Practical Standalone Tuning: Step 6: Idle Tuning
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Step 6: Idle Tuning
14.36
| 00:00 | - For the next step of our process we're going to deal with making sure that we can get our engine to idle at a sensible RPM and this might seem like a sensible step and a lot of people will overlook this but it is a step that's relatively straightforward to complete and it can uncover the potential for some mechanical faults with your engine or your electrical system that could waste a lot of time when you go to start tuning on the dyno. |
| 00:24 | I've had this happen to me numerous times in the past where perhaps the cam timing was in fact a tooth out, easy to overlook if we're not trying to get the engine to idle at a sensible RPM and once you actually start tuning you end up wasting a lot of time when you realise that the cam timing is incorrect and have to basically go back, set that correctly and then start again. |
| 00:45 | Of course if you are hiring dyno time this is a double expense because you are going to be paying for that time. |
| 00:52 | So what we're going to be doing during this step is making sure that first of all we can get our engine to idle at what I'd consider a sensible RPM and this will highlight those problems that I just mentioned, cam timing being out, maybe also inlet manifold leaks, something of that nature. |
| 01:09 | So the obvious question is what RPM would we consider sensible? And of course we can use the factory RPM as a bit of a guide here. |
| 01:17 | We should, for a mechanically standard engine of course, be able to expect that the engine will idle comfortably at the standard factory RPM. |
| 01:26 | Of course things get a little bit less black and white when we start modifying the engine, particularly with aggressive cams. |
| 01:32 | With very large cams we may not be able to get an engine to idle below perhaps 15 or even 1800 RPM so a little common sense is required here. |
| 01:40 | In our case, with our factory B18C with stock type R cams, I would expect an idle speed of somewhere around about 800 to maybe 950 RPM should be achievable. |
| 01:52 | We've left the engine running from our last step and let's just have a look at what we've got going on now. |
| 01:58 | And we can see that at the moment we are holding a 950 RPM idle. |
| 02:02 | You can see at this point my foot is completely off the throttle. |
| 02:06 | We are right on our lambda target of 0.95. |
| 02:10 | Also worth mentioning here that if we look at our coolant temperature, we aren't quite up to temperature yet so our idle speed will be Influenced by our coolant temperature a little bit but at this stage, mechanically speaking, I've got no concerns there, the idle speed is safe and sensible for this type of engine and we can actually hear that the engine is running quite nicely on all four cylinders. |
| 02:34 | Another element that we do want to consider as part of this as well is making sure that our alternator is charging. |
| 02:41 | This is another one that's really easy to overlook in the excitement of getting the engine up and running for the first time and I've been caught out in the past, putting the car on the dyno, beginning the tuning process and after five or six minutes we start noticing that the fuel pressure is dropping away, maybe we've got ignition misfires because the battery voltage has dropped down to maybe 10 or 11V. |
| 03:02 | So we want to make sure that our battery is charging or more specifically that our alternator is charging our battery so we can have a look here at our battery voltage and we can see at the moment we're sitting at about 13.3V. |
| 03:16 | Now that is a little low, typically the charging system on most vehicles will be achieving a battery voltage somewhere between 13.8 and 14.2V so that's typically what I'm aiming for, essentially somewhere around about that 14V so we are a little lower but if our alternator wasn't charging at all, we're most likely going to see that our battery voltage will be sitting at or maybe somewhere just below 12V so I'm pretty confident at this point my alternator is charging. |
| 03:47 | What we can also do as a bit of a sanity check here is bring the RPM up a little bit because sometimes at a low idle speed, particularly if the pulley sizes have been changed, the alternator might not actually be running fast enough to charge so let's just use a bit of throttle, bring the RPM up and see if that battery voltage jumps up a little bit. |
| 04:11 | Alright so we can see there with 2500 RPM onboard, we're now up to 14V so we can tick that one off the list, we know that our alternator is charging. |
| 04:21 | The next element is to look at our idle speed control strategy itself and make sure that we can control the idle speed and this one's a bit tricky for us with our B18C because we have no idle speed motor on the engine so really we're stuck with just mechanically setting the throttle stop and beyond that there's not a lot else we can do. |
| 04:40 | I know this will be the exception to the norm though so I will just go through this process broadly so you can see what's involved. |
| 04:48 | And in order to do this, for a start we actually need to set up an output for an idle speed control solenoid or motor so let's go ahead and do that. |
| 04:58 | Let's start by heading over to our outputs and we'll expand that out and we'll click on our output configuration and essentially here we can choose any of our outputs that are spare so let's just come down here to our GPO2 and what we want to do is obviously select idle speed control so we can come down here to our idle control or alternatively type this into the search bar to achieve the same thing. |
| 05:25 | Let's expand that out, and we've got a few options here with solenoids or stepper motors, I'll keep things really simple here and let's just choose a pulse width modulated solenoid. |
| 05:34 | We'll tick that little box and click OK and that will set the output. |
| 05:37 | Once I've done this, we can see that we now have an option for our idle pulse width modulated solenoid, we'll click on that and now we can choose the frequency that this is going to operate at. |
| 05:48 | We need to choose a frequency that the solenoid is actually able to function at because if we choose a frequency that's too high or too low, the solenoid may actually not be able to operate so this is going to be a little bit dependent on the specific solenoid you're using. |
| 06:03 | Typically I would expect that to be within about 30 to 100 Hz so you can try that out and test within that range and make sure that it physically is functioning. |
| 06:13 | Now we can close that down and what we're going to do is come up to our idle control itself and let's start with our idle control target RPM. |
| 06:23 | So what we can see here is we've got a 2D table vs our engine coolant temperature and we want to start by setting sensible idle speeds within this and we've already mentioned about the sensible idle speed and it's going to depend on your engine. |
| 06:38 | A stock LSV8 for example might happily idle at 550 to 650 RPM, we're probably not going to achieve the same with our B18C so it is very engine specific and of course then it comes down to that mechanical setup which we already discussed. |
| 06:53 | The other element here is at colder temperatures it is normal to set our idle speed target a little bit higher so everything we've got in there is probably pretty much on the money at the moment. |
| 07:04 | We can also set some idle ups for our air con or our clutch. |
| 07:09 | In this case I'm going to leave those as they are so we've got our idle speed target table set to sensible numbers. |
| 07:16 | Let's next come up to our idle control settings. |
| 07:19 | Let's start with our control, we can see at the moment that that is open loop and this is where I suggest you get started here because this will allow you to set up the base duty cycle to get the idle speed in the ballpark, If you start in closed loop then you could be masking errors in your base duty cycle table because the closed loop system will be operating to get us to our target. |
| 07:41 | So we are in open loop at the moment, of course we can choose closed loop from that drop down menu. |
| 07:46 | The after start duty, so you can start here immediately after the engine starts with fixed values, or alternatively from the table. |
| 07:56 | In this case, our idle duty, cranking duty is going to be 90%. |
| 08:00 | Obviously this needs to be chosen to suit your particular vehicle. |
| 08:03 | If you go too high here, you may end up with an overshoot in your RPM immediately after start up so some manipulation of these numbers will be required to suit your particular engine. |
| 08:15 | That 90% will be held for half a second here. |
| 08:18 | Then we've got our open loop duty table. |
| 08:21 | So what we're going to want to do here with these numbers is basically adjust the duty until we actually get pretty much onto our target idle speed, you can see that table is relative to our engine coolant temperature. |
| 08:34 | I'd demonstrate this but of course with no idle speed control it's not going to do anything. |
| 08:39 | The important part here to make sure the system is functioning though is to make sure that when you make a change to that duty that you can actually notice the idle speed changing. |
| 08:49 | If not, you've either got a hardware or a wiring issue or perhaps your frequency is set outside the range that the solenoid is actually going to be able to work with. |
| 08:59 | So at this stage with our example, there's not a lot more we can do here. |
| 09:03 | Of course once we've got our idle speed control dialled in, we would typically revert to closed loop so that the ECU can make any small adjustments as required. |
| 09:12 | There is one trick that we can use here with our B18C without an idle speed control motor and I typically would also encourage you to use this in conjunction with an idle speed control motor solenoid anyway, and that is our idle ignition control. |
| 09:29 | So let's have a look at that, we'll close down our idle control, come up to igjnition. |
| 09:33 | We want to come down to ignition lock and idle control. |
| 09:37 | At the moment we can see that this is disabled and what we want to do here is set our idle ignition with a separate table. |
| 09:44 | Alternatively you can have this controlled by the idle control system. |
| 09:49 | For our purposes here, I'm going to start with a table. |
| 09:52 | What we've got here is essentially a table with the axis set to our idle error. |
| 09:59 | Obviously this is the difference between the current engine RPM and our idle speed targets. |
| 10:04 | And this is why it's also important even with our system to make sure that our idle targets are actually set sensibly because those will be the basis of our idle ignition control. |
| 10:15 | And this table here we can see what it uses is ignition targets based on that error. |
| 10:23 | Principle here is that if we retard the ignition timing from MBT, we'll reduce engine torque and this will have the effect of reducing our idle speed. |
| 10:33 | Conversely if we advance the timing towards MBT, we're going to make more torque and this will bring our idle speed up so that's how this system works. |
| 10:42 | Before we can actually make adjustments to this table and demonstrate this, we actually need to make sure that the system is becoming active and that is where our parameters here come in. |
| 10:53 | Basically we want to make sure that the idle ignition control is only working when we genuinely want idle ignition control to occur. |
| 10:58 | Obviously when we're off the throttle and the car's stationary so our first setting there is our maximum throttle position setting, or sensor setting. |
| 11:07 | You can see we're sitting very nicely at 0% now. |
| 11:10 | So I'm going to actually bring that down a little bit, maybe 0.4% will be OK there. |
| 11:15 | Maximum RPM, so basically above this RPM, the idle ignition won't function. |
| 11:20 | 1500-1600 is generally a good point there, particularly with our idle speed sitting around Maximum manifold absolute pressure. |
| 11:29 | So you can see that's currently set to zero. |
| 11:31 | We can see our actual manifold pressure sitting at about 28 kPa so this is actually making the system inactive at the moment but let's bring that up to something that will allow us to test this so 35 kPa should be a pretty good point. |
| 11:45 | Straight away we can hear the engine note change and if we look at our ignition angle, we can see our ignition timing is now moving around based on that table. |
| 11:53 | Our idle speed is still a little high, remembering we're targeting at 900, we're about 1000 but we're much closer to the mark. |
| 12:01 | Now let's actually have a look and see how this system works. |
| 12:04 | So if I highlight the cell we're currently in, currently it's got 10° in there and if we set that just for argument's sake to zero, we will see our idle speed drop and now we're actually transitioning between two cells, interpolating between them. |
| 12:19 | Let's change our zero RPM error cell to 5° and we can see we've brought our idle speed pretty much right down onto our target there of 900. |
| 12:31 | What we do need to be mindful of with this is what our actual ignition timing is doing and we can see now we're sitting down at around about 3-4°. |
| 12:38 | It's a lot of retard, I don't generally like to see my idle timing sitting much below about 5° and certainly not for prolonged periods because it will create a lot of heat in the exhaust manifold and hence the engine bay so generally five would be about my hard limit and I'd prefer to see the timing around about 10°. |
| 12:58 | We are compromised though with this system given that we don't have any idle speed control motor so essentially we have to set our throttle stop to a point where we can get a good compromise between the engine not idling too low when it's stone cold and not idling too high when it's hot. |
| 13:15 | So what we're going to have to do is compromise this a little bit. |
| 13:18 | Let's put some numbers in here that are a little bit more sensible. |
| 13:20 | We'll go 10° at zero, I'll go to 5° with 100 RPM error and then we can go to 0° above that. |
| 13:29 | On the other side of this where our idle speed is lower than target, pretty happy with those numbers so we'll leave those there. |
| 13:36 | So at the moment I'm still pretty happy actually, we're idling at 950 RPM, let's see how this interacts with our idle speed target though, we'll come back to our idle control and our idle control target RPM. |
| 13:47 | So we can see in our cell here, 90°C, we're targeting 900 RPM, let's just bump that up to 1000 and we'll press enter, we can hear our idle speed picks up and straight away we have picked up almost onto our target idle speed there. |
| 14:04 | Obviously with our engine idle speed, we're looking for a range that's probably a little bit broader than some other elements and essentially when I say I'm targeting 1000 RPM, if I'm within plus or minus 50 RPM of that I'm going to be pretty happy with that. |
| 14:17 | So at this stage we've got our idle speed control as dialled in as we can on this particular engine, we know what we're trying to do there, what we're trying to achieve and we've learned how our idle ignition control settings can be used to help us with or without an idle speed control motor, let's move onto the next step of our process. |
