Practical Reflash Tuning: Full Power Tuning
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Full Power Tuning
07.45
| 00:00 | - The last step of our tuning process on the Dyno is to perform wide-open throttle full-power ramp runs, and in this section, we're going to see how we can replicate that out on the road or the racetrack. |
| 00:12 | Now, this part's actually incredibly simple, because we are just going to be performing a wide-open throttle acceleration test from low RPM all the way through to the engine rev limiter, and we're going to be data-logging, or scanning, the results from the ECU while we perform this test. |
| 00:29 | After the test, we're simply going to come back to the pits - or, stop on the side of the road in relative safety, and we can have a look at the results from our scan data and make decisions on what we're going to change in our calibration next. |
| 00:44 | Now before we head out on the track, we'll just talk a little bit about the gear that we're going to use to perform our testing, and whereabouts we want to perform our testing. |
| 00:53 | Now, first of all, we really want to use a long section of straight road. |
| 00:58 | We don't want to be worrying about negotiating curves or bends or any bumps in the road during this test, more so if we're testing a car that's quite powerful. |
| 01:08 | We really want to be concentrating on keeping the car straight on the road so we can stay at full throttle. |
| 01:15 | The other aspect of this obviously involves the speed that we're going to be performing our testing at, and this comes down a little bit to the gear we select. |
| 01:24 | Now, what we want to do is perform our testing in a high gear, or a relatively high gear, so that, first of all, the engine is put under sustained high-load, and this is going to give us realistic results in terms of our air-fuel ratio data, as well as, if the engine is going to suffer from knock or detonation, it's more likely to do so under sustained high-load. |
| 01:50 | On the flip side of this, if we were to perform our testing in a low gear such as first or second gear, the engine will accelerate so quickly through the rev range, that it's not really applying much load to the engine and our results may not be truly indicative of what's going to happen in a higher gear. |
| 02:09 | Now, the other aspect of this, of course, is that, in a powerful car, with the torque multiplication that we'll see in, perhaps, first or second gear, we're going to end up with the car being much more likely to suffer from wheel spin, and obviously, those are going to negatively affect our results as well. |
| 02:29 | So, in our instance, with our ZL1 Camaro here, super-charged v8, we're going to be performing our acceleration test in third gear. |
| 02:37 | This is going to give us a good compromise between not overpowering the tyres near the start of the run and also, not reaching excessive speeds at the top of the run. |
| 02:47 | If we move to a higher gear, obviously this is going to result in a higher terminal speed when we get to the end of our rev range or reach our rev limiter, and this is another aspect we need to consider, particularly if you're going to be performing your testing anywhere where there are speed restrictions, obviously you need to keep this in mind and make you sure you stay within the speed restrictions in your area. |
| 03:12 | Okay, let's head out on the track and we'll see how we can perform our testing. |
| 03:16 | Now, as usual, before we perform our testing at the wide-open throttle, we want to make sure the engine isn't suffering from heat soak, so it's sensible to drive the car for a few minutes or a couple of laps, to allow the engine coolant temperature and intake air temperature to get down to normal levels. |
| 03:32 | Now, I've just selected third gear, just coming on to the longer straight of the track, and I'm just going to go smoothly to full throttle and scan the data. |
| 03:53 | Okay, so that's our first full-power acceleration test completed there in third gear. |
| 03:59 | Now, during the actual acceleration test, we can concentrate solely on controlling the car. |
| 04:06 | I've got a wideband air-fuel ratio metre suction-cupped to my windscreen, and I can view this out of my peripheral vision which allows me just to confirm that the air-fuel ratio is where I want it to be. |
| 04:18 | If I see the air-fuel ratio either move excessively rich or excessively lean during the acceleration test, I can simply back off the throttle, abort the run, make the necessary changes to the calibration, and then try again. |
| 04:32 | There's no need to stay in an acceleration test under full throttle if the air-fuel ratio is deemed to be dangerous. |
| 04:41 | Now that we're back in the safety of the pits, let's analyse our data log and see what changes we may want to make. |
| 04:48 | First of all, let's look at the actual run we've made and we can see that if we look at our engine RPM and, at the point where we first went to full throttle, we've gone from about 2500 RPM. |
| 05:00 | At the end of the run, you can see that we hit the rev limiter at about 6200 RPM. |
| 05:06 | The green trace here shows our throttle position so we can see exactly where we were at full throttle. |
| 05:11 | So, exactly the same as when we're on the Dyno, the two aspects we're looking at here, first of all, is our air-fuel ratio, and secondly, our ignition timing. |
| 05:20 | If we analyse our air-fuel ratio, we can see that, for the majority of our run, air-fuel ratio emission, air-fuel ratio emission lambda, very closely matches our target lambda. |
| 05:32 | We can see that, in particular, right at the very beginning of our run, the measured air-fuel ratio lambda is a little bit leaner than our target. |
| 05:42 | So in this case, we would pinpoint this particular area and go back into either our MAF calibration or our speed-density calibration, and make the appropriate changes to correct those errors. |
| 05:54 | Let's move on and analyse our ignition timing. |
| 05:57 | And what we can see here is that, in the middle of the run there, at about 4,322 RPM, we had a little bit of knock activity, and this is resulted in the ignition timing being retarded by 3.2 degrees to prevent that detonation occurring. |
| 06:15 | So again, just like when we're on the Dyno, we can use this information, our engine RPM coupled with our cylinder air mass, which we can see at this point is 1.36 grammes per cylinder, to make the appropriate changes to our ignition table. |
| 06:31 | So really, the process of full-power tuning is almost identical to what we've already looked at on the Dyno. |
| 06:39 | We're simply going to be making a full-power acceleration test through a gear, and then we're going to be using the data that we've logged or scanned, in order to help us optimise either our fuel delivery, in terms of our mass airflow sensor scaling, or speed-density calibration, and then, our knock retard, to help us calibrate our ignition timing if the engine is suffering from knock or detonation at any points. |
| 07:05 | So, at this point we should have a completely tuned engine that we've tuned from start to finish on the road or the racetrack. |
| 07:12 | Now, under our six-step process, the last step is to confirm our tuning out on the road or track, however, obviously if we've already performed all our tuning on the road or track, there's no work to do here. |
| 07:24 | We already know that everything that we've seen while we've been tuning, has been in real-world conditions, so at this point, our task's complete, we have no work left to do. |
| 07:35 | Now, if you have any further questions, as usual, please ask them in the form below, and I'll answer them in the forum. |
