Practical Standalone Tuning: Step 2: Trigger Setup
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Step 2: Trigger Setup
12.29
| 00:00 | - For the next step of our 10 step process, we're going to look at setting up the trigger inputs to the ECU and these are the most mission critical inputs to the ECU. |
| 00:09 | If we don't have these right, essentially all bets are off, nothing is going to work properly. |
| 00:14 | All of the ECU's calculations for both fuel and ignition are based on these signals being valid accurate and reliable. |
| 00:21 | In our instance, we are sourcing these signals from the factory distributor although as we've already discussed, we're no longer using it as a distributor, it is simply the source of the engine speed and position information. |
| 00:35 | So let's jump back into our MTune software and we've come back to the inputs menu structure here and we want to come back up to the top here to our trigger and home inputs. |
| 00:46 | In the case of the MaxxECU, the trigger input is considered the engine speed or engine RPM input and the home is the synchronisation input so just to get some clarification around what those two terms actually mean. |
| 01:01 | Let's start with our trigger input here and the first setting here is our trigger sensor type. |
| 01:07 | In the case of the Honda, both the trigger and home inputs are a VR or variable reluctance, in other words a magnetic input. |
| 01:16 | Again from our drop down menu we can see we can have a digital which would cover a hall sensor or optical sensor style or we can have a bipolar VR sensor so we're choosing a zero crossing sensor and what that means is that the trigger input will be valid or considered to have occurred when the signal passes through zero volts. |
| 01:36 | Now an aspect that is important with setting up a VR sensor is that it needs a trigger threshold so this is just the threshold above which the voltage needs to rise, before the ECU essentially arms and starts looking for a valid signal and the idea behind this is that it's just used to help ignore background noise. |
| 01:58 | So our trigger arming voltage table here is relative to engine RPM because as the RPM increases, the amplitude of the voltage from the sensor also increases. |
| 02:08 | We can see here, this is a generic table that is the default values and in general terms, this should be enough to get you up and running. |
| 02:18 | However we'll see exactly how we can use some of the functionality in the MaxxECU to help us set this anyway. |
| 02:26 | Looking at these values here, we've got a value of 5V above 4000 RPM and down at 1600 RPM we're 1.5V. |
| 02:34 | Next we'll move onto our home input and we can see that here, again essentially everything is the same here, again we've got a VR sensor zero crossing. |
| 02:44 | What I haven't mentioned here is the polarity for both of these triggers. |
| 02:47 | We can see here we've got the trigger polarity for our trigger input is set to a falling edge which means that the signal will initially rise above zero and then it will arm and then it will trigger when it drops back down through zero. |
| 03:01 | On the other hand here, we can see that our polarity for our home input is actually the opposite to rising, the signal is inverted. |
| 03:08 | We'll have a look in a moment at why that is the case here. |
| 03:12 | We've got an arming threshold table essentially exactly what we've already looked at. |
| 03:17 | What I will mention here is at the moment I've got this set to manual table, can also do automatic tracking as well where essentially the ECU will monitor the amplitude of the signal and set the arming threshold acccordingly. |
| 03:29 | Next up we have our trigger decoder which is going to tell the ECU what it's expecting from the trigger input. |
| 03:38 | This is important because there are a huge variety of different signals and if the ECU isn't knowing what it's going to expect, it's impossible to properly decode it. |
| 03:46 | First of all we have the actual trigger system itself and in this case it's saying here that we are expecting to see a multi tooth plus home. |
| 03:54 | What this means is that the actual trigger input is multi tooth, evenly spaced teeth, no missing teeth in this case, plus there will also be a home signal as well. |
| 04:03 | If we click on the drop down menu there are a huge range of options here and every ECU, sorry every engine manufacturer seems to have their own take on what's going to work best for their application so in a lot of instances there will be engine specific modes that you simply are going to have to choose based on your engine. |
| 04:24 | There are also some generic modes which will be useful, particularly if you are making up your own trigger system. |
| 04:29 | This is critical so if you are in any doubt, it's always a good idea to consult with MaxxECU, they will be able to advise on the correct trigger mode for your specific application. |
| 04:39 | So that's our trigger system, next we have our home signal which is essentially telling the ECU where the home signal is going to be derived from, in this case we can see that we've got it set to on cam. |
| 04:51 | On crank is another option, there are some other specific options in there. |
| 04:54 | Ideally the home signal does need to be derived from the camshaft because the camshaft of course rotates at half engine speed, meaning the ECU is receiving only one signal per complete engine cycle which is what it needs to know where in the engine cycle it is. |
| 05:09 | We also have the cam signal position as our next option and we can see that that is set to before top dead centre and lastly here we've got our tooth count so essentially how many teeth is the trigger signal going to comprise of? So we've got 12 evenly spaced teeth there. |
| 05:27 | Moving down we've got our trigger angle as well so this is where our first tooth angle is in terms of degrees before top dead centre, cylinder number one. |
| 05:36 | Now for common engine combinations, Maxx will be able to advise on what this number should be but this also becomes part of the process of calibrating our base ignition timing so we don't actually need to worry too much about this right now, we'll be able to calibrate this accurately with our timing light when we get further into our worked example so we'll leave that at the moment. |
| 05:58 | We've also got our trigger angle options here so this really comes again into setting our base timing. |
| 06:05 | This allows us to, as we can see here, tick these little boxes here to disable our fuel, our ignition and then lock our ignition angle which we've already discussed, so that we've got a fixed value irrespective of the table values that may be used at any time and this allows us to make sure that we're accurately setting our base ignition timing, again we'll look at this in detail in its own special step. |
| 06:29 | Now that we've actually got our trigger setup complete, we want to test it and make sure that the ECU is actually receiving valid information. |
| 06:36 | And there's a couple of ways we can monitor this. |
| 06:38 | Before we do that, we want to ensure that the engine isn't going to try and start and we also of course don't want the engine injecting fuel and potentially flooding so this is where these disable fuel and ignition check boxes come in, we can click these and this will automatically disable fuel and ignition so we'll do exactly that. |
| 07:00 | Now what we're going to do is just click here, that's going to expand out our real time monitoring and if we come through, we're going to find here there is a specific set of options for monitoring the trigger inputs. |
| 07:13 | We can expand and contract any of these by pressing on the little plus and minus. |
| 07:18 | So there's a couple of things we're going to be looking at here. |
| 07:20 | First of all, down in our bottom bar here we want to monitor our engine RPM. |
| 07:26 | And generally what we should be expecting to see is a relatively smooth and consistent RPM once the engine has started to crank. |
| 07:34 | Typically that's going to be somewhere in the region of maybe 200 to 300 RPM while we're cranking so if we see that, that's a good sign. |
| 07:42 | If we're seeing really erratic RPM or unrealistic RPM, that's a bit of a red flag for us. |
| 07:47 | At the same time, there's a few things we can note here in the actual real time values. |
| 07:53 | One of these is this particular value here, in sync, and that will simply mean that the engine is synchronised, the ECU is synchronised, it's getting all of the signal data that it should be, or it's expecting and it knows what the RPM is and where the engine position is. |
| 08:10 | Got a little bit more information in there as well but just concentrate on those two. |
| 08:14 | So what I'll do is just briefly crank the engine now and we can have a look at what's going on there. |
| 08:22 | OK that's a good sign, essentially once the engine had established cranking, we were seeing around about 213 RPM and our in sync went from zero to one, doing everything it should. |
| 08:33 | So that's good, that suggests we're getting the information we need. |
| 08:37 | Let's have a little bit more of a look in detail and one of the nice functions in the MaxxECU is that it does have a built in oscilloscope. |
| 08:44 | The oscilloscope function just allows us to see the actual signals that the ECU is receiving from the trigger and home inputs and this is very helpful for analysing trigger input problems. |
| 08:57 | So essentially no different to a conventional oscilloscope so what we're going to do is click on the start measurement as we're cranking the engine, we'll crank it for a few seconds and then we can stop that measurement and analyse the data. |
| 09:09 | Let's go ahead and get that done. |
| 09:15 | Alright so as we're measuring we see the signals pop up here so at the top in orange, we have our trigger output, our engine RPM input and then below that in blue we've got our home input. |
| 09:28 | Now the signal at cranking speed is a little bit erratic because of the cranking RPM variation due to compression in the engine but we can see we've got a relatively nice looking signal here. |
| 09:37 | Couple of things to note here is this is helpful with deciding on the correct polarity, particularly with a variable reluctor sensor. |
| 09:45 | Little more difficult to see this with the higher tooth count with our trigger input, we can see that signal here and this is actually correctly set on a falling edge. |
| 09:58 | We can see here with our home input on the other hand, we can see the way the signal changes, as we come up to the tooth we can see the actual voltage there drops down below zero volts and then it rises up so this is the opposite to how we'd conventionally set this up. |
| 10:17 | This is a rising edge as opposed to falling edge and we can see there is a little star that the scope will show us and that star is the actual point where the trigger event is occurring. |
| 10:30 | So really important to have the polarity around the right way with a variable reluctance sensor cause otherwise as the RPM increases, the actual trigger point moves and this gives us a drift in our timing. |
| 10:42 | So that's how we know with this instance that the home is a rising edge and the trigger is the conventionally falling edge. |
| 10:50 | Fortunately in the MaxxECU, really easy to change those. |
| 10:53 | The other value of this particular oscilloscope is that it helps us with our arming threshold table. |
| 10:59 | So we can see here that our arming, our amplitude I should say, is reaching somewhere around about 0.7 to 0.8V and remembering this is only at cranking, that voltage is going to increase as the engine starts and the RPM climbs. |
| 11:14 | But the general rule of thumb is we want to set our arming threshold somewhere around about 1/3 of the peak amplitude so in this case if we're sitting at around about 1V for example, we'd want to be around about 0.3, 0.35V so that's just helpful, we can use this scope when the engine is running as well, to help us fine tune that table. |
| 11:36 | So at this point our trigger setup is complete, we're getting valid information to the ECU. |
| 11:41 | One last step before we move on though, we want to come back to our inputs, back to our trigger and home inputs and we want to make sure that we untick the little boxes, disabling fuel and ignition.. |
| 11:55 | If we just reclick that for a moment though, we will actually see that the MaxxECU MTune software does give us a flashing warning up the top that this is something that's still easy to overlook and this can be a source of significant frustration if you forget that you've ticked those boxes, get to the point where you want to start the engine and for some reason it won't actually fire up. |
| 12:17 | Lot of time can be wasted there and it's really frustrating when you figure out your mistake. |
| 12:21 | Anyway, we've got our trigger setup complete, let's move onto the next step of our process. |
