we're moving the point we're operating in with our cam target table. |
| 15:13 | So if our cam target changes for a fixed volumetric efficiency, that's not going to work that well. |
| 15:19 | So as I've mentioned, most instances, this won't need a lot of thought but it is worth checking just making sure that you are running the same load axis there. |
| 15:27 | Next thing we need to consider here is the break points for both of these axes. |
| 15:31 | And in the Ecumaster we've got a fixed number of bins or break points for this axis so not a lot we can do there, we don't necessarily need as many beak points as we've got here but generally somewhere around about 20-25 kPa for our load break points is sufficient so we can come through here and we'll just clean this up now. |
| 15:58 | So you can see what I've set up there is 20 kPa break points up to 200 kPa and then I've split those and gone a little bit further with 50 kPa at 250 and 300. |
| 16:09 | The reason for this is we don't specifically need this many break points anyway so we don't typically see the cam targets need to change that much once we get past a certain load level so particularly for a naturally aspirated engine, we're going to obviously be spreading all of those break points across 0-100 kPa so we're going to end up with very tight break points, we don't need that, we just won't see the requirements for that. |
| 16:34 | Likewise we can do exactly the same with our RPM axis and typically something like what I've got here is probably pretty typical maybe every 500 RPM would be sufficient. |
| 16:46 | We may find there are some areas where slightly tighter break points may be beneficial around an area where there is a large VE change and we want to move that cam timing but we can always address these once we get into it. |
| 16:57 | For now we've got a pretty good starting point there and the last aspect here is while we do have a target table set up in here at the moment, what we're going to do before we get up and running, we're going to just zero out that table so we've got a nice blank table to get ourselves started and begin our actual tuning. |
| 17:16 | So there you go, a little introduction into some of the considerations around base table configuration. |
| 17:21 | Obviously it's not all encompassing there and there will be variations between different ECU brands and different setups that you may be wanting to do but we're going to get a little bit more specific with some of these as we move into our library of worked examples later in the course. |
