In this webinar we’ll look at the tuning strategies for individual throttle body (ITB) naturally aspirated engines. For this webinar we’ll be using a Honda K20 fitted with an Emtron SL4

00:00 - Hey team, Andre from High Performance Academy here, welcome along to another one of our webinars.
00:04 And today we're going to be diving into ITB or individual throttle body tuning.
00:09 Specifically we're going to be looking at the Jenvey ITB setup that is fitted to our Honda K20, fitted to our CRX endurance car.
00:18 This is controlled with an Emtron SL4 ECU however, most of what we're going to be talking about is some of the generic aspects of ITBs, where people get tripped up, the things we need to understand and the techniques and processes we need to go through with tuning.
00:36 So regardless what ECU you're personally using, or for that matter, what style of throttle body, this will be helpful.
00:43 We are going to be focusing here solely on a naturally aspirated application.
00:47 There are some other intricacies that come into this when we add forced induction as well.
00:52 If you are interested in learning about that, we do have webinars in our archive covering the ITB twin turbo setup on Nissan's RB26 so you can check that out and that will give you the further information you need.
01:07 Alright so for a start, let's talk about conventional tuning, how we conventionally tune engines with a single plenum and throttle body.
01:16 So what we've got of course is that plenum chamber which usually will have a volume somewhere around about maybe 1.5 times the capacity of the engine.
01:25 So that acts as a damper and an air reservoir that each of the individual cylinders can draw from when they are on the intake stroke.
01:33 Now generally the way we go about tuning this is the speed density principle where we are basically calculating the mass of air in the cylinder and this is coming from the manifold absolute pressure in the inlet manifold.
01:47 So what we're doing is using a MAP sensor to measure the average pressure in the inlet plenum and because that's a large capacity, that's essentially a good approximation of the pressure or the air pressure available when an individual cylinder is on the intake stroke.
02:03 So what we need to know from this is that our fuel and our ignition tables will be set up as 3D tables.
02:11 We are going to have manifold absolute pressure, typically on the load axis and we'll have RPM on our other axis so pretty straightforward, this is how probably 95% of aftermarket ECUs would be tuned.
02:26 However when we get into a individual throttle body situation or application, this gets a little bit trickier and the reason for this is we now really have no common plenum chamber.
02:38 Before I go through this, let's just have a quick look at a couple of photos of what we're talking about here for our application.
02:45 So this is the K20 in our CRX.
02:49 As I mentioned, we've got a Jenvey ITB setup.
02:52 We've got a couple of photos here, obviously pretty generic here.
02:56 You can see a little bit more going on when we've got the air filter off.
03:01 So this is what we're dealing with here, we've got 4 individual throttle bodies, we've got a relatively short runner length, this is the carbon plenum backer up here, so the air is going this way and yeah you've got a relatively small volume of air between the throttle plate which runs through here.
03:23 And obviously down out of shot, we've got our intake valve.
03:27 So really small volume in that area in comparison to a conventional plenum with a single throttle.
03:35 Right just let me get back across to my notes here.
03:40 Alright so where this gets a little bit tricky is that we don't have that common plenum to add our manifold absolute pressure sensor to.
03:50 That is still an important consideration though and we do definitely want to add a MAP sensor, most of the ITB setups will make this nice and easy for us by offering some sort of balance bar and again if we just jump across to my laptop for a second, this is something I just stole from our friends at Speed Academy but this is an ITB setup showing how they've incorporated a vacuum balance bar.
04:17 So essentially what we want to do is take a tapping into each of the runners between the inlet valve and the throttle plate so it has to be after the throttle plate on the engine side of the throttle plate.
04:31 And then we want to run all of those up to a little common plenum or manifold, doesn't need to be a huge volume here, just a small plenum that we can use to basically balance out all of those individual pulses and then we can take our manifold pressure sensor reading off that.
04:50 So even with the ITBs, it is still important to use a manifold pressure sensor.
04:56 Couple of reasons for this, one is that even when we're using alpha-N, which we're going to talk about in more detail, with throttle position on our load axis, we do have a background compensation going on in the ECU and this compensation is simply that if all other things being equal, we double the manifold pressure, what this means is that we need to double the amount of fuel being delivered in order to maintain a consistent air/fuel ratio.
05:22 Now of course as we double the manifold pressure, we may not want to keep a consistent air/fuel ratio but what this does is it gives us more resolution in our fuel table and we're not having to manually make that correction ourselves.
05:34 So that's a really important element.
05:36 The other aspect with this, and you absolutely can run an engine on throttle position or alpha-N with no manifold pressure signal at all but what you're going to find, particularly with a street driven car, is there will be situations where maybe you're at let's say 3000 RPM and 15% throttle just cruising, so on a flat piece of road, 15% throttle, 3000 RPM, that defines the cell for your fuel delivery.
06:04 Now the problem with that is you can also get yourself into a situation where you're going up a very slight incline at that same throttle position and RPM setting, or a slight decline, going down a hill under those same conditions and if we were monitoring manifold absolute pressure, we would see that despite the fixed throttle position and the same RPM, we actually see a small but real fluctuation in our manifold pressure.
06:27 Now if we don't have manifold pressure going into the ECU for that background calculation, what you're going to see under these part throttle conditions is some fluctuations in your air/fuel ratio, so your drivability is going to suffer and that can be quite problematic.
06:41 So highly recommend we do want to include manifold absolute pressure in our alpha-N system.
06:48 Right let me get back to my notes again.
06:52 So we're going to be using throttle position in this situation for our load axis, instead of manifold pressure.
07:00 But the question that quite often comes up is why can't we just use manifold pressure? We've now gone to the trouble of taking the pressure signal from behind each of those throttle plates, we've got our little manifold balancing everything out and we've got our manifold pressure sensor there.
07:17 So why can't we just use that, why can't we just tune this like a conventional engine with a large plenum and a single throttle body? Now the problem with this is what's happening to the manifold pressure signal, that's the average of all 4 of our cylinders, in this case being a 4 cylinder.
07:34 But what's important as far as a fuel and ignition timing delivery is what's actually being delivered to the cylinder that is on the intake stroke.
07:43 So what happens is when the cylinder on the intake stroke opens, the intake valve opens on the, cylinder on the intake stroke, particularly at part throttle, what we're going to end up getting is a massive drop in our manifold pressure as the engine or the cylinder draws the available air from behind that throttle butterfly and as soon as it's open, essentially it's going to draw a vacuum there.
08:08 So the actual manifold pressure on that cylinder is going to be dramatically lower than what we're seeing as the average of all 4 so it doesn't give us a real indication of what's happening as the engine goes through, or the cylinders go through their intake stroke.
08:22 So that's the key point and the other element, the other concern I've heard raised is if we actually look at what's happening to manifold pressure, we'll probably find that once we get past about 40 or 50% throttle, we'll probably be very close to atmospheric conditions but again we're not actually looking at the manifold pressure instantaneously when the intake valve is open on the cylinder we're interested in so that's why using the manifold pressure signal from our balance bar, while it seems like it should be all good, should be a sensible idea and bring us back to just a conventional speed density tuning style, it will not work.
09:00 What we're going to end up with instead, is if we try doing that, we'll be able to tune the engine at idle, we're going to be able to tune the engine at wide open throttle but the part throttle area, that's where we're going to have massive problems and essentially what we get is a situation where we can be either pig rich at part throttle and our air/fuel ratio will be OK at wide open, or alternatively we're going to be relatively correct at part throttle but we'll be lean at wide open throttle.
09:29 You'll just end up chasing your tail, trying to get this right, I can guarantee you that you won't.
09:35 So with all of that said, I really needed to get that out of the way to explain what the problems with ITB tuning is, the solution is that we're going to be using alpha-N which is throttle position for our load axis, for both fuel and ignition.
09:49 This is going to give us the opportunity to get nice rock solid consistent tuning.
09:56 Now before we get into the actual tuning, we're going to jump into the MTune software and have a look around and understand what's required.
10:02 There are a few fundamentals that we do need to consider first.
10:06 The first of these is throttle body selection, there's a number of manufacturers making throttle body setups for a lot of the popular engines and often they will be available in different diameters.
10:17 This is getting a little bit beyond the scope of today's webinar around the actual tuning process but bigger is not always better.
10:26 It really is going to depend on the useful power range of your engine and the higher up in the revs you want to make power, good rule of thumb is you're going to be moving to a larger throttle body but the downside of this is it can affect or reduce air velocity so we can end up seeing a reduction in torque, particularly at lower RPM so there is always a trade off here and there is always a bit of a balancing act.
10:53 The other element here is the throttle, let me just get back to this, the throttle, sorry not the throttle, the trumpets, so if we jump across to my laptop we've got a set of bolt on trumpets here.
11:07 There is the ability with ITBs to take advantage of the tuning nature of the entire inlet track.
11:15 So basically you could think if this as a musical instrument and we can adjust the length of these trumpets in order to affect a tuning effect which can allow us to improve the volumetric efficiency of the engine, essentially ramming more air into the engine.
11:33 But there's no free lunches here, basically we're going to be optimising that ram effect for one RPM range in the engine's operating range and we're probably going to be losing in other areas so it's essentially deciding where you want your powerband, but a really important aspect of ITBs, if your budget and time allows, is to test a range of different runner lengths and see how that actually affects the torque curve, the powerband and what that does for the actual outright power numbers in the area that you're going to run that.
12:08 That is one area so far with this K20 we have not been able to try and we just simply haven't had the time so we will be bringing out some content around that once we actually get the opportunity.
12:19 Now clearly this can be a bit of an expensive exercise, these trumpets aren't exactly cheap and if you're going to go and buy 4 different lengths of trumpet just to try, that can get a little bit pricey, I don't obviously have a way around this but if you can find a shop that has a bunch of these that they use for testing and you can borrow them, maybe a box of beer or something of that nature, that could be a good way of bringing your costs down.
12:47 Right the other element that's really really important and so often overlooked with ITBs is balancing them.
12:54 A number of cars that I have retuned, which have ITBs fitted to them and they drive horribly at part throttle.
13:02 A really good giveaway that the throttle bodies are not balanced is if the engine is audibly missing or backfiring at idle or part throttle.
13:13 And the reason for this is that again, all of our fuel delivery and our ignition timing, but here we're really more worried about our fuel delivery, is based off the output from our throttle position sensor.
13:24 So we're really just correlating that to airflow, it's not a direct measurement of airflow and the problem with this is if we have one or maybe two of our throttle butterflies that are cracked open just a little bit more than the others, then what we're going to have is much more airflow to those cylinders than the others so we could be looking at our average air/fuel ratio and it looks like it's OK, what we've really got is two cylinders that are probably way too rich and then two cylinders that are way lean, well one cylinder maybe that's way lean and that can bring about this lean misfire so it's really important before you get involved in the tuning process, to spend the time and actually balance the throttle butterflies.
14:09 So what this is, is a case of adjusting the butterfly opening so that the airflow essentially through all of the cylinders is the same.
14:18 Obviously next questions is well how do we do that? So what we do is we use a device called a carb balancer because unsurprisingly, carburettors are very similar in their sensitivity of things like this.
14:29 So this is just one that I found a photo of on the internet but essentially it's something that we can insert into the trumpet, the engine has to be idling while we're doing this.
14:41 You can insert that into the trumpet so it's basically forcing all of the airflow through that particular cylinder to go through this particular unit and here we've got a little gauge on it which essentially shows us the airflow through that cylinder.
14:54 So what we want to do is basically use that in each of our cylinders and then, if we just come back here, most of these individual throttle body setups will have a way of adjusting the relative positions of the throttle plates on each cylinder.
15:10 That's what I've just circled here on these Jenvey ITBs.
15:15 But that's what we want to do is basically adjust the throttle butterfly opening so that we've got essentially an equal reading on all of our 4 cylinders of 6 cylinders or however many we've got using the carb balancer.
15:29 So this is a really essential tool for anyone who wants to tune ITBs.
15:33 I have seen people hook up a manifold pressure sensor, maybe the likes of the one on the dyno, to an individual runner at a time and use that for balancing.
15:44 It's probably going to be better than guessing, better than nothing but really ultimately if you're going to be tuning ITBs I'd highly recommend you purchase a carb balancer.
15:53 Probably get something like this for between $50 and $100 USD so they're not the most expensive tool and they are very quick and easy to use.
16:03 So that's the essential first step, once we get ourselves up and running, make sure that the throttle bodies are balanced.
16:11 It's going to make the drivability and the tunability just infinitely better and you're going to just get a far far better product.
16:19 Now we're going to just into the MTune software and have a little bit of a look around and see what we need to understand here.
16:27 So we are open here on our main VE table.
16:31 Getting a little bit beyond the scope of just tuning ITBs but for those who are maybe looking at the shape of this and wondering, why our volumetric efficiency at high RPM where VTEC should be working, our engine should be screaming, is so low.
16:46 This is because for this particular application we are using two VE tables, likewise two ignition tables, switched based on the VTEC changeover point, so when we come into this, we switch to our VE table two and now we've got something that actually looks a little bit more realistic or a little bit more how you'd expect for a K20.
17:07 Having said that, we'll come back to our main VE table 1 and what we want to do for a start is set up what our engine efficiency calculation is going to be.
17:18 And likewise if we come across to our ignition table, again we've got exactly the same thing going on here we can see that that is set to load calculation.
17:28 So not particularly meaningful, essentially what we need to know is what do these parameters mean or what are they using for those load inputs.
17:38 So let's have a look at that.
17:39 If we go into our config and into channels and then into calculated run times and main.
17:46 Bit of a handful there, mouthful.
17:49 We've got the ability to set what our efficiency and our load calculations will be.
17:54 So if we look at our list of options here, it is pretty broad but generally in most instances, for a conventional tuning operation, that is going to be set to manifold absolute pressure.
18:06 So what we want to do there of course is change these to throttle position which has already been done, so that's the key, that essentially then sets up what the Emtron is going to be using as the load input because, again if we come back to our tuning workbook and our fuel main VE 1, efficiency calculation on its own is not really describing too much and right now if we hadn't gone and looked at what that channel actually is, this could be manifold absolute pressure for all we know, so that's really critical, we need to make sure that we've done that before we get started.
18:44 Now there is another element that is important for our fuel tuning and this is the way the airflow is affected by our throttle opening.
18:54 Because throttle butterflies are very very non linear.
18:58 What I mean by this is we don't get an equal increase in airflow when we go from 0-5% throttle and then 5-10% throttle and that affects our resolution in our table so I'm going to do a horrible drawing here which I'll do my best to make clear but let's see how I go.
19:14 This is essentially what we're going to end up with for our airflow, so if we do a couple of axes here, and what we'll have is on our bottom axis, this is our TPS and on our vertical axis, this is going to be our airflow.
19:32 So as we go from 0 here to 100%, what we end up with is quite a sharp quick increase in our airflow as our throttle position initially opens and then as we get higher in the throttle position, you can see it sort of flattens, and again, not the best drawing but hopefully you can get the sense of what that actually looks like.
19:52 From closed throttle, we very quickly ramp up our airflow and then once we get past about 80 to 90% throttle opening we see very minimal increase in the actual airflow with our throttle opening.
20:06 So what this means is that if we want to do a good job of getting the engine running nicely and smoothly and consistently, we want to take that into account when we're choosing our break points for our axes so we can see what I've done here is on that vertical axis, we've got break points at 0 then 2.5, 5, 7.5 and 10% so 2.5% break points initially.
20:30 Once we get to 10%, we go 10, 15, 20 so now 5% and then 20, 30, 40, 50, 60, once we get to 60, I'm now doing 20% jumps.
20:41 So really important to get that tight grouping of our break points down near closed throttle, that's going to give you really good control down in the idle, transition off idle and those cruise areas and these of course are so crucial, particularly for a street driven car.
20:57 So really important to understand that.
20:59 If you're going with what you might use in a MAP based load calculation, maybe 10 or 15 kPa increments, you're going to almost certainly find that there will be holes or differences between cells and maybe the engine's going to run a little lean, a little rich, you're not going to have the control that you'll have when you set it up like this.
21:22 But the flipside of that is you can get away with the more coarse break points at higher openings, going from 10% break points up to 20% once we get past 60% throttle opening because again, we get into that area where we're not actually seeing a massive increase in airflow with an increase in throttle position and while yes you could absolutely have 5% break points up here, all you're doing at that point is simply making more work for yourself so absolutely not necessary.
21:54 We're going to into questions really shortly so this is a good time to let you know, if you've got any questions, please go ahead and ask them, we'll get into those in a moment.
22:03 Before we do that, let's just jump across to our ignition table and have a quick look at that.
22:07 As I mentioned, again we do have two ignition tables that we are using here.
22:13 But all I really wanted to cover here, the ignition side of the tuning, really as far as alpha-N's considered, other than the fact we're using throttle position for our load axis, not really a lot more that we need to understand or take into account, compared to a conventional tuning strategy but we can see here that the break points here are a bit coarser.
22:34 While we've still got that same situation occurring where we're going to have a rapid increase in our airflow from closed throttle to maybe 15, 20%, the accuracy or the importance of our ignition timing across those ranges is not quite as critical as our fuelling so we can get away with being a little bit coarser here so as you can see, 10% increments until we get up to 60% and then we're jumping to 20% increments again.
23:03 So that's probably the biggest consideration there for our ignition tables, just don't need to be too tight with our break points.
23:12 Alright let's come across to our fuelling and really when it comes to the actual tuning process, this is really quite simple, it's no different than the process of tuning manifold absolute pressure and if anything, it's possibly a little bit easier to be accurately in the centre of a cell because we're controlling this with our right foot.
23:30 So what I'd do, as we recommend in our standalone tuning process, is start with low RPM and low load.
23:38 So maybe we might get the dyno started running here at 2000 RPM, we might be able to get down to maybe 5% throttle before the torque drops away enough that we don't actually have enough to keep the dyno running.
23:53 So what we'll do is come into the centre of that cell, hold the engine in the centre of that cell and then adjust our fuelling until our air/fuel ratio, our lambda matches our target and then all we're going to do is increase our throttle position and slowly but surely ease our way up until we're at wide open throttle and we're at the top of that table.
24:11 Now again no different here to a conventional MAP based setup but what we do want to be mindful of as we're doing this is just taking note of the number in the cell we've just tuned and then the number in the cell ahead of it, or above it.
24:26 So if we were in this cell here, it's got a number of 43.5% in it, let's consider that that is tuned.
24:33 Let's say though, we're just getting started with this particular vehicle and we've got no map in it at all, so we're actually building this up from 0, so if we're in the 5% throttle, 2000 RPM zone and we've tuned it, our lambda's right on our target, so we're next going to increase our throttle opening and we look at the cell above it and this time that cell has a value of 30.
24:54 Well I'm going to be pretty certain that as I increase my throttle opening from 5-7.5% at 2000 RPM, I'm almost guaranteeing I'm going to need more VE, more fuel, more airflow.
25:07 So 30% to me, that's definitely not going to be right so not really going to be any damage done, definitely not a risk damaging the engine if we open the throttle to 7.5% and find out that we're way too lean, chances are possibly that could be lean enough just to have a lean misfire, it's going to sound horrible and that's about it.
25:26 But what we can do is just take a bit of a stab in the dark and look at that and sort of think well if we've got 43.5% there, maybe we might want to start by entering a value of 50 there.
25:35 So then we can open the throttle, if we've guessed right we should be close or hopefully a little bit too rich which is obviously nice and safe.
25:44 We can then optimise that cell once we get into it and carry on.
25:47 So by just taking into account the trend that we're seeing, and particularly as we get more and more of these cells complete, we're going to get a sense for a 10% increase in throttle opening, what is the increase in VE that we need to enter into this table? We can sort of guess ahead and it just means that first of all, our engine's going to be nice and happy running, it's not going to be too rich, it's not going to be too lean, and it's also going to speed up our tuning process.
26:12 This becomes more important once we get to higher load and higher RPM regions.
26:17 Obviously more important again if we were tuning a turbocharged engine where the specific power output of the engine becomes higher.
26:23 So it's always a good idea to keep this in mind even though, as I say, at 2000 RPM and such low throttle, almost any fuelling's not going to do damage to the engine but a good habit to get yourself into.
26:36 Now I haven't mentioned this yet but if we just come back up to our fuelling.
26:41 This also of course works in conjunction with our lambda table, our lambda target table.
26:47 So we do need to also have this filled in.
26:50 It is important to make sure that we have throttle position on the load axis of our lambda target table as well, by default this will probably be manifold absolute pressure.
27:01 If we haven't noticed that, we can get into a situation where this in and of itself is causing some inconsistencies so we want to make sure for naturally aspirated engines, this is set to throttle position.
27:11 Again I'm not going to go into a turbocharged ITB setup but in that setup, we would actually have this as manifold pressure.
27:20 So making sure that we've got some sort of sensible numbers in here.
27:23 We're sort of lambda 1 or a little bit richer, this is a race only application so cruise fuel economy is not really our biggest concern here.
27:32 And then at wide open throttle we're sort of 0.94 down to 0.88 lambda so we want to make sure that that is set because that's going to be what we're tuning to.
27:42 And it is a VE based ECU so if we've tuned the VE table and then we go and make changes to our lambda target table, that will actually affect the ultimate fuelling that the engine has so really important to make sure that that is where we want it to be.
27:57 As we can also see, quite coarse resolution here, I don't need tight resolution.
28:02 If it was a street car where I was more concerned about the cruise fuel economy then I might go a little bit further with this but essentially we're aways going to be cruising at probably 30% throttle or less so essentially we are going to be in this area here where we are pretty much lambda 1 so job done.
28:18 Alright we'll move into some questions now, if you've got any, please ask those in the chat and we'll see what we've got.
28:32 Actually before we get into questions, I just wanted to add one more consideration with an ITB setup where we're using throttle position and that is around idle speed control.
28:43 So in this application, we have no idle speed control.
28:47 It's not something I'm worried about, it's a race only application so pretty common to not have idle speed control in ITBs.
28:54 But if you are going to add it, then some consideration needs to be made around how you're going to do this.
29:00 Conventionally what we would normally do is have an air bypass around the throttle plates and this could be a stepper motor or an idle speed control solenoid.
29:09 And what that's doing is simply bypassing air around the closed throttle plates.
29:13 Now the problem with this on a alpha-N style system is our throttle position obviously isn't changing but our airflow into the engine is.
29:23 So generally that's going to cause some problems with our air/fuel ratio control at idle as that idle speed control stepper or solenoid opens and closes to control our idle speed.
29:34 The holy grail, at least as far as I'm concerned is to do away with those styles of system completely and go to a drive by wire throttle body, drive by wire throttle actuator.
29:46 Jenvey actually make one for their individual throttle body kits so it's nice and easy.
29:51 Then for idle speed control we're actually using the throttle opening, so we're opening and closing the throttle butterflies in order to control the idle speed, it's obviously pretty straightforward from there.
30:02 Other than that, you could incorporate a 4D table for your fuelling based on maybe your idle speed solenoid percentage, duty cycle and make a correction to your fueling around that but if you're just bypassing air that the engine essentially, the ECU doesn't know about, you're going to end up with some inconsistencies in your fuelling there so I just wanted to mention that before we get into the questions.
30:31 The first of those from The Snow Wolf, who's asked, can you use MAFs with ITB setups if using an airbox? Yeah absoutely you can.
30:40 And that really takes all of the complexities that I've just covered out of the equation.
30:44 Very very rare on an aftermarket ECU to use a mass airflow sensor so it would be very uncommon to do so but absolutely yes you can.
30:57 Next question comes from RPSS who's asked, can the trumpets be adjusted and can you give some guidance regarding size, efficiency, eg larger ones benefit low RPM or higher RPM? So yeah I mean you can adjust them, they're made to be unbolted and as I mentioned, you can buy a range of different length trumpets from Jenvey or a range of other suppliers so yeah absolutely no problem there.
31:19 Except for the expense.
31:21 The general trend here is that the longer the intake runner, that will favour lower RPM efficiency, shorter runners tend to favour high RPM efficiency.
31:31 Now that is of course purely just a rule of thumb, there's a lot more specifics come into it than that but that's probably enough of a guide to at least get started.
31:40 Ultimately the dyno's going to tell you what the engine wants.
31:44 Point 0 has asked, ITBs in a 4 cylinder turbo road race application, can you make it work or is it too much trouble to make it worth it? I'd like to have the throttle response and the extra horsepower from running ITBs.
31:57 Honestly absolutely you totally can, it's no problem at all as long as you understand the process.
32:06 And again, I'm not dealing in this webinar with turbo plus ITB.
32:11 There is a little bit more work involved with that but really not that much.
32:15 We need to have a target air/fuel ratio table based on manifold pressure instead of throttle position.
32:24 Reason being that we don't necessarily want to run the same air/fuel ratio target at 100 kPa atmospheric pressure and wide open throttle that we would at 200 kPa, 1 bar of boost and wide open throttle and we can get into both of those situations so that's important.
32:39 Basically we also would run the ignition table in that instance based off manifold absolute pressure, not off throttle position but absolutely you can.
32:50 To your point about throttle response and the extra horsepower.
32:54 Extra horsepower in particular, I would not say there is any guarantee at all in that.
33:00 You can get great results with a single throttle body and plenum and there's a lot of urban myth around ITBs and what is an advantage and what isn't.
33:12 Particularly around the throttle response as well.
33:15 I've never done any back to back testing on the throttle response between an ITB setup and a single throttle body and plenum so it's hard for me here to stand up and say here are the facts because I just haven't done that testing but anecdotally I've driven both and I've never really been able to say, hey you know what, ITBs they are just so much sharper in their response but that's up to the individual I guess.
33:39 Manitou Black's asked, given the choice, would you opt for vertical or horizontal throttle shafts and are there advantages either way? E.g. slides vs butterflies? So slide throttle bodies would be a bit different to vertical or horizontal shafts.
33:56 I don't know if vertical vs horizontal butterflies themselves would be any advantage.
34:02 Maybe there's possibly something in the way it favours the airflow to one side of the port but I really don't know, I guess again that would come down to some testing.
34:13 Slide butterflies or slide throttle bodies though are a different style of throttle body where instead of butterflies, we actually have a plate that slides and the advantage with that is when they are wide open, there is absolutely nothing in the way so with our butterfly, our conventional butterfly, even when it's wide open, you've still got the actual butterfly and the shaft in there blocking a small but measurable amount of the airflow so quite common on very high end naturally aspirated race engines to either run barrel style throttle bodies or slide style throttle bodies but again, have not been able to do back to back testing on that.
34:50 I would see potential advantages but I can't say if I can see any disadvantages other than the cost.
34:59 RPSS has asked, is it worth just using a sensor for each horn to have the correct reading for the air mass that's coming in, even with the equaliser seen at the beginning of the class? No it isn't.
35:09 So even in that situation we're not going to still be able to make use of the manifold pressure sensor for our fuelling.
35:17 THe other problem is here, or twofold, cost, MAP sensors aren't the cheapest sensors, so needing 4 of them vs 1, that's a significant bump in cost.
35:26 The biggest issue though is I have not found an ECU where you could actually input 4 MAP sensors like that and make use of the signal so it's basically not something that you're going to be able to do.
35:38 Ash has asked, if using drive by wire and ITBs, can you not use motor gearing steps to determine throttle position from the stepper servo motor? Maybe more involved solution, therefore not required but for a very high performance engine, maybe more accurate.
35:53 Not something I've actually though about before.
35:59 Really the way a drive by wire throttle works though is it's driving the servo motor using a PID algorithm to target a specific throttle percentage or opening so that's the feedback circuit, It isn't a stepper as such, it's a servo motor.
36:14 Beyond that, yeah I'm not sure I could really give you much more.
36:19 I mean the position feedback comes from the throttle position sensor so yeah it's an accurate system, it works incredibly well.
36:27 There's a lot of, again, urban myth and legend about problems with drive by wire throttle.
36:32 Most of those came from early OE production drive by wire throttle setups.
36:36 Modern drive by wire using a good quality ECU, the response, accuracy, precision, repeatability are really really good.
36:45 Simon B's asked, can you discuss butterfly vs barrel vs plated guillotine? I think I have now, I hadn't inside of the webinar so thanks for bringing that up, so I won't repeat myself, I think I've said what I needed to there.
36:59 Next question, do ITBs affect transient fuelling? What tuning strategy would I use to get that crisp throttle response? Yeah probably they will affect, if you were to take an engine that had been properly tuned with a plenum and single throttle, switch to ITBs, I would almost certainly expect some tweaking of the acceleration or transient enrichment would be required.
37:24 I would expect that to be relatively minor though, I'd say you'd already be at least there or there abouts, somewhere in the ballpark so shouldn't need a dramatic change.
37:34 There a couple of ways, without going too deep on this, there's a couple of ways of dealing with transient enrichment and it's very much ECU specific.
37:42 Most traditionally have just used rate of change of throttle position.
37:45 Which does work pretty well but it's kind of a bit of a bandaid on the real problem which is the fuel film that has formed on the port wall when the fuel is injected by the fuel injector so again, not going too deep on this but that's the real principle that's happening in there so there's a couple of ECUs that do model this fuel film behaviour properly.
38:07 Basically it's not too difficult though, essentially what we're just looking for is tuning the transient enrichment until the respnse feels and sounds crisp.
38:17 I don't generally use the feedback from my lambda sensor too much, or I don't lean on it too heavily when I'm tuning transient enrichment.
38:26 You're almost always going to see a bit of a rich and a bit of a lean spike through a transient event if you're logging your lambda but to me, if the engine is crisp in its response, that's the most important thing, I'm not chasing a flat lambda curve that doesn't vary as I open the throttle.
38:47 Next question comes from Plohl who's asked, have you have a chance to do this on an M1 using their ITB tuning method? You end up tuning the manifold pressure estimate table instead of the main efficiency table.
38:58 I have and yeah it's a little awkward on the M1.
39:02 They've kind of built themselves into a bit of a corner with it just based around the way the M1 works.
39:09 So definitely if you came into the MoTeC M1 world and you had no clue what you were doing with ITBs, it would be confusing.
39:16 They actually have a PDF I'm pretty sure on how to set up an ITB calibration so following that guide is pretty effective.
39:28 Plohl's also asked, how applicable would you say this info is to running a larger cam or overlap NA engines with a single throttle and plenum? Yeah there is an argument that a really large cam, where you've got very low manifold pressure or vacuum I should say at idle, doesn't give you good resolution for your tuning so then TPS can be a better input.
39:55 I sort of take this on a case by case basis.
39:59 Yeah it's going to be a problem on some really aggressive cams but unless you're there, almost always I can make even a really big cam idle and run and drive nicely using manifold pressure as the load input but yeah if I'm in a situation where it's marginal, I don't have what I consider to be enough vacuum being pulled at idle then absolutely tuning on throttle position is a viable technique, even though we've still got technically a single plenum, single throttle body and plenum.
40:32 Simon has asked, have you ever seen unequal length inlet trumpets used on cars? They were used on Can Am cars and some current small block endurance cars? I wouldn't say on cars in general I've seen this but I was involved with the tuning on a Toyota 86 endurance car many years ago that was fitted with a Synergy V8.
40:54 So the Synergy V8 is based around a billet block and Kawasaki ZX12 barrels and cylinder head so it's basically two 4 cylinder Kawasaki motorcycle engines.
41:06 And using the factory inlet runners on that, inlet trumpets I should say, on that for their ITBs, they have two long and two short trumpets so my understanding around this was it's used to make the torque curve a little less peaky but of course there are some issues around the fact that we will have cylinder to cylinder variations in terms of volumetric efficiency.
41:32 So really to tune those properly, ideally in the perfect world you'd want individual cylinder lambda so you can actually see where individual cylinders are richer or leaner and correct.
41:42 But yeah that's my only run in with that style, I haven't seen them used anywhere else.
41:49 Alright that's taken us through to the end of our questions so thanks to everyone for watching.
41:54 For our members, if you are watching this at a later point in our archive, please feel free to ask any questions you've got on the forum and I'll be happy to help you out there.
42:03 Thanks for watching and we'll see you next time.