Practical Standalone Tuning: Full Power Tuning
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Full Power Tuning
11.35
| 00:00 | - Now that we've completed our steady state tuning of our fuel and ignition tables, it's time to move on and look at some full-power, full-throttle acceleration tests. |
| 00:10 | So in this section, we're going to look at how we can replicate the ramp runs that we looked at on the dyno section of the course, out on the road or track. |
| 00:21 | And this is relatively straightforward, because we are simply going to be doing a full-throttle acceleration test out there on the road, or on our racetrack. |
| 00:30 | Now, when we're doing this, particularly in a powerful car, we really want to be concentrating all of our energy on controlling the car. |
| 00:38 | So we don't need to be viewing the laptop screen for this process, much like the dyno, we're going to be performing our acceleration test, and then we're going to be looking at our data logging after the acceleration test is complete and deciding on changes based on this data. |
| 00:56 | We don't need to actually be making changes during the acceleration test. |
| 01:01 | Now while we need to be concentrating on controlling the car, it's beneficial if we have a wide band air-fuel ratio meter that's within view. |
| 01:10 | Now, we don't need to stare at this, but it's simple to view the air-fuel ratio out of our peripheral vision during the acceleration test. |
| 01:18 | And just like on the dyno, if we notice that the air fuel ratio is either too rich or too lean, we can simply abort the run, make some changes and try again. |
| 01:26 | Likewise, I'd normally be audibly listening to the engine for detonation, using audio knock detection equipment, and just like on the dyno, this allows me to abort the run if the engine suffering from knock during the run. |
| 01:39 | All right, let's head out on the track and see what we need to do. |
| 01:42 | There's a few considerations we need to make about our full-power turning. |
| 01:46 | Just like our steady state turning, we need to start by making sure the engine isn't heat-soaked, and our intake air temp and engine coolant temp are at normal operating temperatures. |
| 01:56 | The next aspect we need to consider is the piece of road we select. |
| 02:00 | Obviously we'd be ideally looking for a very long, straight piece of road. |
| 02:05 | We want to be able to perform our test without worrying about negotiating corners or needing to brake very hard. |
| 02:13 | So we need to use the longest section of straight road that we can. |
| 02:16 | This will influence the next aspect that we need to consider, which is what gear to perform our testing in. |
| 02:22 | Now, if we use a very low gear, perhaps second gear, we're much more likely to have the engine suffer from wheel spin, and also because the engine's going to accelerate quite quickly, we're not really placing enough load on the engine. |
| 02:36 | The higher the gear, on the other hand, the faster the car's going to be going at the end of our test. |
| 02:43 | So generally, we're going to be looking at either third or fourth gear. |
| 02:47 | In this case, I'm going to perform my test in third gear. |
| 02:50 | And what I'm going to do is get the engine down to my starting RPM, this case I want to perform my test from 1500 RPM. |
| 02:57 | I'm just coming onto the straight now, I've got my data logger running, so let's perform our acceleration test. |
| 03:20 | Okay, so that's our first acceleration test complete there, as you can see, it's relatively straightforward. |
| 03:25 | I spent most of my time there simply watching the road, the racetrack, however I could glance occasionally at the dash just to view the air-fuel ratio and make sure that I was happy with where the air-fuel ratio was. |
| 03:40 | Let's head back to the post now, and we'll have a look at the data log. |
| 03:43 | All right, we've completed our first acceleration test. |
| 03:46 | We've made a data log, and now we're going to have a look at that log file and analyze it. |
| 03:52 | Really, this is exactly the same as how we would use the dyno. |
| 03:55 | We perform our acceleration test on the dyno, and then we look at our log file, our logged lambda, and see what changes we need to make. |
| 04:04 | Now, while we're using the G4 plus for this example, it doesn't really matter, we're simply looking at the concepts here, so how your own ECU will log and what you'll be looking at may very slightly, but the parameters essentially remain the same and the concepts remain the same. |
| 04:22 | So here we have our engine RPM at the top of our log file, and you can see the area of our acceleration test being shown here. |
| 04:31 | We ended up going out to 6500 RPM, and at the start of the run, where I first go to full throttle, you can see we're at 1500 RPM. |
| 04:40 | And the next group here in our log is our throttle position, and this simply allows me to see where the engine was being operated at full throttle. |
| 04:50 | Now the first part we're really going to talk about here is our lambda, or air-fuel ratio. |
| 04:56 | And here I've logged the measured air-fuel ratio lambda value, versus our target. |
| 05:02 | And exactly the same as how we'd use the dyno here, we're simply going to analyze this log file. |
| 05:06 | Any time we've got a discrepancy between our measured and our target lambda value, we can go back into our fuel table and make the required changes. |
| 05:18 | This is very easy, and essentially exactly the same data that we would have on the dyno, so tuning the fuel is incredibly easy. |
| 05:23 | How we approach the ignition timing is a little bit different. |
| 05:27 | Now, I've got a log here that shows our knock thresholds, our knock values from the ECU, so this particular ECU has on-board knock control and this just allows us to graphically view what's going on. |
| 05:41 | Now remember, while we're tuning, I always recommend that we're using audio knock protection equipment so we can audibly listen for detonation occurring. |
| 05:49 | The onboard knock control that I've logged here just gives us a graphical way of seeing whether the engine is suffering from knock. |
| 05:57 | And what I'm really looking for here, as you can see, we have this gray line which is our knock threshold. |
| 06:04 | If at any particularly point, any of the individual cylinder knock levels exceed the threshold, this means that the engine is suffering from knock. |
| 06:12 | So how we're going to approach tuning the ignition timing here on the road is a little bit more complex than on the dyno. |
| 06:19 | Again, as we've discussed, we don't have feedback on the engine torque and power. |
| 06:24 | And the way we're going to approach this will depend on whether the engine is knock-limited, which is to say that the engine begins to suffer from knock before we reach MBT, or whether the engine is not knock-limited. |
| 06:39 | In my experience, around about 95% of the engines I tune, particularly those running on pump fuel and those that are turbo-charged will be knock-limited. |
| 06:50 | Now if this is the case of the engine you're tuning, then the results we can get on the road actually are very much the same as what we can get on the dyno, that knock threshold, the point where the engine begins to knock, that ultimately limits how much timing we can put into the engine. |
| 07:07 | In fact, we need a safety margin, we don't want to have the engine running right on that brink of detonation. |
| 07:14 | So if we're tuning an engine that is knock-limited, we can advance the timing under full power slowly until we find the knock threshold, and then retard the timing slightly to give us a safety margin. |
| 07:27 | So that will give us results very similar to what we see on the dyno. |
| 07:31 | There is one difference here to how we apply these changes, though. |
| 07:36 | If we find from our base ignition table that at one particular RPM, for example, the engine will take, let's say, an additional four degrees of ignition timing before we get to the knock threshold, what I'd do, rather than simply applying that change only at wide-open throttle, if the engine at that particular RPM range wants more ignition timing at wide-open throttle, there's a pretty good change that the engine will also want more ignition timing at lower load, at part throttle. |
| 08:10 | So instead of just advancing the timing at wide-open throttle, I'd also extrapolate that change and apply the same change at lower load values. |
| 08:19 | Now this does become an iterative process, because if we advance the timing in those lower load areas of our ignition map, we do want to go and revisit those in steady state and ensure that the engine now isn't suffering from knock. |
| 08:34 | In a lot of cases we'll find, though, even with an engine that is knock limited at wide-open throttle, we may find that at lower load values, at lower throttle openings, the engine won't be knock-limited and we could end up with the ignition timing over-advanced, and this is really why we can't hope to advance the timing until the knock threshold at lower load values. |
| 08:59 | So this is going to give us the best possible result that we can hope to achieve if we're going to be tuning our ignition table on the road or racetrack. |
| 09:09 | It may not be as good as what we can get on the dyno, but this is a compromise we need to accept if we're going to be performing our tuning on the road or track. |
| 09:20 | Now the second category of engine is a little bit more tricky to tune the ignition timing, and I wanted to discuss that now. |
| 09:28 | So if our engine is not knock-limited and we'll often find this'll be the case on the engine running a very high-quality fuel such as race fuel, or perhaps E85. |
| 09:38 | In these instances, we may not be able to make the engine knock at all, regardless if we're at high load or low load. |
| 09:48 | In these cases, we can't advance the timing to the knock threshold, obviously, and there's a risk that we could end up over-advancing the timing. |
| 09:57 | While the engine won't be suffering from knock, it's not going to be detrimental to the engine, we can find if we over-advance the timing that we end up with less torque than the engine could be making at MBT. |
| 10:11 | And in these cases, with this sort of engine, we have no option but to be conservative with our ignition table. |
| 10:19 | We can't find MBT, so we have no option and we need to accept here that we might be leaving some power on the table on comparison to what we may be able to achieve on the dyno. |
| 10:33 | So at this point, we've got our engine completely tuned. |
| 10:36 | We've gone through the steady-state tuning process, we now know how to apply the steady state tuning process that we use in the dyno tuning section of the course if we're on the road or track. |
| 10:48 | We've also looked at how we can apply the full-throttle ramp run tuning process that we look at on the dyno out on the road or track, and we've got to a point where we should have a completely tuned engine. |
| 11:01 | The last step in our 10-step process of course is to optimize and confirm the tune out on the road or track. |
| 11:09 | Of course if we're doing all of our tuning on the road or track, we've already done this. |
| 11:13 | So at this point, essentially, our tune is complete. |
| 11:15 | We should have an engine that provides good power and torque, good throttle response, good fuel economy, and most importantly of all, good reliability. |
| 11:25 | As with all of our courses, if you do have any questions, please ask them in the form below, and I'll answer them in the forum. |
