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Practical Standalone Tuning: Step 6: Idle Tuning

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Step 6: Idle Tuning


00:00 - Now that we've got our engine initially up and running we can start fine tuning our calibration slightly and we're going to begin here with our idle tuning.
00:08 Essentially this is always the first place we want to start because if we have trouble getting our engine to idle smoothly, then this could indicate that there's either mechanical or electrical issues and if we ignore these, we can end up wasting a lot of time performing the wide open throttle and part throttle tuning only to find, later on in the tuning process that there is an issue that we're going to have to resolve.
00:31 Once we've got that resolved, obviously then we'll have to go back and retune the engine.
00:35 So some of the key aspects we want to take care of in this particular step of the process is to get the engine up and running and make sure that it can maintain a sensible idle speed on its own.
00:47 We've got a basically stock standard Mazda B6 engine here so we can assume that at operating temperature, normal operating temperature of 70-90°C, we should be able to get this engine to easily idle around about the 900 RPM mark, perhaps slightly slower than that.
01:06 So first problem is if we can't maintain a stable idle around that 900 RPM and maintain and achieve consistent fuelling around that RPM, this is indicative that we've got a problem.
01:17 The other aspect we want to take care of during this is to make sure that at that idle speed, we're achieving a reasonable amount of vacuum and that our battery voltage is where we'd expect it to be.
01:29 In terms of the vacuum, this is a good sign that there's some mechanical issues with the engine such as perhaps the cam timing not being correct.
01:38 Given that our engine again is stock standard with factory cams, we'd expect a reasonably high level of vacuum, we should be able to pull somewhere around about 35 kPa of vacuum when we are idling at around that 900 RPM mark, give or take a little bit.
01:53 If I'm seeing significantly less vacuum than that, then again this is indicative that we've got a problem that we're going to need to look at.
02:01 And also with our battery voltage, with our engine up and running, our alternator should be charging and we'd expect to see our battery voltage between about 13.8 and 14.2 volts, again if we've got something that's still sitting around about 12, 12.5 volts with the engine running, this would indicate that our alternator isn't charging and we want to address that before we get too deep into the tuning process.
02:24 So the first step here is we're going to have a look at our idle control parameters.
02:28 So in order to do this, we're going to jump into our software and we're going to come to our startup/idle menu and what we want to do is come down to our idle control.
02:39 Now for a start we just want to make sure that our idle parameters are set up, in other words we've got the correct output to control, in this case a pulse width modulated two wire solenoid and we also want to make sure that our frequency for this solenoid is correct.
02:56 In this case that's all OK, the other aspect you want to look at here is our control algorithm which at the moment I've got set to open loop.
03:03 So what this means is that there will be no close loop control in order to try and achieve our target idle speed.
03:09 Instead we're just going to have a warm up idle solenoid position table.
03:14 Let's go back to our startup idle drop down menu and we're going to come down this time to our idle warm up duty/steps table.
03:23 Now this is just a table, a two dimensional table of our idle speed solenoid duty cycle versus our coolant temperature, we've got that represented graphically here as well as numerically on the right hand side.
03:35 The columns here on the right hand side, the left hand column is our coolant temperature, the right hand is our idle solenoid duty cycle.
03:43 So we can manipulate this once we've got our engine up and running in order to achieve our target idle speed.
03:49 We'll close that down and we'll also just come back up to our startup/idle drop down menu and we just want to have a quick look at our idle cranking duty steps.
03:58 Very similar this is a table that's used for our idle speed control during cranking, so what we want to do is set this so that the idle speed drops in nicely to our target idle speed without the engine struggling to start without throttle or alternatively flaring.
04:15 So the two basically work in conjunction with each other.
04:19 So at this point we're ready to start our engine up again.
04:21 Before we do that, we'll just bring up our idle control duty cycle table again, and we'll just locate that so that we can see the information that we're interested in.
04:29 So on the left hand side we've got our engine speed.
04:32 Down below this we've got our manifold pressure, so we'll be able to see what our manifold pressure is at idle.
04:39 Of course we've got our lambda being represented here and then we've got our battery voltage.
04:45 So let's get our engine up and running.
04:50 Now we see at the moment with no throttle, we're sitting at around about 1300 RPM and we're dropping down as we come out of that warmup mode.
04:57 So we're 1000 RPM now.
05:00 So the first things we want to look at, first of all our air/fuel ratio, 0.97, 0.98 lambda, nothing wrong with that considering our tune at the moment, let's have a look at our battery voltage.
05:11 We can see that's sitting at 14.2 volts, essentially exactly where we'd expect.
05:15 And our fuel load, we're sitting at 32 kPa so we know that we're pulling a good amount of vacuum, so everything's looking really good here at the moment.
05:23 What we can do is manipulate our duty cycle table for our idle speed control, remembering again this is open loop at the moment.
05:31 And what we're going to do is just highlight for the moment the cells that we are operating in and again we can use the comma and full stop keys to increase or reduce this number.
05:41 So we're starting around 1030 RPM and I'll just bring these numbers down and we can see as I do this our idle speed drops down to 930, 920 RPM now.
05:51 And you can see we can maintain a nice stable idle speed at 900 RPM.
05:57 Obviously this table is going to need some fine tuning, in particular once we've got the rest of our calibration tuned, we're going to want to come back and revisit this and make sure that it's adjusted right through the entire range from a complete cold start through to our normal operating temperature.
06:13 So at this point with our idle speed control working correctly, our engine we know is mechanically healthy, we've got a good amount of manifold vacuum being pulled, our battery voltage is stable, we can move on with the next step of our process.

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