Engine coolant temperature is something that most people don't give too much thought to until the engine has overheated and has potentially been damaged.

There is however a bit to understand about what range of temperature you ideally should be targeting, and this will vary depending on the application. In this webinar we'll cover what you need to know.

00:00 - Hi team, Andre from High Performance Academy here, welcome along to another one of our webinars and in this webinar, we're going to be discussing engine coolant temperature which I know on face value doesn't sound like the most interesting topic but it is a really important one, particularly for engine reliability as well as engine performance.
00:20 One of the common questions we do get asked is what is the ideal coolant temperature range I should be targeting or running my engine in? And it's a great question to know because if we run the engine too hot, or we run it too cold, we risk the potential for reduced engine performance and potentially even damage to our engine so obviously we want to avoid both of those elements.
00:44 In today's lesson I'm going to hopefully help answer some of those questions.
00:49 It is a little bit tricky because as most of you can probably appreciate, there isn't really a lot of black and white when it comes to this.
00:56 It's more a case of understanding the sort of likely ranges you want to be targeting and understanding what happens when we get too hot, what happens when we go too cold and what we can do about each of those extremes so I want to be really clear right here, I'm not going to give you one magic number that you must target, it is simply not that cut and dried.
01:18 At the end of the lesson we will be having a Q&A session so if there is any questions that come about as part of this, please feel free to ask in the chat, the team will get those through to me and we'll deal with them at the end.
01:29 I will note this is probably a slightly shorter topic than what we normally deal with so we will be getting into that Q&A probably a little bit quicker.
01:37 Alright so coolant temperature, I mean at a high level, why do we need to care about it? Well it's of course there to get rid of heat that is a bi product of our combustion process.
01:49 And generally if we're talking about an internal combustion engine, they're only somewhere about 35-40% efficient, at least the sort of engines we're likely to deal with which means that the rest of the energy stored in the fuel that we're burning is going to be wasted in the form, primarily of sound and heat and it's the heat that we're dealing with today.
02:12 So essentially what we're trying to do with our cooling system is make sure that we can manage the heat that is being rejected from the engine and make sure that we can get that basically transferred back out to the airflow around the car.
02:28 So that's the point of the cooling system and if the cooling system is too large and too efficient, we don't have good control over it, we're going to likely find that our engine coolant temperature stays too cold.
02:41 And we'll talk about some of the problems that that can result in a little bit later.
02:46 The more common situation though is that when we start modifying an engine and it makes more power, or we take that more powerful engine that we've modified and we now take it out onto a racetrack, we're now using the thing under sustained high throttle operation where we're producing more and more power for longer periods of time, that creates more heat and usually we're going to find that the cooling system is one of the weak points and can't keep up.
03:14 How that manifests itself is we start to see our coolant temperature climb.
03:19 Now this can also be problematic with factory road car because the little coolant temperature gauge on the dash doesn't usually actually work that accurately.
03:33 It's really only there as an indication and I mean of course every car is different but when we start tuning vehicles where we've got a laptop in front of us with access to the ECU software and we can actually see the specific temperature being reported by the coolant temperature sensor, and we start correlating what we're seeing on the laptop screen to what the gauge is showing us, what we'll generally find is that those gauges will sit perfectly in the middle of their range, anywhere from about probably 50-60°C through to about 100, 105°C and then once you get up above that temperature, they'll start to move quite quickly.
04:11 So it doesn't really give you a really good granular understanding of what that temperature's likely to be.
04:17 I will just mention as well that primarily I am going to be working in °C today, I've got a couple of areas where I'll transition and talk about °C and °F but primarily here in New Zealand we use the metric system and I'm not that great at converting between °C and °F on the fly so I'll apologise in advance to anyone who does deal with the imperial system but I'm sure you can probably Google and convert pretty quickly if you can't do that in your head.
04:48 So what are the effects of the coolant temperature on our engine? Well there's actually a number of them, some more subtle than others.
04:58 Obviously at the extremes, if we really cook our engine and get that coolant temperature too hot, we're likely to do some very very expensive and pretty catastrophic damage to the internal components.
05:10 We can warp cylinder heads, they can end up losing their hardness, they go soft basically which means that they will no longer clamp properly to the head gasket, resulting in head gasket failures.
05:24 We can also bring on a situation where our pistons will seize in the bores because our clearances will change with temperature so there's a whole range of things that go on here.
05:35 Those are at the extreme end, but slightly more subtle element, we also see that the coolant temperature will affect our combustion efficiency, it will affect our emissions and it will affect our engine power.
05:50 So in terms of what we're focusing on in the aftermarket, generally the reliability element is probably our key driver, we really want to maintain our engine within a coolant temperature range that is going to ensure that our engine remains reliable.
06:06 If we look at what OE manufacturers are doing though, they actually tend to focus a little bit on those other elements, particularly emissions and particularly combustion performance or combustion efficiency I should say.
06:22 And what we've seen over probably the last couple of decades is a lot of OEs will actually strive to increase coolant temperatures, particularly under cruise conditions, to improve those elements.
06:36 What we also need to be very mindful of in a performance application is that as we increase our coolant temperature, the knock on effect here is that this can affect the combustion charge temperature as well.
06:51 A subtle element there but it can.
06:53 Basically anything that affects the combustion charge temperature, increasing it I should say, will make the engine more prone to suffering from detonation and that is the biggest killer of any performance engine so we want to be mindful of monitoring that and there are ways we can deal with that and mitigate it but we need to understand that it is a problem we need to look out for.
07:16 So as I mentioned, we can be operating our coolant temperature either too hot or too cold.
07:22 I would say that the typical range that I see and that I'm comfortable with would generally be somewhere in the region of about 80°C at the low end and about 105°C at the top end.
07:35 In Fahrenheit, that's approximately 180 through to about 220°F.
07:41 But again it isn't that clear cut and there is a wider range that can be acceptable depending on some of the specifics that I'll get into.
07:50 And if we look at what some very highly developed race engines are doing, they fall well outside this range.
07:59 I don't have any data because no one's likely to share from the likes of Formula 1 but I did find some interesting information on NASCAR engines and depending on the spec that these are running in and depending on the exact variant, NASCAR engines are 800, 850+ horsepower and operate at 9000 + RPM and do so for sustained periods of time.
08:22 So they are incredibly hard worked engines.
08:27 So they operate or at least have been operating more around about 145°C in terms of the coolant temp, that's about 290°F and the oil temp actually slightly higher than that.
08:43 Now that is a long way above the range that I previously mentioned.
08:49 Now there's some reasons that they are doing this, more importantly though there's a lot of engineering that goes into these engines to ensure that the materials that they're using, the clearances inside the engines are actually up to the task of running at that temperature.
09:04 But the key is why would they choose to do so? Interestingly for NASCAR, one of the main reasons is actually for aerodynamic effiency because they're running these engines so much hotter, they don't need to shed as much heat and what that actually allows them to do is run a smaller cooling package.
09:24 And what this means then is that there's less airflow through the radiator and this reduces the aerodynamic drag of the vehicle.
09:32 So subtle element but with NASCAR being so highly developed, the teams are looking for any 10ths of a percent advantage they can get over the competition.
09:41 Probably not much of an advantage because I'm guessing every team does this but just showing the sort of range that is potentially possible if you're developing your engine around that as well as also understanding the implications and why.
09:58 Now I also will come back to aspects that are really important in our engine design such as our piston to cylinder wall clearance as well as our ring packs.
10:09 So I've got a piston here that we'll just have a quick look at under our overhead camera.
10:14 So our clearance between the piston skirt and the bore.
10:18 This is one of our most important clearances inside the engine.
10:22 The other element is we can see here, I've got the second ring installed on that piston.
10:28 And when we are installing the rings on a performance engine, the rings will be what is referred to as a file fit piston ring.
10:37 This means that they are purposefully delivered slightly oversize for a given bore diameter and it's our job then as the engine builder to actually measure the piston ring end gap, decide on what our optimal ring gap is for that particular engine, the fuel, the application, everything else around it and then file the ring to get to our desired ring end gap.
11:02 But all of these elements come down to, a number of factors that come into it of course but the coolant temperature is one of them.
11:10 So for example, when we are boring and honing the block to get our piston to cylinder wall clearance where we want it to be, normally this is done at room temperature.
11:23 However what we do find is that as the engine heats up to operating temperature, the bores will change in size, obviously the materials do expand, there's a thermal expansion coefficient with all of the materials so we know that that's going to expand.
11:40 That's fine because our piston manufacturer's give us specifications to suit setting our clearances at normal room temperature.
11:49 However another subtle element with this is that quite often as the bores come up to operating temperature, they will move or distort a little bit compared to what we're measuring at room temperature.
12:01 Long and short of this is that if we bore and hone the cylinder at room temperature and we have everything perfect, we've got our clearance exactly where we need it to be, we know that our bores are perfectly round, there's no out of round going on, there's no belling or taper from the top of the bore to the bottom, chances are that when that bore is at operating temperature, all of those elements will move slightly so an element that is used by a lot of race engine builders is what's called hot honing which is where they actually flow fluid at operating temperature through the water jacket of the engine and then they bore and hone the block at hot operating temperature.
12:41 The idea here is that we're getting a truer bore finish, a truer bore that is round and straight at the actual, under the actual conditions that the engine is going to operate in.
12:53 Now without getting too deep into the elements of boring and honing a block, because I am not an engine machinist, one element, if you are using a hot hone is that the target clearance will understandably be dramatically different to what we see at room temperature so there's a bit to learn here.
13:12 The reason I'm going down this path is that hopefully from that you can understand that while there are other elements that will affect our desired clearance range, the coolant temperature would also be one of those and particularly with the NASCAR I can only assume that the engine builders will be adjusting their clearances to suit that sort of operating range.
13:37 So what are the other advantages with running the coolant temperature hotter? So frictional losses do decrease at higher operating temperatures.
13:49 Now that again is difficult to say as a blanket statement because there are some other elements at play in here as well.
13:56 Some of this comes down to the oil selected and how that works at that desired operating temperature as well.
14:04 But to keep things nice and simple, there can potentially be a small decrease in our frictional losses if we run a higher operating temperature for our coolant.
14:14 So again this comes into why some of the OE manufacturers are choosing to specifically target higher coolant temperatures.
14:22 If we look at older cars from maybe the 80s and 90s, a pretty typical operating temperature for the thermostat would be around about 82°C, again around about 180°F.
14:36 And that would be the temperature where the mechanical thermostat would physically open and start flowing water through the cooling system so the idea there is it should be maintaining somewhere around about that 82°C.
14:49 More modern vehicles, particularly ones fitted with electronically controlled thermostats where the ECU can also map the target temperature range that the manufacturer wants to run in, it's not uncommon to see cruise coolant temperatures in the 95°C+ vicinity so you can see things have changed there and again, that is one of the reasons for that.
15:16 The other element here is thermal losses inside of the engine.
15:19 So obviously we've got our combustion temperature inside the cylinder, the cylinder wall and then the water jacket is going to be cooler and this creates what's referred to as the thermal gradient so the larger that thermal gradient, in other words, the larger the difference between our combustion charge temperature and our coolant temperature, the more heat transfer we will get from one to the other.
15:44 The disadvantage of this is that this does lead to some losses and basically reduces the thermal energy that is available during combustion to be converted into work.
15:56 So that's another benefit of running things a little bit hotter on purpose but the biggest thing for me is that this does lead to a higher propensity for the engine suffering from knock which we need to absolutely avoid.
16:12 So there are limits to this and what I'd consider is safe for an OE manufacturer targeting reduced emissions and better fuel economy, more thermal efficiency, maybe doesn't always go hand in hand with what we want for a dedicated race engine.
16:30 Another element that we do need to consider with our coolant temperature is making sure that the coolant doesn't boil.
16:39 And this is one that, it's not very complicated but it is easy to overlook if you haven't really thought about this or got a real basic understanding of some of the physics going on here.
16:49 Most of us would understand that water boils at 100°C at atmospheric pressure, one atmosphere of pressure.
16:57 Think, off the top of my head, that's about 212°F.
17:01 If we however increase that, double the air pressure to two atmospheres, that actually brings our water boiling temperature up to 120°C which is almost 250°F and if we jump across to my laptop screen, this is the sort of graph of how the boiling temperature of water relates to our pressure.
17:26 This is important because if we didn't have a sealed cooling system with the radiator cap that allowed the pressure to increase, we'd basically have to make sure that our engine coolant temperature never exceeded 100°C, otherwise it would boil.
17:41 Downside with our water boiling is that we end up creating steam.
17:46 These steam pockets do a really really good job of insulating the material that they're contacting, probably most likely around the combustion chamber in the cylinder head and this dramatically reduces the heat transfer so what it does is very very quickly leads to the coolant temperatures, or the engine operating temperature spiraling out of control so we've got to make sure that basically irrespective of anything else, our coolant doesn't boil.
18:16 Particularly for a racing application, we may look at increasing the cap pressure, the radiator cap pressure, that maintains that pressure in the cooling system and therefore increases the boiling temperature.
18:30 There are also other elements to consider here as well because when we add in an anti freeze, be that ethyl glycol or maybe some of the more performance orientated anti freeze or corrosion inhibitors, these also have the effect of increasing the boiling point of the fluid.
18:54 There's some downsides with that as well though that are worth diving into briefly.
18:58 So for example, water on its own, just clean fresh water, actually does a much better job of transferring heat from material it's contacting, the cylinder wall or the combustion chamber, than when we start adding in a glycol based anti freeze, that actually dramatically reduces the heat transfer so yes we're stopping the water from boiling, the coolant from boiling, we're stopping it from freezing and we're stopping it from corroding, all great things and we do need some of those properties but it does come at the cost of the ability of that fluid to transfer heat away from the hot material.
19:38 So this is why we start seeing some of the products out there like waterless coolants which are designed with the properties that we need for anti corrosion, anti freeze etc but they are still designed for very very good heat transfer properties.
19:56 Another element with glycol based anti freeze is that they are really slippery so you actually find that a lot of racing classes specifically outlaw the use of glycol based coolants in the cooling system because if you do have a cooling system failure where it leaks out onto the track, it can potentially be quite dangerous for other people.
20:18 The other element we do need to consider, I don't have the number in front of me, the NASCAR engines that I talked about before running at 140°C odd, they run at several atmospheres of pressure so very very high pressures and this in and of itself creates another problem because most conventional motorsport based or OE based radiators would simply blow apart at those sort of pressure so this really comes down to the whole engine and all of the cooling system need to be designed with the end result in mind, otherwise you're likely to have problems.
20:58 Now in terms of targeting specifically higher coolant temperatures like NASCAR or like some of these OE manufacturers, we do need to understand that the material suitability and reliability comes into play here at these higher coolant temperatures.
21:15 And what I mean by this is that a lot of the materials that we conventionally see probably aren't that well suited to vastly elevated temperatures.
21:23 Specifically cylinder heads and blocks when made out of alloy.
21:27 Alloy cylinder heads will anneal at around about 350°C.
21:34 Now obviously we're not advocating getting our coolant temperature up to that but you've got to also understand that we're monitoring the coolant temperature but on the other side of the combustion chamber in the cylinder head, we've got much much higher temperatures presented as a result of the combustion process.
21:54 So we're not able to directly correlate our coolant temperature necessarily to the surface temperature of that alloy material on the inside of the combustion chamber but one can probably understand, it's going to be significantly hotter.
22:08 So once we get to that point where the 350°C in this case, we're going to start seeing the material soften significantly and that's going to actually start happening, it'll anneal around about 350°C, sorry I'll just get my facts straight here, but it'll actually start to soften from as low as about 280, 290°C.
22:31 And that's when we start sort of losing the mechanical properties of the material that are so important for head gasket sealing and making sure that the cylinder head remains straight and true so obviously if you were going to target much higher temperatures, that might require a different alloy being used that is dimensionally stronger and going to maintain, or going to withstand those higher temperatures reliably.
23:00 Now I wanted to dive into clearances, I've already mentioned these briefly.
23:06 So obviously these do depend on the operating temperature.
23:10 Now if we run the engine too cold, most people think that if the engine's too cold, well it's at least safe and I mean to a degree it is but there are some downsides with this as well and a lot of people will run with a cooling system that is excessive for use for the application and make things a little bit worse by then removing the thermostat out of the system and what this results in is over cooling or the potential for over cooling of the engine.
23:39 And again, just coming back to my statement about the temperature gauges, if you don't have a digital read out from maybe an aftermarket dash or your ECU of what the coolant temperature is, you're likely to still find that the factory gauge will sit nice and central in the middle of the range but your actual coolant temperature might be down in the 50° range and at that point what we're going to end up with is essentially excessive cylinder wall to piston wall clearances, so again that's the clearance between the side of our piston skirt and the cylinder wall.
24:14 This can result in a few potential problems, none of them in and of themselves necessarily are tragically detrimental but not what we want.
24:23 What we're going to end up with with the excessive clearances or increased clearances, is additional blow by.
24:30 So that's our combustion pressure escaping down past the rings into the sump.
24:34 Your engine's going to be breathing heavier, this will also potentially put more contaminants into the oil.
24:40 We're also going to end up with the piston more prone to rocking and this is particularly an issue with a forged piston like this one here.
24:50 Forged pistons do expand more as they come up to operating temperature than a cast piston so typically we set the piston to cylinder wall clearance a little bit more, a little wider with a forged piston.
25:05 So if the engine isn't operating at a normal reasonable temperature, what we can end up with is what's called piston rock and you can hear this with a forged engine when it's cold if the clearances are excessive and it sounds like a rattling sound so basically the piston isn't supported properly and it can rock side to side.
25:23 This can result in premature wear to the piston skirt.
25:26 It can also kind of exacerbate the problem with blow by because as the piston rocks, that can be detrimental to the ring seal so we end up with an increase again in our blow by so nothing really that we want to see going on there.
25:42 But again, not necessarily something that's going to instantaneously result in a dramatic or catastrophic engine failure, just probably will wear over time.
25:53 Another element that's easy to overlook though is that if you are consistently, you're running your engine that cold, let's say just 50°C as an example, you'd almost certainly be dropping back into some level of coolant enrichment or warm up enrichment which means that we're simply going to be adding additional fuel that would be necessary during warm up but under these conditions is just essentially creating an overly rich air/fuel ratio that we don't need, that's going to be detrimental to fuel consumption and it's also going to end up hurting our power.
26:29 So again all of these things can happen if you're not actually aware that your coolant temperature is too low.
26:35 Hotter temperatures, obviously as I've kind of mentioned, these are a little bit more dramatic and in terms of our clearances, and again it's not just driven by our coolant temperature, there's a lot more that goes into this that will also drive what our clearances end up being but we can end up with our piston expanding to the point where it actually siezes in the bore and when that happens it's generally going to be a catastrophic failure, the conrod will generally pull the pin boss out of the piston and then basically throw whatever is left outside of the block so there's not usually a lot left of that.
27:14 Likewise, our rings can end up expanding to the point where the ring ends actually butt together and when they do that, there's nowhere left for them to continue expanding except outways and when that happens, again the ring will seize in the bore, rip the crown off the piston and you kind of get the same result so nothing good is going to come from that.
27:37 So how do we achieve a desired target temperature range? We'll jump into what that range is likely to be shortly.
27:45 First of these is radiator sizing so most people would think that the factory radiator would have a fair bit of headroom in it but often that's not really the case.
27:58 Kind of for the same efficiency reasons as I mentioned with NASCAR, OE manufacturers don't really want to put an excessively large radiator in a car and I would expect, not having worked for an OE manufacturer but they will probably size the radiator and cooling system to suit the hottest market that the vehicle's going to run in and give a little bit of buffer or headroom in there just to cover a worst case scenario.
28:24 But when we take that same car that's a pedestrian road car, maybe modify it so it's got another 20% more power which means we're now introducing more heat into the cooling system and then we take it onto a racetrack and we beat on it hard lap after lap for 15 or 20 minutes, it's very easy to exceed the capability of that factory cooling system.
28:44 So this often can require us to thing about the size of the radiator and upspec that but radiator sizing is not just a case of bigger is better, there's actually a lot of science that goes into radiators and particularly the design of the fins and the passes through the radiator have a really big impact on how efficiently the radiator will be able to get rid of heat that is in that coolant.
29:11 In this instance, I am definitely not a specialist on this area, I would suggest that you talk to a specialist radiator supplier who can run through the calculations for you, PWR would be one that jumps to mind, CSF in the US and they will be able to size something and provide a core design that's going to suit your application and make sure that you've at least got a radiator in the vehicle that's capable of handling the temperature that it's going to need to inject.
29:41 Also worth talking about thermostats or blocking plates, blanking plates.
29:47 I'm not really opposed to thermostats, a lot of people, as a rule of thumb, throw them in the bin for any competition car.
29:55 If they're working properly, I see absolutely no problem with a thermostat.
30:00 If we are running a thermostat, understand that they are available in different ranges and if you've got a factory delivered car that's maybe running a 88 or a 90°C thermostat, then for competition purposes if you can get access to a 78 or an 80°C thermostat, this can be beneficial.
30:20 Important to understand though that the cooling system is only going to be able to achieve that target if it has enough thermal capacity to do so.
30:31 So if you've got a tiny little radiator that's woefully undersized for the amount of heat that you're trying to put through it, then it really doesn't matter what radiator, sorry what thermostat you fit, it's not going to be able to get you down to that temperature so all of these elements work hand in hand.
30:49 The other common approach though with a racecar is to remove the thermostat entirely.
30:54 If you're going to do that, it is common practice though to fit a restrictor plate because if you just simply take the thermostat out of the system, what we can end up finding is that the water actually flows too fast through the system and it won't build pressure inside the cylinder head and the engine block so typically we'll run a restrictor plate with a 3/4 inch or 19 mm hole, that seems to work pretty well but a little bit of experimentation may be required.
31:23 Also worth understanding that there is a relationship between your engine coolant temperature and your engine oil temperature.
31:33 Both are actually doing the same job of removing heat from the internal components.
31:38 Obviously the oil has some other pretty important tasks while it's inside the engine as well.
31:44 What I'm getting at here though is if you've got an engine where you are struggling to maintain coolant temperature, first of all, really good idea to at least monitor the engine oil temperature, you can quite often get a bit of a shock at what that's running at.
31:59 And I know that not every club day car is going to go to the trouble of fitting an oil temperature sensor to the sump or something of that nature, can be quite a big job to do so.
32:08 In the past, I have used a simple digital voltmeter with a temperature sensor, K type thermocouple probe and I've just put that down the dipstick tube after I've come back into the pits and that will give you a really good idea of what the oil temperature is doing.
32:24 So obviously if your oil temperature is starting to get too high, then adding a cooler is going to be a good way of getting heat out of that which as a knock on effect would also help your coolant temperature.
32:40 Last part of this, fans, a lot of people think that radiator fans are going to be the cure for an engine that is overheating.
32:48 What's easy to miss is that the fans are almost completely ineffective at racing speed.
32:53 To the point where you'll find that a lot of professionally built racecars don't actually include electric thermofans of any type and the reason for this is that it helps them reduce weight and obviously as I mentioned, they really don't do anything at racing speed.
33:10 On the other hand, in the pits, yes absolutely when the car is stationary, particularly when you've come in from a track session and all of a sudden you are at a stop, at that point fans will be really important to help maintain that temperature.
33:25 Cars, racecars without fans, you'll quite often see them plug in an external fan unit into the front of the front bar when the car is in the pits, you see Formula 1 cars that do the same, they've got little blower fans that they place onto the radiator inlets for that purpose so that they've got airflow through when the car is stationary but yeah, do not think that your fans are going to be a cure all out on the racetrack.
33:51 Once you're above probably about 20 or 30 miles an hour, the fans are really going to do absolutely nothing for you.
33:59 Alright so onto the crux of all of this, what is this ideal range that we should be aiming for? And my own personal recommendation here is ideally I'd like to see the coolant temperature in the range of 80 to 90°C.
34:17 That's kind of my real sweet spot, that would be absolutely perfect if I could maintain that.
34:22 Sometimes that is pretty unlikely and a wider range that I'm still perfectly comfortable with is 70°C up to about 100°C.
34:33 I don't really like to see my water temperature go much above about 100°C and I'll show you in a second some of the safety protocols I put into place with our 86 to add engine protection once we go above about 105.
34:49 Below 70, if we're just not there, well that's actually a much easier problem to solve.
34:54 If we're using an electric water pump then you can look at pulse width modulating that or pulsing it on and off to reduce the flow and allow the system to build more heat.
35:04 Or you can use blanking plates to partially blank some of the airflow into the radiator, reducing the effectiveness of the radiator to get you into the ballpark as well.
35:16 Now we're going to jump into some questions really shortly so good time if you do have any questions to ask those.
35:24 Before we jump into those, let's just head across to my laptop screen at the moment and I'll show you through the engine protection I'm using in our 86.
35:33 This is in the MoTeC M1, it probably looks a little bit more complex than some systems if you're not used to it but don't worry about the intricacies of it, the two elements that I want to show you are really really simple so at the moment I am looking at the boost control tab and what we've got here, I think this is it.
35:52 This is our target boost pressure vs RPM and throttle position.
35:58 This is maximum, I can pull it back from this on the dial so you can see that at wide open throttle and higher RPM we're targeting 170 kPa, 1.7 bar of positive boost which is around about 25 psi if you work in psi.
36:13 Alright so that's our maximum and that's if everything's running properly but we do have the ability to bring in some boost limits and warnings and we just scroll down through here, coolant temperature boost limit is the one I wanted to talk about so let's click on that and we'll expand that out.
36:34 So here we've got a 2D table relative to our coolant temperature and basically values of 100% just mean that we'll be operating off that maximum table that we just looked at so we'll have all of the available boost and then as we move from 105 and above you can see that I'm starting to drop that down, 110°C I'm at 80, I don't really want that engine operating above 110 at all so we can see that once we get up to 115 we're really dramatically dropping that in half essentially.
37:07 So that's one element, the car is just simply going to lose some pace because it's pulling all the boost out of it.
37:15 That will potentially, or hopefully the aim here is that as we reduce the boost, we're reducing the power that the engine is going to be producing, hence we're putting less heat into the cooling system and that in and of itself is going to help bring those temperatures back down.
37:29 Now other than the fact that the car is going to start feeling a little bit sluggish to the driver, this shouldn't be too overbearing, at least not until we get up above about 110°C so it's kind of fairly subtle.
37:42 Another one that's a little bit more overbearing and a little bit harder to miss is what I'm doing with my engine speed limit so that's on our engine speed limits tab here.
37:52 Again a bit going on but all I really wanted to show you here is the additional engine speed limits and let's just full screen that so we're only looking at that.
38:03 And here we've got our rev limit versus our coolant temperature, again simple 2D table.
38:08 Up to 105°C, 9000 RPM, that's actually not our maximum, there is an overall maximum RPM limit which depending on the event, I'll normally have set at about 8500.
38:23 I do this just to make sure that with all of these additional limits, they're not going to come into play when I don't want them, so I basically set the normal limit well outside the range that I'm happy with or going to want and then the ECU will use the maximum limit which is lower than these under normal conditions but then once we get up to 110, we're at 8200 and then 111, you can see I've got a break point there that's quite sharp so up to 110 it'll still allow me to rev out to 8200.
38:54 As soon as we go above 110, straight away we're down to 6000 RPM so that is probably above the engine's normal operating rev range so with a close ratio six speed sequential paddle shifted gearbox, if I'm changing at let's say 8400 RPM, it's probably only dropping down to maybe 6500, 6400, 6200, something like that, depending on exactly which gear I'm changing from so you're not going to miss that, it's going to be very obvious to the driver and it's going to straight away pinpoint you've got a problem.
39:30 Of course I'm going to be using this in conjunction with warnings on the dash, if we've got a digital dash, to tell the driver, hey something's wrong.
39:38 And this really again comes down to personal preference and understanding what's going on and what you're trying to protect.
39:45 If you're doing this for yourself, well obviously you're going to have a bit of a better understanding of what's going on.
39:52 If you're trying to protect a car that you're tuning for a customer and you're doing this commercially, it can be a good idea to incorporate these things because a lot of customers maybe don't have the mechanical sympathy that and engine that's highly tuned does require so this kind of enforces that mechanical sympathy.
40:09 But you definitely want to explain to the customer what you're doing so that if the engine does get hot and all of a sudden it starts misfiring, it's actually not misfiring, it's just because that engine protection rev limiter has come in, they're going to understand what's going on.
40:24 Right so that's a couple of the protection strategies, there are a range of others as well, we can start targeting richer air/fuel ratios, we could also pull ignition timing out.
40:35 Because as I've mentioned, one of the biggest concerns with running excessive engine coolant temperature is it does make the engine more prone to suffering from knock and that will very quickly destroy your engine.
40:48 You can test a little bit of this on the dyno as well just for your own interest sake.
40:52 Run the engine at a normal operating temperature, let's say 80-90°C and get the ignition timing dialled in and at a point where it is not suffering from knock and once you're happy with that, what you can do is see how the engine responds to higher coolant temperatures, simply by blanking the radiator and try and get it up another 10°, maybe to 100 or something of that nature and just see if the engine does start to become more prone to knock.
41:21 Particularly if you're dealing with a turbocharged engine on pump gas with a relatively poor octane rating, it almost certainly will in which case you can start using some engine protection strategies there to start pulling timing out at higher coolant temperatures and higher loads if you want.
41:39 There's really a number of areas you can explore, depending on how complex you want to get with this.
41:46 Right, we'll, just let me get back to my notes for a second.
41:56 I already talked about coolants a little bit in terms of water being really really good at heat transfer, water with glycol is not as good, about 20% worse depending on your pre mix of water to glycol, about 20% worse in terms of heat transfer than water in its own.
42:17 Then there's the water wetter style products, what you do need to be careful of if you are running just plain water, as I mentioned already, is there is no freeze inhibitors in them so if you do live in a cold climate, where you are likely to get down below the freezing temperature of water then that can very very quickly destroy an expensive engine so you don't want that.
42:37 But also the corrosion inhibitors are really important so make sure that you use some kind of additive there.
42:45 Right we'll get into our questions now.
43:01 Gareth has asked, a really good question that I don't have data to answer.
43:07 What range of delta temperature, and he's talking here inlet vs outlet, would you consider good? Yeah I do not have an answer for that Gareth, I have not been in a situation where I've been able to monitor both the inlet and outlet temperature of the radiator unfortunately so yeah great question but one that I can't actually help you out with.
43:30 Obviously monitoring the actual coolant temperature inside the engine wherever the factory temperature sensor is, that's the most important thing because that's the temperature that the engine components are actually being exposed to so that kind of becomes essentially a knock on effect from how efficiently, how well that radiator's working but what you're talking about there, that delta temperature, I would suggest, gives you a pretty good indication of the ability of the radiator to get rid of that heat.
44:03 Eric Vaughn's asked, how would you control over-cooling? Hopefully I did answer this inside of the webinar but thermostat, if you have it, if you've removed a thermostat, a restrictor plate if you really don't want to run a thermostat and then you can start using blanking plates infront of the radiator.
44:19 So this would be quite common in a lot of race classes where the cooling system is essentially sized to deal with the worst possible conditions, heat of summer maybe 35°C day, sitting behind a car in traffic with limited airflow so they've sized the radiator to cope with that worst case scenario.
44:36 Then of course if you run that car under cooler conditions, maybe autumn or winter, it's almost certainly going to overcool so that's when you can use blanking plates.
44:45 I mean worst case scenario if you really get stuck, you could just use race tape to blank off some of the airflow into the radiator.
44:54 Little bit of caution with that, and a little bit of testing to see how that actually responds to get you into that sort of sweet range that you want.
45:02 Now that's another element that is worth mentioning here, particularly for road race style competition cars.
45:08 A little bit of driver awareness does come into this.
45:13 So for example, even with a reasonably well sized cooling system that works perfectly under a qualifying lap where you don't have other traffic around you, if you're battling hard with other cars and you're sitting right in the slipstream of the car in front, that is going to dramatically reduce the airflow into that radiator so that's why you'll quite often see drivers that have been sitting in traffic for a few laps will actually purposefully jump out of the traffic, out of that slipstream down a long straight to get fresh airflow into the radiator so these are some of the little tricks that the driver can use to help keep the coolant under control.
45:57 Next question comes from Ben who's asked, ​K20 NA tuned on a dyno at 88ºC, turns out was miscalibrated so actually running 11°C higher.
46:07 Calibration's fixed now, but what impact will it have had on the tune that should be relooked at? OK probably under those conditions, little to none.
46:17 It would be very unlikely if you're running at 88°C or 99°C, you're 11°C hotter, that you would be in any kind of warm up enrichment.
46:30 It would be very unusual to have any additional enrichment within that range.
46:34 By all means check but that would be the only thing that immediately jumps to mind.
46:39 Another element which should be subtle, quite often you'll find a lot of ECUs use a charge temperature estimate table.
46:48 And without diving too deeply into that, what that does is instead of just using intake air temperature to estimate the charge temperature, charge temperature is the important thing, that's the temperature of the air charge as it goes past the valves into the combustion chamber which is what we care about.
47:04 The charge temperature approximation or estimate table uses both coolant temperature and intake air temperature and it biases between the two depending on the airflow.
47:14 Principle being that at very low airflows, idle and cruise, the air speed is so slow that the charge temperature will increase based on the coolant temperature.
47:24 Basically it's drawing heat out of the intake ports, the cylinder head etc in the inlet manifold on its way into the engine.
47:31 At wide open throttle, 8000 RPM, not enough time for that to happen so we bias more towards the intake air temperature.
47:39 If you are using that sort of a system, then yeah that could affect your charge temperature estimate.
47:44 I would imagine that you'd be talking a few percent at the most so I doubt it would be something that would be significant but if I've got my numbers around the right way, 99°C is pretty hot for a naturally aspirated K20, I would be looking at ways to get that down a little bit.
48:02 Brian has asked, are you an advocate for fan shrouds vs none? Do you believe they play a role in fan cooling? You know what Brian, I haven't actually had the opportunity to do back to backs on this.
48:16 I've run both with and without fan shrouds and I think there's levels to what we call a fan shroud as well so if we're talking about the, a viscous fan that's driven by the engine with a big plastic shroud around the fan and the radiator, absolutely I consider those to be an essential because otherwise you've kind of just got this fan hanging out in the middle of space and the chance of it doing its job efficiently is pretty limited but if we're talking electric fan and putting one just directly on the back of the radiator which would be the norm, vs a proper maybe an alloy shroud that the fans then bolt to, yeah I think it's probably safe to say that the alloy shroud will improve things but again I haven't done a back to back to be able to actually prove that sorry.
49:08 Nathan has asked, ​is it worth opening an alloy radiator to create a two pass setup or just get one sized correctly? I'm tight on space with a street Exocet kit car, MX5 NB radiator running an LS1.
49:20 Yeah OK so radiator design Nathan, absolutely is not my forte so I could not really give you a good guide on that.
49:30 As I mentioned in the webinar, I'd probably be talking to companies that specialise in radiator construction and get their input on it.
49:40 There is a lot that goes into this and again I'm just not the one to be talking about that sorry.
49:48 Next question, expansion tank vs a swirl tank.
49:50 A number of new cars will use a pressurised expansion tank as a fill point.
49:53 Have you seen this as a common practice for more fit for purpose race car cooling systems? Swirl tanks aim to swirl the hot side coolant at high point of the system to help any air escape.
50:02 Have you seen this used often? What does the 86 run and have you ever tested power vs engine temperature on the dyno? OK bunch of questions there, so to answer your last question first cause it's nice and easy.
50:14 Yeah I have done some testing on engine temperature vs power and within sort of a reasonably range, and I'd say maybe sort of 20-30°C, I haven't really seen a dramatic difference in engine power.
50:29 What I see more, the engine is much more sensitive to is oil temperature.
50:36 Particularly our K20 powered Honda, basically until we get the oil temperature up above 100°C, the thing's just an absolute slug so again I can't say that that goes for every engine but the FA20 powered Toyota 86s are another one which are really sensitive to oil temperature.
50:54 The other one would be inlet air temperature so those would take my president over engine coolant temperature but obviously as we start going massively outside of that normal range, yeah absolutely I would start to see that affecting the engine performance.
51:10 Swirl tanks though, swirl tanks generally used as a way, as you've mentioned, of evacuating chance of air pockets, steam etc out of the system and get air out of that system, particularly if you've got multiple bleed points.
51:26 The RB26 would be a good example where quite often additional air bleeds are added into the cylinder head.
51:32 Yeah really good way of making sure that you don't have air pockets or bubbles going through that cooling system.
51:39 Expansion tank as a fill point, I mean I've done just about anything and everything or seen and involved in cars that I've tuned, if it's well designed, it's going to work.
51:52 I don't say that you absolutely need an swirl pot, with our SR86, we have a remote mounted expansion tank which is our fill point, that's worked really well, I don't quite know what more I can expand on that question with sorry.
52:11 Next question from Ignacio I think it is, ​my BMW N20 engine runs at 115°C when in eco pro mode and 90-95 in sport.
52:20 Whats the advantage, the first time I saw the temperature I thought it was broken? ​What I meant is why is eco pro targeting a higher coolant temperature and higher engine coolant temperature increases MPG? OK so this is kind of what I was referring to and I used the BMW example because I've had personal experience with this, they do use that electronic thermostat to purposefully run a higher coolant temperature.
52:45 I don't think I've seen 115°C but I haven't spent a huge amount of time working on or tuning BMWs.
52:52 But essentially it's everything I was talking about, there's the improved thermal efficiency, there is the reduction of frictional losses, so generally the engine will be slightly more efficient when you're in that eco pro mode.
53:06 But probably not as well set up for production of maximum power.
53:12 I'm not sure if, you've said your higher engine coolant temperature increases MPG, because definitely at cruise that absolutely should not be the case, that's why after all these OEs do that.
53:24 Kyle has asked, is it common practice to run dedicated drag cars at a lower temperature due to not always having time to bring the vehicle up to temp? I mean I can only speak from my own personal experience and I've run drag cars with and without cooling systems.
53:42 I wouldn't have said that I tried to target necessarily a very low temperature.
53:48 But particularly with cars where we've got a closed in front window, actual airflow to the radiator or no radiator at all, in my own drag car we had a solid filled block and we just circulated water through the cylinder head but there was no radiator, I would try and start the run, or maybe not start the run, start the process, when I started the car up to drive into stage, I would try and be targeting somewhere around about 70°C.
54:20 A reason for that is obviously I've got no way of the coolant temperature coming down and if someone wanted to hang me out to dry on the lights or something or mess around or something else went wrong, it just gave me a little bit more headroom before I sort of got to a point where I wasn't comfortable with the temperature and it was too hot and I had to abort the run.
54:44 Next question from Wedge has asked, thoughts on using a cylinder head temperature sensor instead of a coolant temperature sensor? Yeah I mean that's the way air cooled engines often work, basically a temperature sensor that goes under one of the head bolts or something similar.
54:59 I mean if you do run a water cooled engine then directly measuring the coolant temperature is probably still a much more efficient and effective way of doing that though.
55:13 JD Tuning, ​is a 0-150psi temp sensor good for coolant temperature and pressure combined sensor? Or is that too much of pressure range? Yeah if you're getting up to 150 psi, you've got a few problems on your hands there.
55:29 So it's way more range than you would need but it's absolutely going to be fine.
55:34 The resolution of most decent loggers, dashes and ECUs is going to give you an absolutely fine range with that 0-150 psi sensor so yeah not a problem at all.
55:50 Predex has asked, any differences in regards to diesel applications compared to gas/spark ignition, considering diesel doesn't suffer from knock? I am not really the right person to be talking about performance diesel at that level, I do not have enough runs on the board with that sort of engine to really speak to that with any authority.
56:14 What I would say is that everything I talked about in terms of ring end gap, piston to cylinder wall clearance and material reliability still would absolutely hold true for the diesel, albeit these engines are generally built much much stronger than a conventional gasoline engine in the first place.
56:31 Right I think that has got us to the end there of the questions, some great ones in there.
56:36 And for a simple topic, pretty impressed with the number of questions we got so thanks to everyone who has watched, thanks for everyone who has been asking those questions and hopefully you've got a better understanding of the sort of range of coolant temperatures that we should be targeting but more importantly a bit of an understand of what the implications of running the engine outside of those ideal ranges is likely to be.
56:58 As usual if you are watching this as an HPA member in our webinar archive at a later point, if you've got any further questions, please ask those in the forum and I'll be happy to answer them there.
57:08 Thanks for watching and we'll see you next time.