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Practical Standalone Tuning: Step 6: Idle Tuning

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Step 6: Idle Tuning

10.59

00:00 - Now that we've got our engine physically up and running, before we actually get into our tuning on the dyno, we want to address our idle speed tuning.
00:08 We want to do this for a couple of reasons.
00:10 First of all we want to make sure that mechanically the engine is sound.
00:14 Making sure that the engine can idle at a reasonable speed and pull a reasonable amount of vacuum is a good indication that the engine mechanically is sound, that we don't have any inlet manifold leaks, that our cam timing is correct.
00:28 These sorts of things that if we overlook and skip past this idle tuning, can end up wasting a lot of time later on when we find out that we have had a mechanical problem the whole time.
00:40 We also want to make sure that our fuel tuning, which we've currently done very very coarsely, is a little bit more accurately dialled in, in those idle areas.
00:50 So this becomes an iterative process.
00:52 What we're going to be doing at this point, is we're going to be leaving our ignition timing table untouched.
00:59 15 degrees, our fixed value that we've set for the entire vacuum area of operation is going to be absolutely fine for the moment for our idle areas and instead what we're going to be doing is focusing on our fuel tuning.
01:13 So we're going to be looking at our base fuel table, and we're also going to be going backwards and forwards between that and our idle speed control table.
01:19 Now in this particular engine the idle speed control is controlled or affected via the drive by wire throttle body.
01:27 So the ECU is physically opening and closing the drive by wire throttle body.
01:31 So let's just have a quick look at exactly what we've got in our SCal software that we need to be adjusting here.
01:38 So at this point we'll come down to our idle speed control.
01:41 And we've got our idle bypass or base bypass duty one table.
01:47 So if we open this up, this is a three dimensional table, you can see we've got engine coolant temperature on the x axis and we've also got engine run time on our vertical axis.
01:58 So this allows us to increase the air bypass or open the throttle body a little bit further, during the initial startup, then we can drop that down.
02:07 And obviously at cooler temperatures you can see that we have a slightly larger throttle opening compared to when we're at operating temperature.
02:16 So we're going to be using this to adjust the idle speed control until we are on our target.
02:21 And then the other aspect that we need to consider here as well is our actual target idle speed, target engine speed so we can find that here.
02:30 And again this needs to be set sensibly.
02:33 We may find that a four cylinder engine with a very aggressive cam with a lot of overlap will struggle to idle maybe much below 950 or even 1100 RPM when it's warm.
02:44 Conversely if we've got a large displacement V8 with a very mild cam, it may idle really happily at 550 RPM.
02:53 So a lot of time can be wasted trying to make the engine idle at an RPM that it's just simply not going to be capable of idling at.
03:01 In this case the engine is relatively stock, it's running stock cams, and at this point we're going to be using a relatively conservative idle speed.
03:09 You can see here in the normal operating temperature areas of the map, we're sitting at around about a 950 RPM target.
03:17 You can see this table also uses engine run time as an axis and we have, even at 80 and 90 degrees, during initial startup we're targeting 1100 RPM before quickly dropping away.
03:31 Likewise with this table we've got engine coolant temperature as an axis, so we're targeting a higher idle speed when the engine is cold.
03:39 So this needs to be set sensibly, this is our first point, our first place to perform our work and then beyond this we are going to be moving backwards and forwards between our base bypass duty one table and then of course our run mode fuelling base injection time one table.
03:56 So this is going to allow us to more accurately dial in the idle area of this table which currently, as you can see we've just left with our block change set to 2.4 milliseconds.
04:07 So let's get our engine up and running and we'll start making some changes.
04:15 OK so our engine's up and running and what we want to do is just allow the idle to settle.
04:20 The other thing we need to note here is our engine coolant temperature.
04:24 We're sitting at about 49 degrees now.
04:26 And obviously as the engine warms up, both our fuelling and our idle speed targets are changing.
04:32 Remember we have got engine coolant temperature multipliers there for our lambda target.
04:38 So we're just looking at our lambda at the moment.
04:42 And really we're using this fuel multiplier closed loop one, so guide us with our tuning.
04:47 And right now we can see that that's sitting very close to 1.0 so this means we're pretty close.
04:53 And at the moment our idle speed is sitting at 1070 RPM.
04:58 So everything is actually looking pretty good right now.
05:02 What we're going to do is just allow the engine to continue warming up, and we're going to be making any changes that we need to.
05:09 For example right now you can see, now that the engine has been running for a little bit of time, we can see that our closed loop multiplier has dropped a little bit and we're now sitting at 0.97 So this means that the ECU is now removing 3% of fuel from the current cell that we're accessing.
05:29 You can see that cell is displayed here in white.
05:33 And we can also see there is a little dot that follows around our graphical map to show exactly where the ECU is accessing.
05:42 So at this point what I'm going to do is just remove a little bit of fuel from this particular cell.
05:48 Now if we press the minus key, that will remove 0.1% fuel, so we've taken that value down to 2.3 I'll continue, and we're back to our fuel multiplier of 1.00 So we need to follow this through until our engine comes up to temperature.
06:07 Now if we jump back across to our idle control base bypass duty one table, we can have a look at the requested throttle opening versus what we actually have.
06:16 So at the moment we're sitting at about 60 degrees centigrade.
06:20 And you can see that the value in this table is 3.7% So that's the requested base throttle opening.
06:26 And we can actually see exactly what is happening if we move over to the right hand side here, we can see our idle duty base, in terms of what is actually being requested there is 3.6%.
06:40 This takes into account any interpolation between the surrounding cells.
06:44 So what we want to do is compare that particular value to the current throttle position.
06:50 So you can see at the moment, the actual throttle position's sitting between about 3.1% and about 3.3% So this means that the base bypass duty one table, at that particular point is just a touch high.
07:02 And the ECU is actually using closed loop control to pull that back down.
07:07 So we can make some changes to that.
07:08 We can use the plus or minus keys to add or remove duty from that table and we'll just do that now, we can bring that down a little bit closer to our actual throttle opening.
07:20 So the process we're going to follow here is to allow the engine to come up to operating temperature and we want to make adjustments to our base bypass duty one table until the numbers in our duty one table are close to the actual throttle position opening that we're seeing to achieve our target idle.
07:40 As a little bit of a tip here, it's generally a good idea to set our base bypass duty one table just a little bit higher, maybe 0.2 to 0.3 of a percent higher than what's actually being used in closed loop control.
07:54 And this will just allow the idle speed to come down towards our target without dropping below and risking stalling.
08:01 At the same time we're also still watching our air fuel ratio.
08:04 And you can see while we have been adjusting our base bypass table for our idle speed control, you can see fuel multiplier closed loop one has now dropped to 0.81 So this means that it is now pulling almost 20% of the fuel out.
08:21 So what we're going to do is jump back into our run mode fuelling, and we'll go back to the cell that we're currently accessing.
08:30 And what we can actually see here as well, is we've only made adjustments there initially to the 400 millibar cell.
08:37 What we can actually see is our current manifold absolute pressure is 300 millibar.
08:43 So we're actually interpolating now between the 400 and the 200 millibar cell.
08:47 Because we've only adjusted that one cell, you can see that as we drop down here to 200 millibars, our fuelling actually increases which is generally not what we'd expect.
08:58 So what we're going to do is make an adjustment to that cell now.
09:02 Now there's a couple of ways we can do this, we've already been using the plus and minus keys.
09:06 In this case I'm going to directly enter a value of 2.1 We'll just allow that change to take place and we want to see the effect on our closed loop multiplier.
09:16 That's brought it back up from about 0.8, 0.81, to about 0.85 but we are still a little way off our target.
09:24 We'll try a value of 2.0 in there.
09:26 Now what I'm going to do is highlight the two cells together and we can just use the minus key to remove further pulse width from those two cells.
09:36 So let's just continue doing that until we get back to our closed loop multiplier being 1.0 So we've just overshot a little bit there, got down to 1.02 so it's actually adding fuel back in now.
09:48 So we'll just add 0.1, so at the moment we're in a position where we need to make a smaller or finer change.
09:56 So we can do that by going to the options menu which we can access either by clicking on it, or pressing the O key.
10:02 And we want to press F which is the top option that's highlighted at the moment.
10:06 This will change between coarse and fine increments.
10:09 So we'll do that now.
10:10 Now instead of a 0.1 millisecond change, we'll make a change of 0.01 So at the moment you can see our closed loop multiplier sitting at 0.97 so we're pulling around about 3% fuel out of those two cells.