Summary

A wastegate is critical to accurate boost control, however there’s a lot of decisions to make before you purchase one, and even more to know about properly installing one and selecting a suitable spring. In this webinar we’ll take a deep dive into everything you need to know.

00:00 Hey team, Andre from High Performance Academy, welcome to another one of our webinars and this time we're going to be diving into everything you need to know about wastegate selection, wastegate operation and also boost control as it relates to how we should be plumbing up our boost control systems.
00:16 And I think over the years I've been tuning cars, problems with either wastegate selection size or installation or probably more commonly actually just simply how the boost control system has been plumbed up, these would be the most common issues that I would come across when I was dynoing a car that had been built by an owner or even another shop.
00:38 The upside of all of this though is that most of these things are actually really really easy to fix while you're building the car or in other words keep these things in mind, it's going to save you time and it's going to save you a huge amount of money and you should have a relatively seamless experience when it does come time to actually set everything up on the dyno.
00:57 As usual we will be having questions and answers at the end so if there's anything related to this specific topic that you'd like me to go into a bit more detail on or anything I don't touch on that you'd like to know about wastegates, you can ask those in the chat and we'll get into those at the end.
01:12 First place to get started really is what is a wastegate and I'd like to think that anyone watching probably has a reasonably good idea but essentially a wastegate is a boost control device that's designed to help control the speed of the turbine wheel which in turn controls the speed of the compressor wheel and therefore the rotational speed of the whole turbocharger which then defines how much boost pressure is going to make its way into the engine.
01:37 I've got a couple of options when it comes to wastegates, I'm just going to get this one under our overhead for a moment and we can actually see inside the back of this turbo, this is either the turbine side or hot side and what we've got here is this little valve, this is the wastegate itself, it's cast into the exhaust housing and we can see as well the turbine wheel there.
02:00 If I turn it over on its side, we can see what is referred to as an internal wastegate.
02:05 So, this canister here has a little spring in it, we supply boost pressure to it.
02:10 When we supply boost pressure to it, it overcomes the spring pressure, it extends the shaft which in turn will then rotate and open the wastegate valve inside the exhaust housing that we just saw.
02:21 So, it's an internal wastegate, we've also got an external wastegate and I've got a couple of examples here, one that's looking a little bit the worse for wear.
02:30 This is off our Toyota 86 endurance racecar.
02:35 Slightly different design but essentially the operating principle's the same.
02:39 We've got the valve here which opens and closes in order to allow exhaust gas to flow basically through the hot side of the wastegate.
02:49 And then we've got the canister on the top of the wastegate which includes a diaphragm and then a spring and as we'll find out as we go through this, as we manipulate the way the boost pressure is supplied to the diaphragm and the spring, we can then control the amount of boost pressure we're getting.
03:07 So, again just to reiterate, the important part with the wastegate is the turbocharger is essentially being provided energy by both heat and exhaust gas flow and by bypassing some of that exhaust gas flow around the turbine wheel, we're reducing the energy being supplied to it so that is how we control the speed of the turbocharger and as I mentioned, in turn that controls the amount of boost pressure that's being produced.
03:32 We'll dive a little bit further into the internal versus external wastegates and where they sort of fit in.
03:39 Probably nearer the start of my career in tuning, internal wastegates were almost exclusively for factory turbochargers.
03:49 These days it's a little bit greyer, there's not quite such a defined sort of step between internal wastegates and external but generally still for a performance aftermarket turbocharger, particularly as we get into the larger frame turbochargers, you're much more likely to see an external wastegate.
04:07 So, why do OE's or OE manufacturers use internal wastegates? It's really sort of about simplicity and packaging really does simplify the whole packaging of the turbocharger assembly and really where we can get away with an internal wastegate versus an external wastegate comes down to the required size of the valve.
04:27 Obviously as we get into larger valves and this one here's a 45mm, that's the diameter of the valve, obviously these start to get harder to neatly package into the actual exhaust housing like we can see has been done with this one, it just becomes a bit cumbersome and a bit more difficult to achieve.
04:48 But there's not a lot of black and white when it comes to motorsport and modifying cars and turbochargers and BorgWarner would probably be one of the name brand manufacturers of performance aftermarket turbochargers where they do offer internal wastegate options on a number of their larger frame turbos.
05:06 Not all of them but definitely some of them.
05:09 So, these days it's not quite so cut and dried as to whether you're going to need to go internal or external for your wastegate but there are options on both.
05:17 The good news is that really as far as we're concerned, a lot of what we're going to be talking about, there's a crossover or correlation between what works for internal and external wastegates.
05:28 Now, the operating principle here with the internal wastegate, as I mentioned, I'll just grab some photos here, just give me one second.
05:39 If we jump across to my laptop screen here, this is the typical arrangement that we're going to see for an internal wastegate.
05:46 So, what we have here is that canister that we looked at on the top of our wastegate.
05:52 And if we open that up and look inside of it, what we're going to have is a diaphragm in the middle here and that diaphragm simply allows the whole assembly to move without any air leaking, hopefully.
06:05 We've got a spring underneath that and that diaphragm is working against the spring.
06:10 So, essentially the idea is that we supply boost pressure, most of the time with internal wastegates, we're going to find a single port on it and that single port will be on the top of the diaphragm exactly like we've seen here but again there's not a lot of black and white, there are some aftermarket internal wastegate actuators now that have dual ports on them but this is still far and away the most common arrangement we'll see.
06:35 So, when we add boost pressure into the top of the wastegate here, on top of this canister, it works against that diaphragm which in turn works against the spring pressure.
06:45 And once we overcome that spring pressure, we're going to end up with the actuator here moving, that actuator as we can see is attached to our internal wastegate valve inside that exhaust housing.
06:58 It'll rotate that and open it and allow exhaust gas to flow around the turbine wheel.
07:03 Basically, controlling boost just like we were talking about before.
07:07 So, that's the operating principle and in this instance our boost pressure is going to essentially be controlled or set by whatever the pressure of this spring is.
07:19 I'm going to dive a little bit deeper into the different ratings of the wastegate springs for both internal and external as we get further into this but essentially as that sits, we don't have any real control over the boost pressure, it's just going to be set by whatever that spring pressure is and if we want more, we're going to have to have a way of manipulating the control of the wastegate somehow.
07:43 There's options to do that with both pneumatic and electronic boost control systems which we'll dive into in a little bit.
07:51 Next, we'll jump across and have a look at a typical external wastegate.
07:57 And this is exactly like the Turbosmart wastegate that we just looked at.
08:01 Very similar but things are kind of turned around a little bit.
08:04 So, we've got our valve that we looked at which is in the bottom of the wastegate housing.
08:10 And this time in order to open the valve and bypass exhaust gas, what we have to do is actually move the valve upwards.
08:18 So, opposite direction to what everything looked like on our internal wastegate.
08:23 And for that reason the assembly of the wastegate does look a little bit different in that we have the spring now on the top of the diaphragm.
08:31 So, if we want to open this wastegate, what we now do is we supply the boost pressure into the bottom port on the wastegate.
08:42 So, these don't actually have any ports on them at the moment but basically that's where we're going to be adding our boost pressure.
08:51 And then we've got our top port as well which again I've got no valve in, no fitting in at the moment.
08:57 So, we're going to supply our boost pressure to the underside of that diaphragm.
09:01 And what's going to happen there is again it's just going to be working against the spring pressure, spring pressure's trying to push down, at some point we overcome that spring pressure and it's going to open that valve and start bypassing air.
09:13 Exactly like our internal wastegate, in this instance the way I've just talked about it, we have no control over the actual boost other than the pressure of that spring that's being provided, supplied inside of the wastegate.
09:26 So, we've kind of got a one set boost pressure and if we want to add some control, get more boost pressure, we're going to need to either add pneumatic or electronic control on top of that but again we'll get into that in a moment.
09:39 Let me just head back across to my notes here for a second.
09:45 So, with the wastegate operation, a lot of people, probably one of the most important parts that people overlook when they're sort of thinking about how the wastegate works is they fixate on the spring pressure.
09:58 So, I've got a couple of these springs here.
10:00 And these again are for a Turbosmart wastegate but essentially they're the same irrespective of the brand.
10:06 And you can see this one's got a blue colour on it.
10:09 We've actually got three springs here so you can sort of stack these up.
10:12 We've got a pink coloured middle spring and then I think this is a black inner spring.
10:18 And if you go to Turbosmart's instruction manual for their wastegates or online, you'll find a nice little chart of what springs you need to install inside the top of the wastegate in order to achieve a specific base pressure.
10:32 And again people fixate so much on that and think that well if I want 15 psi of boost pressure then I need to fit the springs that Turbosmart tell me in order to get 15 psi.
10:45 And the reality is that maybe that's the case but in a lot of instances it's not because the part that is very easy to overlook is we also have exhaust manifold back pressure that's also acting on the wastegate trying to force it open.
11:01 So, to have a look at how that works, we'll jump across to my laptop screen for a moment.
11:06 And this is some data here where we are looking at boost pressure which is our orange trace here in the middle.
11:14 So, that's inlet manifold pressure and then we've also got our exhaust back pressure.
11:19 So, this is a sensor that's not that common but it does give us a lot of information about the turbo sizing, how hard we're working the turbocharger and what's actually happening in the system.
11:33 So, if we take a given point here, what we can see is at this point we have 246 kPa of boost pressure and we've got 290 kPa of exhaust manifold back pressure.
11:46 So, we've actually got more exhaust back pressure, so more pressure in the hot side of the turbocharger between the exhaust valves and the turbine wheel.
11:55 So, basically you can imagine that sensor being tapped in right about here just before the exhaust gas makes its way into the turbine housing or turbine wheel.
12:06 That's what it's measuring so we've actually got more pressure in the exhaust manifold than we do in the inlet manifold.
12:13 And that probably comes as a bit of a surprise to a lot of people who aren't that familiar with turbochargers.
12:19 This is pretty much the reality though and it's all about sizing the turbocharger to achieve our aims.
12:26 Particularly if you're looking at a factory turbocharged engine, the manufacturer's less interested or less worried about how much outright power that engine's going to produce than they are about the drivability and particularly the boost response and boost threshold.
12:42 What we want is to be able to get boost pressure at low RPM very very quickly.
12:47 That's going to make the car feel torquey, it's going to make it easy to drive and people like that sort of feeling.
12:53 In order to do that, what we end up typically with is quite a tight exhaust housing and a small turbine wheel that provides that quick response but conversely at higher RPM it becomes a restriction and we start to see that exhaust manifold pressure climb.
13:11 And that ultimately chokes how much power we can produce, how much airflow we can get through that turbocharger.
13:17 So, if we look at the flip side of that, if we're looking at a drag engine, we obviously don't really care what the boost response is doing down at 2000 or 3000 RPM.
13:27 What we're really interested in is what we're getting at very high RPM and if I look at my old Evo drag car, which was a 2 .0 litre 4G63 Mitsubishi, that engine didn't really produce usable boost until about 7000 RPM and from there we could rev it through to 10500, 11000 RPM and we were running around about 50 to 55 psi depending on the track and the application.
13:52 So, on the street it would have absolutely been smoked by a completely stock standard Mitsubishi Evo 3 but when we're launching off the line using a two step limited build boost at 7500 RPM and we never drop below 8000 RPM during a run, it really doesn't matter.
14:09 Now, the turbocharger that we'd use to do this has a very large turbine wheel, it's very open, it's non restrictive, we've also got a large exhaust housing which makes it very free flowing.
14:21 So, there's not a lot of restriction to flow so that results in the slow spool, we don't have a lot of exhaust gas energy helping the turbo to spool up at low RPM but conversely we're not choking or strangling down the turbocharger at high RPM either.
14:36 And that's why we can make in this case 1100 wheel horsepower from a 2.0 litre four cylinder engine.
14:43 So, it's all about choosing what you actually want out of your turbocharger.
14:48 When it comes back to the exhaust manifold back pressure, if we look again at my data here, we're 290 kPa there on a 246 kPa, let's call it 250 kPa inlet manifold pressure.
15:01 So, our exhaust pressure has just slightly exceeded our inlet manifold pressure.
15:06 It's actually a pretty good combination for an endurance racecar.
15:09 On the other hand though if we're looking at a factory car, as I mentioned, they want response, it would not be uncommon to see the exhaust back pressure as high as two times the inlet manifold pressure.
15:21 Meaning that if we've got 15 psi in the inlet manifold, we could have 30 psi or more in the exhaust.
15:28 Then looking at the other end of the spectrum with our drag application, with my old drag car, even at 50 plus psi of boost, we actually had less back pressure in the exhaust system.
15:39 So, there's no sort of black and white with this, it really is so application specific depending on what you're trying to achieve and the size of the turbo.
15:47 So, why is all of this important and why am I talking about it? Because if we go back to our drawing here of our wastegate, we've got our spring pressure trying to hold the wastegate closed and then we've got our boost pressure on the underside of the diaphragm trying to force it open.
16:06 But the part that's really easy to overlook is we've got this valve down here which has got quite a large surface area and we've got that exhaust back pressure in the exhaust manifold that's also working on that valve trying to force it open.
16:22 So, what you'll find is that even if you disconnected the boost supply through the wastegate completely, and I definitely don't recommend you do this, on smaller turbochargers at higher RPM you're going to actually find that at some point that wastegate will just be forced open by the exhaust back pressure.
16:43 Unfortunately probably by the time that's done that, in a lot of instances, the engine's already going to have suffered some damage so again I'm not recommending this, it's just a case of trying to explain this is how powerful that exhaust back pressure is.
16:55 And that is why when you're choosing springs with Turbosmart's PSI rating on them and you've got your combination that on paper should be good for 15 psi, it's probably going to be there or thereabouts but it almost certainly won't be absolutely perfect.
17:13 So, just covering off what we know now, we've got our 15 psi spring in there and we've got a really really small turbocharger, something like this one here, that's providing let's say 30 psi of exhaust back pressure.
17:26 So, that's going to be helping force that wastegate open.
17:29 In that instance with a 15 psi spring, I would not be surprised if we only saw 12 or 13 psi, basically somewhere less than what we think we're going to be getting.
17:40 Flipside of that is if we use that same spring with our very very large drag racing turbocharger that's now got way less back pressure, we've got less back pressure trying to force the wastegate open, so we're likely to see our actual boost pressure in the inlet manifold a little bit higher than what that spring suggests.
17:57 So, I just wanted to make it really clear, the spring is not the be all and end all, it's probably going to get you close, it's probably going to get you into the ballpark but you're also probably going to find that from there, you're going to need a little bit of manipulation to actually get your boost pressure exactly where you want it to be.
18:15 However, do we want to do that with our springs alone? It's quite a coarse way of adjusting our boost pressure and also what we're going to almost certainly find is that we're not going to get a perfect flat boost curve.
18:29 So, I'm just going to do a really terrible drawing here and try and give you sort of an idea of what this might look like.
18:36 So, if we've got RPM on our horizontal axis and we've got boost pressure on our vertical axis, if we look at what we'd get with maybe a factory turbocharged car, probably going to have a boost curve that looks something like this where we have very little boost at low RPM, then our boost pressure's going to come up, it's going to peak, and then because factory turbochargers are normally sized for response, not high RPM performance, we're going to probably see the boost pressure fall over at higher RPM a little bit like this.
19:07 And if we are only manipulating our actual spring pressure, or our spring rate I should say, we can move that curve up and down a little bit but we're not going to be able to fix the drop off that we've got in high RPM, we're not going to get a nice flat boost curve.
19:22 Realistically the only way we're going to be able to do that is with electronic control.
19:26 So, that's why I don't necessarily suggest that trying to get your boost pressure dialed in perfectly just with the spring is a great idea.
19:35 That is just to get you into the ballpark and from there you're going to want to either add pneumatic boost control such as a boost bleed valve or you're going to preferably want to set up electronic boost control.
19:48 Alright, just let me get back to my notes here for a second.
19:55 OK next big point of choosing a wastegate really is what size wastegate should I be putting on my car? And this is one of those areas where I'm going to unfortunately have to say it depends.
20:11 This is really one of those areas where there isn't a black and white answer that you can apply to every application.
20:18 And I know this doesn't really help and it's probably more confusing than it is helpful but don't worry I do have some tips on how you can actually get the answers for your application.
20:28 The reason for this is that the sizing of your wastegate, what you actually need in order to be able to control boost is going to depend on your engine size, your turbocharger size and also the boost pressure that you want to achieve.
20:42 So, let's sort of dive into that in a little bit of detail.
20:46 Let's say we've got a given engine, it's a two litre engine, we've got a large turbocharger on it, maybe it's a GX, let's try and get this out properly, 3582, there we go, an older GTX turbocharger which was a pretty common combination that I used to use on a lot of our 4G63 upgrades that we were doing for customers.
21:12 So, if you wanted to run relatively low boost on that particular turbocharger, in order to do that, knowing what we know now, that would require us to bypass more exhaust gas around the turbine wheel in order to control the turbo speed and our boost pressure.
21:29 So, in order to run low boost, if we only wanted to run say 10 or 12 psi, I don't know why we'd want to do that with that particular turbocharger but if we wanted to run low boost pressure, we would need to bypass more exhaust gas energy around the turbo, hence we'd need a larger valve in our turbocharger.
21:45 Conversely if we want to run this thing on absolute kill, maybe 3540 psi, in that case we don't need to bypass as much exhaust gas energy around the turbocharger so we could get away with a smaller wastegate.
21:59 So, hopefully you can see it's not as cut and dried as a lot of people think when it comes to wastegate sizing.
22:07 There's a lot of things that we need to take into account.
22:10 The other part that's equally important and the other part where a lot of people go wrong is how the wastegate is actually fitted to your exhaust manifold in terms of flow priority.
22:25 So, we'll jump across to my laptop screen here.
22:27 This is a really simple example and it's not always going to look quite like this but what we need to understand is essentially exhaust gas is really lazy.
22:37 It doesn't like changing course, it doesn't like changing direction.
22:41 So, what we want to do is basically design our exhaust manifold and our plumbing to our turbocharger so that we offer good exhaust gas priority to the wastegate.
22:51 So, in this example on our left, we've got our run straight to the turbine wheel there but we can see that we've got also our wastegate coming off at a nice 45° angle or maybe less.
23:02 So, it's not going to be very difficult for the exhaust gas to basically divert out through that wastegate when it opens.
23:09 So, this is kind of what we're trying to achieve.
23:11 Basically, analyse your exhaust manifold design and try and come up with a solution where it's going to be easy for the exhaust gas to flow out of the wastegate.
23:21 So, that's what it looks like when we get it right.
23:24 However most people don't get it quite that right.
23:28 This is probably an unlikely case example, you're not going to necessarily do this, it's kind of just exaggerating the principle but you can sort of see what's happening here.
23:37 On the right we've got our exhaust gas again flowing straight into the turbine.
23:40 And this time the exhaust gas would have to actually just about do a 180° turn back on itself in order to flow out the wastegate.
23:48 It doesn't want to do that and this is not going to work well.
23:52 Now, as I've mentioned, these are two absolute extremes.
23:55 Chances are you're probably going to end up somewhere in between.
23:59 Often you're compromised by just the amount of room you've got in the engine bay, where the turbocharger and the exhaust manifold are, that sometimes can drive what you can physically do in terms of fitting a wastegate into an application.
24:14 And that's sometimes why now some of these larger motorsport based turbos that still offer internal wastegates can actually be a nice packaging solution because you don't have to worry about how to fit this external wastegate.
24:28 So, what happens if you basically get this really wrong? What you're going to end up with is a boost curve that looks something like this.
24:38 And you're going to see initially your boost sort of rise and it'll probably start controlling and then as you get further through the RPM range, once you're starting to build more and more exhaust gas energy to drive that turbocharger, that's where we sort of start seeing this boost pressure start, this exponential climb to infinity.
24:56 And the further you rev the car, the worse it gets.
24:59 Now, when you've got a situation like this, it's also really important as a tuner to recognise this.
25:05 I've seen this just so many times, it's an instant red flag.
25:09 So, what I would do with a situation like this, if I'm tuning a car and the further through the ramp runs I get, the higher the boost is going, first of all I'm going to come back to bare basics, I'm going to make sure that the pneumatic plumbing for the wastegate is in fact set up correctly.
25:27 So, if this was running electronic boost control, I'd start by just removing the electronic boost control solenoid from the application entirely, basically make sure that I've just got boost pressure plumbed to the wastegate in order to open it and nothing else and I'd do another run and see if I was getting any better results.
25:46 In this case because we're looking at a physical installation issue, obviously we're not going to be able to fix that and this is where we'd have to stop the tuning because there's no solution to this, it physically needs modifications to the installation.
26:02 A sidebar with this as well, this is also why it's really really important when we're doing our initial setups of our ECU to set up a suitable boost cut.
26:13 Probably if I'm expecting an engine to run 15 psi, I might set my boost cut at 18 or maybe 20 psi, just making sure that it is in fact there so if we get this exponential runaway because sometimes this can happen very very quickly and if you're not catching that fast on the dyno, you don't notice, it's very easy to get to a situation where we've got way more boost in the engine than it can handle or we're intending and obviously that can have some pretty severe consequences.
26:40 So, when we're tuning any turbocharged engine, a boost cut or boost safety is absolutely your friend and is essential.
26:48 So, this is what we're going to be facing with if we've got a wastegate that is located on our manifold in a way where we can't prioritise flow into it.
26:58 We're going to get a similar situation though if we've got this installation here and our wastegate is simply too small.
27:06 So, let's say we've got a 38mm wastegate, we've got the flow prioritised as well as possible but it's just simply too small for the job, we're just going to see that gradual creep in boost, it might not be quite so exponential as what I've just shown there but that's what we're going to see.
27:23 So, if you're seeing that sort of boost curve, you've got one of those two problems.
27:27 Interestingly, and I've done this as a test, the situation on the right where we've got the wastegate sort of almost coming right back on itself, in that situation you could actually physically remove the wastegate from the exhaust manifold and run the car, it's going to be much slower to initially come up on boost but probably somewhere around the middle of the rev range, you're going to match the boost pressure from the run with the wastegate and from there it'll continue to just climb exponentially out of control because the exhaust gas is just physically not flowing out through the wastegate.
28:00 So, there's no real solution to that.
28:03 Alright, let me just get back to my notes here for a second.
28:09 The other, so we've talked about sizing and I've basically said at this point that there's no sort of magic formula for sizing the turbocharger for the wastegate but of course that's not very helpful as I mentioned so how do we go about this? What I would always recommend here is deal with the wastegate manufacturer.
28:30 I deal specifically with Turbosmart, they're on our side of the world, they make a great product, we've been dealing with them for years and I really like what they do.
28:38 However we've also got manufacturers all around the world.
28:42 Tilesport would be another high quality brand that I would absolutely recommend.
28:47 If you, when you're in the market for a wastegate, deal either directly with the manufacturer or you deal with one of their distributors and you explain the combination of engine size and turbocharger that you're running, what sort of power level you're aiming for, the fuel that you're running and what your actual application for the car is, they will then be able to guide you on a suitable sized wastegate because they've simply got thousands and thousands of data points, they know for their own products what is going to work.
29:19 The other point as to why it's not necessarily that easy just to say a 40mm or a 45mm wastegate is the perfect solution for the XYZ combination is because the size of this valve is not the be all and end all when it comes to flow.
29:36 And a lot of it comes down to the engineering and design of the actual wastegate itself.
29:42 So, the lower housing here, the design of this, Turbosmart I know have put a lot of work into this and CFD to help it flow as well as it can.
29:52 And when you've got a really well optimised flow path with a wastegate like this, what that means is that a 40mm valve can actually possibly outflow a 45mm for example.
30:04 So, again there's a little bit more to it than just saying I need a 45mm wastegate for my application.
30:11 Having said all of that though, if I was to choose between a wastegate that's too small and a wastegate that's too big, I would be going a wastegate that's too big every time.
30:22 A wastegate that's too small's going to get you into those boost control issues that we talked about before, you're just simply not going to be able to control the boost pressure and you're going to end up with much more than you want.
30:32 A wastegate that's too big, the only real downside that I've personally seen, and this is coming from running a 60mm wastegate on a 2.0 litre engine, what we can find is that when the wastegate initially opens and cracks off its seat, what we're going to find there is that because it flows so much exhaust gas, we can actually end up with the exhaust energy to the turbocharger dropping off more than we want and we can sort of end up with our boost pressure taking a bit of a dive before we sort of get back into control.
31:03 So, obviously a lot less dangerous to our engine than running too much boost.
31:10 Alright, we'll move into some of the boost control issues that we're going to see and how to highlight those and we're going to move into some questions really shortly so this is probably a good time to mention if you've got any questions on anything I've talked about so far or anything related to wastegates and wastegate plumbing, please ask those in the chat.
31:32 I should mention before we move on, I have only been dealing at this stage clearly with a traditional poppet style wastegate and I am aware that Turbosmart in particular have had their straightgate on the market now for a little while.
31:49 It operates essentially like a conventional throttle style butterfly valve, it opens and closes.
31:55 Not quite the same as the poppet style in terms of its operating principles and there are some advantages to that.
32:03 I personally at this stage haven't had any hands on experience with a straightgate so I'm going to stick at this stage to what I have hands on experience with and despite the straightgate being available, I think it's fair to say that the poppet style wastegate is still easily far and away the most common that we're going to see out there.
32:23 One thing I did want to just mention here as well, just get this under our overhead, let's see if I can get this out.
32:30 And it looks like I can't, I don't know, maybe.
32:34 The way these are designed, no I'm not going to be able to get it out.
32:37 This little unit here which I've been struggling to remove, this is the wastegate seat.
32:43 I'm still going to give it a crack but it's definitely not going to play ball for me today.
32:47 So, this is a removable seat and on the top of it, it's got a mating surface that's angled that mates with the valve.
32:57 So, it's really almost exactly like what you'd see in a cylinder head where the valve closes against a valve seat.
33:04 So, the problem with these is the number of times that I have seen wastegates like this installed and the valve seat still sitting nicely in the box in comfort back in the workshop somewhere is actually ridiculous.
33:20 It happens so often with people who have never installed a wastegate before and they don't understand all of the parts and how they work together.
33:28 So, if you haven't got that valve seat in place, basically you've got a massive leak around the valve so the wastegate's never going to close, you're going to have really really really lethargic boost response and it's going to take an eternity for your turbocharger to come on boost.
33:45 So, tip number one, make sure when you are installing these components that the wastegate seat is there and tip number two, if you're dealing with an unknown vehicle that maybe an owner or another shop has built and the boost response is just much much slower than you expect it should be, then I'd be very suspicious that potentially the wastegate seat has been left out during the installation.
34:14 Now, the other thing that comes with this as well is just testing whether the wastegate is opening, how it's operating and quite often, this can really only be done with a turbo installation where the wastegate dump pipe is dumping to atmosphere rather than back into the exhaust system itself.
34:33 So, common for racecars, not quite so common for streetcars.
34:36 It can be quite difficult with an open exhaust to actually hear with the wastegate's opening and just as a really quick and simple way of eliminating that, one of the techniques that I had was I would just put a small piece of race tape over the wastegate dump pipe, basically the end of it and basically just bring the car up onto boost and then if the wastegate was in fact opening, the exhaust gas would blow straight through that race tape so you can visibly see that yes the wastegate has in fact been opening.
35:07 Right what we'll do is we'll just have a quick look, just let me get my slides in order.
35:19 Right let's start with our internal wastegate.
35:25 So, if we jump across to my laptop screen again, for boost control this is probably the most common installation we're going to see with a factory style boost control strategy.
35:36 Not always but it's very very common.
35:38 And we already know that in order to open our wastegate, we need to provide boost pressure to the top of this little canister.
35:46 And if we were just running a pure control strategy with no bleed off, no electronic control, basically none of this would exist and we'd just have our boost pressure source here on our turbocharger or our intercooler plumbing and that's going to just go straight to the top of our wastegate.
36:03 But that's no fun because then we can't increase our boost pressure.
36:07 So, if we're using electronic control in a factory system, what we'll often see is this style of installation here where we've got a T piece.
36:14 The T, one side of that will go to the top of our wastegate and the other side will go to our 3 port boost control solenoid.
36:22 The one that we've got drawn in this picture is the very very common MAC 3 port valve but obviously if we're talking about an OE installation, they'll be using their own controller but essentially it all works the same.
36:33 And the principle behind this is that normally we'll have this valve here closed.
36:39 So, basically under that installation, the boost pressure is all going to the wastegate and that will give us what I call wastegate spring pressure or wastegate base pressure, the minimum amount of boost pressure that we can achieve with this particular mechanical setup.
36:53 That's going to be remember defined by the spring pressure which often in an OE wastegate we can't adjust and it's going to be defined by the turbocharger size etc.
37:05 Ok, but now we want to increase our boost pressure.
37:09 So, how can we do that? Well what we can do is we can open this valve and we can allow some of the boost pressure to escape.
37:16 So, what that essentially does is it creates a boost leak and that's going to reduce the amount of pressure that we're going to see at the wastegate.
37:25 The problem is that the turbocharger moves so much air that even having that electronic solenoid completely 100% open is actually not going to dramatically increase our boost.
37:38 We might get another few psi but not probably what we're hoping for.
37:43 So, the solution we see quite often in factory turbocharger installations is this little guy here which is often very easy to miss.
37:52 This is a restrictor valve or restrictor pill that's normally just pressed inside the vacuum line.
37:59 So, what this does is it might take the size of our vacuum hose from 4 or 5 mm internal diameter down to maybe 1 mm or 1.5 mm.
38:08 And what that does is it essentially limits the amount of air pressure or air flow that can come from the turbocharger.
38:16 Now, if we open this valve, we're essentially leaking more boost pressure, relatively speaking, from the wastegate than we could before because we've restricted that air flow.
38:26 So, by adding this little restrictor pill into our vacuum plumbing, what that does is it gives us the ability to increase the range over which we can change the boost pressure.
38:37 So, here we might be able to go from maybe a base spring pressure of 7 psi to maybe 18 or even 20 psi.
38:45 There's still going to be an upper limit because remember we still have that exhaust manifold pressure acting on the system.
38:52 So, why I bring this up is that it's really really common for people to replumb their factory wastegate system using nice blue aftermarket silicon hose or something like that to replace their old tired cracked black factory plumbing, they don't know about this little restrictor pill, they throw it away and then all of a sudden you've got no boost.
39:13 If that's the situation you're facing, that's quite likely why.
39:19 Then the other option is, and this would be my preference when we're using a three port solenoid like this, is basically to ditch the factory plumbing which I call a bleed off style and replace it with our three port solenoid.
39:32 So, here we've got our three ports and these are labelled how they will normally be labelled on one of these solenoids.
39:38 So, first of all we have COM which stands for common.
39:41 What this means is that this is always going to be connected to one of the other two ports depending on whether the solenoid is energised or not.
39:50 Then we've got NO, doesn't stand for no, it stands for normally open.
39:55 So, when this solenoid is not energised, we don't have 12 volts and ground hooked up to the wiring, we've got a direct path connecting our normally open and common.
40:06 So, under these circumstances in this installation, this would give us our minimum or wastegate spring pressure, our minimum boost pressure that we can achieve.
40:15 Then we've got our third port here which is called NC which stands for normally closed.
40:21 Now, when we provide power to the solenoid, when it's powered up, we then connect our common and our normally closed ports together.
40:31 So, if you think about what would happen there, when that's open like this, we're venting all of the air pressure that's in the top of the canister, it's going to go out to atmosphere.
40:42 Or sometimes this would actually be plumbed back to our intake system, maybe post mass airflow sensor if we're running an airflow meter.
40:51 So, that's how that would work and that would obviously raise our boost pressure because now we've got nothing trying to force that wastegate open.
40:59 The reality is what happens is that these solenoids will pulse on and off, they're pulse width modulated and they might pulse at 20 to 30 times a second.
41:09 And by varying the amount of time that they're switched on versus the amount of time they're switched off, this will give us very fine control over our boost pressure.
41:17 So, there's nothing wrong necessarily with the previous example I showed with the bleed off, this is just my preference for an internal wastegate.
41:25 Now, we'll have a look at our options for an external wastegate.
41:30 And there's a couple of ways we can do this and also I'll touch on four port solenoids when I'm finished but only briefly.
41:38 So, this is our external wastegate and as we already learned, we need to provide pressure to the bottom of the wastegate in order to make this one open.
41:46 So, we could again get rid of our boost control solenoid altogether and just plumb our turbo or pressure source straight to the wastegate, that will give us our minimum but also so will this installation here which looks remarkably like what we just saw with our internal wastegate and it essentially operates exactly the same, it will get the job done.
42:06 My preference though with this installation with an external wastegate is to actually use both sides of the wastegate.
42:13 And what we do here is we plumb boost pressure straight from our pressure source, turbocharger, intercooler plumbing, whatever it might be, straight to the bottom of the wastegate but we also install this T here.
42:25 And from the T, we're then providing a boost pressure reference to our normally closed port on our solenoid.
42:33 So, again normally closed, when this is not energised, there is no airflow through here and you'll remember that our common and normally open ports are connected.
42:43 So, essentially this just vents exactly the same way as what we saw in this instance, it's no different to the top of the wastegate being plumbed to atmosphere.
42:53 However this time when we pulse the solenoid, we now have the normally closed and the common port connected, so we'll get airflow through here, that provides boost pressure to the top of the diaphragm and that tries to actually force the wastegate closed.
43:13 So, by doing this, by energising the solenoid here, we're actually increasing our boost pressure and again by manipulating the duty cycle, how long we have that solenoid energised versus not, we can again control our boost pressure quite accurately.
43:30 Now, with both of those instances, as I mentioned, installations, as I mentioned, we still have an upper limit which a lot of people kind of miss.
43:38 We can't sort of put in a 7 psi spring, use that for our base boost pressure and let's say miraculously this time we do get 7 psi.
43:47 Using this installation we're not going to necessarily be able to get from 7 psi to let's say 30 or 40.
43:55 We're going to get to that situation where the boost pressure, the exhaust back pressure forcing on the bottom of that valve, coupled with the fact that we still are providing boost pressure to the underside of the diaphragm here, that will overcome the amount of pressure that we're applying down on top of the spring and it will just force the wastegate open.
44:18 And that is where we get into the option of using something like a four port solenoid.
44:24 Again, I haven't got one here to draw up but basically the four port solenoid allows us to actually disconnect the boost pressure to the underside of the wastegate.
44:34 It gives us the ability to get a wider range from our minimum or wastegate boost to our maximum boost pressure because we don't have so much pressure trying to force that wastegate open.
44:46 The downside of the four port solenoid though is you lose a lot of resolution in your control.
44:51 And what I mean by that is if we, with a conventional three port solenoid, maybe we add 5% duty cycle and we get 1 psi.
45:00 What we might find, 1 psi of additional boost.
45:03 What we might find with a four port solenoid is that we get an additional psi for every 1% duty cycle or 2% duty cycle.
45:12 So, it can make our boost control tuning much much trickier.
45:17 And generally in the instances where I want a wider range of boost control, that's generally going to be drag racing where we need to launch with low boost in order to maintain traction but then in the deep end of the track we can really ramp in the boost pressure.
45:32 With those there are other options that I prefer instead of four port solenoids such as maybe CO2 boost control.
45:40 Obviously we've also got electronic wastegates coming online, definitely not a new thing at this stage and those really get away with all of these problems that I've talked about with exhaust manifold back pressure but that's sort of a topic in and of itself I believe.
45:56 So, we'll leave it there, hopefully that's given you a little bit more insight into wastegates, what they do, how they operate and some of the things you need to know.
46:05 We'll jump in now and have a look at our questions, if you've got more please keep them coming.
46:11 Elton has asked, "Water cooling plumbing for wastegates, can the feed be teed off the feed to the turbo and the same with the return?".
46:18 Yeah, absolutely it can, I mean it really depends what you want to do.
46:23 The Turbosmart wastegate I've got here, we'll just get it under our overhead.
46:27 This port here and again here, these are our water cooling ports.
46:33 At this stage I haven't actually found a need to use water cooling.
46:39 I don't say it's useless but actually this wastegate is a pretty good case in point.
46:45 Believe it or not, the top of this wastegate used to be black.
46:50 So, it's pretty well known that anodised aluminium will discolour if the temperature's high enough.
46:56 Clearly this has got pretty damn hot.
46:58 We have not ever even gotten close to a diaphragm failure, everything inside of it still looks like new.
47:06 I'm not saying that there aren't installations where water cooling can be beneficial.
47:10 But I think a lot of people probably would jump to water cooling maybe where it isn't necessarily essential.
47:18 But yes you can tee that feed off some of your existing water plumbing to make it easy.
47:23 Obviously, the downside of that is you're kind of limited to the temperature of the water in the engine and that might be 80 or 90°C.
47:33 The other option if you really want to get fancy, obviously it's a lot more complexity, you could plumb up a separate little cooling system with a very small heat exchanger and a pump to circulate water through the wastegate.
47:44 Is that necessary? Probably not.
47:49 Initial DIY Mods has asked, "What are your thoughts on the wastegate pressure source location, often hook up post intercooler pre throttle body but would it overspeed the turbo due to the pressure drop across the intercooler or pre intercooler with boost?".
48:03 Ok, yeah, a lot of debate on this.
48:06 I think it's probably not something that is that critical.
48:10 Yes, it can affect your ultimate boost pressure slightly but not much.
48:16 Generally, unless you've got a horrendously restrictive intercooler, your pressure drop across the intercooler should be probably less than a couple of psi.
48:24 So, depending on whether you take your pressure source pre intercooler, that will be a higher pressure source resulting in lower pressure in the inlet manifold or post intercooler, obviously the reverse goes, I don't think it's as critical as a lot of people make out.
48:41 Ultimately, what we are controlling and what we need to worry about the most is the pressure inside of the inlet manifold.
48:49 We do need to consider the pressure ratio that the turbocharger is working at though to make sure that we are staying in the efficiency range of the turbocharger.
49:00 And essentially if we want to know what the pressure ratio is, that is the compressor outlet pressure, in which case we're measuring it right here at the outlet which is why often turbochargers will have a pressure source there and we want to divide that by the pressure at the compressor inlet.
49:17 And I'm not talking here about the airbox because there can be restrictions through the air filter and the plumbing to the turbocharger.
49:23 So, that's really the key metric that the turbocharger cares about, it doesn't care less what the boost pressure in the inlet manifold is but we certainly do.
49:32 But once we start pushing the turbocharger near its limits, understanding and monitoring things like the pressure ratio of the turbocharger is quite critical.
49:42 Next, question, "Do I feel that electric wastegates are ready for daily driving during racecars, reliability wise and is the control strategy overly complicated for the tuning side?".
49:53 I mean, yeah, the answer is clearly yes and the reason I say that is that a lot of OE turbocharged cars are now running electronic wastegate actuators.
50:03 So, the technology is definitely proven.
50:07 In the aftermarket, I'm a little bit less prepared to jump in boots and all at this stage.
50:14 And I mean this is no disrespect to Turbosmart but they're probably the first manufacturer that's come out with these products and at least in their early days, there's definitely been a few issues with heat around the actuator.
50:28 I'm in a position where particularly for our endurance racecar, I don't really see an advantage to going to an electronic wastegate actuator.
50:39 It's sort of one of those if it isn't broken, don't fix it sort of situations.
50:44 And it really also is a case of I try and keep things as simple as I can and I say that yet our car is about as complicated as we can get so maybe do as I say, not necessarily as I do.
50:55 But, yeah, I think for me to jump to an electronic wastegate actuator, I would need to be able to justify it with some viable advantages and I'm not seeing those.
51:07 Drag racing on the other hand, absolutely I can see some really key advantages, particularly around the ability to just seamlessly have such a massive range and boost between our lowest and our highest boost settings without any of these problems with exhaust manifold back pressure and without adding the complexity of CO2 boost control.
51:26 So, I think it's just horses for courses there.
51:29 Otis has asked, "I'm looking to fix a bit of wastegate rattling in my 2014 BMW M5, I'm waiting for a new upgraded turbos, but want to cut some of the boost loss, I tighten up the preload by about three turns, am I OK?".
51:41 Yeah, generally I don't know about that specific application but generally that is what I would recommend.
51:47 Usually, what you're going to find is that the factory wastegate actuators, just like the one, if we jump to our overhead again, just like the one I've shown you already, we've got the ability to basically adjust the preload here.
52:00 It's not uncommon for you to find that the wastegate will rattle at idle.
52:04 If it's rattling at idle, clearly that also means that it's not 100% sealing, that's going to result in a slower boost response, it's going to raise your boost threshold so by basically winding in a little bit of preload until it's positively closing the wastegate, that's exactly what I would do.
52:22 You do obviously need to check carefully here, if you wind in too much preload, it can be possible that you're going to end up overboosting or at least a minimum with more boost than you intended.
52:37 Boosted Stuff has asked, "What are the effects of plumbing, hosing size and length on the boost control system, solenoids and wastegates specifically, not charge piping?".
52:46 Probably another one of those situations where it's probably not as critical as you think.
52:52 Now, I'm not going to necessarily go and fit the wastegate solenoid in the rear of the car and run the plumbing from the front engine bay to the back and vice versa, clearly that's not going to make a lot of sense but within reason inside of the engine bay, you're probably only talking about a maximum distance of a few feet and that's realistically not going to make very much difference at all.
53:18 You're simply producing so much airflow through the turbocharger that's in turn going through the vacuum plumbing that it's just not that critical.
53:27 In terms of plumbing size, I would just use the existing nipples on your wastegate such as this one here to guide you, 3-4mm internal diameter, that's generally probably going to be there or thereabouts in the ballpark so yeah not something that needs to realistically be overthought.
53:50 Next, question, what are the implications of running a T to reference the boost for the wastegate and the blow off valve from the same line? Yeah, not probably something I would recommend.
54:01 The bigger issue I think is people who try and run from their map sensor to the wastegate solenoid in a bleeding air off there, that's obviously going to have the potential for implications on the entire engine operation.
54:15 It's possible but unlikely that doing what you've mentioned there is going to affect the blow off valve operation but again I highly doubt it but best practice would always be to run individual feeds to those different items.
54:31 Tiger Sharks asked, "What's my opinion on the Turbosmart electronic wastegate? I think I've probably covered that.".
54:38 And also is "... updating his R34 GTT Skyline, just after 300 kilowatts of street cruising but want today's control system, is it worth going electronic wastegate?".
54:48 Again, personally I don't think so.
54:52 I've just covered really I think the product is most suited to a drag racing application or if you just really have to have the latest technology and you want to have a play with how an electronic wastegate works, well obviously absolutely all power to you.
55:08 But I don't believe that you're going to see a significant advantage in a street application.
55:15 Alright, we'll leave it at that for today.
55:18 If there's any other questions after this webinar has made it into the archive, please ask those in the forum and I'll be happy to answer them there.
55:26 Thanks for watching and hopefully we can see everyone next time.