Practical Standalone Tuning: Step 4: Base Ignition/Fuel Pressure
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Step 4: Base Ignition/Fuel Pressure
09.23
| 00:00 | - In the next step of our process, we're going to set our base ignition timing as well as our base fuel pressure. |
| 00:06 | Now in a lot of instances, we're not going to have the ability to set the base fuel pressure, particularly if we're dealing with a factory engine that has a stock fuel pressure regulator, of course these aren't going to be adjustable. |
| 00:17 | Even so, it's always a good idea to at least attach a fuel pressure gauge temporarily if you don't have a fuel pressure sensor or gauge fitted to the car permanently so that you can actually monitor what the fuel pressure is. |
| 00:30 | This is important because that differential pressure across the injector will affect the injector flow. |
| 00:37 | We've already seen as we've gone through the initial setup with the Sard 800 cc injectors, these are rated at 800 cc nominal flow at a fuel pressure of 3 bar or 43.5 psi. |
| 00:50 | Now that's not strictly to say that we need to set our fuel pressure at 3 bar. |
| 00:56 | There are no set in stone rules here. |
| 00:59 | If we increase the fuel pressure slightly, this can give us a little bit of additional flow from the injectors. |
| 01:04 | We do need to be mindful though that if we choose to set our fuel pressure at a pressure that is different to 3 bar, the rated fuel pressure for the injectors, then that will affect the injector flow and we really need to go back and readdress that. |
| 01:18 | In our instance we've got sufficient fuel system head room at 3 bar so we're going to stick to that. |
| 01:25 | Now the process of setting this, in this case we don't have the fuel pressure sensor in the EMtron which we've already discussed however up on the A pillar here I do have a set of Defi gauges which give us fuel pressure. |
| 01:37 | So the process here comes up with basically we want to start by just running the fuel pump and we can set the fuel pressure roughly to get us close to 3 bar. |
| 01:47 | Ultimately though the actual flow from the pump when we do this test won't be truely indicative of what we'll get with the engine running. |
| 01:55 | The reason being that if we just power the pump right now with the engine not running, we're only going to have 11.5 or 12 volts to the pump. |
| 02:03 | On the other hand, when the engine is up and running, we're going to have the alternator charging, so we'll have a full 13.8 - 14.2 volts. |
| 02:10 | So this can increase the flow from the pump and what we can end up seeing is our fuel pressure will come up a little bit. |
| 02:17 | Not always but it's something to bear in mind. |
| 02:19 | So the idea here is that generally I'll set the base fuel pressure statically just with the engine off and then I'll come back and revisit this once we've got our engine up and running and we've got it idling. |
| 02:30 | When we do this though, with a manifold pressure referenced fuel pressure regulator, once we've got the engine running, when we want to set our base fuel pressure, it's really important to take that vacuum line off the regulator while we're setting it. |
| 02:44 | We can then adjust the regulator, get our fuel pressure where we want it, lock up the mechanism on the fuel pressure regulator and then we can reconnect our pressure hose, our manifold pressure reference hose to the regulator. |
| 02:56 | So that covers our fuel pressure, in this case we're going to leave it as it is sitting at 3 bar differential and we'll move on and we'll have a look at how we can deal with our ignition timing. |
| 03:08 | And we're not going to be able to deal with this completely accurately right now either but let's go through the process. |
| 03:14 | We'll start by heading back to our config tab and what we want to do this time is go across to our engine setup. |
| 03:22 | And the specific parameters we're looking for here are crank index offset setup so we'll click on that. |
| 03:29 | So this allows us as I've mentioned briefly to lock the ignition timing so we can calibrate what we're seeing with a timing light to what we're seeing on the laptop screen. |
| 03:38 | Now what we're going to have to do is initially set this with the engine cranking and that's going to get us in the ballpark, close enough that we should be able to get the engine to actually fire up. |
| 03:50 | However at cranking speed, particularly given we are quite low, around about 150 RPM, it's likely that you'll actually see the timing fluctuate very slightly and that's quite normal so for this particular part of the process, I'm only going to be trying to get us within a few degrees of the correct timing, we don't need to be pinpoint accurate. |
| 04:08 | We can come back and revisit this once we've got the engine actually running. |
| 04:11 | At the same time we're doing our fuel pressure checks and with a slightly higher operating speed, we'll actually be able to accurately set that timing. |
| 04:20 | So what we want to do here is enable our ignition lock so we can click on that and we can set it to 1 which is for on. |
| 04:28 | And when we do this we can see that there are another 2 parameters that come up that are visible, we've got our ignition lock angle and then our crank index offset so how these work is first of all, the ignition lock angle, this is the timing that the ECU will output so it'll be fixed to this timing irrespective of any table values and any compenations, we've only got that 1 value heading out, that's what's going to be delivered so what this means is this is what we're going to be looking for with our timing light. |
| 04:56 | Now there is no fixed rule on what we must use there, a lot of this will be driven by what we can actually see with the crank pulley and that's going to be very dependent on the particular engine that you are tuning. |
| 05:08 | For instance some engines will only have a TDC marker and a TDC pointer so what this means is we are going to need to set that value at 0 unless you've got a dial back timing light. |
| 05:22 | Do need to keep in mind, once we get the engine up and operating though, the engine's not probably going to idle particularly happily or run particularly happily with the timing set at TDC so it's going to require a helper to keep the engine running while we are checking our timing. |
| 05:37 | In this case we've got timing marks on the RB26 from pulley from 0° all the way through to 30° so really anywhere within that range we're absolutely find to use. |
| 05:47 | It's also really important to make sure that you thoroughly understand what the timing marks on your crank pulley as well as the timing cover actually mean. |
| 05:55 | These vary quite dramatically from one engine to the other. |
| 05:58 | Some will have a marker at TDC, some will have a marker after TDC so you can get yourself into a lot of trouble if you assume incorrectly that the timing markers mean something that they don't. |
| 06:10 | So once we've got our timing set at a value that we know we can see, we then need to hook up our timing light. |
| 06:18 | And this is another challenge with the RB26. |
| 06:20 | Now there is a timing loop made for this purpose at the back of the engine. |
| 06:26 | Over the years I've seen some mixed results with this so I actually don't like to rely on this and while it is a lot more work, my own personal preference, I'll always remove the centre cover and get access directly to number 1 coil. |
| 06:42 | In some instances, your timing light will be able to pick up off the low voltage side of the coil wiring. |
| 06:50 | However if you're not getting an accurate result there, another foolproof method is to actually temporarily remove the coil and hook up a short ignition lead between the coil and the spark plug. |
| 07:00 | Then you can connect your timing light directly to the coil itself. |
| 07:04 | It's really important, this part is absolutely critical to make sure that your timing is correct. |
| 07:10 | So once we've got to that point we're going to again enlist the help of someone to crank the engine over while we're actually looking at the timing using the timing light. |
| 07:20 | This is another good place to make sure that our fuel pump is still disabled like we looked at in our last module so that the engine won't try and start. |
| 07:28 | And what we're going to do is crank the engine and we're going to look at where the timing is vs the timing marks. |
| 07:33 | Then we're going to come in and we're going to adjust our crank index offset value here until the 2 allign. |
| 07:41 | In this case, I already know that the value I've got in here, 101° is spot on for the new timing setup, the trigger system that we are using. |
| 07:50 | However if we're starting from scratch, we could be anywhere. |
| 07:53 | And it's just a case of iteratively moving through until you actually can start to see the timing marks. |
| 08:00 | If you can't see the timing marks at all on the crank pulley, I'll start by making quite coarse changes, maybe 50 to 60° until I can actually see the timing marks, then you can get a little bit smaller in your adjustments and zero in on the actual numbers. |
| 08:13 | Another point here though is that we could still have our timing completely incorrect, even while we are seeing the timing marks on the pulley. |
| 08:22 | So this is something that can catch you out and you'll find this when we get to our next step where we finally get to try starting the engine for the first time. |
| 08:29 | If you're cranking the engine, everything's looking good, you're getting RPM, you've got fuel injection, you've got spark occurring but the engine will not start. |
| 08:37 | Then it is quite possible that you've timed the engine up correctly but you've timed it up on the exhaust stroke as opposed to the compression stroke. |
| 08:46 | So to do this, simply we take the number in our crank index offset and we can add or subtract 360° to it to move it to the opposite engine cycle and that will fix the issue. |
| 08:58 | So again all we're trying to do here is get our timing in the ballpark, within about 5° of our timing mark, that's going to be close enough but it is very important to remember to come back and fine tune that timing once you've actually got the engine up and running and it's going to comfortably idle by itself. |
| 09:14 | So with our base timing and our fuel pressure roughly set, at this point we can move on with the next step of our process. |
