Practical Standalone Tuning: Step 6: Idle Tuning
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Step 6: Idle Tuning
11.06
| 00:00 | - Our next step involves setting up our idle speed control parameters and essentially making sure that we can get the engine to idle at a sensible RPM and this can save you a lot of time particularly if you have an engine that won't idle at a sensible RPM or with sensible manifold pressure, this can indicate that you may have an issue with aspects such as your cam timing. |
| 00:23 | And again it can save a lot of time because if you go to the trouble of doing all of the steady state and wide open throttle ramp run tuning on an engine with cam timing that's out, you're going to waste all that time because you're going to have to redo it all once you've got the cam timing corrected so it's always a good idea to take the few minutes out at the start of the tuning process and just make sure that the engine actually is in good mechanical health and everything's working out. |
| 00:47 | Now to start with this, we really need a couple of points that we can expect from our engine in terms of the idle speed. |
| 00:56 | What idle speed should we expect the engine to idle at and at the same time, what manifold pressure would we expect the engine to be producing at that idle speed? And there's no fixed answer for this, the idle speed that a large capacity V8 will happily idle at with a small cam with limited overlap is very different to a small capacity 4 cylinder for example with a large aggressive cam profile that provides lots of overlap so we need a little bit of understanding of what is likely to work with our engine. |
| 01:26 | Stock RB26 we could typically expect the idle speed to be somewhere between maybe 800 and 900 RPM. |
| 01:33 | Given the cams that are fitted to this, I'm expecting to bump that up a little bit so I'll be looking for a hot idle speed, somewhere between maybe 950 and 1000 RPM. |
| 01:43 | It should give us a good idle quality. |
| 01:46 | At the same time, as I've mentioned in the last module we know that with the cams with a bit more overlap that we're running at the moment, we're not going to see very low manifold vacuum at idle so we saw in the last module we're around about 75 to 80 kPa and that's to be expected with this setup. |
| 02:04 | If on the other hand, we're running standard cams and we saw something like this, this would be a bit of a red flag, a bit of an alarm bell for me. |
| 02:10 | Alright so that's what we're going to be looking at, at the same time once we've got the engine up and running we're also going to be checking that our battery voltage is sensible. |
| 02:20 | Ideally that should be somewhere in the region of about 13.8 to 14.2 volts and we want to check this and just make sure that it is there or thereabouts so that we know that our alternator is charging. |
| 02:30 | And again this can waste a lot of time if the alternator isn't charging because our battery voltage isn't going to be where it should be so we're going to have to come back and revisit our tuning once we've got the alternator fixed. |
| 02:41 | Always best to find these things out right at the outset. |
| 02:44 | Alright so let's dive into the EMtune software and we'll have a look at our idle parameters and see how these work. |
| 02:51 | So what we're going to do here, on our tuning tab we're going to come across to our engine functions and we'll come down to idle speed control. |
| 02:57 | Directly below this we can see we've got idle ignition control, we'll talk about that as well but let's start with our idle speed control and we'll start with our idle speed control setup. |
| 03:08 | You can see our control method at the moment is set to closed loop. |
| 03:13 | While there's nothing strictly wrong with that and we do want to be running closed loop control, particularly when we are just getting started out and we're dialling in the base position table which we're going to go through briefly here, it's actually better that we start in open loop here so I'm going to turn closed loop control off. |
| 03:29 | We also have a couple of other parameters, I'm not going to dive too far in detail here on our startup idle hold timer and our DK rate. |
| 03:37 | We will have a webinar that goes into more detail in our archive on idle speed setup, we're just going to go over some of the very basics here. |
| 03:44 | Alright so now we're going to come down to our main idle target table. |
| 03:49 | This isn't strictly too relevant for our open loop control but when we come back to closed loop control we want this to be set up with sensible values. |
| 03:59 | So what we've got here is a 3D table, we can see we've got our drive speed in km/h on the vertical axis here. |
| 04:06 | And we've got our engine temperature on the horizontal axis. |
| 04:10 | So particularly for idle when we are stationary we're going to be obviously sitting here in this particular column. |
| 04:17 | We've had our engine running briefly from our last module so we can see we're up to about 40° engine temperature. |
| 04:24 | You can see down at lower engine temperatures we're targeting a slightly higher idle speed, may even want to bump this up a little bit, might want to start around 1200, maybe 1250 RPM. |
| 04:35 | And then once we're in our normal operating region we are targeting 1000 RPM idle. |
| 04:42 | You can see at the higher road speeds or ground speeds, we've bumped this up a little bit and this just helps avoid the idle dropping or maybe even stalling when we come to a stop because as we come to a stop, as we're coasting, then idle speed can be affected, or the engine speed can be affected if we are in gear so what can happen is the closed loop control will start trying to pull the idle speed down so we want to try and set this up. |
| 05:07 | This also works with our speed lockout as well, another parameter which I won't go into any further detail on. |
| 05:13 | So key point here is we've got sensible idle speed targets. |
| 05:17 | Now the next point here, the next table that we're going to look at is our initial position table and this is really where we're going to be spending the main amount of our effort. |
| 05:27 | Again 2D table here, we have our engine temperature on the vertical axis and we've got our target idle speed on the horizontal axis so this is why the idle speed is still relevant even when we are in open loop. |
| 05:42 | So what's going to happen, at the moment we are at 40° and we've actually got an idle up for post start here so our target to start with is going to be 1200 RPM. |
| 05:49 | And this essentially just defines the idle duty cycle that will be delivered to the solenoid. |
| 05:58 | Higher numbers, as we can see off to the right hand side will give us a higher idle speed. |
| 06:03 | So what we want to do is basically adjust the numbers in this table until our idle speed is on our target or as close to as we can. |
| 06:11 | That's going to be helpful because when we do reenable our closed loop control, the closer this target table, base position table is, the less work the closed loop control is going to have to do. |
| 06:21 | So this is where we're going to be making most of our changes, we'll just go back though because the idle speed control also works in conjunction with our idle ignition control setup. |
| 06:31 | So at the moment this is turned on. |
| 06:33 | Nothing strictly wrong with that and I do want to run the idle ignition control strategy but for our initial startup I'm actually going to turn that off. |
| 06:41 | The reason for this is it can mask errors in our idle position base table. |
| 06:47 | Basically our numbers could be too high or too low and it would be accounted for by the idle ignition control either adding or removing timing. |
| 06:56 | The principle behind this operation is that provided we are idling with our timing below MBT, if we advance the timing towards MBT the engine makes more torque so the RPM climbs, conversely if we retard the timing further from MBT, torque drops so so does our idle speed so by very quickly advancing and retarding the timing, the ECU can do a really good job of tracking our idle speed targets but to start with we're going to leave that disabled. |
| 07:23 | Alright so what we're going to do is get our engine up and running and we're going to come back to our main fuel table, our main VE table, we're going to do a better job now of doing some fine tuning in this table, so let's get our engine started. |
| 07:39 | We can see that our idle speed is a little bit lower than our target so let's just head across to our idle speed initial position table here and we can see in particular our target idle speed error, so we can see how far we are away, in this case, 170 RPM away. |
| 07:54 | We have warmed up a little bit more now so we are tracking up towards our 60° zone, we're actually interpolating between two here so what I'll do is I'll just increase those values and we should be able to get ourselves up towards our target. |
| 08:09 | And it's just a case here of making appropriate changes until we get our idle speed to track our target. |
| 08:16 | Once we've got onto our target, we'll just allow the engine to warm up and that will just allow us to basically fill out this table. |
| 08:24 | Once we've got the table filled out, what we're going to do as well is come back to our engine functions, we'll come back to our idle speed control setup and we can reenable closed loop mode and we also will come back to our idle ignition control and we will reenable our idle ignition control. |
| 08:42 | That's just going to allow the engine to, the ECU to do a little bit more with our idle speed control and get us really accurate so now that I've reenabled that in particular, if we look back at our idle target error we can see that we are still moving around a little bit but we're pretty close, we can see we've got a pretty aggressive ignition idle angle change there which we can also hear in the exhaust note. |
| 09:04 | If we're looking at what our actual ignition angle's doing, it's moving between about 25° positive and as much as minus 10. |
| 09:11 | There's a lot of control over that to allow you to get the idle speed exactly how you want. |
| 09:17 | Now while I've been talking there, the engine has been warming up so let's go back to our main VE table and we can see that now with our engine temperature coming up to about 62°, we can see that we are a little bit richer than our target, we're not too bad there. |
| 09:33 | So let's just press the space bar, it'll jump to the active cell and we are still interpolating between the cell for the left as well so I'll just use our page down, shift page down there and remove a little bit from our VE table there. |
| 09:47 | And we can see that while our fuelling is moving around a little bit, we're pretty close to our target there. |
| 09:53 | So for this point, our fuelling is a little bit more accurate and our target idle area, we've got our idle base position table in the ballpark, our idle speed is where we want it to be, so everything's looking pretty good. |
| 10:05 | We will also have a quick look over at our manifold pressure, so again sitting around about the 70, 72 kPa so no big change there but again probably pretty close to what I'd expect given the combination and we also want to check our battery voltage which we can see here. |
| 10:24 | So that's actually sitting a little bit low so not necessarily anything to worry about, we can see some alternators do struggle to do a good job of charging at low RPM like this, we are above the normal battery voltage. |
| 10:36 | If the alternator was doing nothing, I'd expect to see this probably in the 11.5 maybe 11.2 volt vicinity and it'd probably be dropping. |
| 10:44 | What we can do though is bring that RPM up, we'll just use a little bit of throttle. |
| 10:49 | And we see that our battery voltage does come up. |
| 10:52 | Come up to about 13.5, 13.6 volts so I'm happy enough with that. |
| 10:57 | We know that everything's looking pretty good at this point, so we're ready to move on with the next step of our process. |
