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Practical Standalone Tuning: Step 4: Base Ignition Timing/Fuel Pressure

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Step 4: Base Ignition Timing/Fuel Pressure

12.07

00:00 - Our next task, before we start tuning the engine is to check and set our base ignition timing and our base fuel pressure.
00:09 Now these are two of the key aspects to any tuning job, and they're so often ignored or overlooked, yet they are very critical, particularly if you get them wrong.
00:21 Now we're going to deal with these two parts separately, and the first part with our Nissan 350Z we're going to discuss is the base fuel pressure.
00:30 In our case, with the 350Z, we're running the factory return-less fuel system, so in this case there is nothing for us to adjust.
00:39 We can't physically adjust or influence the base fuel pressure.
00:45 If we were running an adjustable after-market fuel pressure regulator, this would be the point where we adjust the fuel pressure to whatever particular base fuel pressure we'd decided on already.
00:59 Even if we have a non-adjustable fuel pressure system like we do here, it's always still advisable to actually measure and check the base fuel pressure.
01:10 It can indicate if we do have a problem with the fuel system and if that is the case it's going to save us a lot of time, because we're not going to find this out once we've already wasted expensive dyno time.
01:23 So, even in a completely stock fuel system, it's always worthwhile fitting a fuel pressure gage so we can physically watch what the fuel pressure's doing and make sure it's acceptable.
01:36 Of course, with our AEM Infinity installed here, we have fitted a fuel pressure sensor as an additional sensor, so that allows us to view exactly what the fuel pressure's doing.
01:49 Now, one aspect of how that influences the engine operation is if we look at our injector tab here, which shows us all of the information related to the fuel injector set up.
02:02 You'll remember that we already addressed that by selecting the correct injectors from our injector set up wizard.
02:09 However, you can see that the injector characteristics are dependent on the fuel pressure, or more correctly, the differential fuel pressure.
02:21 So, in this case here, we can see we have our injector flow and CCs per minute, and we can see that this is a 2D table versus injection pressure.
02:32 So this is the differential fuel pressure difference between the pressure and the inlet manifold and our fuel pressure.
02:40 So the fuel pressure will influence where on this particular flow graph the ECU will be accessing, and also, at the same time we have our injector offset or injector dead time or latency as it's also known.
02:55 Again, the injector offset or dead time is related to both injection pressure, our differential fuel pressure, and our battery voltage, so that's where these elements come into play and why it's important to know what our fuel pressure is.
03:12 At the same time, as I've said, it will indicate if there's a potential problem with the fuel system.
03:21 The next step, which is absolutely critical is to correctly set our base ignition timing.
03:27 And when I talk about setting base ignition timing, what I'm talking about is calibrating the ECU so that the ignition timing numbers we see in our ignition table are actually what's being delivered to the ignition coils on the engine.
03:44 So the spark timing that the engine is receiving is exactly what we see in our table.
03:52 Now this is something that is really often overlooked, particularly with a situation like this, where we have a plug-and-play ECU, the data for that ignition timing, base ignition timing is already configured.
04:05 So, it can be tempting to just leave that and trust that it is correct.
04:11 Likewise, if we have a car that is being brought to us that's previously being tuned, it can be tempting to trust that the last tuner has done their job.
04:21 When we've got a digital number on the laptop screen, such as ignition timing, it's always tempting to simply believe that number blindly.
04:31 However, if the ignition timing hasn't been correctly set, the actual ignition advance the engine's receiving may be dramatically more or dramatically less than the number on the laptop screen.
04:45 Now, if the engine's receiving less timing that's not likely to be dangerous, but we can potentially get into a situation where the ignition timing is so far retarded from what we think the engine's receiving that we end up leaving potential power and torque on the table.
05:04 The more dangerous situation is where the ignition timing is more advanced than we think.
05:09 And while we may have what we expect to be safe numbers in our ignition table, the actual advance the engine's receiving could be much more than this and it's possible to run the engine into knock or detonation and damage it very quickly.
05:25 So the process for doing this is going to be in two steps.
05:29 First of all we can actually test this without the engine running, just simply by cranking the engine.
05:37 So if we go back to our setup wizard, and this process is done under the ignition sync tab, and you can see we have our ignition timing and we have a little tick box here that says lock timing at, in this case 20 degrees.
05:55 Now we can lock timing at whatever ignition angle we want, so in this case let's choose 10 degrees.
06:01 The idea is to choose an ignition advance angle that first of all the engine will run happily at, and also an ignition advance angle that we can see easily with a timing light on the crank pulley.
06:15 So doing this procedure will actually require us to get out of the driver's seat and hook a timing light up to the ignition lead or the ignition coil on number one cylinder, so we can physically see what the timing is doing while we're going through this process.
06:32 So we start by setting the timing at a sensible angle that the engine will run at.
06:39 If we click on our advance tab here, we can see we have our trigger offset.
06:44 So what we do is we use this trigger offset value and we adjust this if there is an error or a difference between our 10 degree ignition timing, the ignition timing we've locked the ECU at and what we're actually seeing on the crank pulley with our timing light.
07:04 It's worth pointing out that when we've ticked this little lock ignition timing box, regardless of the numbers in the main ignition table or any other compensations active, the ECU will ignore all of those tables and simply output a fixed timing at 10 degrees.
07:23 So what we can do now is we've got a few options.
07:26 We can advance or retard our trigger offset until the timing matches.
07:33 We can use these little arrows here to perform that task, or alternatively, we can do this directly in the trigger offset box.
07:45 So what we want to do is correct any error we've got there.
07:48 At the same time, particularly if we're dealing with an unknown trigger system or one that is being wired up to the ECU and not through a factory harness or adaptor loom, we want to check and make sure that the polarity of the trigger system is correct.
08:06 And we can do that by setting the base timing initially at idle and then we'll bring the engine RPM up to about 3000, maybe 4000 RPM.
08:17 And while we're doing that, we're looking to see if the ignition timing stays stable.
08:23 We're always likely to see a small fluctuation of perhaps a degree or so, but if we see a large shift as the RPM is increased, that would indicate that in the case of a magnetic or reluctor trigger pick up, that the wiring has been, the polarity of the wiring is incorrect and we need to address that.
08:44 One last aspect that's available in the AEM Infinity is our pick up sensor delay.
08:50 Now, as I just mentioned, it isn't uncommon to see a very small drift in our ignition timing between perhaps 1,000 RPM and 6,000 RPM.
09:01 The AEM Infinity allows us to account for that or correct for it and what we want to do is adjust the pick up sensor delay.
09:13 If we are seeing a timing drift what we can do is increase the delay.
09:18 We test that at idle or 1,000 RPM and then bring the RPM up to a higher, perhaps five to 6,000 RPM and see what the timing difference is at the higher RPM.
09:30 We can adjust the pick up delay until the timing is essentially rock solid across our entire RPM range.
09:40 Now, at this point, remember that we haven't actually got an engine that is in a situation where we can start and run it.
09:48 So that makes it a little bit tricky to do this process and if we've got an engine that we can't start at this point, then we're going to do the base ignition timing process in two ways.
10:00 First of all, we're going to make a coarse adjustment and we can do this simply by cranking the engine.
10:07 So this requires a helper.
10:09 Someone can crank the engine while we're physically looking at the timing marks with a timing light, and we can use the ignition synchronization worksheet here to roughly get our ignition timing correct.
10:25 At this point, we're not going to be too worried about getting it absolutely accurate, as long as we're within about three to five degrees, the engine will be able to be started and run.
10:35 Then, we're going to revisit this step once we've got the engine idling comfortably and we're going to proceed and go through this configuration again so we can much more accurately configure and set the base ignition timing.
10:53 Now, the reason we need to do that twice is we're not necessarily going to get a stable RPM pulse into the ECU at cranking speed.
11:03 So we're quite likely to see the ignition timing wander around a little bit at cranking speed.
11:10 Of course, once we've got the engine running and the engine RPM is higher, that will all become a lot more stable and we can much more accurately set our ignition timing.
11:21 For that reason, it's also worth actually setting our ignition timing slightly above idle speed.
11:28 Again, if we're seeing the ignition timing fluctuate a little bit at a low idle speed, at perhaps 750 or 800 RPM, if we bring the engine RPM up to perhaps 1500 to 2000 the trigger input should become a lot more stable in the ECU and the ignition timing, hence, should become a lot more stable and that's where we want to set our base timing.