Practical Standalone Tuning: Step 7: Steady State Fuel Tuning
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Step 7: Steady State Fuel Tuning
18.56
| 00:00 | - Now that we've got our idle under control, we can move on with the actual tuning process and we're going to begin with our steady state fuel tuning. |
| 00:08 | What we're going to do here is use our load bearing Mainline dyno to control our engine RPM and given that our main VE table is simply based on throttle position, it's going to understandably be very easy to move through the majority of that table accessing each site individually. |
| 00:25 | We're then going to be using our little graph display here which shows us the difference between our target air/fuel ratio or lambda and our measured lambda and we're going to make corrections until we get on track. |
| 00:36 | There are a variety of ways that we can make those changes, we've already looked at the different options avialable. |
| 00:41 | One of the ways I will be leaning on here is to use the quick tuning or auto tuning functionality, by pressing the L key on the keyboard, this will make a change to the current cell based on the measured lambda compared to the target. |
| 00:55 | So this does speed up the tuning process. |
| 00:58 | What's really important before we do that though is to make sure that we are central in the cell we want to tune. |
| 01:04 | We don't want to be interpolating between different cells. |
| 01:06 | It's also really important to make sure that our engine coolant temperature and our inlet temperature are in a normal operating range otherwise we could be adversely affecting our tuning conditions. |
| 01:17 | So what we're going to do here is start by getting our engine up and running at let's say 1250 RPM, we should be able to apply a reasonable amount of load here and we're going to go through our 1250 RPM column. |
| 01:29 | Also important to mention here that when we do this we want our boost controller turned off or our wastegate duty cycle set to 0, we want to start on the minimum wastegate spring pressure, the lowest boost we can get to. |
| 01:42 | So let's get ourselves up and running on our dyno now. |
| 01:45 | Alright so now as I've got the fan running on the dyno, and we're just applying a little bit of load trying to come up onto the set point on the dyno we can see that our air/fuel ratio is incredibly lean, we're right off the chart here. |
| 01:56 | So this isn't unexpected so we can again quickly correct this with some block changes here so let's just highlight the entire block and add 6 to that block which should get us at least a little bit closer. |
| 02:09 | We're still a little bit lean there so let's just make a guess there, go to 55% and straight away we can see our lambda comes back into the zone so let's just get ourselves down to our 1250 RPM column. |
| 02:34 | And what we want to do is start by bringing ourselves down as low in the throttle position or load as we can while still maintaining wheel speed and that's about as low as we can get down there, 2.5% throttle, much below that we're actually going to find that the car just slows down so we'll get to that cell there, we can press the spacebar to jump straight to that cell and we can see that we are quite rich there. |
| 02:55 | So again, variety of ways we can make that change but we're just going to use the L key there, get us onto our target. |
| 03:01 | Now we might find that the L key doesn't correct the entire error in one hit so if that's the case, we can see that our lambda is just stepping slowly up towards our target and we are moving around a little bit, I can't quite get into that cell. |
| 03:15 | It's alright, we'll talk about that and what we can do to address that shortly. |
| 03:19 | We're getting pretty close there, I'll leave that for the moment, we'll come up to the first cell that we can truly get into the centre of while running and we can see again we're a little bit rich, about 0.91 lambda in that cell so we'll just use the L key and two presses on that should pretty well get us onto our target there so really quick and easy way. |
| 03:38 | Remember it's not the only way, you can manually make these changes but it is quite effective. |
| 03:43 | So what we'll do now is we'll bring our throttle up to our next set point, 10%, our next break point I should say, 10% and we're just going to repeat that process, now you can see there, as I move up into that point, 10%, we have moved a little bit lean so we do need to be mindful of this. |
| 03:58 | At this point because I'm using so little throttle, I'm not specifically too worried about being at 1.1 lambda but of course if we were in boost, then I would be considering maybe backing out of the throttle and making a change. |
| 04:10 | So let's just use our L key again here and we'll get ourselves onto our target. |
| 04:14 | But what we're going to do is learn from that and we're going to apply some more changes to the cells up above. |
| 04:21 | So we've gone 49%, 64%, you can see 12.5% throttle we're back down to 55% so it's not likely to be correct obviously so let's take a bit of a stab in the dark here and let's just enter a value of 68%. |
| 04:33 | We'll come into the throttle, come up to our 12.5% throttle point and we can see that that guess was actually pretty good, we are a touch lean but we're not too bad. |
| 04:43 | So here we'll just use the L key, again making sure that we're nice and central in the cell before we make that change. |
| 04:50 | And we're on our target now so again learning from what we've seen there. |
| 04:54 | We've gone up around about 6-7% in our VE there so let's make a change here, let's go to 78% for our 15% throttle cell. |
| 05:04 | Come up in our throttle opening and our guess was pretty good there, we're right on our target. |
| 05:10 | So just going to continue here and proceed through our 1250 RPM column, just guessing ahead, adjusting the guess that we've made until we're on target and repeating the process so let's go ahead and do that now. |
| 05:34 | Alright so we've got our 1250 RPM column complete there. |
| 05:37 | Except of course down in this very low throttle position which we can't really adequately access on the dyno here. |
| 05:44 | So there's a few things that I wanted to just point out here so first of all, this really just goes to reiterate what I was talking about with the non linearity of the flow through the throttle body. |
| 05:55 | So we can see from 5% throttle which we were able to tune properly in steady state, 49% VE and we see that we really quickly step up, 64%, 71, 78, 84. |
| 06:07 | Now look at what happens once we get above about 40, 50% throttle. |
| 06:12 | We see 96, 98, 100, 101 then 102. |
| 06:16 | So we see that the VE tapers off so that's just to do with that airflow through the throttle body which is why we need that additional resolution down at light throttle. |
| 06:27 | So what we know is that we could not really get into our 2.5% throttle area. |
| 06:34 | That's OK, this is an area that we will need to address when we're out on the road and we're going to find that while on the dyno we don't have enough RPM or power or torque I should say really to keep the engine rolling on the dyno and maintaining RPM at such a light throttle opening, particularly in overrun coming down a hill we will be able to get access to those areas so that's an area where we are a little bit limited on exactly what we can do on the dyno. |
| 07:01 | But what we can do is just sort of extrapolate the trends that we are seeing there down into these other areas because of course we can expect that these areas won't be right either. |
| 07:12 | So again we're just going to take a rough stab at this, we're not going to be accurate here, it's not going to be perfect but it's going to be close. |
| 07:21 | What we're going to do now is take our 1250 RPM column, I've clicked on the top break point there at 1250 RPM, that highlights the entire column, control C, we'll come over to our 1500 RPM, control V pastes that in. |
| 07:35 | So again we're going from low RPM to a slightly higher RPM, we could rightly expect our volumetric efficiency to increase so what I'm going to do before we actually move to that higher RPM, let's just take a bit of a guess at what that might be. |
| 07:49 | And we'll start with 3%, so we'll enter a value of 1.03, use the asterisk key and that's going to increase the fuelling, or the VE at 1500 RPM. |
| 07:59 | Alright let's get ourselves up and running at 1500 RPM and we'll see how close we are. |
| 08:05 | Alright so initially going into the 1500 RPM column, I want to use a little bit of throttle, we can see we're sitting at about 20% there. |
| 08:11 | And what I want to do is make sure I'm in an area where we were able to tune accurately at 1250 RPM. |
| 08:17 | Looking at the air/fuel ratio plot, that 3% guess was actually pretty much on point, everything's looking good, that's not always going to be the case of course and what I want to do before we get down to being pinpoint accurate on individual cells, I'll actually start here by just making an overall adjustment to the entire column, if I find that I'm too rich or too lean. |
| 08:38 | In this case though, as I've said, we are pretty good so let's just come back down to as low in the load as we can get while maintaining RPM on the dyno, we'll see if we can get down to, we should be able to get down to our 5% column, cell, that's about as low as we're going to get there. |
| 08:56 | We can see that we are a little bit rich there so what we'll do is we'll just use the L key, pull a little bit of fuel out there, a bit of VE out of that cell in the table until we're on our target. |
| 09:07 | Now we're pretty much there or thereabouts right now so what we're going to do now is just come up to our next cell, our 10% cell. |
| 09:15 | Looking at our 10% cell, we're pretty close there and this is another aspect we tend to see with our TPS based volumetric efficiency maps as well, at lower throttle position at higher RPM we tend to need to make more dramatic changes to the numbers. |
| 09:34 | So we're on our target there using the L key, we'll keep coming up here. |
| 09:36 | And at the moment I haven't really talked too much about our ignition timing. |
| 09:40 | Obviously I've said that we're going to be focusing on our fuelling. |
| 09:43 | And the numbers that I put in the ignition table, I know from experience, these should be pretty safe but we never want to take the gamble that we are right so it's always a good idea. |
| 09:55 | Even when we are adjusting the fuelling table, always want to be listening to our knock headset, making sure that the engine isn't suffering from knock. |
| 10:02 | So the only reason I'm doing that at this stage is I'm already familiar with this engine and we are presenting here a worked example so for simplicity here, I'm not using the knock headset but I always advise that you do so. |
| 10:12 | Alright we're up to 25% here and we've seen that changes I needed to make here as we've gone are very very small and this is just again a benefit of copying that column across. |
| 10:24 | While we are doing this as well, we also want to be mindful of our engine coolant temperature, just making sure that our engine temperature isn't doing anything silly, we're sitting at 79° at the moment so relatively cool here, likewise our charge temperature 61°. |
| 10:37 | Alright so really not needing to make much in the way of changes here. |
| 10:42 | And I'm not expecting that to change dramatically as we go up to wide open throttle. |
| 10:49 | Alright so everything's looking pretty good there, what we'll do, just at wide open throttle, we are just a touch rich so I'll just pull a little bit of fuel out there. |
| 10:59 | Now you notice that we did actually start here down at 5% throttle and we did need to pull some fuel out, some VE out. |
| 11:08 | We went from 49% down to 44% so we've pulled out about 5% there. |
| 11:13 | What we want to do now is really extrapolate that same sort of change we've seen down into this lower area that we again can't get to. |
| 11:21 | Again we're not going to be absolutely pinpoint accurate here, we don't know that we're going to be quite right but it's a safe assumption that we are going to need to remove some VE from this section as well so we'll just make that similar size change around 5%. |
| 11:36 | OK we're done with 1500 RPM, control C and we'll control V copy that over to our 2000 RPM column and we're going to go through the same process so we're going to speed this up a little bit now. |
| 11:49 | We're going to do this through to 4500 RPM. |
| 11:51 | Particularly as we get out to the higher RPM regions, probably between 3500 and 4500, that's where we're going to start to be building up a little bit of boost so we need to be a little bit mindful of managing the heat. |
| 12:03 | Particularly in the higher throttle settings so we want to be in those settings for as little time as we possibly can and we may need to actually bring the engine back to idle occasionally and allow the temperatures to stabilise so we'll just play that by air and see how things go. |
| 12:17 | Particularly at the higher throttle openings as well we do need to be a little bit more mindful of knock although again as I've mentioned, we should have a really safe conservative ignition table, we never want to take that for granted. |
| 12:29 | Really important, particularly when we get into those higher RPM areas, as we increase our throttle opening and move further into the boost, if we do find that our air/fuel ratio is lean, we don't want to sit there making changes. |
| 12:41 | It's very easy, pull your foot out of the throttle, come back into vacuum, even come back to idle, make the appropriate block changes to that area to safeguard everything and go back and check again. |
| 12:52 | We always want to be tuning from a rich target and leaning it out towards our desired air/fuel ratio than moving into an unchartered area and finding out that we're lean, that's the safe way of tuning. |
| 13:02 | Alright so let's go ahead now and we'll get up to 2000 RPM. |
| 14:32 | Alright we can see there, we've just had our warning for our engine coolant temperature come on at 100° and I've already taken a little bit of a breather out here previously just to allow the temperature to come down so this is just pretty normal with running any car under steady state conditions. |
| 14:48 | Particularly as I mentioned as the RPM comes up and the load comes up, we're creating a lot more heat so we do need to be mindful of managing that. |
| 14:54 | Just going to take a moment here and allow that temperature to come back down. |
| 14:58 | Alright we've got our temperature back under control now so we're going to continue and do our last row here, copying our 4000 RPM column across to 4500 RPM. |
| 15:08 | Now as I've been going here, I've just been building up a bit of a picture of what changes need to be made. |
| 15:13 | And we're seeing a general trend whereas the throttle position is lower, we're pulling VE out again, that's pretty typical with a TPS based VE map like this. |
| 15:25 | At higher RPM we're seeing pretty much a plateau at the moment, we haven't seen much change so for this next 4500 RPM column we're actually not going to add any VE, we'll just go into that column and see how it looks, let's get going and complete our last column. |
| 15:53 | Alright so at this stage, we've completed our steady state fuel tuning out to 4500 RPM and as we can see from our graphical view of our VE table here, we've got pretty much what I would expect to see. |
| 16:05 | Relatively smooth trends and shapes to that table. |
| 16:09 | And this is a good place to just stop and if we've got any big obvious holes that just don't follow the trends of the surrounding cells, go back and have another look at those individual areas and see if maybe you've got a bit of a mistake going on in there. |
| 16:22 | Now we can't just finish off here though, what we are going to do is just extrapolate the shape of that table out into the untuned areas and make some educated guesses at what we might likely see in those areas as well. |
| 16:35 | So we'll start by copying the 4500 column out and we'll go all the way out here through to 8500 RPM. |
| 16:49 | Alright so we've got that done, now we can see just in the general trend here, the shape of the table that we have seen, we've got a bit of a bump up at 4500 RPM. |
| 16:59 | Now it's isolated, we don't know if that's going to continue but what we will do is start by just increasing the fuelling a little bit as we move out into those unchartered areas and we might not be right but again always safest to begin a little bit rich and need to pull fuel out than find that we're lean as we move into those unchartered areas so what we'll do is we'll start by increasing the fuelling at 6000 RPM and now we'll go between 5500 and 6500 RPM, add a little bit of VE there and then finally we'll do the same out to 7000 RPM and down to 5000 RPM. |
| 17:33 | So again just trying to add a little bit of shape to that table. |
| 17:38 | While we're not strictly going to be running out at 8500 RPM, we will also incorporate 8000 and 8500 RPM and just pull a little bit out, again we're expecting that the VE would be dropping away at that point. |
| 17:52 | So it's not going to be perfect but it's going to be a pretty good starting point. |
| 17:55 | What we can also do here is address our VE numbers down in this unchartered area that we can't get to, we can't really steady state tune the engine that well at 1000 RPM so what I'm going to do is start by just taking note of the VE values at idle here so we've got 34% and we're actually a little bit richer than our target but we're close enough so what we'll do is we'll take our 1250 RPM column and we're just going to copy that across and again for the moment we're not going to be really running in this area so it's going to be close enough. |
| 18:28 | What we can then do is just take our idle areas, we'll pick that up to 2.5% throttle and we'll just again increase those numbers back to where we were. |
| 18:39 | So it's going to get us a pretty good starting point for our table, we're going to remember to store that change by pressing F4. |
| 18:47 | Steady state fuelling is done, we can now move on with the next step of our process. |
