Summary

Staged injection is a popular option for providing additional fuel without fitting excessively large injectors which can compromise fuel delivery at idle and light throttle conditions. Additionally in high output naturally aspirated engines, staged injection can be used to provide improved mixture formation with a set of injectors mounted further away from the intake valves. In this webinar we'll cover what you need to know, as well as how to approach your tuning.

 

00:00 - Hey team, Andre from High Performance Academy here, welcome along to another one of our webinars where this time we're going to be diving into staged injection.
00:07 We're going to be talking a little bit about what staged injection is, why we would use it and there are a variety of ways we can incorporate staged injection so we'll talk about the hardware implications and considerations when it comes to choosing your own staged injection setup.
00:26 We'll talk a little bit about the ECU configuration as well and we'll go through the process of tuning this system so that you can make sure that you're getting the most out of it.
00:37 Now of course we aren't doing any dyno tuning live here, we will be looking through some data logs here so you can see the sort of stuff that we are looking for when we do have the car on the dyno.
00:49 As usual, we will have questions and answers at the end of the lesson so if you do have any questions, please keep those until the end and we will cover those then.
01:01 Alright so let's start with the obvious, what is staged injection? And don't really need to be a rocket scientist to figure this out.
01:09 Staged injection is simply a situation where we incorporate more than one injector per cylinder or per inlet runner.
01:17 So traditionally this is most likely going to require two injectors per cylinder but there's no reason why we can't have more than that.
01:26 We've got ECUs these days that will support 3, 4 stages or potentially even more than that if you really need a stupid amount of fuel.
01:36 Now we see this in the aftermarket industry where we're in a situation where we've run out of fuel capability which we'll talk about in a little bit more detail shortly and we simply add another injector.
01:47 However the staged injection strategy is actually used in OE applications as well, just to name one engine that is commonly seen which comes out the showroom floor with staged injection is the Mazda rotary engine.
02:02 13B for example comes with 2 injectors per rotor.
02:07 Some of the RX8 Renesis engines, a certain trim of those actually comes out with 3 stages from factory so it's not anything particularly unusual.
02:17 If we jump across to my laptop screen for a moment, this is my old shop car, my EVO 3 and unfortunately these days I don't have a lot of photo evidence of this car which is a real shame so I don't have all of the details that I would like to show but what we can see here is it ran a large custom plenum chamber.
02:38 This engine was a 2 litre 4 cylinder and at the time we didn't have the benefit of the huge range of quality injectors that we have today.
02:48 About the biggest that was easily available to us was the old Bosch Indy Blue injector and if you've never come across those then you are very very lucky because they are a truly evil thing.
03:03 However they were a 1600 cc injector that did a passable job of getting fuel into the engine.
03:09 They weren't refined, they were really really ugly at low flow, they were pretty ugly at high flow duty cycles as well but they did get the job done.
03:19 However when we're running close to 1200 wheel horsepower and 54 psi of boost on methanol fuel, we need a huge volume of fuel to keep the engine happy and run the air/fuel ratios we're targeting.
03:33 So to do that, I actually ended up incorporating 3 Indy Blue injectors per cylinder on this engine.
03:40 And again unfortunately I don't have the benefit of showing you this but basically anyone who's familiar with the 4G63 would probably understand that there is a factory fuel rail that runs along the back of the cylinder head there, basically between the rocker cover and the plenum chamber that I've just drawn.
03:59 So there's the factory location for the injectors there is cast into the cylinder head.
04:05 So we ran a set of primary injectors in that location.
04:08 Then what is unfortunately invisible is down in behind there, we CNC machined some little mounts that welded onto the underside of the inlet runners and that took two more Indy Blue injectors side by side so we actually had two injectors running simultaneously as secondaries and a single injector as a primary, even as it was by the time I'd finished the development on that car, we were really really close to the limits of the fuel system.
04:39 Now the other question that comes along with this is why we would need staged injection.
04:46 And really it comes down to two reasons there.
04:49 The first is kind of what we've just covered off here where we simply need to get more fuel into the engine than we can with a single injector.
04:58 Now as I mentioned, back in the days when I was developing Docile, my EVO 3 which is longer than I care to think about now, probably hasn't turned a wheel in anger in over 10 years.
05:09 We didn't have the range of injectors available and these days there's 5000 cc per minute injectors available that a lot of these methanol drag engines are using.
05:22 So we didn't have those injectors available, 1600 cc was about as big as we had and 1 single 1600 cc injector wouldn't cope.
05:32 So to get the fuel in, we need to add more injectors.
05:35 However the flipside of that is these days we potentially do have injectors on the market that are big enough, the 5000 cc injectors that I just talked about, I think we've got bigger ones than that available now because as engine builders improve power output and turbos become more efficient, we see the power numbers increase which obviously just drives the need for more fuel higher and higher.
06:00 The problem with these very very large injectors is that they do a great job of pouring fuel into the engine but trying to make a small capacity engine idle on such a large injector is probably going to be pretty futile.
06:15 The reason for this is that they just can't accurately meter a small enough amount of fuel in order to get the engine to idle at a normal or suitable air/fuel ratio so it's a bit of a catch 22 there.
06:27 So it's not just because these days we can't buy big enough injectors because often we can.
06:32 So that's why we go down the staged injection path, we can split our fuel demands up over 2 or more injectors, often what we'll do is we'll choose a smaller injector as a primary which will give good control over that fuel mixture at idle and light throttle, light load where our fuel demands aren't that significant and then what we'll do is we'll bring in our secondary or tertiary injectors as the load and airflow increases and we need more and more fuel to keep our air/fuel ratio in check so basically giving us the best of both cases.
07:09 However there is another case study for staged injection as well so that is where we are running a naturally aspirated engine and it's not just about getting more fuel volume into the engine.
07:22 So we'll jump across to my laptop screen and this is an Alpha V6 DTM engine that I snapped when we were over at Goodwood Festival of Speed a couple of years ago.
07:34 And this actually may or may not be running staged injection, it doesn't really matter because I'll be able to talk through the implications here so what we can see is the V6 inlet trumpets here and we've got 6 injectors sitting up above the trumpets.
07:51 So as I say, I'm not actually 100% sure if this particular engine was running staged, we do quite often see where there is only one set of injectors, they are sat outside of the trumpets like this and the engine tuner and builder just simply accepts the poor response when the throttles are closed, it's idling or just cruising.
08:14 Another option though is to incorporate primary injectors that are fitted down out of sight here right by the inlet valve.
08:21 So basically kind of in a factory location where the injector is nice and close to the inlet valve allowing a pretty good straight shot at the valve to get the fuel into the cylinder.
08:30 So that'll work really nicely at idle and low RPM and under those conditions as you could imagine, our throttle blades are relatively closed so the formation and mixture that we get with an injector mounted outside of the trumpet like this isn't that great.
08:46 Yes the engine will run but it is a compromise.
08:49 However if we look at high RPM wide open throttle operation, going to an injector that's mounted outside of the hat like this, outside of the inlet trumpet like this can potentially give the benefit of better mixture formation, a more homogenous fuel/air charge.
09:07 What that can do is mean that we get a little bit more potential power.
09:13 We're basically mixing all of the available oxygen with fuel and making sure that it is all being consumed.
09:20 Now obviously in highly strung naturally aspirated engines, we're really after every single horsepower that we possibly can.
09:27 Particularly if we're in a restricted class where there might be a limit on engine capacity and RPM ceiling for example.
09:36 We want every advantage we can.
09:37 So even if we're only able to extract a few extra horsepower by going to this technique, the extra complexity, the extra trouble and weight is often deemed worth it.
09:48 So that's our two options, one where we are simply looking to get more fuel volume total into the engine, the other where we're looking to not necessarily increase the fuel volume but just try and improve our mixture formation, our mixture preparation and extract a little bit more power as a benefit.
10:08 And I'll mention there, with the naturally aspirated engine that we've just looked at, generally with the staged injection in this style, we would stage all the way out to the secondary injectors entirely so at high RPM wide open throttle, we would find that only the secondary injectors are operating and the primary injectors are shut off.
10:28 So again just a way of getting the best of both worlds.
10:33 Remember if you've got any questions on any of this, we will have some questions at the end.
10:39 Alright so we need to consider our hardware that we're going to need for this.
10:45 And the first part of this comes down to the actual injector itself.
10:50 And obviously, well hopefully at this stage you can understand that the injector selection is going to come down a little bit to exactly which of the methods we are looking at.
11:02 Whether we're looking at trying to get more fuel into the engine or whether we are trying to go with the staged injection where one of the injectors is outside of the inlet trumpet where we could go with equal sized injectors.
11:16 If we come to our own Nissan SR20 example which I'll just try and find, that's not going to work, there we go.
11:27 If we come across to our Nissan SR20 picture here, this is our Plasmaman inlet manifold that we are running on that and you can see we've got a pair of Injector Dynamics injectors side by side there.
11:42 We'll talk a little bit more about the options when it comes to mounting these injectors shortly but in our instance here, we went with a pair of Injector Dynamics ID1050X injectors.
11:53 Which if anything it is a little bit of overkill for our application.
11:58 One of the reasons we went down this path is it gave us the ability to generate some data and content around staged injection.
12:08 So given that our power aims, we were only in the region of 600 to 650 horsepower on E85 with this engine, we could definitely have achieved that with a single injector, albeit we'd have probably stepped up to something in the region of the ID1700 or thereabouts.
12:27 So equal injectors, that's one option.
12:31 As I mentioned though, when we're looking at very very high output drag engines running on methanol fuel, we might be considering secondary injectors like a 5000 cc injector or larger.
12:44 Now that's going to be great at high boost and high RPM but if we were to incorporate two 5000 cc injectors per cylinder, A it's going to be complete overkill and B you're still in that situation where you've got one 5000 cc injector that you're trying to make the engine idle on, it is not going to work very nicely so probably on methanol fuel, depending on the engine capacity, you're probably going to struggle to get an engine to idle nicely on much under about sort of, much over about 2500 cc per cylinder or thereabouts.
13:19 As our fuel changes from methanol to pump gas, things actually get worse and the reason for this is that the amount of fuel volume that we need to deliver to the engine to match with a given volume of air will depend on the fuel.
13:39 So trying to keep this relatively simple here, if we consider that probably still the most popular fuel that we use is pump gas.
13:48 And let's say we've got our engine operating nicely on pump gas and we've got a nice safe air/fuel ratio that we're happy at and we're making X amount of power.
13:59 So if we swap from pump gas to E85 and we make no other changes, we just retune it so that our air/fuel ratio is still safe and we're still going to be making approximately the same amount of power because all things being equal we've still got the same volume of air going through the engine.
14:16 We need to add approximately 35-40% more fuel volume to keep that engine happy.
14:23 So that's between pump gas and E85 where things get really really out of hand though is when we go to methanol fuel.
14:31 With methanol fuel, first of all the stoich air/fuel ratio is all the way down at 6.4:1.
14:38 The other thing is we run methanol fuelled engines very very rich relative to stoich in comparison to E85 or pump gas.
14:47 Long story short, when we go from pump gas to methanol, same things being considered, same volume of air still going into the engine, we need to add or we need to go to about 2 times, sometimes as much as 2.5 times the volume of fuel that we were running on pump gas.
15:04 So the reason I just wanted to go over that is it gives you some insight into the reasons as to why staged injection and these very large 5000 cc injectors and above become the go to options when we're looking at methanol drag engines in particular.
15:21 Alright back to what I was saying though.
15:23 So yeah very large injectors, we're going to almost certainly go to an unequal size distribution between the injectors in order to get our combination of good idle quality but still keeping our engine safe and happy at high RPM and high load, of course it's the airflow that we really need to consider.
15:46 And then at extremes we could choose to add a 3rd stage of injectors if your ECU is capable.
15:52 So that's the injector requirement so how do we know what size injectors we are going to need? This particular webinar really isn't about specifically sizing your injectors but my go to is always the Injector Dynamics fuel flow calculator that you'll find on the Injector Dynamics website.
16:12 Now obviously and understandably it is based around their range of injectors but if you are running similar sized injectors from another manufacturer, shame on you but you will be able to extrapolate your results.
16:25 It gives you a really good indication of what sort of power you're going to make with that size injector and the other thing that Injector Dynamics incorporate which a lot of injector calculators seem to mysteriously overlook is that they factor in engine RPM.
16:40 Because the cycle time available to inject fuel at 7000 RPM which we might see as a red line on an unmodified street engine is vastly different to the amount of time we've got available to inject fuel if we're running a drag engine to 10,500, 11,000 or 12,000 RPM.
16:59 So it really is important to consider.
17:00 So that would be where I'd suggest you'd get started with looking at your injector sizing, however if you are running one of the more specialised fuels like methanol and you are into serious power drag engines then I would be looking at some of the injector manufacturers like the billet atomiser series, they'll be able to give you some guidance more specifically around what would suit your application, they've done it for 100s of other engine builders over the years.
17:32 Now the next aspect is your ECU capability and this probably goes without saying but you're going to need an ECU that is able to run the number of injectors that you're going to be incorporating and we'll also need staged injection firmware as an option.
17:52 We're going to be covering the MoTeC M150 here today.
17:55 These days most modern ECUs will incorporate staged injection.
18:01 The only trap that I would suggest is if you are dealing with a more basic entry level ECU, often what you're going to find is you'll be limited by the number of injector drivers.
18:12 So ideally we want to be able to wire up an individual injector to each drive and this gives us full sequential control of our primary and our secondary injectors so that would be the only trap and where you might get into a situation like this is if you've got an ECU that's designed for a 6 cylinder, maybe you've got it on a 4 cylinder engine, giving you two spare injector drives on face value but really if you're going to then step up and go staged injection, you really ideally would want an ECU that can provide 8 injector drives so again you've got that sequential option.
18:49 The other thing that is worth considering here is whether your injectors are saturated drive or peak and hold.
18:57 We've been a little bit spoilt over the last 5 or 10 years in so much as most of the modern injectors we deal with in the aftermarket are based around the Bosch EV14 injector and these are what's referred to as a saturated drive injector.
19:12 Older injectors but also some of these larger injectors are what's referred to as a peak and hold injector and what these require is a special driver circuit in the ECU that's able to control the current that is sent out to the injector.
19:29 Essentially what the peak and hold injector requires is a high opening current.
19:34 So might be something in the region of maybe 4 amps and that high initial current allows the injector to open relatively quickly.
19:41 Once the injector's actually open it no longer requires that high peak current so the injector driver will pull that current back to a lower holding current, maybe that will be 1 amp.
19:52 So that is quite a specialised drive, not all ECUs have that so just making sure that your injector drive is compatible with the injectors that you have selected.
20:02 Alright, last aspect here is the physical mounting of the injectors so how are we going to physically incorporate these into our engine and I want to just show you a couple of options here.
20:16 We'll head back across to my laptop screen here, obviously we've already seen this, our Plazmaman intake and we've got the injectors, again just so we can see, side by side.
20:25 Now the nice advantage with this is it greatly simplifies our fuel plumbing because while it is primarily out of shot, we can see up the top there, this plenum is actually delivered with a billet machined fuel rail from Plazmaman as well which is designed for these two side by side injectors.
20:46 What this means is we only have one fuel rail to plumb.
20:50 Now we put a post up about this on Instagram quite a long while ago and there was a little bit of heated debate about the downsides of having your staged injectors sitting like this.
21:05 And I found it quite interesting because it was something that I really didn't think was worthy of debate.
21:13 The consideration there was obviously if we've got just one side, one primary injector running, we're delivering the fuel basically offset into the port.
21:22 Where the theory then was that the fuel was going to go primarily down one through one intake valve and we're going to get an unequal fuel distribution.
21:32 My own personal opinion was it wouldn't matter at all.
21:38 We've got a pretty turbulent airflow going down through the port, these are still quite a way off the actual intake valve, by the time the fuel's gone through the intake valve and basically made its way into the combustion chamber, I'd have been very surprised if we didn't have pretty good fuel mixing.
21:56 Now two aspects with this, first of all I tested this theory to prove it, I'll talk about that in a moment.
22:02 But secondly and more importantly anyway, the way we were running this is that once we were actually up in the load and RPM, we have both of these injectors running the same volume of fuel so taking any unequal flow essentially out of the equation.
22:18 After that post was made though, I did a little bit of testing the next time I had the car on the dyno.
22:25 I ran a single primary and then we ran both injectors the entire time for a dyno run and there was absolutely no discernable difference in power, torque, EGT or the air/fuel ratio so I kind of think that backs up what my initial suspicion was.
22:44 Obviously I can't say that's going to work out for everything but really what I'm more interested in with this application is what's going to be happening at high load and high RPM which is what I care about anyway, as opposed to idle and cruise, this is a race engine.
22:58 Obviously I want it to idle nicely which is why we go down this path anyway.
23:02 But if our flow distribution of fuel is not absolutely perfect, it's probably not going to be the end of the world.
23:10 Alright so that's one option, side by side and we are seeing a lot of the aftermarket plenum suppliers making our life really easy with that option.
23:18 Other option here, and this is a 2JZ drag engine that is running probably what was the more conventional setup of staged injection where we can see there are simply two fuel rails fitted, one injector upstream from the other.
23:37 Absolutely nothing wrong with this and I've done this a number of times in the past.
23:42 Works just as well, again I can't really say there's an advantage or a disadvantage in it.
23:48 What I would say though is there is a little bit more complexity in the fuel plumbing that you do need to consider there, you're going to need to split your fuel feel up as well as your return.
24:00 So it just makes it a little bit more work and generally I would say there's probably a little bit more expense in this type of setup by the time we've gone down the path of purchasing two fuel rails and the additional fittings and lines.
24:13 Actually just one thing I will mention is if we come back over here, again it's not in this shot unfortunately but one of the other concerns that was raised is basically, let's call it charge robbing I guess, when we've got these injectors open at very high duty cycles, we've had concern raised about whether or not we're going to end up with unequal fuel distribution to the injectors, particularly the ones at the end of the rail.
24:42 This can be a valid concern, there are certain factory 6 cylinder, inline 6 cylinder engines where we tend to see the injectors at the very end of the fuel rail are known to run a little bit leaner or supply a little bit less fuel than those at the start.
24:59 To combat that, Plazmaman incorporate a centre return out of this fuel rail.
25:05 So again while I can't show you but basically we feed fuel in, both ends of the rail and then we return it out the centre.
25:14 So that essentially negates any problem with charge robbing.
25:18 And then of course our third and final option, going back to our Alpha V6 there of course, mounting them outside of the inlet trumpets does require quite a lot more work there, you're going to have to fabricate some way of holding the injectors into the rail as well as a rail and supports for that rail itself.
25:39 Just mention as well with the strategy where these injectors are mounted outside of the trumpets, this should be less of an issue with staged injection but it was relatively common to see airbox fires occur in engines where only a single set of injectors external to the trumpets are fitted.
26:00 Because you're getting a lot of fuel standoff occasionally depending on the RPM range and basically you can end up with fuel vapour sitting up in the airbox, all it's going to take is a back fire or something of that nature and that can ignite it so there is some danger around this style of setup but just something that is worth mentioning there.
26:21 Alright we're going to go through a bit of the setup in the MoTeC M150 and look at some data and this is a perfect time to let you know if you do have questions, please ask them and we'll get into those shortly so what we'll do is well start by heading along to our M150 software and again obviously unfortunately I am offline but not a big issue, we can talk through everything we need to understand here.
26:48 So from the actual tuning perspective when it comes to fuel delivery, nothing really changes from running a single set of injectors.
26:55 This is our conventional volumetric efficiency table, we've got it numerically here on the left hand side and graphically over on the right hand side.
27:04 For anyone who is wondering about this little step in here, this little bit of weirdness that you can see, this is a result of the VTEC I'm gonna call it, VTEC mechanism switching on the VVL cylinder head, Nissan VVL cylinder head which for those who aren't aware, essentially this is Nissan's take on Honda's VTEC, it's a 3 lobe cam system and at a certain RPM it switches from low lobe to high lobe.
27:33 So kind of gives us the best of both worlds.
27:36 Now what we will find though is that it's not just RPM related where we want he VTEC system to switch, it's also going to be dependent on load.
27:47 This being a race motor, I've kept things nice and simple and basically when we are under wide open throttle, we're kind of operating out in this region of the map if not a little bit higher.
27:59 So everything there, if we've got everything set up for our VTEC shifting point, we should see a relatively smooth progression through the VE table.
28:07 If anything, maybe a little bit of a step upwards but generally it should be pretty smooth and kind of that's what you can see.
28:14 However in the ideal world we will find that the VTEC shift point at low load will be at a different point, a different RPM point and that's what we see here.
28:26 In this case we actually see the volumetric efficiency drop away quite significantly when we switch.
28:33 Now again I don't really care about this for a race engine because we're never there, if we are there, we're completely off throttle.
28:40 But what I would generally do on a street application is we would run a window VTEC changeover point and depending on our RPM and our load we would basically move that window around, optimising that to suit.
28:56 I digress though, that's not really the purpose of our conversation today, what I really wanted to just mention is that our actual fuel tuning, it doesn't look any different.
29:05 This efficiency table is where we do our tuning.
29:09 Now the actual setup for staged injection on the M1 is really critical and to do that, we come through to the initial setup workbook and we want to come over to our injectors worksheet.
29:24 Now the M1 makes things nice and easy here because we don't need to go through and provide a huge amount of information on the injectors that we have fitted.
29:31 Not that long ago we would need to provide deadtime table, offset tables, short pulse width adders, reference flow and pressure.
29:41 Instead what we can do with the M1 is simply choose the injectors, provided they are characterised by MoTeC or a MoTeC dealer, simply choose that from the available list in the drop down menu which as you can see is relatively extensive.
30:01 So that basically populates all the information that we need in the background.
30:05 In this instance as I've already said, we are running a set of 1050X injectors for our primary and we are running exactly the same in our secondary.
30:17 Important point to note which doesn't really affect us with our application is the injector location.
30:25 So you can see for our primaries, we've got that and we can choose from after throttle not in use, before throttle air box referenced or boost referenced.
30:34 Now why that's important is that we need this information programmed correctly so that the ECU knows what the differential fuel pressure across the injector will be.
30:46 So depending, the amount of fuel that the injector will flow is not just a factor of the fuel pressure and the pulse width that we deliver to the injector, it's actually a factor of the differential pressure across the injector.
31:01 So on one side we've got fuel pressure on the top of the injector, on the underside of the injector we've got the pressure that the tip of the injector is exposed to.
31:10 So in our example with our Nissan SR20, that's into the inlet manifold so it's going to be exposed, it's post throttle body, it's going to be exposed to vacuum or it's going to be exposed to boost.
31:24 In our case because our fuel pressure is also manifold pressure referenced, what this should mean is that our fuel pressure and our manifold pressure rise and fall together, the differential fuel pressure across the injector should always be relatively fixed.
31:39 If on the other hand we were setting up our secondary injectors for the Alpha V6 that we've already looked at, that is pre throttle so in that instance the tip of the injector is only going to be referenced to atmospheric pressure.
31:56 It's not going to go up or down with manifold pressure so that means that if our fuel pressure is varying up and down because it's manifold pressure referenced, then we will find that our differential fuel pressure across the injector varies.
32:10 Not something we need to really factor into ourselves, we just need to understand it so we can program the setup correctly in the MoTeC and then the MoTeC's going to handle all the heavy lifting there in the background.
32:26 But it's really important just to understand the importance of those selections because otherwise we're going to find that our fuel flow won't be what the ECU expects it should be and we're going to be chasing our tails with weirdness around our fuelling not following our target as we'd expect.
32:45 Alright so when it comes to actually tuning the secondary injection, that's where we come down to our secondary injection fuel injector secondary contribution main.
33:00 Bit of a mouthful, MoTeC always like to use the most words possible I find to describe a table.
33:06 But if you understand their logic there's really no way of confusing that.
33:11 So that's the table that we've got out here on the right and what I'll do is we'll just full screen this so that we can see it in a little bit more detail.
33:19 So we've got it represented numerically here and of course graphically as well.
33:27 So what do the numbers in this table mean and how do we need to program them? So first of all, if we get rid of the graphics, because they don't really matter for the moment, we've got a calibration table here which uses inlet manifold pressure on our vertical axis and it uses our engine RPM on the horizontal axis.
33:47 Numbers in this table are between 0 and 100 so number of 0 means that all of the fuel is being delivered by our primary injector and you can see there's a good chunk of this table where that is absolutely the case.
34:03 Particularly down in our idle and cruise areas, so those sort of incorporate down in this area, we are only running on those primary injectors for all of the reasons that we've already drummed in so I won't go over it again.
34:15 Likewise at high RPM but low load, so even up to 150 kPa there, 50 kPa of positive boost, we are still running purely on the primary injectors.
34:27 However, if we're doing a dyno run we're probably going to come up through that dyno run that's going to look something probably approximately like that and we can see that we start bringing in those secondary injectors around about 4000 RPM, 200 kPa, 1 bar of positive boost and 20% of our fuel's been delivered with our secondaries.
34:51 By the time we get up to 5000 RPM and 250 kPa, 22 psi of boost, we're at 50/50 so this is important though because the numbers that we put into this table, we need to understand what we're actually trying to achieve and again what those numbers mean.
35:08 So 50/50 means that 50% of the fuel volume is being delivered by each injector and for us, with injectors that are the same size, that's perfect because what it's going to mean is that we have a matched duty cycle or injector pulse width being delivered to our primary and our secondary injector once we reach 50%.
35:30 What that means is it gives us the headroom to deliver the maximum amount of fuel possible from those two injectors.
35:38 So that's fine when we are running a matched size primary and secondary.
35:43 Where I see a lot of people make the mistake though is when they're running unmatched injectors.
35:50 Maybe 1000 cc primary, maybe a 2000 cc secondary is they still stick to 50%.
35:56 Now that's not going to give us the maximum fuel capability, remembering that gives us the same fuel flow for each injector.
36:05 Now to make things nice and easy here, MoTeC actually provide a little help file, I'll pop this out just so I explain it properly and don't make a mistake here, you can always access this by pressing F1 on anything that you're interested in.
36:20 So 0%, no fuel delivered by the secondary injectors.
36:26 100%, all of the fuel is delivered by the secondary injectors.
36:30 Now the other aspect with this if we were tuning that Alpha V6 or anything where we wanted to switch to the high injectors outside of the trumpets, at high RPM and load, that's what we'd want in this table, we'd want numbers of 100%.
36:44 Then 50% which is what I've just covered off, half of the fuel by volume is delivered by each set of injectors.
36:52 So what this means is if you've got a primary injector that's half the size of the secondary and they're delivering the same volume, then the primary injector is being driven harder than the secondary injector, hopefully that makes sense.
37:06 If we were driving them the same, the secondary injector would be providing twice as much fuel.
37:11 So that's the bit that we need to get our head around and that's what's described here.
37:15 If we want optimum secondary contribution then we can calculate this really easily.
37:21 What we do is we take our secondary reference flow and we divide that by our primary plus our secondary.
37:28 So in simple terms, let's say we had 1000 cc primary and we had a 2000 cc secondary, we'd go 1000 + 2000, obviously 3000, then to calculate the correct duty cycle or percentage to put in here, we would take 2000, our secondary reference flow and divide that by 3000, that would give us the number to put into this table.
37:49 So really important if your injectors don't match in size to make sure that you do that and I will just do that anyway.
37:59 So we take our secondaries, 2000, let's probably not be in programmer mode.
38:04 That'll work.
38:06 2000 divided by 3000 and we want to multiply that by 100 to give us 66, let's call it 67%.
38:15 OK so just a little trick there for non matched injector sizes.
38:20 Alright so that's how the table works but how do we actually go about setting this up.
38:24 Well this is where unfortunately we're simply going to need to go through the process of doing some testing on the dyno or on the racetrack to find out what our injector duty cycles are getting up to.
38:38 If you are trying to provide more fuel then what we obviously want to do is make sure that we don't exceed our preferred maximum injector duty cycle for our primary so let's say we only want our primary injectors to ever run maybe 70 or 80% so we'd just be monitoring that and once we're starting to get close to that point we want to start bringing in our secondaries.
39:05 The flipside of this is we don't want to bring in our secondaries too soon.
39:10 Because if we're only running relatively low primary injector duty cycle, our pulse width is still relatively low there, we can get into a problem where our secondaries, particularly if they're larger injectors, when we try and switch them on, we may be at or very close to the minimum pulse width that they can actually deliver and what this can show up in, when we're on the dyno or when we're logging our data is we can see steps or erratic nature in our mixture, fuel mixture target, sorry our fuel mixture that we are logging versus our target so if you're seeing that, then it's possible that you do have an issue where you're staging in your injectors.
39:53 So we can see what this all looks like, let's bring in some data from i2.
39:57 So this is actually data off the dyno.
40:00 This is probably slightly older data and there's a couple of problems with it which I won't recommend but you can learn from this anyway, in so much as the data that we've got here which is for our fuel injector primary and secondary duty cycles, that was for some weird reason at this point, only logged at 1 Hz so 1 sample a second which is not very useful.
40:25 So generally for this sort of data, I'd be wanting to log at sort of 20, 25 Hz to get some really good solid data.
40:32 Anyway let's look at what we've got here and in the top we've got our engine RPM obviously on the dyno so a ramp run, no big surprises there.
40:41 We've got our throttle pedal position so you can see what's happening there.
40:45 Key input when we are doing this is our fuel mixture aim vs our measured fuel mixture and I've got those overlaid.
40:54 And then we can see our primary and secondary injector duty cycle, we've already talked about and our inlet manifold pressure.
41:01 So this is fairly low boost tuning I think, yeah maximum of 202.8 kPa so about 15 psi of positive boost.
41:12 So what we can see here though is again looking at my relatively low resolution data here unfortunately, we are at 0% secondary injector duty cycle up to about 22% primary flow.
41:27 We are at this stage at 140 kPa and 3500 RPM so because I just want to show this is very early on in our testing, if we jump back to my calibration which is current, 140 kPa, 3500 RPM, we are around about here so you can see this is not from the current map that we are running in the car, I'm actually waiting now much longer to stage those secondaries in.
41:58 However if we come back across to our data, nothing particularly wrong with this, we're at 22% injector duty cycle on our primaries, possibly a little bit lower than where I would choose necessarily to start bringing in the secondaries but nothing particularly wrong with that.
42:12 If we look at the next sample here where we're at 4000 RPM, we've got 36% duty cycle on our primaries and we've got 8.2% on our secondaries.
42:23 Now unfortunately again what we would normally see if I had logged this at a decent frequency, is we would see our primary injector duty cycle start to ramp up and then at our staging point we'd see that momentarily drop off as it brings in the secondary and likewise we'd see the secondary jump up so we aren't seeing that nature in this and that's just simply a case of my poor quality low frequency data but that's what we would normally see because of course to allow the secondary injectors to start providing fuel and not go excessively rich, we obviously need to pull some duty cycle out of the primaries.
43:02 So we sort of see these two converging lines, the primary duty cycle drops down and at the same time our secondary jumps straight up.
43:09 Now the key that we want to monitor just to see how well this system is working is we want to look at what our fuelling is doing as our secondaries start to stage in.
43:22 I've already mentioned this here but basically a bit of a tell tale that maybe our staging isn't working quite as well as it could is if we've got a big spike or a rich hole in our fuelling across that staging point that then comes right so we shouldn't have that, nor should we have a situation if everything's been set up correctly where need to make changes to our efficiency table as we change our staging numbers so that's really important.
43:55 If you've got anything weird going on like that, you do one run then change your staging and find that you need to make significant changes to your fuelling, that would indicate that potentially there's some problems with your setup.
44:08 There are a couple of caveats to that though.
44:12 Now if you are running a staged injection system where the injectors are fitted side by side or one's directly above the other, that should be the case.
44:22 If on the other hand your injectors are fitted a significant distance apart then there can be a bit of travel delay or latency in that fuel making the cylinder, so that could cause a momentary change in your fuelling and the other caveat there is if you're running a naturally aspirated staged injection system which we've already looked at, one of the reasons as we've said that we do this is to potentially provide improved mixture formation and we may see that with a change in our air/fuel ratio which we may need to account for.
44:57 That's different though because that's the benefit that we're getting, why we did that in the first place so basically that suggests everything is working as we'd expect.
45:05 Right, moving on, the other aspect we do need to be mindful of is our maximum duty cycle here.
45:12 So you can see at this point, 200 kPa and 7600 RPM, we've got 74% injector duty cycle on our primary so still plenty of headroom there.
45:25 I'd be quite happy to run these primaries to 85, 90% no issues, 22% on our secondaries.
45:34 So at this point it's questionable whether we even need the secondaries at all but I've already explained why we've got those there and of course again we are only at 200 kPa so as we step up the boost pressure, that's when we really come into a situation where those secondaries may be required but again on our application we're doing this more as a teaching tool as opposed to strictly needing the staged injection.
46:01 More often than not we wouldn't bother on an application at this sort of power target on E85 simply because it isn't necessary and it would only be if we were starting to run 2 bar of boost or more that we would start to consider staged injection might be beneficial.
46:20 Right let's get into our questions now and if you do have any more questions, please get those through.
46:37 Right our first question, is a port fueller setup another name for staged injection? I would have to be honest, port fueller is not a term that I am familiar with so I'm sorry I can't answer that.
46:53 Ders88's asked, are there any downsides to running an overly large secondary injector like a 5000 cc to future proof a fuel system? Or is it best to size the secondaries to meet current power goals and run a smaller secondary? OK I'm a firm believer in future proofing your setup as far as possible but you'd want to be very very sure that you are going to need or going to be able to justify a 5000 cc injector down the track.
47:22 That is an incredibly large injector and it is a very niche product made almost exclusively for drag racing.
47:31 If you are not using the capability of such a large injector, then you're probably going to be compromising the rest of your setup.
47:41 The issue with such large injectors is that basically no matter how good the injector manufacturing technology is, you'd basically have a firehose fitted to your engine and it's just pouring fuel in.
47:55 Which is obviously important, we need the amount of fuel, the volume of fuel into the engine to get the air/fuel ratio correct but if you didn't need anywhere near that amount of fuel, you're going to be compromising the atomisation, probably the fuel mixture formation as well so yeah definitely if you don't ever envisage needing such a large injector, I would be sizing something a bit more appropriate, you could easily give yourself 20 or 30% margin for headroom, that won't affect it but what I'm getting at is if you think you might need at the moment 2000 cc secondary and you go and put in a 5000 cc, it's probably going to be a compromise at that point.
48:40 David has asked, what about a combination of direct injection and port injection like the VW EA888 Gen 3? Yeah we run exactly that system, I'm not familiar with the Volkswagen but we run exactly that system in the Subaru FA20 that's one of our test cars that incidentally is run by MoTeC M150 as well with a specific package.
49:05 So this is a nice feature and we're seeing this incorporated a lot with direct injection engines in the aftermarket.
49:13 One of the problems with DI is that within reason we don't have the amount of availability of larger aftermarket injector sizes out there, it just doesn't exist at the moment on the market and that means that if you want to take a factory DI engine and maybe double or triple the power output, you're not going to be able to do that purely with DI.
49:37 So adding aftermarket port injection as well in a staged manner is a really nice solution, also gets around some of those problems with the carbon build up that we see on the back of the intake valves with DI engines because there's no fuel flowing through there so yeah the process there is essentially the same, there are some advantages though depending on the particular direct injected engine you're talking about, here are some advantages with running basically as much direct injection as possible and just adding the minimum amount of secondary injection through your port injectors.
50:16 This on some engines can make the engine a little bit less prone to suffering from knock so that can allow you to creep in a little bit more timing, maybe a little bit more boost or sometimes both so that's one consideration.
50:32 Where your secondary contribution or staged injection table, the tuning of that becomes quite a critical element in getting the most out of your engine.
50:42 Eric has asked, I have trouble with a lean spike when I blip the throttle on my MoTeC M130, is there a place where I can correct this? OK Eric we do try and keep these specific webinars very narrow focused onto the topic we are talking about, obviously today staged injection so you've got a pretty big question there which will be more around acceleration or transient enrichment and the answer there is the MoTeC M1 series uses a fuel film model and getting that fuel film model set up properly is really critical so if that isn't set up, you will see problems with either lean or rich conditions.
51:24 However, without going too much deeper into it, a slight lean spike, even on a really well tuned engine under transient conditions is actually quite normal.
51:35 When I tune for transient, I am tuning for smooth response, a sharp crisp response, as opposed to trying to see a perfectly flat line on my air/fuel ratio table.
51:45 We do have webinars in our archive which covers transient enrichment on the MoTeC as well as other platforms.
51:52 Barry's asked, does the MoTeC have any hysteresis for a secondary injector in the event you're operating injectors close to the point where the secondary injectors are being brought on and off? Not specifically through our controls, at least not in this particular firmware.
52:08 However, there are some considerations with this in terms of the injector characterisation data which makes our job as the tuner a little bit easier.
52:18 The injectors, one of the characterisation items will be their minimum injector pulse width so basically the secondary injectors won't operate even if you ask them to if you are asking for them to operate below that minimum pulse width but no, there is no specific hystersis.
52:35 I generally find that we're stepping through the load zone so quickly that this becomes an irrelevance in my opinion, I haven't really seen that as an issue come up Barry.
52:50 Next question comes from Hot Boys who's asked, can I run two injectors on a single input on the ECU? OK the answer there is yes it is possible.
53:01 Caveat there is check with your ECU manufacturer because this is going to put more load on the injector drive so you will want to check and be certain that the particular ECU you are dealing with is capable of doing this, really comes down to the amount of current being drawn when those injectors are operating.
53:20 This does add a layer of complexity in terms of your injector characterisation though which a can of worms that I'm not going to open right here.
53:30 EH Jake's, I may have missed this but would this method work for separate tanks of E85 and pump gas to apply the higher octane fuel under higher load with separate fuel system of course? OK yes MoTeC actually do deal with this, I haven't used it myself but they have what they call their alternative fuel model.
53:50 So that's a slightly different take on staged injection where you are running better quality fuel maybe ethanol, maybe methanol through a secondary fuel system and pump gas maybe on your primary.
54:04 As you mentioned, a lot more complexity in that, you need two fuel tanks in the vehicle, you need two fuel pumps, fuel lines etc but it can be a really nice technique for particularly a daily driven street car where most of our daily commute will be at relatively low load and RPM running probably almost exclusively on the primary fuel.
54:27 Whereas if you want to give the car full throttle at a track day, it'll stage in the alternate fuel so it does need an ECU that's set up for that specific model because the differences in the fuel characteristics need to be incorporated as well as the differences in the injector size and characterisation but yes it is possible.
54:50 Next question comes from AE rotary who's asked, should I be concerned with fuel temps on a secondary fuel rail on a rotary if the rail is dead head and fuel is returned back to the tank through a bypass in the fuel pressure regulator? I guess it depends how often you're using the secondary injectors.
55:09 At least on the rotaries I've tuned, we're not relying on just using the secondaries under very high boost so they probably would be utilised more often than a conventional staged injection system.
55:24 I haven't set up a rotary as a dead head or non return style but yeah it could be an issue, I mean at worst you're probably going to have maybe some momentary weirdness when you bring in the secondary injectors and it clears that fuel.
55:42 It may have potentially vapourised or something of that nature.
55:45 Not something that I've personally come across, not something that I've thought about until you've brought it up but yeah definitely it could be an issue.
55:53 If you are concerned I would probably be inclined to either reroute the flow, I'm just trying to think on the fly, I'm not too sure if we could do that so that it would prevent the fuel sitting there, probably not, or go to a return style system which negates that as being a problem.
56:13 Right last question from Francoise I think, has asked, what should be the correct psi used for staged injection? I've talked with different tuners and seems like there are different opinions, should staging injection be set earlier around 2 psi or hold the staging injection engagement until higher psi are reached like 10 psi, what's my opinion? Simply put, there's no answer to that, there is no specific answer, no tuner can tell you that this is the psi that you must stage your injectors on, it just isn't like that, there is no black and white here.
56:47 On our particular example there, I could stage the secondaries in probably at 3 psi or I could stage them in at 20 psi and I would probably have largely identical results.
57:00 So the considerations you need to keep in mind are as exactly what I said.
57:04 We want to pick a staging point so that we aren't going to be trying to stage the injectors in too soon so that we're sitting at or very close to the minimum injector pulse width, so that we're basically staging the injectors in so that they're already operating at a point where they're in their linear area of operation.
57:24 So that's the first consideration.
57:26 So we want to generally see a reasonable jump in our duty cycle for our secondary straight away when we bring them in and the other aspect is in terms of how, if we stage them in too late, we're going to get to that situation where our primary injector duty cycle gets too high so it's monitoring the minimum duty cycle for our secondaries well as watching our maximum duty cycle for our primaries and basically balancing those so that neither become too small or too high so yeah hopefully you can understand from that, there is no magic number that you must stage your injectors in at and it's also going to depend completely on your injector size as well.
58:08 Alright that brings us to the end of our webinar, thanks to everyone who has joined us and if you are watching in our archive then if you've got further questions, please ask them in our forum and I'll be happy to answer them there.
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