Practical Reflash Tuning: Step 6: Confirm Calibration on the Road
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Step 6: Confirm Calibration on the Road
26.20
| 00:00 | - Now that we've completed our dyno tune, we've got the car off the dyno, I'm ready to go ahead and do a road test. |
| 00:05 | Some of the things I'm looking to confirm on the street are that the driving behaviour is acceptable in terms of smoothness, feel and of course making sure our fuel trims are still appropriate. |
| 00:17 | Depending on the type of dyno you're using, you may find a significant shift in fuel trims or other behaviour when switching from the dyno the road. |
| 00:27 | So that's why we double check. |
| 00:29 | So let's head out, we'll do our first test loop and check things over. |
| 00:33 | Got our software logging and we're ready to head out. |
| 00:41 | So at this point, just doing some gently normal driving, everything's feeling great so far. |
| 00:52 | It's actually quite cold here, we're in the northern United States in the middle of December so with the amount of torque this thing puts out, on these typical street tyres, we're going to be hard pressed to put so much torque down today but what we're going to mainly focus on is drivability. |
| 01:14 | Cause we've essentially performed all of our full throttle tuning on the dyno, that's all good to go, really looking for anything else that we might have missed on the dyno or can improve upon that doesn't involve full throttle. |
| 01:29 | So as I'm driving, one of things I'm thinking about since this is a drive by wire application is how does the engine respond to my accelerator pedal inputs? Does it provide the output I'm wanting under all conditions? Or perhaps do I want a little bit more response in some areas, maybe a little less in others and just keep that in mind as you're driving because again, this isn't necessarily something that's right or wrong across the board, this is more of a driver preference thing so get a feel for it, see what you think and that way when you go back to look over not only fuel trims, you can think about making potential changes to the driver demand tables which would impact that behaviour. |
| 02:24 | Sure does sound good though. |
| 02:31 | Alright at this point, I'm going to drop into manual mode and the reason I'm doing that is this way I can get through a broader range of engine speeds without going exceedingly fast. |
| 02:48 | So still cruising down the road, about 35, 40 mph but now I'm up to about 3000 RPM, cruise there for a little bit, that way we'll gather more data in that area. |
| 03:06 | And giving little bits of increased accelerator pedal position, backing off a little bit, just moving through different areas of RPM and load. |
| 03:17 | And that way we'll just gather a bigger picture of vehicle behaviour under a broader range of conditions, give us more data and more range of data to look through when we cut back from our quick test drive. |
| 03:33 | Alright now I'm going to go all the way down into second gear. |
| 03:37 | That gets me up to about 4000, now 4500 RPM. |
| 03:43 | Check that area briefly and then go for the next gear to bring the RPM back down. |
| 04:00 | So again when you're on your test drive, anything you can do to vary engine conditions as much as possible is prudent. |
| 04:06 | That includes vehicle speed, engine speed, different gears, different accelerator pedal positions, different driving behaviours all around. |
| 04:14 | That way you get a really full picture of what's going on with the vehicle, make sure you got everything checked out before you wrap things up. |
| 04:25 | Alright so we got just a little more speed there, little more load, everything still feels really smooth so I'm quite happy at this point but at the end of the day we gotta go back and look and see what the data says. |
| 04:47 | So I'm incorporating some small windy little roads for low speed and then some broad multi lane roads to get up to a bit higher speed. |
| 05:06 | Alright I think I've got a pretty good amount of data so I'm going to start heading back. |
| 05:15 | That way we can stop and take a good look at it. |
| 05:22 | Well it looks like we've been caught out by a passing train so, see what I've got right now. |
| 05:29 | Looking pretty good, like in a transient condition coming off idle a bit here. |
| 05:37 | We've got a bit of a positive trim but at the same mass frequency, we also have negative so looks like a bit of a transient, unlikely we can really improve upon that and that's OK because it actually feels quite smooth there so not an issue. |
| 06:01 | Other than that everything looks great. |
| 06:04 | Nice small trims, that's what we want to see. |
| 06:05 | Tiny bits of knock retard at some moderate loads, we'll give that a closer look when we get back. |
| 06:13 | So back to the shop and we'll get a better look at this data. |
| 06:18 | So now that we're back, found a nice spot to stop, going to stop our log. |
| 06:27 | I'll save that as test drive 1. |
| 06:37 | And let's take a look at those fuel trims. |
| 06:39 | So at this low RPM area here what we're seeing is as we come off idle, so in this low RPM column here, we're hitting a bit of a positive trim but as soon as we really get any airflow moving, as soon as we really get into driving, those trims get very small, some positive, some negative, as long as we're seeing a net effect of the fuel trim being surrounding zero, there really isn't much room for improvement in terms of the MAF scaling portion of the airflow calculation equation. |
| 07:17 | So we know that we have the virtual VE speed density system functioning in this area as well as the MAF and here if you see a situation like this where at a given mass airflow sensor frequency, say 3150, we have some negative numbers as well as a positive number, there really isn't something you can do at that given point to add or subtract from the MAF scaling and correct both a positive and a negative fuel trim. |
| 07:50 | So in reality, there really isn't room for improvement there, even though we are seeing values that are a bit far from zero such as a 7 or a 10 here. |
| 08:00 | And again, really when it's a transient like that, it's not of much concern. |
| 08:05 | And then looking down at higher airflow areas, as the vehicle settles into higher airflow, more steady state conditions, it looks really really good, these numbers are quite small, most of them +/- 5% which is fantastic. |
| 08:22 | Another thing I'm going to look at is my long term fuel trimming because the long term fuel trim gives a great indication of areas where perhaps we've actually got it a little bit wrong and for the most part, we need to shift the MAF scaling just a little bit. |
| 08:38 | So in this case, here, we see a bit of a negative trim in a very small area, so 1716 to about 1800 Hz, let's see if there's any other areas like that. |
| 08:59 | No, extremely minimal long term trims everywhere else so in this area, let's go back to our long term plus short term trim and see what that looks like. |
| 09:14 | OK so this is that area where for the most part, we're a bit negative, then we jump a bit positive as we come right up off idle and some of that is due to the automatic transmission as well. |
| 09:26 | But it looks like we probably could take a tiny bit out of the MAF scaling right in that spot, that said there were times on the dyno when we had the vehicle idling for a bit where those trims would actually trend positive so because they're small, because I've seen that behaviour vary a little bit and this is actually quite common, especially on a forced induction application, it can get quite heat soaked in the engine bay. |
| 09:53 | So if the idle wanders a bit sometimes from a slightly negative trim to a slightly positive trim and you're really for the most part keeping within that +/- 5% window, certainly well within the +/- 10% which is still great, we're probably good to go as it is. |
| 10:13 | So next let's look at the spark retard that we caught on our test drive. |
| 10:17 | It looks like it's really centred in the moderate load ranges, so not at light throttle, not at idle, certainly not at full throttle, because we already dialled that in on the dyno. |
| 10:28 | But let's see what's going on here in these moderate load ranges because I want to confirm whether this was actual knock or just a knock retard monitored without actual knock events occurring like we saw at these RPMs on the dyno during our full throttle pulls. |
| 10:47 | In order to do that, I'm going to quickly zip through my log and see what the actual behaviour was at those times. |
| 10:55 | So I'm going to use the RPM trace at the bottom here just to jump to some areas that I can tell might correspond with this behaviour. |
| 11:05 | So I've jumped to one here, and then if we go up here, I see the knock retard and total knock retard. |
| 11:16 | It is ramping up towards the values we were seeing during full throttle pulls so let's go ahead and check, yep so our knock retard per cylinder showing zero actual knock in that area. |
| 11:32 | So it really seems like this is an area that is perhaps sensitive and GM's chosen to indicate that as such but as long as we're not seeing actual knock, really not of a concern at this point. |
| 11:51 | So I'm just going to check a few other areas where that's occurring. |
| 11:56 | Here's another one. |
| 12:00 | And I'm just gradually scanning through and watching my knock retard per cylinder values. |
| 12:07 | All zeros, alright let's check a few more. |
| 12:12 | Here's another section. |
| 12:17 | All good, so at this point we've covered everything that I would really like to cover in terms of confirming the tune, making sure the fuel trimming behaviour, making sure the knock behaviour is as desired, just like it was on the dyno when we wrapped up there. |
| 12:34 | At this point, one thing we could do to take it a step further is talk about the driver demand torque setting that I mentioned on the test drive. |
| 12:43 | So with that setting, we can manipulate the engine output based on the driver input on the accelerator pedal. |
| 12:52 | But what might we want to do there? Again we might want to make increased response at a certain RPM or accelerator pedal input position or perhaps less if we felt like the vehicle lurched forward perhaps more than we were expecting. |
| 13:07 | In this case, I can't really say that there was anything I didn't like but just as an exercise, I'm going to give you a demonstration of what you might want to change if that suits your fancy. |
| 13:19 | In terms of driver demand torque tables, there are a few on this vehicle so we have normal, winter/4WD, of course this vehicle does not have 4WD and that's a good example of where sometimes the labels don't necessarily apply specifically to your vehicle in the way you think they would, however they may actually come into play on the vehicle. |
| 13:41 | So it's good to check them all over. |
| 13:43 | Next we have Sport/Tow/Eco and then a reduced power mode. |
| 13:49 | Now let's look at reduced power mode first and compare it to driver demand A which is typically the one that takes effect most of the time. |
| 13:59 | So as you can see, at accelerator pedal 100%, the values in the A table are dramatically higher than the reduced power demand table. |
| 14:13 | So even at low accelerator pedal positions, values here are also dramatically lower. |
| 14:21 | So this is typically a table that will only come into play when a fault is at play. |
| 14:27 | So let's just leave this one alone. |
| 14:30 | I really suggest that, it's essentially a safety measure so I never want to touch that table. |
| 14:35 | Next, let's look at the sport table, compared to the A table. |
| 14:46 | And typically if we're going to see a change in something like this, they're both probably going to offer full power at 100% accelerator pedal, however at moderate or mid throttle, one of them might provide more or less than the other. |
| 15:02 | So we'll just confirm at 100%, values are looking essentially the same at a glance but let's see what happens if we look at the 40% row. |
| 15:20 | OK and in this case it's looking like they're actually the same so what I'm going to do is copy the A tables, paste it into C and as we discussed earlier, when a table has been changed, it will be changed in terms of the highlight colours, so this blue would have turned a colour, I'll give you an example. |
| 15:51 | Right so now that I've changed that, this has gone red, change it back, now back to blue. |
| 15:58 | So what that effectively tells me is these tables are identical. |
| 16:03 | Now that we've confirmed that, we also have a pretty good feeling that if we make a change to one, we likely want to make it to both. |
| 16:12 | What we don't want to do, especially in a driver demand table, is cause a situation where we get unintended behaviour, unintended acceleration or otherwise can be not only detrimental to the driving experience, can be cause for concern so if you're going to adjust these tables at all, do so with extreme caution and care and always check your work very carefully. |
| 16:37 | So let's look now at map B which is labelled winter/4WD and just see what the difference is. |
| 16:49 | Now straight away I can see there actually is a difference here. |
| 16:54 | And at 100%, I'm seeing values that are slightly lower here but slightly higher at a high vehicle speed. |
| 17:09 | Yep slightly lower again at lower speeds. |
| 17:15 | But higher at high vehicle speeds, very interesting, so that's not really what I would typically expect of a winter driving tune because the reduced torque on the low end isn't really reduced much and then the increase on the top end wouldn't really make a whole lot of sense for the winter, you wouldn't only want to run absolute maximum power at very high vehicle speeds, only in the winter. |
| 17:45 | So let's take a bit more of a deep dive here into the mid range. |
| 17:59 | From 24 to 40% pedal. |
| 18:03 | I'm just going up to 80 mph for now. |
| 18:09 | OK so in this area, we're seeing increased values in the B table on the low speed and reduced values at the higher speed. |
| 18:23 | So quite a bit different than what we're seeing at 100% accelerator pedal. |
| 18:31 | So really it just looks like the whole shape of this is dramatically different. |
| 18:36 | I don't know if this table is even active under any condition in this particular vehicle, really hard to say. |
| 18:44 | We do have this mode switch here which I'm going to change. |
| 18:48 | Now this is indicating that the vehicle has tour mode, sport mode, track mode and snow and ice mode. |
| 18:58 | So something to note there is it's quite possible that some of these but not all will cause a change in the driver demand table being used. |
| 19:09 | Some of them might change steering, suspension, something of that nature. |
| 19:14 | So it doesn't necessarily mean that we should be looking for four unique driver demand tables. |
| 19:22 | And in this case, we seem to have three exposed in our HP Tuners software, two of which are identical, one of which is different and really uniquely shaped. |
| 19:32 | So one thing you can do, and again with extreme caution, would be to take this driver demand B table and make a change which you can easily identify on a closed course in a safe location. |
| 19:49 | For example, let's say you want to figure out when you're in this B table. |
| 19:57 | So what you could do is take 28% accelerator pedal output and copy that, we're going to blend this all the way down just to copy those values into that whole section. |
| 20:17 | So essentially what would happen here is if you're at 28% accelerator pedal position or higher and you get up to about 50 mph, you're going to end up, regardless of pedal position, over 28% with only the output you would get if you were at 28% and anything less than that will continue to operate normally. |
| 20:40 | So this would allow you to get up to that speed with caution, then floor it and see if you get normal output or very reduced output. |
| 20:51 | And what that will do is kind of give you a hint that OK, I'm in this driver demand B table now and so essentially you would effectively try it in each drive mode, then see if you get the behaviour you're expecting or not and then you know which modes are associated with that driver demand table. |
| 21:11 | Now again, use extreme caution doing this at your own risk, you may not want to floor it into that area, you may want to gradually roll onto the throttle and just see if you're getting a gradual increase in torque as you roll it on further or if the torque plateaus at a very low level and that would be an even safer way to do it, on a vehicle that makes a significant amount of torque like this one. |
| 21:35 | Depending on your application, if it's a rather low torque application, you may need to reduce this down even further, for example maybe grab the 20% accelerator pedal output and bring that down. |
| 21:56 | And again we can interpolate down just to copy that whole area. |
| 22:01 | So in this case if your vehicle doesn't put out much torque, you could still at least tell the difference between what happens at 20% accelerator pedal position and let's say half or full throttle. |
| 22:14 | So again if you're going to get into this, I can't stress enough how much you have to use extreme care, do it on a closed road, do not do this out on the street. |
| 22:23 | In our case, I'm really happy with what's going on so I'm not going to dig super deep on this but once you've identified which mode each table is active in, then you can get in there and make the changes to have the desired effect in terms of your driving behaviour that you're hoping for, based on your personal preference. |
| 22:42 | If you determine you'd like to increase the torque output available at a given vehicle speed, and a given accelerator pedal position, here's what you might do. |
| 22:51 | For example, let's say at 20 to 30% accelerator pedal, between 30 and 40 mph, the vehicle doesn't really feel like it's responding as much as you would like. |
| 23:05 | So what you can do is make a modest increase in the torque that we're demanding under that condition, for example we can do 3%. |
| 23:17 | And then as we've discovered in stock form, driver demand table A and C have the same values so what I'm going to do is I'm going to maintain that consistency and I'm going to copy the entire table and paste the entire table into driver demand C. |
| 23:36 | Now I could have just selected this little area and pasted that over but since I want to make sure the entire tables are the same, it's just easier to select it all, paste it all and know that you're good to go. |
| 23:48 | After that, you would shut the car down, turn the ignition on, write calibration, go through the reset process, then get back out in a closed course this time, not out on the street, and test and see if you get the desired effect that you were hoping for. |
| 24:05 | So that's an iterative process, something that you would do over and over until the car drives exactly as you'd like. |
| 24:12 | Because driver demand torque really comes down to personal preference, if it's something you want to do for yourself, for your own personal vehicle, that can be much easier. |
| 24:21 | If you're doing it for a customer, at that point you need to understand what they like and don't like about how the vehicle behaves before you make any changes. |
| 24:31 | What I like to do once I've completed my road test otherwise, is give the vehicle back to the customer, have them drive it for a week or two then come back to you and say look, this is what I like, this is what I don't like, can we do something to change that? In some cases, what they like is wonderful, what they don't like might not be something you can necessarily address. |
| 24:55 | For example, if it's a big turbo vehicle and they're saying, you know what, I wish it had a little less lag, maybe they shouldn't have got such as large turbo, there probably isn't a whole lot you can do about that. |
| 25:06 | But if they say look, when I'm going 30 to 40 mph and I apply about quarter throttle, the vehicle isn't really picking up as much as I think it should, that's a chance where you could potentially just get in and make a small change to the driver demand table to give them what they're looking for. |
| 25:24 | It's all about that conversation, that back and forth and also finding ways to ask your customer questions that give you the feedback that you need to make the changes that are going to make them really happy. |
| 25:37 | Now that we've completed our road test and final review of datalogs, we're going to go ahead and take one more step. |
| 25:44 | I'm going to save the file, even though we haven't made additional changes, and I'm going to call it tunedfinal-93 as a reminder of the fuel octane present. |
| 25:57 | Now the reason I do that is perhaps I won't go back to this tune for a year or two and if I go back in that folder and I just see iteration11, I might be uncertain whether that was the final product or not, but when I see the name tunedfinal, I know for certain, that was the completed and final tune. |
| 26:15 | Thanks for joining us, we hope you enjoyed this worked example and we hope to see you again soon. |
