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Practical Standalone Tuning: Step 6: Idle Tuning

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Step 6: Idle Tuning

07.55

00:00 - The next step of our process is to dial in our idle control and just make sure that we can physically get the engine idling without us needing to use the throttle.
00:07 Also making sure that we can get the engine to sustain a sensible idle speed.
00:13 And again this really comes back to highlighting if there potentially could be some potential issues that we need to address before we go further with our tune.
00:21 A good example of this would be if our cam timing is out or maybe there's a problem with severe valve leakage, we'd be in a situation where it can be difficult to get the engine to hold a sensible idle.
00:32 And the first place we want to start is by deciding on what a sensible idle speed should be.
00:38 Now this is going to vary depending on the engine but the factory idle should be a pretty good guide, particularly for a stock unmodified engine.
00:46 In this case, with our version 11 STi, the engine mechanically is standard so we could expect reasonably to be able to maintain an idle speed somewhere in the region of maybe 800 RPM, maybe to 900 RPM once the engine is up to operating temperature.
01:01 Let's have a quick look through the available parameters here inside of the Ecumaster ECU so we know what we're doing.
01:09 I will mention here, this is not intended to be a complete guide on idle speed control tuning on the Ecumaster.
01:16 Rather just a cursory examination to get you up to speed and get the engine idling.
01:20 We will cover the intricacies of the idle control in our member's webinars so you can check in our archive if you want to learn more.
01:29 Let's start by looking at one of the key tables here which is our target idle speed.
01:35 So this is a two dimensional table, of course we have our coolant temperature on the horizontal axis here.
01:41 You can see down at the lower temperatures we've got an idle speed target of around about 1135 RPM.
01:47 Let's just increase that a little bit, that's probably a touch low so we'll highlight the cells that we're interested in at 20°C and below and set those to 1250.
01:58 Now essentially by the time the engine temperature is up to 70°C, I'm going to consider that I should be able to hold my hot idle speed.
02:06 In this case we've got that set to 900.
02:09 What we can then do is interpolate between these cells.
02:12 So we'll just select 70°C and we'll highlight out to 20°C and we can use the horizontal interpolation function.
02:21 We can use the key there which is control H which will do that.
02:26 If you do forget about these functions, these hot keys, you can right click here and we'll see that horizontal interpolation is shown there.
02:35 You can click that from the menu or use the control H shortcut.
02:39 So this is our first place to start, making sure that this table is set correctly.
02:42 At the moment, this is only going to be a guide though because initially at least, we're best to start with the idle speed control in open loop.
02:50 So we can see that the functions control and closed loop control are over here on the right hand side.
02:57 We can easily disable this just by unticking the enable PID control.
03:00 So now we're in open loop control mode and essentially the ECU won't influence the idle speed at all.
03:08 The idle speed therefore will be influenced from this particular table here.
03:12 You can see we've got a 3D table, we've got our coolant temperature on the horizontal table, we've got our target idle speed on the vertical axis.
03:20 We've also got a graphical representation of that table out here on the right hand side.
03:26 So the premise here is that at lower temperatures and at higher target idle speeds we're understandably going to need to increase our air bypass.
03:36 Now that's done with the percentage values in this particular table but we also need to understand what those values actually mean.
03:43 And that comes down to how our idle control is set up.
03:47 Now that's over here on our idle parameters table.
03:49 We can see that our idle valve type here is set to drive by wire, so this is understandably a drive by wire throttle motor, of course depending on your particular engine you can choose from a range of different options here.
04:02 Another key parameter that we need to understand that influences what the numbers in our idle duty cycle table actually mean, it comes from our drive by wire parameters.
04:11 So let's just scroll back up and we'll find that.
04:13 We'll click on drive by wire and double click on parameters to bring those into view.
04:19 Now we're not really interested in too many of these parameters except for this one here which defines the idle range.
04:25 So essentially this defines a range of zero to 10% throttle opening which will be used during idle control.
04:32 It's important to make sure that that number is set high enough that you can maintain your target idle speed when the engine is cold, however if it's set too high, we're not going to have the resolution in our idle control that we'd really like.
04:45 So what this means, simply put is that a value of 100% in the idle duty cycle reference table here would be a throttle opening of 10%.
04:55 So now that we know what we've got in there, we can actually get the engine up and running and we're going to look at how we can make some changes to this target table.
05:04 Let's do that now.
05:06 Now that our engine's up and running and our idle speed has settled down after the post start setup, we can see that our target idle speed is sitting at 900 RPM right from our table.
05:16 We can however see that our actual RPM is sitting a little bit low, it's sitting at about 750 RPM right now.
05:23 We can address this by coming down into our duty cycle reference table here.
05:27 We can see the red cross hairs showing where we are accessing in that table and we are interpolating a little bit at the moment so what I'll do is highlight all of the cells that we're interpolating across and using our plus key we can simply add duty cycle in and we're going to do that until we get our idle speed up to our target of 900.
05:46 So we can see straight away with a relatively small change there, we've pulled our idle speed up to about 850 RPM, we're still a little bit low, so we can continue to increase this.
05:56 So at the moment it's important to understand here that there is no feedback from the closed loop system, remember we have disabled that so that will make sure that there is no interaction overriding the fact that there are errors in this table.
06:09 We can just simply go through and make changes until we've got our idle speed onto our target.
06:15 While we are dialling in our idle control it's also worth just heading back across and checking our fuelling and making sure that we are still on our lambda target.
06:24 If we've got big discrepancies and we're very rich or very lean, that's also going to influence the engine's ability to idle properly.
06:31 As you can see here we're right on our target so that's not a big consideration.
06:34 Now that we've also got our idle dialled in a little bit better, this is another good place to have a quick look at our manifold pressure and make sure that that is sensible.
06:44 Again we're seeing about the same numbers we saw in the last step, around about 50 to 60 kPa so I'm comfortable that everything's looking good there.
06:51 Let's head back across to our idle tab and one last thing I just want to bring your attention to here is that we do have our idle ignition control active.
07:01 So this will have a minor impact on our idle speed as well.
07:05 Now the idea with this table is that it will advance or retard the ignition timing depending on whether our idle speed is above or below our target.
07:14 So again if you want more information on this, check our webinars archive under Ecumaster idle tuning and you'll learn a lot more detail about this.
07:24 At this point though, our idle control is set up, we've got our engine idling at least at our warm operating temperature.