Practical Standalone Tuning: Step 4: Base Ignition Timing/Fuel Pressure
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Step 4: Base Ignition Timing/Fuel Pressure
09.14
| 00:00 | - The next step of our process is to set our base fuel pressure as well as our base ignition timing. |
| 00:06 | In both instances we're only going to be able to do a broad job of getting this dialled in at this point because obviously we don't have the engine running. |
| 00:14 | Once we've actually got the engine up and running, we're going to come back and revisit both of these and do them a little bit more accurately, particularly with our ignition timing it is critical to make sure that this is absolutely accurate. |
| 00:26 | We need to do this both at idle and then also at a slightly raised RPM just to ensure the accuracy of our timing values. |
| 00:35 | In a lot of installations you're not going to have the ability to set or adjust your fuel pressure. |
| 00:41 | In our case we're running a adjustable TurboSmart fuel pressure regulator so this does give us the ability to set our fuel pressure wherever we want to. |
| 00:50 | In this case as I've already discussed, we've chosen a differential pressure of 350 kPa however there's no fixed rule on where you need to set that. |
| 00:59 | To start with, what we're going to do is come back across to our outputs selection and we're going to come down to our fuel system and you'll remember, as we've already discussed, we have our nominal fuel pressure value here, 350 kPa so this was the target that I've chosen here. |
| 01:18 | In most instances, if you don't have an adjustable fuel pressure regulator, you're going to be stuck with whatever the factory regulator is and that's probably most likely going to be 300 kPa for a return style fuel system. |
| 01:30 | Regardless, even if you don't have an adjustable fuel pressure regulator for the purposes of testing and for setting everything up, it's a really good idea to temporarily install a fuel pressure gauge so you can actually see what your fuel pressure is. In this case, we've got our engine in a position where we can start it or test it by powering it up and test the actual fuel pump so we'll do that and while I'm going that, what we'll do is look at these values here, so we've got our fuel pressure used for the calculation, we've got our measured fuel pressure and then our differential fuel pressure. |
| 02:04 | So we'll just power the ECU up and we can see differential fuel pressure, sitting during that at about 336, 338 kPa, that drops down of course once the fuel pump has finished priming. |
| 02:19 | So at this point that's close enough. |
| 02:21 | Given that we haven't got the engine running, we don't have full battery voltage going through to the pump at this point, we can rightly expect that that fuel pressure will come up a little bit so this is something again we'd like to come back and revisit once we've actually got the engine in a position where we can make it idle, we can go through, do a bit of a systems check and make sure that our differential fuel pressure is what we set it. |
| 02:42 | Particularly if you don't have a fuel pressure sensor, it is important as I've already talked about to make sure that your nominal fuel pressure is set accurately to the actual fuel pressure because this is what the ECU will be basing its fuel pressure calculations on and this has a dramatic effect on the accuracy of your fuel system in general. |
| 03:03 | The next process we're going to go through here is setting our base ignition timing. |
| 03:07 | And this is going to be critical to at least get the engine to a position where we can start it for the first time and once we've got it started as I've mentioned, we can come back and review this and get it dialled in a little bit more accurately. |
| 03:20 | So what I'm going to do here is move back over to our inputs and then on our inputs screen we're going to click on triggering. |
| 03:28 | We've already had a look at the basis of this screen here before. |
| 03:31 | We'll go back over the fundamentals. |
| 03:34 | The two aspects we're going to be dealing with here are our timing lock enabled and we're also going to be adjusting our base angle. |
| 03:42 | So what we're trying to do here is essentially align the numbers in our ECU so that the timing that the engine is receiving, which we're looking at with a timing light, matches what we're actually seeing in our ignition tables. |
| 03:54 | If this is out, it's very easy to have what looks like conservative numbers in your ignition timing tables but if the engine's actually receiving 10 or 15° more ignition advance than we think we're giving it, it can be very easy to do damage when you think that you're being conservative with your tuning. |
| 04:11 | We're actually in a novel position here with the FD RX7 because if we're using the setup from one of the Adaptronic base configuration files then we're going to be very close straight out of the gates but of course we don't want to ever assume that this will be right and we need to check. |
| 04:31 | So it's this number here, our base angle that we're going to be actually adjusting to align the timing in our laptop with the timing we're seeing on the timing light. |
| 04:39 | Now that brings us to what timing should we be using here and this is where our timing lock enable comes in. |
| 04:45 | As I already discussed, there is a rotary specific mode here. |
| 04:49 | What that's going to do is lock the timing that is being delivered to the engine to -5° or 5° after top dead centre on the leading plug and there's a 15° split in there so it'll be -20 on the trailing plug. |
| 05:05 | This timing mode is helpful however with the FD RX7, we've only got one timing mark or timing pointer and this is at -20° so this is a rotary specific thing, we do need to understand and it will vary depending on which generation of RX7 or 13B you are tuning. |
| 05:23 | With the crank trigger we've got that one timing marker at -20° so what this means is that if we do want to use the timing lock rotary, what we're actually going to have to do is check on our trailing plug. |
| 05:38 | Our trailing plug will be firing at -20° so of course that should align with our timing marker. |
| 05:44 | On the other hand, we're not actually going to be able to confirm the timing on our leading plug. |
| 05:50 | So there's a couple of ways we can deal with this, we can use that rotary mode, we can check our trailing ignition timing, we can then also check the leading plug and what we're going to find of course is that it's going to be off that mark. |
| 06:03 | What we can do there is we can set our timing lock to normal and when we bring that up we can see we've got our timing lock angle -20°. |
| 06:11 | So if we set this to -20°, then our leading plug will be firing at -20. |
| 06:18 | The problem with doing so here is that the engines not going to really like running at -20°. |
| 06:25 | For the purposes of this test, that's fine because remember we aren't actually running the engine, we're just going to be turning it over on the starter motor. |
| 06:32 | So this requires us to have a helper to go through the process and what we're going to do is have the helper crank the engine over while we're physically using our timing light to check the timing. |
| 06:44 | I do recommend that for the purposes of this you use a simple conductive timing light, not one with a dial back style function. |
| 06:55 | Or if you are using a dial back style function like our Snap-On timing light that you set the dial back to zero so that it should be triggering exactly when the spark is occurring. |
| 07:05 | So it's always a good process to go through and make sure that both your leading and trailing plugs are firing where you expect them to. |
| 07:14 | Remembering again we're only doing this close at this point, getting into the ballpark. |
| 07:18 | While the timing should be reasonably consistent at cranking with the FD RX7 crank trigger, on a lot of engines you will find that the timing is going to move around maybe 2-5° at cranking RPM and that's why we're just getting ourselves into the ballpark there, once we've got the engine up and running, the engine RPM will mean that the timing is going to be more consistent so we come back and revisit that and make sure we've got it dialled in really accurately. |
| 07:44 | Now another consideration here that's more common or going to be more of a problem on a four stroke piston engine is that you can end up with your timing dialled in, it's happening exactly on the timing mark that you expect but when we get to the next stage and we get to start the engine for the first time, you may find that there's still no chance of the engine running and in this instance you may find that there's no sign of life at all, there's no popping and banging inside any of the cylinders. |
| 08:13 | Now what this can mean, and a really good check here is that you may be firing at top dead centre but on the exhaust stroke rather than on the compression stroke. |
| 08:21 | In that instance, what we're going to do is come back simply to our base angle here and you can change this by 360°, that will put it on the opposite cycle but with our rotary engine that's not going to be necessary. |
| 08:34 | Remember as well, once you have adjusted your base timing, you want to come back to our timing lock option here and set it back to no timing lock. |
| 08:44 | This can be really frustrating if you overlook this because you're going to get through the tuning process and find that it doesn't really seem that your engine responds to ignition timing because the ECU of course is completely ignoring the numbers from your timing map. |
| 09:00 | So at this point we should be in a position where our base fuel pressure and our base ignition timing are in the ballpark, close enough at least to get our engine up and running for the first time and we can move on with the next step of our process. |
