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Practical Standalone Tuning: Step 6: Idle Tuning

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Step 6: Idle Tuning

08.21

00:00 - Now that we've got our engine running for the very first time, we're going to address our idle tuning.
00:05 What we want to do here is just physically make sure that we can get our engine idling.
00:09 Now of course this is going to be an iterative process and we're going to readdress or revisit our idle speed tuning once we've got our complete fuel and ignition maps tuned.
00:22 And the reason for this is that we need to address our idle speed tuning from a cold start.
00:28 And this is going to ensure that when our tune is complete, our engine is going to start and idle correctly, regardless of the temperature.
00:35 So at the moment we're only really looking at a broad aspect here just to physically ensure that the engine will maintain a solid idle by itself.
00:45 And the reason we're doing this is to ensure that mechanically the engine is sound, we wanna make sure that we're seeing reasonable engine vacuum at idle and that we can maintain a reasonable idle speed.
00:58 Now we do need to make some considerations here, for a start this particular Corrado engine has been fitted with a slightly more aggressive cam profile that stock.
01:08 So we know that this is going to affect the amount of vacuum that the engine will pull at idle.
01:15 While a stock engine such as this may pull somewhere in the region of perhaps -60 to -70 kPa at idle, I'm expecting that here we may be more in the region of about -40 to -50 and that's not going to indicate we've got a problem.
01:32 The next aspect we need to consider is what we actually have controlling the idle speed.
01:38 And in this case we're using the e throttle or drive by wire throttle body for idle speed control.
01:44 Let's just jump into our laptop software for a second and we'll have a look at a few settings regarding the idle speed control.
01:50 So what I've done for a start is I've gone into the idle speed control mode and I've set this to open loop.
01:58 And I like to have the idle speed control system in open loop while I'm first configuring the idle speed control and getting that set.
02:05 This will allow me to set the base idle speed control position or in other words how far open the throttle body will be to control idle speed versus engine coolant temperature, without any interaction from the ECU.
02:19 So the ECU will be ignoring the actual idle speed and not trying to make any adjustments.
02:26 This allows us to set the base position table correctly and then when we do enable closed loop control a little later on, the ECU is already going to be really close to its target, this is going to give it less work to do and this is going to mean we're going to get better idle speed control overall.
02:43 Now another aspect that we need to address here is our idle target RPM table.
02:48 So it's really important to have this configured sensibly before we start.
02:52 As we can see here, this is a two dimensional table with engine coolant temperature on the X axis.
02:58 And it's typical that we will target a slightly higher idle speed, in this case you can see I've got 1200 RPM, when the engine is cold.
03:06 So I've got a really basic table here, we're targeting 1200 RPM at 50 degrees centigrade and below.
03:13 Once we get above 50 degrees, that drops very slightly to 1100 RPM.
03:17 So it's important that this is a sensible target, we're not probably going to get too far if we're trying to make our four cylinder engine idle at perhaps 600 RPM.
03:27 That on the other hand may be quite acceptable for a large displacement V8 engine with a standard cam.
03:35 OK there's one other aspect we'll just touch on here and that is our idle ignition control.
03:41 Now in this case I've got this turned off and that's how we're going to start our tuning.
03:46 The idle ignition control allows the ECU to advance or retard the ignition timing if our idle speed isn't matching our target.
03:54 Now initially what I want to do is have this off so there's no interaction with the ECU advancing and retarding the timing and affecting the actual idle speed.
04:04 Again, this allows me to get my base e throttle position table set close, and then once I enable the idle ignition control as well as closed loop control, this is going to give the ECU a really solid starting point for idle speed control.
04:22 Now there's a few more conisderations here.
04:24 First of all we can see that at this point our engine coolant temperature is now up to 48, 49 degrees centigrade and we're not going to be able to complete our idle speed tuning table because we're not going to be able to tune the areas below this temperature.
04:40 Realise as well that at the moment we still have an incomplete volumetric efficiency table.
04:47 Remember we've only at this point made broad changes in order to just get the engine up and running.
04:52 So what we're going to do now is start the engine and there's going to be a couple of aspects that we're going to look at here.
04:57 First of all, we may need to revisit our VE table and make changes to our volumetric efficiency in order to be a little bit more accurate with our air fuel ratio target, you can see that the air fuel ratio target will be displayed down here on our laptop screen.
05:14 The other thing we're going to be doing is going backwards and forwards between our VE table and our idle base position table in order to tune the idle base position until our idle speed matches our target.
05:26 So we can see at 50 degrees, remember our target idle speed was 1200 RPM, let's get our engine up and running now and we'll see how well it idles.
05:40 OK so straight away after the engine starts up, we can see that our idle speed is already pretty close.
05:47 We're a little bit low here at about 1000 to 1100 RPM, so what I'm going to do is just go into my idle base table and we're going to increase our throttle position at that particular point until we get up to our target of 1200 RPM, we can see that we're there now.
06:08 Now we're still interpolating very slightly down to our 40 degree zone.
06:13 So the changes I'm making here, I'm making to both positions.
06:17 And at the same time we're going to look at our air fuel ratio.
06:20 We can see that that is a little bit rich, so we are still in warm up enrichment mode as well so it's important to understand that there will be an interaction here with our warm up enrichment.
06:32 We can't really make changes to our tuning accurately until we're at a normal operating temperature.
06:39 So what I'm doing here is just reducing my fuelling and we'll just highlight the entire area that we're operating in here and I'm just bringing that down until we're at our target of 0.95, 0.96 in this instance.
06:55 OK so we've got our fuelling pretty much on target right now, we're matching our target, and you can see here because we're interpolating between -40 and -50 kPa, I have actually reduced the fuelling at -50 kPa or the efficiency at -50 kPa, and the reason I've done that is 'cause as our vacuum drops, we know that our volumetric efficiency is likely to decrease.
07:19 So I'm just trying to get a sensible shape to our efficiency table here.
07:23 OK so we're up to 60 degrees now and we can see that our idle speed is still sitting a little high now, it's out to 1250 RPM.
07:31 So I'm just going to go through to my idle base table again and we'll just reduce our idle base position down here.
07:40 Remember our target at 60 degrees and above was 1100 RPM.
07:46 So we're just making a small adjustment there and now we're at 1100 RPM.
07:50 Just again checking my lambda and we're on target.
07:54 So in this case I'm happy with the engine, we've got a good idle speed, we're maintaining a reasonable idle speed, we've got the sort of manifold vacuum that I'd expect, given the cam profile we're running.
08:06 And we'd just continue this process, tuning and adjusting our idle speed and our fuelling, until our engine comes up to a normal operating condition, normal operating temperature.