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Practical Standalone Tuning: Step 2: Trigger Setup

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Step 2: Trigger Setup


00:00 - For the second step of our process we're going to set up the trigger inputs to the ECU and these are probably the most critical inputs that the ECU relies on.
00:08 Everything the ECU does in terms of calculating fuel and ignition timing based around solid information from the trigger inputs so if these aren't there and they aren't accurate, there's no way that the ECU can expect to run the engine properly.
00:23 In the case of our FD RX7 this runs a crank trigger system with two reluctor or magnetic sensors that are picking up directly off a trigger wheel that is attached to the front of the eccentric shaft and of course there are a wide variety of different trigger systems.
00:40 Ultimately what we really want is a sensor that gives the ECU information about engine speed or in other words how fast the crankshaft or eccentric shaft is turning as we also need some information about engine position so where abouts in the engine cycle the engine is at any particular point.
00:58 In a conventional four stroke piston engine, ultimately what we normally end up doing is sourcing engine RPM where possible directly from the crankshaft and we use another sensor for synchronisation that is sourced off the camshaft.
01:12 The reason for this is because the camshaft spins at half engine speed, we're going to get one input per full engine cycle from the camshaft, we can't get all of that information directly from the crankshaft.
01:26 But again there's a variety of different systems that are employed by different engine manufacturers based on their own personal preference so let's jump into Eugene and have a look at the options we've got.
01:37 And we get to this on our inputs triggering tab which we've got here and we start with our trigger mode.
01:45 Now if we click on our drop down menu here we can see there's a reasonably wide list of different options for different popular engines and interestingly there are actually a couple of options for the Mazda RX7 so in particular here we've got Mazda RX7 FC and FD.
02:03 There are also some predefined setups here for some of the more popular aftermarket trigger systems from the likes of Full Function Engineering.
02:14 Now despite the fact that there is a defined FD and FC RX7 mode, for this particular engine the correct trigger option is general.
02:24 Likewise if you are piecing together your own trigger system, you'd also want to use general so that's where we're at there.
02:31 There are a few other options that we do need to consider here on this particular tab.
02:36 For example we start here with our angle increment.
02:40 This is simply the angle between teeth on our trigger wheel so what we need to do here is note how many teeth there are.
02:47 So if we bring up our calculator here, we've got 360° and in this case the FD RX7 has 12 teeth so we'll divide 360 by 12 and that shows us we've got 30° between teeth.
03:02 The next setting here is for our base angle so we're going to worry more about this once we actually get to setting our base ignition timing.
03:09 At the moment it's set to 5°, we'll just leave that as it is, essentially this tells the ECU where abouts in the engine cycle number one TDC is.
03:20 We've also got the ability to set our cranking RPM so what we want to do here is make sure that our cranking RPM is set a little bit above the actual cranking speed that the engine's going to achieve.
03:31 So the engine won't go into run mode.
03:34 We've got our timing lock which we've already talked about here, again we'll look at that in a little bit more detail.
03:39 So what we're going to do now is have a look at our setups for trigger one and trigger two.
03:45 I'll look at trigger one here.
03:46 So trigger one is always going to be the input with the highest tooth count.
03:51 So in this case our engine speed sensor.
03:54 So this is connected to CAS one, cam angle sensor one input and we can choose the type of sensor here.
04:02 In the case of the FD RX7 as I mentioned, it is a reluctor pickup and we can choose whether we are going to run a reluctor or a digital input.
04:12 With the reluctor it's important to know that the polarity of the sensor, how it's wired is really critical here so you can see that it's reluctor, falling edge, we don't get the option to choose a rising edge so it is really important that our polarity is correct, otherwise we're going to end up with timing drift as our RPM increases or changes.
04:31 And we'll see how we can know if our trigger system is wired correctly when we get into our trigger scope shortly.
04:37 We've got the reset mode as well which as you can see at the moment is set to none.
04:42 Interestingly as well, there is a base map provided for the FD RX7 so you don't have to come up with all this information yourself, you can actually use that base map to populate all of these values.
04:55 That reset mode essentially is used internally for telling the ECU where the TDC is occurring so where it's going to actually reset and start counting from again.
05:05 In this case this is not a missing tooth wheel so we aren't using the reset mode here.
05:11 We've got the ability as well so also set an automatic trigger voltage which is quite helpful so particularly with a reluctor pickup the ECU needs to vary the trigger voltage or the arming threshold based on engine RPM, the voltage output, the amplitude of the voltage output from a reluctor sensor does increase as the RPM increases so getting this correct is important because it does a good job of suppressing noise, background noise on the input while also triggering accurately so here again the Adaptronic does a lot of the heavy lifting for us.
05:48 We've also got a filter table as well and again the default values here in most instances, unless you've got a very high tooth count input aren't going to need to be changed from the 20 microsecond value.
06:02 We'll head back to our triggers and we'll head across to trigger two.
06:06 So trigger two in this case is essentially a synchronisation input, again we've got reluctor and falling edge as our input.
06:14 In this case we are using this as the reset so the location or reset mode here is crank, that's where we are getting that input from and it's going to reset every time it gets and input on the CAS two input there.
06:31 Again all of this information is available in the FD RX7 base map.
06:36 Again we've also got the option for our automatic trigger voltage, the filter time exactly was we've already seen.
06:42 Trigger three is available for engines that run cam control and have an engine synchronisation and a cam position input.
06:50 In this case of course we're not running that.
06:52 So we've got everything set up there and what we can do here is a couple of checks to make sure that everything is working properly.
07:00 First of all what we'll do is we'll just enable our gauges here and what we want to do is actually just crank the engine over and see what our RPM's doing.
07:08 We want to make sure that we're getting a smooth RPM once it's actually up and running and we want to make sure that that RPM is believable.
07:15 Generally an engine's going to crank over somewhere probably between maybe 200 and 300 RPM so we want to make sure that that's the case.
07:23 Let's have a go at that now and we'll look at our RPM.
07:29 So what we can see there is with the engine cranking, we're sitting at a pretty constant, about 215 to 220 RPM.
07:36 It's not jumping up and down so it's nice and accurate, nice and consistent like I'd expect.
07:41 So no big surprises there.
07:44 The next thing to dive in a little bit deeper and see what's actually going on, what the ECU is receiving is we can have a look at our trigger scope function.
07:51 So there's a couple of ways of getting to this, we can go to our diagnostics tab and we'll see our trigger scope is available here.
08:00 Alternatively we can also click on built in scope down in the bottom toolbar there.
08:06 So this is literally just an oscilloscope that allows us to look at up to four channels.
08:11 We can look at the voltage on each of those channels versus time so it gives us a good idea of exactly what's going on.
08:19 At the moment we are showing channel one which is our cam angle sensor one voltage.
08:26 We've got cam angle sensor two voltage as channel two and the other thing the Adaptronic will show us as well is the current calculated engine angle and it's quite helpful for diagnosing problems with our triggering as well.
08:37 So what we'll do, down the bottom here we can see we've got a little pause tick box so that will, as it's name implies, simply pause the scope.
08:47 So what we're going to do is just crank the engine briefly and then once we've got a scope trace that is visible we're going to pause that and inspect what we're looking at.
09:01 Alright so we can of course manipulate the time divisions as well by looking at our time base down here.
09:11 In this case we're looking at 20 ms per division so you're going to need to vary that depending on the cranking RPM.
09:18 So we're looking obviously at cranking at the moment, may want to look at this at higher RPM as well.
09:22 So we've got a pretty good trace here showing what's going on so the yellow trace that we can see is our engine speed.
09:29 Important to look at the shape of that trace there so what we want to do is see that rising up, coming up through zero volts and then it will peak and it's dropping straight down through zero again.
09:42 And the ECU will actually be triggering at this point here where that signal drops down through zero volts.
09:49 So this is when we know that we've got our polarity right.
09:51 If we had our polarity wrong, we'd see that yellow trace simply inverted and that's when we're going to get that timing drift.
09:58 Likewise, our red trace here for our synchronisation input there, you can see again that rises up and then falls vertically down through zero so we're triggering off our falling edge on both of those triggers, everything's working nicely there.
10:11 Our purple trace here which we can sort of see a little bit of that moving through here, this is our calculated angle so this will work from -360 and it will increment up to 360 regardless of the fact we have got this set up as a two stroke, it still shows us that trace so again we should see this moving nice and smoothly.
10:31 So at this point everything's looking good, our trigger setup is configured correctly, we're getting valid information, valid RPM, we're ready to move on with the next step of our process.

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