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Practical Standalone Tuning: Step 9: Full Power Tuning

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Step 9: Full Power Tuning


00:00 - For our next step, we're finally going to get to a point where we can start performing some wide open throttle ramp runs.
00:07 Here primarily what we're going to be doing is optimising the fuelling as well as the ignition timing in these high boost areas.
00:15 And this is something as we've discussed, we don't really want to be spending a lot of time holding the engine under wide open throttle at high boost during the steady state tuning so this differs a little bit from how we'd deal with a typical naturally aspirated engine.
00:31 However given that while we haven't really tried to optimise our ignition timing out in steady state to full boost, we've got some conservative numbers in there, we have got our fuelling dialled in pretty accurately and that's going to give us a good place to start so let's just jump back into our software for a moment and just refresh ourselves on where we sit.
00:52 So finishing off the last section, the last step of the worked example we can see that we've got our ignition table dialled in and as we discussed here we haven't really done anything around the 200 kPa area that we're expecting to be operating in.
01:08 And I'm expecting with this turbo we should be there or thereabouts by about 3500 RPM.
01:13 So right now, we've got really conservative numbers, you can see the area that we were tuning up to around 120, 140 kPa, we've got still conservative numbers there but we've ended up dropping that back considerably as we've come up to that higher boost point, 200 kPa.
01:32 Again I know that I'm going to be running around that 200 kPa just because of the wastegate springs that have been chosen so we've got a nice conservative place to start with safe retarded timing.
01:42 At the same time, let's head back to our fuelling and we've tuned up to our 200 kPa in steady state, 4500 RPM.
01:52 What I'm going to do before we get started here is we are going to select the 175 kPa rows and above and what we're going to do is just add let's say 2% to those zones for the moment.
02:04 So again here what we're trying to do is start with a conservative fuelling and conservative timing.
02:09 Slightly rich so we've got some fuel that we can pull out to get to our target, slightly retarded on our timing so we can add some timing back in.
02:16 Conventionally in the timing map we would recommend starting by removing timing compared to what we found in steady state and of course as I've just explained, we didn't do that anyway, we didn't optimise to wide open throttle in the steady state tuning elements, that's why we're not doing that.
02:32 That sets us up in a pretty good place to get started.
02:34 Let's also head back across to the home menu here and we're going to be making use of the on board logging here which we can access over here on the right hand side under logging.
02:46 Now there are two ways to view a log file, we'll look at both of these as we go but essentially what is important to understand is that before we actually start doing anything that we want to review, we need to click on that start logging button.
03:00 That's going to then prompt us to enter a file name.
03:04 There's two ways we can do this, we can enter a file name if you want for something specific, alternatively the Adaptronic will automatically timestamp your file and that will be the file name so personal preference.
03:16 There's two ways of then reviewing the log file and we'll look at that more specifically once we get stuck in.
03:23 For now, let's head across to our dyno screen and we'll see how we've got that set up.
03:27 So on our Mainline dyno here we're going to be looking at three pieces of information.
03:31 The bottom of course we've got our power.
03:33 In the centre we've got our manifold pressure, this is coming into the Mainline dyno from the Adaptronic via CAN.
03:43 And at the top we've got our lambda, that's actually going to switch around once we start running, it's going to look more like this.
03:50 Now as you can see, I've also put a reference line in here, 0.75 lambda.
03:55 We're going to be targeting there or thereabouts once we're on full boost so this will just give me a quick visual cue if I am close to my target, allowing me to abort the run if we are too lean or progressively if we are too rich.
04:06 Likewise for our manifold pressure, we've set a reference line in there at 200 kPa.
04:11 Again just to give me a reference on where my boost is.
04:13 Remembering at this stage we do have an overboost cut as well and this is where that element starts to come in and become important, making sure that we're safeguarded, particularly if we're getting boost creep as the RPM increases.
04:26 Now obviously at this point we have tuned the engine under steady state to 4500 RPM so it would make sense therefore to perform our first ramp runs just out to that same point, we know that our tuning should be pretty accurate and this will then give us an opportunity to dial in our fuelling as required and also start to add a little bit of timing and see how the engine responds to that.
04:49 So for this, let's go across to our setup here and what we're wanting to do here is adjust our start and finish point.
04:56 Start point of this run, we're looking at about 1900 RPM, so that's absolutely fine.
05:01 The end point though, 7000 RPM, we definitely don't want to be out there for our first run so let's just dial that back to something a little bit more sensible.
05:10 Now while we have gone to 4500 RPM initially, there's nothing wrong with progressing out a little bit beyond that if you're comfortable with that.
05:20 For this I'm going to choose 4700 RPM so we're just starting to move into unchartered territory.
05:27 But there's nothing wrong with moving maybe 500 RPM past where we've tuned and this will give you a bit of a glimpse of what's going on out there and allow you to make any changes as you require, you obviously don't want to do your very first run all the way to 7000 RPM on the hope that everything's going to be right, that's probably not going to work out well.
05:44 The most sensible approach here is to be conservative, move slowly out into those untuned areas and address any errors in your fuelling as you go, obviously optimising your ignition timing as you go.
05:56 Alright with that being said, what we'll do is we'll get our fan up and running and we'll get our first run going.
06:03 So what we're going to do of course is come back into our tuning software here and we're going to press start logging.
06:09 For this I'm not going to enter a timestamp, enter a log name, I'll just use the timestamp.
06:14 Now it's also, while I'm here, just worth mentioning, you'll see that our lambda over on the right hand side, it's currently flashing red and sitting at around about 21.
06:25 Now we have picked up an error with a faulty lambda sensor onboard so what we've done here for the purposes of filming this particular step of the worked example, we're actually using a MoTeC PLM that's fitted to our dyno and this is fitted in a tailpipe extension in the exhaust system itself.
06:45 The problem with this, which is what we're seeing right now, is at very low airflows through the exhaust system, we don't get a good lambda reading so it tends to read lean.
06:54 This is not my preferred technique but in the approach of actually getting this worked example completed, we are going to progress using this.
07:04 I always recommend a lambda sensor that's fitted to the exhaust.
07:07 That being said, a tailpipe extension, as long it's a properly designed extension, is actually pretty good under wide open throttle conditions, where it suffers is at idle which is exactly what we're seeing now, and also cruise conditions again where the airflow through the exhaust system is relatively limited.
07:23 So I'll just point that out so you understand why we're seeing that moving around.
07:27 Alright with that being said, let's get our first run underway and again, while we're doing this, we're watching for our boost, we're watching for our air/fuel ratio and of course under normal conditions I'd also be listening to an audio headset so I could back off if I hear anything that I'm not happy with in the engine.
07:44 Let's get our run underway.
08:04 Alright so our first run complete there, actually it all looks pretty good.
08:07 We've got 252 horsepower at the wheels.
08:10 Importantly what we're looking for here is more what our boost and our air/fuel ratio's doing.
08:16 We can see our boost near the end of the run, we are on our target of 200 kPa so no overboost there, nothing to be worried about.
08:23 Our air/fuel ratio, our lambda's tracking down onto our target so actually everything straight away is looking really good.
08:30 What we'll do is we'll just come back into our laptop tuning software and what we're going to do is click stop logging.
08:37 Now again as I mentioned, two ways of having a look at this data.
08:39 The first way, let's click on log viewer here so this is the Adaptronic Eugene built in log viewer.
08:47 So we'll have to open that, it'll automatically open that log file and we'll be able to see the channels that we have chosen to view and that's them over here.
08:57 Now we've got a sort of a large outlook on the RPM which is the red trace up the top and then we've got the individual parameters being displayed so the log viewer, in my opinion, a little bit limited for what we're trying to do here.
09:14 And it's a little bit difficult personally for me to decipher, I find it a little bit clunky to work with, albeit it does allow you to dig deep into a number of channels and parameters.
09:27 At the moment though, that's not really what we're actually trying to achieve so I'm going to close that down and I'll show you the technique that I personally use which is the log playback function.
09:34 This is itself has its own set of issues but just bear with us, what we'll do is we'll open our last log file here and it opens exactly as we can see here.
09:45 So the information that we've got present there is just the RPM trace which is great because for our purposes we can see where that ramp run is.
09:55 We can click on the little play button here and it will as its name implies, play through that log file.
10:02 While we're doing this, we can see that the numbers that are on the gauge page over here on the right hand side, they're no longer our live data, they're actually what was happening during that log file and that's pretty good because if we scroll through here, we can just click through until we find the actual point where we were doing our run.
10:21 Obviously that's the important point.
10:23 We can see what for example our lambda versus our target was at any particular point and we can also see where abouts we were accessing in the fuel or ignition table at that particular point.
10:37 So what we're going to do here, I've already seen from the dyno, looks like our air/fuel ratio is pretty well on track.
10:43 Albeit we did add a couple of percent there to those wide open throttle operating areas so let's just click through this file here, so couple of ways we can do it.
10:50 We can click the play and pause or alternatively we can just click through on the status bar and just see what we've got but we'll just come back a little bit and move over the part we skipped.
11:03 So we can see here looking pretty good, maybe if anything just around about a percent, 2% lean so when I'm doing this, if I'm going to make an adjustment, what we can do is look where abouts were we, so we can see our cross hairs showing us we are interpolating a little bit.
11:19 For all intents and purposes, we're around about that 125 kPa, 2000 RPM.
11:25 So when I'm making a change here what I'll do is I'm going to actually highlight the entire column at higher load as well.
11:31 So we actually can't really get there at 2000 RPM, we're limited on how much boost we can create but this is going to keep our trends consistent and as we get further through, particularly if we're going to get to a point where we can raise the boost, chances are that this is going to set us up to be pretty safe.
11:49 So again 2% lean there, really not too worried about that down at 2000 RPM but for the purposes of our demonstration, we can press the P key, that'll bring up our add or subtract percentage, we're going to enter a value of two of course and that will make the change to that relative column.
12:05 So what we're going to do is just continue to go through here.
12:11 Let's just try and get back, it is a little bit difficult to be pinpoint accurate here.
12:15 So of course as we move to 2500 RPM, we can see we're still a little bit lean here.
12:20 Again not enough to really concern me but let's just again for the sake of completeness we'll make that change there.
12:29 P again and again we'll add 2%.
12:32 An interesting observation that I have noticed with this particular ECU and it's just occurred right then is when we are using this log playback to make changes, it doesn't seem to be particularly stable.
12:45 And if you did notice there that change of 2% that I just made, as soon as I moved out of the zones that I made that adjustment to, it reverted back to the previous values.
12:54 I believe this is a bug in the software, I do not see this work repeatedly in this way.
13:02 If you are watching this at some point in the future with firmware updates, it may be that this is resolved.
13:08 However my advice to you is take note of what's happening because I have noticed that not every time the changes you make here will stay active.
13:17 So we've actually just lost those changes to both of those columns I made adjustments to so we're just going to go back, add 2% again and this time you notice as I cursor away from those, those changes have stayed fixed so I'm not sure how to explain that, it looks to me like a bug, I may be wrong, I do not know but be careful of that because it can end up wasting your time.
13:42 We'll move across to 3000 RPM and this time we're a little bit leaner, again we're starting to get to a little bit higher in the boost now, we're 150 kPa.
13:50 And we're 0.87 to a target of 0.82 so actually about 5% lean there.
13:57 So what we'll do is make a change here of 5%, make sure that that stays active and it has, let's keep going through and we'll do this right to the end of our ramp run here.
14:12 Essentially what we're trying to do is make sure that we are as close to the centre of the cells by clicking through on this little status bar here, this progress bar and access each of the cells we've run through.
14:23 So in this case, 0.779, let's call it 0.78 to a target of 0.78, no work to do there, that's pretty good, let's move across to our next cell which is 4000 RPM.
14:33 0.76 to a 0.77 target, for the moment really wouldn't be too worried about that.
14:41 If anything though what we can do is P and minus 1%, we'll make a change there and we'll come across to our next cell which is right at the top of our run, 4500 RPM.
14:55 0.76 on a 0.77 so again maybe 1% lean there.
15:00 You'll notice that all of those changes that I have just made, have now been reverted to nothing, so this is the frustration that I face with this particular ECU.
15:11 In this situation the only thing you can do is take note of the changes you've made, close that log playback and then apply those changes manually.
15:23 But it is really important to make sure that you watch this carefully because otherwise, you'll go and do another ramp run and wonder why your changes didn't have any effect.
15:32 That's because the computer has reverted them back so what we'll do now is go back through and make those changes with our log viewer closed.
15:56 Alright we've got our changes made there so we've gone out to 4500 RPM so we were around about 1% too rich at 4500, 200 kPa.
16:06 I've made a change there but on that basis I'm not going to actually change my calibration there at 5000 RPM.
16:14 Again, chances are we might be a little bit rich and that's absolutely fine.
16:17 Likewise at this point I'm not going to make any changes to our ignition tuning.
16:22 We're going to leave that until we've got a ramp run all the way through to 7000 RPM with our fuelling dialled in.
16:28 So now what we're going to do is save this particular run here, not really too worried about the power at the moment.
16:34 Really all we're aiming for at the moment is to get ourselves dialled in correctly all the way out to 7000 RPM.
16:41 But we'll call this tune one just so we can reference it later on.
16:46 We're going to now come up to our setup screen here and we're just going to extend our RPM out and in this case just to speed up the process here, I'm going to go a little bit further, we're going to go out to 5500 RPM.
17:00 Now as you're just getting started, I would suggest small changes, maybe 500 RPM.
17:04 I've got a pretty good understanding of this engine and of course if something isn't quite right I can always back off so we're going to go out another 1000 RPM beyond where we were, let's get our logger running again and we can get our next run underway.
17:49 Alright so our second run complete there, 330 horsepower at the wheel, again not really too worried about the power, just looking quickly over at our screen, we can see everything's looking pretty good, boost is under control, air/fuel ratio we can see around about 4400 RPM we've got a very slight lean spot here.
18:07 Comes back to our target and then once we get past about 5000 RPM we can see we are moving a little bit lean.
18:13 Not enough at that point that I'd be worried about backing off but of course we always want to be a bit mindful if we start seeing our lambda track really lean of course we'd be getting straight out of the throttle.
18:24 Alright so let's have a look back through our log viewer, log playback I should say and we'll open our last log file there.
18:33 And have a look and see exactly what was happening.
18:36 So little bit smaller this log file, did a little bit less talking before we actually got into that ramp run but again what I'm going to do here is just go through.
18:44 Basically cycle my way through each of the cells, we're going to be comparing our lambda to our target, we're going to be using the correction factor, our measured lambda over our desired lambda will give us a correction factor we can apply and we're going to be using our percentage change to do that.
19:02 Again just being mindful, again making sure that the percentage changes we make actually do stay active.
19:06 So let's go ahead and do that now.
19:30 We're out to 5500 RPM here and what we can see is that this point here, we're on a lambda of 0.77, our target's 0.76, we're actually pretty close, it's not a bad place to be.
19:43 However again being a little bit fussy here, we are around about 1% leaner than our target.
19:50 It's important when you are making changes out in this area that we haven't tuned under steady state conditions, rather than relying on just making our changes to the areas we have tuned, sorry the areas at wide open throttle where we are looking at in our ramp run, what we're going to do instead is highlight the entire column and we're going to make a change to the entire column.
20:09 The reason for this is we're assuming there, making the assumption that best chances are that if we are lean at wide open throttle, given that we've copied the VE numbers across, we're probably also going to be lean in the part throttle areas so this is just going to be a way of getting our map closer for those part throttle areas.
20:26 Of course we're not going to be running the engine much at 5500 RPM and part throttle either so it's less of a concern but still something we need to consider.
20:36 Now at this point we've only gone through to 5500 RPM with our ramp runs so we don't have data beyond this.
20:44 What we can do though is extrapolate the trends we are seeing and in this case the numbers at 5500 RPM I've just added a percent in there.
20:52 I'm going to guess that there's a chance that maybe at 6000 RPM we might be a touch lean as well so what we're going to do is we'll close down our log playback there and we're going to then highlight the entire 6000 RPM column and above and let's just add 2% in there, might be a little bit more than we actually need but again just in the interest of being a little bit safer and a little bit richer, it's always better to have more fuel than less when we start another ramp run.
21:20 Alright let's head back across to our dyno now.
21:23 What we'll do is we'll save that run, we'll call that tune two and we will also of course extend our ramp run out again.
21:34 So we went to 5500 RPM that time, everything was looking pretty good, let's take ourselves out to 6400, that's probably going to be close enough for our next log.
21:45 Should also mention there, as you would've probably noticed, during that set of adjustments that I made, the log playback didn't end up affecting my changes that I made, they stayed active so again something to watch, I believe a bug in the software but definitely something that will frustrate you if you don't notice it so just keep an eye on that.
22:09 Alright we'll start our logger again and we can get our next run underway.
22:41 Alright our next run complete there, we'll just wait for the dyno to come back to a stop and we can see, 378 horsepower at the wheels so everything's going in the right direction there.
22:52 Target with this engine, for the fact it is a stock 13b internally, I wanted to be a little conservative, around 400 wheel horsepower is about where I'd like to see it.
23:02 We can see our air/fuel ratio, it is still moving around a little bit but we're always within about 1-2% of our target there.
23:09 Possibly just a little bit lean again as we move out into these untuned areas so again this is why we want to be a little bit cautious and add a little bit more fuel.
23:19 I extrapolated that change that we saw from 5500 RPM.
23:23 So we'll stop our logger and we'll look at our log playback again and go through exactly the same process.
23:31 So we'll just do that now and make the relevant changes.
23:34 This does become an iterative process so obviously as we get our tune dialled in, our lower RPM range we shouldn't be needing to make consistent changes to but of course as we move out into those untuned areas, this is where we expect to see the need to make more changes so we'll just go through this a little bit more quickly now and make any relevant changes that I feel we need.
24:27 Alright we've got our next round of modifications made to our fuelling so pretty comfortable with what we've got going on in there, everything's looking reasonably healthy so we're ready for another run.
24:37 This time what we're going to do is extend our next run all the way out to where we want our rev limiter, so in this case we're going to save that as tune three and we will set our finish point up to 7000 RPM.
24:53 So let's go ahead and do that now.
25:00 Alright and we'll complete another run now, starting our logger again before we begin that run.
25:32 Alright waiting for our dyno to come back to a stop there, again everything's looking pretty good, 382 horsepower.
25:37 We can see that our air/fuel ratio right at 7000 RPM does start to taper a little bit rich which is understandable and absolutely fine.
25:46 Again better to guess and be safely rich than be a little bit lean so we've stopped our logger there, we'll have a look at that particular area, everything else is looking pretty good in there.
25:58 But if we get out to 7000, we're actually at 7100 at the top of that run, little discrepancy between our dyno setup and the RPM that the engine's actually doing but again here, 7000 RPM, around about 2% too rich so we'll take out 2% there and I'm also going to extend that out to 7500 and 8000 RPM.
26:19 We can take out 2% there.
26:23 We're going to be tapering away, we see our power is tapering away, our torque will also be falling so chances are we can actually pull a little bit more VE out above 7500 but again for the sake of being a little bit safe, we will do that.
26:35 I'll just cycle back through here and just have a look at the rest of our data and everything's looking pretty good.
26:41 We're within about 1% of our target there, most of the way through this.
26:46 What I probably will do there is just at 6000 and 6500 RPM, I'm going to add another 1% to our fuelling there, just make sure that those changes stay active.
26:58 We're going to consider our fuelling at this point complete so the small changes that I'm making there, and this does become iterative, even once we get into this next step of adjusting our ignition timing, there's a better than average chance that we will find that we also still need to make small adjustments to our fuelling.
27:15 We're not necessarily going to get those absolutely perfect at this point but again we can do the fuelling and the ignition simultaneously.
27:22 At this point the important takeaway though is we've got a ramp run on the board there, our fuelling is at least in a safe ballpark and now we want to move on and have a look at our ignition timing.
27:33 Before we do that I do just want to quickly show you how the staged injection is working.
27:38 We've talked about it during our setup but of course now it's actually active so if we look at our log viewer, this will demonstrate what's happening with our injector pulse width on our primary and our secondary so we'll just wait for that to load up from that last ramp run that we were looking at.
27:56 So we can see the light blue line here, this is our primary injector duty cycle, sorry not duty cycle actually pulse width.
28:06 So we can see that peaks around 10 ms here, at a point where we're around about 5000 RPM.
28:12 The light pinkish line here that we've got, this is our secondary injector pulse width.
28:19 So you can see that as soon as the primaries start dropping away, the secondaries come in.
28:24 It's all about maintaining that maximum injector duty cycle on the primaries and we can see that the secondary starts ramping up.
28:30 So we've had to do nothing there, it's happened in the background so it's really nice and seamless.
28:35 We can see as well if we look at our lambda plot which is this pinkish purple line here, really no distinguishable change in our lambda as the secondary stages in so Adaptronic have done a really nice job of this.
28:48 It's probably one of the best staged injection systems I've personally used and requires literally no work from the tuner.
28:55 So I just wanted to show you that before we move on.
28:59 Alright let's head across to our ignition main map.
29:03 And we know that we are operating around about this 200 kPa zone although we are ramping up to this, we're probably taking a line through this table that looks something sort of like this, we're all in by about 4000, 3500 RPM.
29:21 So what we're going to do to start with is we're just going to highlight our 180 kPa and our 280 kPa rows here.
29:31 And we're going to simply add 2°.
29:35 At the same time we can also be a little bit more aggressive with our timing as we ramp into these areas so I'll just add a couple of degrees in this ramping up area.
29:48 So just what I'm trying to do here is maintain a relatively smooth trend to the numbers in the table here, so we can just add a little bit in here so that it all sort of, it's nice and smooth.
30:02 Smooth ignition map is also going to make the engine generally respond more crisply.
30:07 So if you've got large holes or significant changes in your timing from one cell to the next, generally that's not going to be ideal but we are focusing predominantly here on the areas that we weren't able to get to or really weren't focusing on under steady state conditions.
30:24 So what I'm going to do now is over on our dyno, we're going to set this up so that it will show us our last run so it's going to stay active on the dyno screen while we are doing our next run.
30:36 This is going to be important because we'll be able to then compare and see whether or not our timing change that we've just made of 2° has been a positive or a negative.
30:45 Regardless either way I am going to still log this run and we will save that so let's get our next run underway and we'll see how that 2° affects our power.
31:27 Alright so we have seen a gain, it's been relatively small admittedly and this is really one of the things with a rotary engine as I've mentioned, they don't respond dramatically to ignition timing.
31:41 At the moment, I know from my own experience with rotary engines, running 8° at 15 psi on our 98 octane pump fuel is incredibly conservative so we're definitely nowhere near a situation where I'd be worried about this so what I'm actually going to do is I'm still going to highlight the 180 and 200 and 220 kPa and in this case we'll come back here to the point where we're at about 4500 RPM, actually we'll come back to 4000 RPM and we're going to add another 10° so again I'm just going to smooth the changes I've got here, everything's looking reasonably good there and we'll do another run and see the effect of that additional timing.
32:25 If we don't see any gains here, the reality is that we're not getting any potential advantage from the timing so we'll pull that back out.
32:35 Remembering we don't really want to be chasing MBT timing on a rotary engine under boost.
32:41 At the same time I am just going to come back across to our fuel map there and make a couple of changes, as I mentioned we may have to, so we'll just take out 2% here, 7000 RPM and above and then again between 5500, actually let's go 5000 RPM through to 6500 RPM, we're going to add 2% in there.
33:07 Alright let's get our logger recording, we'll save our run again and we'll overlay with that, let's see what our results are for our next run.
33:58 Alright so you can see there we've picked up essentially almost no power except right at the top end.
34:04 We do need to be a little bit mindful of this though because you'll notice that we now have cleaned up that rich spot that we had right at the very end of our run and we are at 0.75, 0.76 lambda.
34:16 This is about the point where much richer than this we will tend to fall over so the gain in power that we've had there is probably more an aspect of the fact that we have leaned out the air/fuel ratio back to our target as opposed to the additional timing that we've actually gained.
34:31 Likewise I have actually cleaned up that slightly lean patch we had there about 6000 to 6500 RPM.
34:38 So we are at a point here where we're right on the edge of the fact, the rotary engine will respond to fuelling quite dramatically so this is important to understand because if you are in a situation where you're making small air/fuel ratio changes run to run, that can mask some of the changes that we have with our timing.
34:56 That being said, our timing really isn't responding here, we aren't seeing a significant change.
35:02 What I want to do here is probably leave our timing as it is right now, even though it is very conservative, that's not a bad place to be as long as our exhaust gas temperature is under control.
35:12 What we want to do is just show some of the effects of our tuning changes in terms of, first of all fuel, the sensitivity of the rotary engine to power versus our air/fuel ratio targets and then also we want to have a quick look at our trailing split and see the effect of that.
35:29 So let's start by just making an adjustment to our air/fuel ratio target.
35:34 So we'll come back to tuning fuel, now of course with a VE table, VE based fuel map, once we've got our air/fuel ratio tracking our target, we don't change the VE table to change our air/fuel ratio.
35:47 Instead what we do is we come into our target lambda table.
35:50 You can see we're targeting 0.76 here.
35:53 So what I'm going to do for a start is show the effect of leaning out our mixture so let's go to 0.80.
36:02 This is definitely leaner than I would recommend but I just want to show you the sensitivity to air/fuel ratio at the point we are running.
36:12 And let's get the car back up and running on the dyno and we'll show that now.
36:55 Alright so during that ramp run we can see that essentially the engine did exactly what I asked of it, we can see our air/fuel ratio plot, we hit 0.75, 0.76 but then immediately it achieves our target of 0.78.
37:09 Hopefully you can see in the live data there, particularly at higher RPM, the effect of that leaner mixture is that we did pick up power, in fact we've picked up about 10 horsepower at the wheels.
37:21 Now on paper that sounds great however this is what we need to understand with the rotary engine that yes if we lean out the air/fuel ratio, unlike a piston engine, we will tend to pick up power.
37:32 However what we're going to do is create a lot more heat, particularly inside the combustion chamber which can be damaging.
37:38 We also make the engine of course more prone to suffering from knock.
37:42 So when I'm choosing an air/fuel ratio for a rotary engine, particularly a turbocharged one, I'm focusing on being a little bit richer than the point where we are making maximum power and I'm going to definitely be comfortable sacrificing a little bit of our maximum power in exchange for a little bit more reliability so important when we are getting to a situation where we're dropping off a few percent of power, that's not a bad place to set our air/fuel ratio.
38:10 We can see if we set our air/fuel ratio significantly richer though, we're going to start falling off a cliff, so we see a sort of a curve much like our MBT timing curve.
38:20 The further away we get from peak power in terms of our air/fuel ratio, the more our power will drop off so in that instance, we're going to go back to our original target there.
38:31 Actually I've just cancelled out the logging there so we'll set our target back to 0.76.
38:37 So as explained, if we set our target to let's say 0.72 then yeah we're going to expect to see our power drop away.
38:47 However we do need to be a little bit mindful of this as we come to our higher boost settings.
38:53 In this case 240 kPa or 20 psi, I'm not going to be running there so becomes a bit of a moot point but just like a piston engine we do need to run a little bit richer as we increase the boost pressure.
39:06 Much past about 0.74 we're really going to be falling off that power cliff.
39:10 Alright so the next change we're going to have a look at, let's head back across to our tuning, and we're going to look at our rotary trailing spark.
39:19 So just to get an idea of how much effect our trailing split has on our power and torque.
39:27 So again we're operating in this 200 kPa region here, remembering we need to be a little bit mindful here because reducing the split has the same effect as advancing the timing overall so that's going to make us a little bit more prone to knock.
39:41 I personally wouldn't recommend advancing the timing on the split much more than about 8° under load so let's just start by going the opposite way, let's go to 10° and we'll see the effect of that.
39:53 We'll come back across to our dyno, now I'm not going to save that last run because we've set our target air/fuel ratio richer than what we had there.
40:02 So we're going to be back to probably our 383 horsepower at the wheels or thereabouts.
40:08 So what we'll do is we will not save this run and this will allow us to overlay with a run that's got a comparable air/fuel ratio where the only difference is that we have retarded our trailing plug or increased our split so let's see the effect of that change.
40:54 Alright so on that particular run we can see we've actually lost a little bit of power up top but that's probably as much a run to run variation, we've done about 2.5 horsepower.
41:04 The thing that I want you to take away from that is essentially during the entire area where we are at 200 kPa of boost, at full boost, we really saw the two runs overlay directly on top of each other.
41:17 So in my own personal experience, chasing power with the trailing split is really futile, you're not going to see significant changes and in most instances I tend to run with the split table that we showed at the start.
41:32 So what we'll do there is we'll just reduce that back that 2° to where we were.
41:36 So at this point we've got to a situation where we're around about that 385 horsepower at the wheels, we've got to a position where the timing that we're adding in really isn't showing significant dividends on our power, we've got our air/fuel ratio under control, we've got a safe tune, it's conservative on both timing and fuelling but we're not running so rich that we're dropping off that cliff power wise.