Practical Standalone Tuning: Step 4: Base Ignition Timing/Fuel Pressure
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Step 4: Base Ignition Timing/Fuel Pressure
10.45
| 00:00 | - Alright, the next step of our 10 step process is to set our base ignition timing as well as our base fuel pressure. |
| 00:06 | And this really becomes a bit of a two step process because obviously at this stage, we haven't actually got our engine up and running for the first time. |
| 00:14 | And particularly when it comes to setting our base ignition timing, if we're setting it while the engine is cranking but not firing, it's likely that we're going to end up seeing a little bit of variation in our ignition timing and what I mean by this is if we're watching using a timing light, we're going to see the timing wander around, depending on the trigger system, it might actually be rock solid, sometimes we might see it move one or two degrees, sometimes it can move quite a considerable amount. |
| 00:39 | Compared to when we have the engine up and running, idling at maybe 1000 to 1500 RPM, the ECU is obviously receiving a lot more trigger inputs, a lot more frequently than it will at a 150 or 250 RPM cranking speed and that gives us better consistency. |
| 00:55 | Getting this base ignition timing in particular correct is really really critical. |
| 01:01 | So we do need to make sure we take our time and do this properly so again two stage process, the first step of this process is going to be setting the ignition timing at crank. |
| 01:11 | Before we do this, what we want to do is get our ignition timing, or timing light I should say, set up and running. |
| 01:18 | I'm using a Snap On dial back style timing light where we can actually set the timing on the dial back function. |
| 01:26 | So for example if we're running 10° before top dead centre, and we only have a TDC marker, true TDC marker, I can actually enter a value of 10 on the dial back timing light and that will align things, basically take that 10° into account and it will trigger right on the TDC mark but absolutely no reason you can't use just a normal inductive timing light as well, it'll work absolutely fine. |
| 01:49 | So this is a case of hooking up power and earth to our timing light and then hooking up the inductive clamp to the ignition lead. |
| 01:56 | Obviously with a coil on plug system, we don't have leads and normally I find that hooking the inductive clamp around the low voltage feed to the ignition coil is enough, that will work. |
| 02:08 | Sometimes it won't though, occassionally you will actually need to remove the coil and a trick I use is to temporarily add an ignition lead from the end of the coil. |
| 02:17 | Just race taping that on and then running the coil to the spark plug, that gives us a ignition lead we can then hook the inductive clamp on. |
| 02:23 | In our case though with the Subaru it worked perfectly, just being around the low voltage side of the wiring to that coil. |
| 02:30 | Let's jump into our tuning software and we'll go through the process here so very similar to what we looked at when we were setting up our trigger inputs. |
| 02:38 | What we want to do is actually start by disabling the fuel injection, making sure that the engine essentially won't start. |
| 02:45 | So we can come down to our fuel main and again, we've already looked at this, we're just going to turn that off temporarily, press F4 to store that. |
| 02:52 | What we're going to do now is press escape, couple of ways of finding this, you'll already note that we've seen this, we'll go to triggers, come down to calibrate, that will get us where we want to go. |
| 03:02 | Or alternatively escape and just type in CAL and it will obviously auto fill with everything that has cal in the name. |
| 03:09 | That'll find it pretty easily, so let's have a look here, we've got set base timing, what we want to do is click on the little spanner icon there and that will put the ECU into base timing mode which essentially ignores any corrections, it ignores all of the values in the table and sets the timing to one fixed value. |
| 03:28 | So in this case, that fixed value is going to be 10°. |
| 03:32 | What we want to choose is a value that's easy to see, in the second part of this we want to also choose a value where the engine's going to idle reasonably happily. |
| 03:40 | For example if we set this to 0° or top dead centre, the engine's probably not going to idle very happily, 10 or 15° though, it's going to work quite nicely. |
| 03:50 | This really comes down to the engine you're working on. |
| 03:53 | In the case of the Subaru, the front crank pulley has timing marks, or the cover I should say has timing marks at 0, 5, 10, 15 so it's very easy to use any of those values so 10°, absolutely fine there. |
| 04:06 | And then what we're going to do is basically adjust the offset, which is this value here, 0°, until the timing that we see with our timing light does in fact match 10°. |
| 04:18 | So in this case, our offset's at 0° so that's what we're going to be doing. |
| 04:23 | So the process requires two people, what we're going to do is crank the engine, again it won't start, and once the engine's been cranking for a second or so, we should see our timing light trigger and we're going to adjust the offset until our triggering or our timing light is triggering right on that 10° mark. |
| 04:41 | And if it's not, we're going to adjust our offset up and down, up or down until we're right on the mark. |
| 04:47 | So that's going to get us broadly in the ballpark, again the engine's not going to run at this stage. |
| 04:51 | And then we can close that down and press done. |
| 04:54 | Before we do that I'll just explain the second step of the process. |
| 04:57 | We're going to come back and revisit this, once we've got the engine idling comfortably and we know everything's essentially working as we'd expect, and we're going to do exactly what I mentioned previously. |
| 05:07 | We're going to reset or recheck our base ignition timing and we're going to basically choose an idle speed of maybe 1500 RPM just bringing that RPM up a little bit and our timing should be rock solid, we're going to adjust that until our timing is exactly on our mark. |
| 05:25 | This is also a good time to double check that we're not suffering from timing drift and although we've already checked our trigger inputs using the scope function and we know the polarity is correct, often with reluctor inputs they won't be correct and we can still get the engine up and running with the incorrect polarity but what you're going to find is that as the RPM increases, you're going to see the timing drift. |
| 05:48 | So it's always a good idea while you're in this base timing mode here, just to bring the RPM up, so from 1500 to maybe 3500 or 4500 RPM or thereabouts and just make sure that the timing does stay rock solid. |
| 06:02 | Might drift a degree or so but absolutely that's fine. |
| 06:05 | If you're seeing significant drift as the RPM increases, then you've got a polarity problem, or that's a red flag for a polarity problem. |
| 06:12 | The last element here, just jumping back into our menu, we can see we've got this setting here to adjust the timing delay, the ignition timing delay. |
| 06:19 | And the idea with this is that we set our base timing at idle, 1000, 1500 RPM and then what we want to do is bring the RPM up to maybe 5000 or 6000 RPM and under steady state conditions, holding it at 5000 to 6000 RPM, we can adjust the delay here, it's currently 115 microseconds, until the timing at 1000 RPM and 6000 RPM is exactly the same so again not really something we should need to deal with too much in this instance because we've got a base map, everything is pretty much on the money and when we actually went through this base timing setup, the timing was absolutely spot on, right out of the box with Link's settings, as you'd expect for a plug and play ECU with a base map. |
| 07:03 | Alright so once we've done that, we can close that down. |
| 07:07 | Really important here as well just to make sure before we frustrate ourselves that we go back to our ignition mode and we turn that back to sequential, otherwise we're going to have problems with the engine not starting and of course we'll store that change. |
| 07:21 | The other element here is we want to set our base fuel pressure. |
| 07:25 | Now again we've got an adjustable Tomei fuel pressure regulator on this vehicle. |
| 07:30 | So we want to check and set that base pressure. |
| 07:33 | Now again we want to do this really in two ways, we can set it broadly right now with the engine not running but the problem is that without the engine running, we've only got battery voltage really going to the fuel pump so maybe 12 to 12.5 volts which is much lower than the 14 odd volts we'll have with the alternator charging. |
| 07:55 | What this means is that we can set the base fuel pressure approximately right now but we will want to come back and revisit this and check it once we've got the engine idling and we've got that full battery voltage or full charging voltage of 14 odd volts going on there. |
| 08:10 | Let's have a look at how we can do that though. |
| 08:12 | So what we want to do here is, we can just type in fuel pump or you can go to your outputs and find the fuel pump that way. |
| 08:20 | Fuel pump control here, and what we want to do is come down to our aux seven test and we can click that on. |
| 08:28 | That'll run our fuel pump, I can audibly hear it running. |
| 08:31 | So what we want to do here is basically just adjust the fuel pressure regulator which is as simple as loosening off the locking nut and then adjusting it in or out until we've got our fuel pressure on three bar. |
| 08:45 | Obviously with the engine not running, it doesn't really matter but once we come back and revisit this, with the engine idling it's really important that before we set our base fuel pressure, we make sure that we actually disconnect the vacuum hose from it. |
| 08:57 | Reason for this is what we're setting is our differential pressure and with the engine idling, the engine is obviously drawing a vacuum in the inlet manifold and what that does is it then reduces the fuel pressure so if we've got a base fuel pressure of three bar, we might find that at idle it's only registering 2.2-2.5 bar or thereabouts. |
| 09:20 | So really important when we come back and reset this at idle, that we pull that vacuum hose off, we adjust it, make sure that we've got it exactly on our target, three bar in this case is fine and then we lock that up. |
| 09:32 | This also comes to a bigger question of what should our base fuel pressure be and there is no black and white answer here. |
| 09:39 | Generally we'll find that with a port injected engine like this, with a return style fuel system, or a manifold pressure referenced fuel pressure regulator, three bar or 43.5 psi is a pretty typical value but again that doesn't mean that you have to have that set in stone. |
| 09:58 | Often if you just need a little bit more headroom out of your fuel injectors and you've got enough fuel pump to cope, bumping that fuel pressure up to 3.5 or even four bar base pressure, that can be enough just to creep a little bit more headroom into your injectors because essentially they flow more fuel for the same injector pulse width. |
| 10:17 | Again, three bar for our case though is going to be absolutely adequate, so at this point we've tested under cranking conditions our base ignition timing, we've got that locked in, we've also tested statically with our fuel pump running, our fuel pressure is in the ballpark, and there's nothing more we can do here with either of those two parameters until we've actually for the engine up and running and we can come back and fine tune this, so let's move on with the next step of our process. |
