234 | How to Choose a Dyno
A dyno is one of the most expensive pieces of equipment that a tuning shop will purchase and these days we have a wide range of choices to consider. In this webinar we’ll discuss the different types of dyno and their pros and cons so that you can make an informed decision and ensure that you’re buying the right product for your business.
1:05 - Not discussing particular brands
2:05 - Chassis vs engine dyno
3:50 - Chassis dyno
7:30 - Engine dyno
9:40 - Pros and cons, engine vs chassis dyno
14:00 - Considerations when choosing a dyno
16:55 - Rolling road pro and cons
28:50 - Hub pro and cons
31:35 - Why you shouldn't compare readings between dynos
32:45 - Hub pro and cons continued
37:45 - Engine dyno pro and cons
39:55 - Power absorbers
42:55 - Software
45:50 - Questions
- Hey guys it's Andre from High Performance Academy here, welcome along to another one of our member's webinars. And today we're going to be talking about the different styles and types of dyno out there on the market. We've kind of seen a bit of an explosion probably over the 18 odd years that I've been involved in the aftermarket tuning industry with more and more dyno manufacturers coming on board. We've seen the technology advance quite dramatically in the dyno world as well. More features being brought out by these manufacturers and it's given us a lot of choice as tuners when we're trying to decide what dyno to purchase, maybe you're looking at opening a performance workshop, maybe you've already got one and you're considering bringing dyno tuning in as another revenue stream, or if you're an enthusiast learning how to tune your own car and you need to hire time off a dyno shop, either way, regardless what situation you're in, it's obviously vital to have a really good understanding of the type of dyno that will suit your application, what you're actually trying to do so that you can get the right results and you don't end up wasting time and wasting money with an inferior dyno.
Now this isn't going to be a case of discussing the advantages or disadvantages of different dyno brands, I'm going to try and stay a little bit out of that. Obviously every dyno brand has its own loyal followers. Every dyno brand, just like every dyno has its own pros and cons as well. I've been reasonably fortunate over my career that I have had the opportunity to work on a number of different brands of dyno. Right now we are using the Mainline brand here at our HPA Labs workshop and we have been supported really well from Mainline over in Australia, really love the brand, but we're going to try and stay a little bit brand agnostic within this particular webinar.
As usual as well at the end of this webinar, we will be having questions and answers, so if there's anything that you want to know a little bit more about or anything maybe that I've missed out that you want me to dive into, please ask those questions and we'll get into those at the end. So what we want to do for a start is just understand that there are broad categories that our dynos fall into and the first and probably the most obvious would be the difference between a chassis dyno and an engine dyno. So we'll head across to the laptop screen for a moment. So this is actually our original dyno from Mainline that we purchased back when we first moved to Queenstown about five years ago now. So this is a two wheel drive rolling road and that did us really well for the start when we weren't really needing to tune too many four wheel drive cars.
So rolling road, probably most people have a pretty good understanding of how that works but simply put, there are two rollers that the wheels are going to drive against. We'll get into a little bit more detail about these as we go through this lesson. The other broad type of dyno that we've got is an engine dyno and this is our engine, remote practice dyno, unfortunately that we have now decided that we're going to shut down. But doesn't change the fact that this is what an engine dyno setup looks like. In this particular instance we've got an LS2, or actually it's an L98, let's call it an LS2 for simplicity, that's sitting on a little stand here with some castor wheels so it makes it easy enough to move it around.
And the flywheel here is directly connected up to a Mainline 1000 horsepower eddy current power absorber. So that's our two broad types of dyno and within these two categories, we can break these down much further which is exactly what we're going to do. First of all, if we look at the chassis dyno, we've already seen we've got the rolling road here in two wheel drive format. If we move over a little bit further as well, we can see here, this is what we ended up upgrading to, so we started with a two wheel drive 600L, we upgraded that to a four wheel drive 1200L. So simply this is two of the beds put together.
With the rolling road technology what we obviously need to be able to do is extend and retract the bed to suit different wheel bases so in this case we've got the wheels really need to be running pretty much exactly perfectly in the centre of the two beds. And there is an adjustable finger follower bed here that is motorised that makes it really easy to extend and retract that bed to suit the different cars that are going on it. So beyond the rolling road style of chassis dyno which always was the most popular, most common, this is probably what most people thought about when they thought of the term dyno, we've also more recently seen an explosion in the use of hub style dynos. Now this is our latest dyno, again from Mainline. This is their Prohub four wheel drive hub dyno.
So what we can see here is we actually take the wheels off the car, they are directly attached to each of the hubs. Each of these hubs has an eddy current power absorber within it and the power absorber, don't worry if you don't understand what that term is, we will deal with this in a bit more detail, but essentially it allows the dyno to apply a variable and controlled amount of load to each of the hubs, each of the axles in order to control wheel speed or axle speed and then in turn that's going to control our engine speed, engine RPM. Now that isn't actually the only type of hub dyno that is available, or the only type of dyno and I'll just check out and make sure I've got the right slide here. Yep if we can jump back across to my laptop screen here. This is my old dyno when I owned my workshop STM before we closed that down or sold that and started High Performance Academy.
So this is a Dynapack hub dyno. So pretty common, particularly here in New Zealand and often in Australia as well, because they are made in New Zealand, they ended up getting pretty well supported with people in New Zealand. This is a hydraulic control dyno, we'll talk about that as we go through this webinar. And very very similar in terms of the way it operates to the Mainline Prohub dyno, now again just obviously you remove the wheels, you bolt an adapter directly to the hubs and then that locks into each of those hubs. The other type of dyno that we also need to talk about here, again on my laptop screen here, this is a Dynojet inertia dyno, so this is a four wheel drive rolling road.
But an inertia dyno, again we'll talk in more detail about what this means, it doesn't have a power absorber, basically it's just a large fixed mass. So these are not really useful for doing any steady state or part throttle tuning. Not a bad option though in terms of tuning under wide open throttle ramp run conditions. So there's the sort of break down of the different types broadly when it comes to chassis dyno. We've got the rolling road in two wheel drive and four wheel drive format, we've got the hub dyno and then we've also got the inertia dyno which is a form of rolling road just with no power absorber module.
When we come back to the engine dyno, and again we'll just jump back to my laptop screen. So we've got the engine dyno, I already briefly mentioned the way this works. We've got the engine on a cart, the flywheel is directly connected to our power absorber. In this instance with our Mainline dyno, this was a eddy current power absorber. This would probably be pretty unusual in the world of engine dynos.
Much more likely that we'll end up seeing what's called a water break for the power absorber. Actually also a much cheaper technology but not without its downsides as well. That's not the only sort of engine dyno that we have access to though, well maybe that's the only type we at the enthusiast and semi professional level are likely to have access to but what I quickly want to show you here, if we jump across to my laptop screen. This is a video that I highly recommend that you go and have a look at in a bit more detail when you get a chance. And this is an F1 engine, it's an older engine, this video was from 2014.
I'll just play it anyway and basically this is on what's called a transient dyno. So this is where the engine can actually be run up and it will simulate a complete lap of a racetrack so all of the data from the racetrack from the car actually running out there under real race conditions can be loaded into the transient dyno. And the transient dyno, as its name implies, it's got the ability to very quickly change RPM so it can actually motor the engine as well. So what I mean by this is on a downshift, or a simulated downshift, the engine RPM obviously needs to increase and particularly with an F1 engine, it increases incredibly quickly and the transient dyno can actually motor the engine to increase the engine RPM to simulate that. So this is probably, I'm going to guess, I've got no actual idea because I've never been in the market for a transient dyno, but this is probably something that's likely to be several million dollars worth of equipment so again not something that we're likely to have access to but incredible to watch those engines, the sound of them in particular on the transient dynos, really really cool.
So just to understand that they are an option there for those who are maybe a little bit more well funded in the wallet department. Alright so as I've already mentioned today, there are pros and cons in each style of dyno, nothing is perfect in the world of dyno tuning and we need to understand these pros and cons so that we can make an educated decision about what we're going to be doing. And I'll actually give you a bit of a recount of one of my first experiences on an engine dyno. And growing and learning how to tune, starting out tuning on the road and then starting to get experience using a Dynapack hub dyno, that was my first tuning where I sort of really learned how to perfect the craft. And then I had the opportunity a few years into my career to fly to Christchurch, which is in the South Island of New Zealand and tune a marathon jet sprint boat motor on an engine dyno.
So this was a supercharged Buick V6 which made somewhere in the region of about 700 or 800 horsepower and it was running on a MoTeC M800 ECU, back at the time this was really the cutting edge so I was very excited about being involved in this project. The customer was really competitive and he had a good budget to do the job properly so really excited to do this. And I was really disappointed with my first experience on this engine dyno, it was an old manually controlled water brake dyno. And of course with EFI tuning what we want to do is start with steady state tuning of our fuel and ignition tables and what I did was some initial checks got the engine to actually start and run in idle, went through all of our base setup checks and then I wanted to actually get started with some light load steady state tuning. So I was the one on the laptop doing the tuning, the owner of the workshop was operating the dyno and to my dismay, what he had was in one hand a throttle, which understandably operated the throttle and in the other hand he had a tap which controlled the water brake on the dyno which controlled the amount of load being applied to the engine.
So I thought a good place to start might be to get us up to maybe 2500 RPM and some light load just so we could stabilise everything and start building up a bit of a fuel and ignition map. And so I pointed to the cell that I wanted to go to and after about two or three minutes of the operator increasing and decreasing the throttle and increasing and decreasing the water flow and basically drawing nice circles around the cell that I was interested in, I quickly realised that with this particular water brake dyno, I had absolutely no chance of being able to tune how I was used to on my old Dynapack dyno. Now that's not necessarily disrespect for a water brake dyno, as I found out a little bit later in my career, they can actually do a great job. A lot of the water brake dynos that have been around for years, the technology in the water brake itself, nothing particularly ground breaking and a relatively cost effective way of providing load to the engine. A lot of these older water brake dynos, engine dynos have now been converted to electronic control and there are quite a few companies providing the electronic control adaption, including DynoLog who provide the electronics for Mainline.
So with electronic control, the valving is all controlled by computer and obviously that takes out the human factor and we get back to a situation where we can hold a consistent RPM, albeit at least with the water brake dynos converted to electronic control, I've been familiar with or been experienced with, they still have a bit of a latency. So what I mean is, let's say you want to set 4000 RPM as your set point. What you'll generally find, at least again in my experience is that the dyno will initially flare above your set point. So if you're at 4000 set point, you might end up flaring up to 4500 or maybe even 5000 RPM before the dyno can actually gain control over the engine and pull it back. Once you've actually at your set point though, they do seem to work really really well.
So there you go, not always to say that the engine dyno is the best option. So really what you need to consider when either purchasing a dyno or selecting a dyno shop with a certain type of dyno to use is what you want to do on that dyno and that's really going to be the key consideration to what's going to be the best dyno for your requirements. So if, for example, we're considering the purchase of a dyno, what we really need to consider is what sort of tasks are you going through, what is your main business? So for example if you're an engine builder building race engines and developing race engines, in that case, an engine dyno might make a lot more sense for you. There are some big advantages with the engine dyno in terms of the ability to work around the engine. In particular because the engine isn't installed in a chassis, it's very easy for example to swap over headers, maybe do cam swaps, intake swaps et cetera.
So for doing testing of parts it's much much quicker and easier. And in particular if you are building and developing engines and customers are sending you back engines, you want to test them before they go out, obviously if you've only got the engine, it's going to be very very difficult for you to run that on a chassis dyno anyway. So an engine dyno would make the most sense in that application. There are a couple of problems with that though. It's often quite difficult to fit all of the components onto the engine when it's on an engine dyno that it would run in the car.
For example, and while it's not impossible, but more often than not you will not see an engine on an engine dyno using the full exhaust system as it would sit in the car. Often that's just not possible because the exhaust system would actually interfere with components such as the power absorber or other components inside of the dyno cell. So that can be quite a big consideration because then you're really not tuning the engine under the exact conditions it is going to be running under so that's a problem there in and of itself. For tuning shops, which are probably the majority of applications where dynos are used, this is really where the no brainer would almost always be a chassis dyno. And if you are in the fortunate position where you're looking at maybe two dynos, the chassis dyno would probably be the one that I'd suggest you purchase first.
The engine dyno, it's a nice addition to the chassis dyno but the chassis dyno almost certainly is going to be used a lot more. And this is particularly important if you are looking at a high turnover of customers through the door where you're perhaps looking at maybe three to 10 cars a week that need to be tuned, there's no feasible way you're going to be able to use an engine dyno for that sort of work. So I'm going to just focus here for a moment on the chassis dynos and we'll sort of break these down a ltitle bit further. So let's start with our selection of a rolling road dyno. So again, pros and cons on each of these, the first is that the rolling road dyno is quite a large unit, particularly if you are looking at a four wheel drive dyno.
So again we'll head across to my laptop screen for a moment. We can see we've got the two beds for the dyno and they do take up a huge amount of room in your workshop. The other aspect here is that you do need to consider that these are going to be pretty difficult to move, not impossible but you're certainly not going to shift them on the regular to make more room in your workshop. So once you've assigned an area for the dyno, basically that's it, you're going to be stuck with that space being very difficult to use. Another aspect with the rolling road dyno is we do need to consider if we are going to build a pit to sink the dyno below ground, or basically level witih the ground, ground level, or you're going to run it above ground like we've done here.
And there are again pros and cons with both of those techniques. So first of all here with our above ground installation, the main advantage of course is that there's no cost involved with having a pit dug, concreting that in and then installing it into the pit. There are some other advantages as well which I think are really often overlooked. Particularly on low cars it is actually quite a lot easier when we've got an above ground installation like this to get access, we can see here we've got a strop on each corner at the front of the car, makes it really easy to get underneath and have a look at that. Also at the back of the car, hard to see but I've got a strop going down there from the lower control arm, down to a point, a strapping point bettween the two rollers in the rear bed.
So again when you're kind of messing around underneath the car at the back, being able to get under the car with the car raised up on that dyno bed does make our life a little bit easier. A big downside and this is one that was a bit of a frustration for us, is the way we've got this installed, so it's going to be installation dependent, We've got these two large ramps here that we need to get the car on and off the dyno, so understandably you're going to have to drive the car forward in our situation. And basically it made one complete corner of our workshop completely unusable. So not particularly great in that instance. Again, this is going to depend on which way around you've got your dyno orientated but it is important to give some consideration to getting cars on and off the dyno.
The other thing with these ramps you do need to consider as well is even with a long ramp, can be problematic with very very low cars because what you can easily overlook is that when the car actually drops down into the dyno bed, the whole car will actually drop down by about an inch so as you've backing the car up these ramps here, as the rear wheels first of all drop down into the front bed, you're going to end up with the whole car sort of dropping down through the centre there. There are some ways around that as well, there's some aluminium blanking ramps that you can put over the front bed as you're backing the car in but these in themselves actually end up creating some clearance problems. So we've actually had a few issues with some very low cars, getting them on and off the dyno and people think that rolling roads are going to speed up the process of getting the car onto the dyno, ready to run. The reality in my experience between a rolling road and a hub dyno, we'll get into this in a bit more detail shortly, is that yep if you're running low powered cars, they are very quick and easy to set the car up on, particularly if it's two wheel drive. Once you start getting into really powerful cars where wheel spin becomes a problem, really really low cars, cars with complete underbodies where there are no strapping points that are easily accessible, in these instances, it can take actually longer to get the car onto a rolling road so it's not all roses there.
Which really comes down to the next point as well is that obviously on the rolling road, you are relying on that tyre contact patch between the tyre and the roller and understandably here, the biggest issue and probably no big surprises is that wheel spin is a real consideration. Particularly on very high power cars, also cars where the, or engines where the powerband comes in very very sharply, this can overcome the available traction quite often. So you can end up finding on these powerful cars that you have to mess around, trying different tyre pressures, different strapping techniques, strapping the car down harder in order to get the best result and allow the car to actually put the power to the rollers. Now, that's probably something that most people can understand but what might be a bit of a surprise and definitely this was an eye opener for me coming from my original hub dyno which was the Dynapack hydraulic hub dyno, to the Mainline rolling road, is that even when you've actually got the car hooked and you've got traction, you're going to find that as you apply more load, the tyre will deform and the car will actually move up onto the roller and you actually want that, you want the car to move forward onto the driven roller because then all of the torque at the rear wheels is being channelled through that rear roller. So that's important, but what you're going to find as well is that as the tyre deforms, you're going to find that your rolling diameter of the tyre actually changes.
So what this means is that when you come up to, let's say 2000, 2500 RPM set point on the dyno, with the Mainline dyno we actually set the RPM based on road speed not engine RPM. So let's say we are at 2500 RPM at light load, the dyno's got control there and it's applying load through the roller to maintain that same road speed. What we'll find is that as we apply more and more power, the engine RPM actually tends to overshoot slightly. So as we go from very light throttle to wide open throttle, 2500 RPM, we'll actually find that the RPM of the engine starts to climb a little bit. That's not to say that the car is wheel spinning, it's just that deformation of the of the rear tyres on the rollers, or the front tyres, whatever tyres they are on the rollers and the result of this is inconsistent RPM.
Now you might think that's no big deal but particularly when we are doing steady state tuning, we always need to be in the centre of the cell for fuel and ignition as we move through the cells. And of course this requires us to constantly make small corrections to the road speed target so that we stay in the centre of our cell as we increase our load. The other problem with this and I've sort of mentioned here that with high power cars, high torque cars where wheel spin's an issue, we need to strap the car down differently or we may need to strap the car down harder. Now that also has the effect of altering or changing the amount of power that the dyno will read. So it actually can be quite a problem, particularly with your strapping technique, if you've got a car that you tuned maybe two months ago, it comes back and you put it back on the dyno and if you don't strap the car basically exactly the same, you will end up with a different power reading and again that's a subtle thing that a lot of people probably would overlook.
And it can be frustrating, particularly if you are developing a car over a course of time, maybe you initially baseline the car, it comes back with a few modifications, you put it on the dyno, you're expecting maybe that the modifications give it an extra 50 horsepower but you can actually end up, due to a strapping technique change, finding that it's only making an extra five or 10 horsepower. So this is where we need to really understand the implications of the tool that we're using. There's nothing wrong with the dyno, that is just the requirements of that particular style of dyno, getting our strapping technique really consistent, making sure that our strapping techniques going to be the same every time that same car comes back in. The other aspect that goes along with this as well is, this actually happened on one of the cars we did some course material on which was a ZL1 Camaro with a supercharged 6.2 litre LSA engine. Originally the car was originally delivered to us with a set of 22 inch wheels and some very heavily worn tyres on the back.
And they were pretty old, they were pretty hard and we ended up doing most of the tuning, I can't even remember the power that the car made now, but what we found is that as the tuning progressed, the tyres were worn to the stage where we were starting to see some canvas show. I wasn't too keen on having a high speed failure blow out on our dyno and damaging both our dyno and the customer's car so go in touch with the customer, he got some new rubber fitted to the rear wheels and basically we put the car straight back on the dyno, the only change was the rear rubber and the car ended up measuring something like 40 horsepower less than it originally had so this is the difference between some old, hard slick rubber essentially and a nice brand new soft, sticky performance tyre. So even aspects like this, or a customer that's done a whole bunch of tuning on their car and then they've actually swapped to a different set of wheels and tyres, this is all going to affect the power that your engine shows on the dyno so just really important to understand that. Lastly with our rolling road dyno, we also need to consider whether we need a linked or we can get away with an unlinked dyno. So this just refers to whether the front and rear rollers are linked together so that they must operate at the same speed.
Through most of my career, this really hasn't been an issue so the majority of dynos out there that are four wheel drive will be what I refer as unlinked where the front and rear beds basically can turn independent of each other and that will be fine for 99% of cars. What we are starting to see though, and this seems to be particularly with European cars, Porsche and AMG are two that I am personally aware of or have had problems with, even though the cars are two wheel drive, they're smart enough now that if you run them on the dyno and the ECU detects that the front wheels aren't turning, then it basically will go into a limp home mode. So you're not going to get anything like the sort of power that the engine is actually developing, generally it'll just close the throttle bodies down so it's running at a much reduced power. Obviously making it impossible to tune the cars. There are some work arounds there, with the Porsche you can, if you've got the factory calibration equipment, factory communication equipment I should say, you can actually put it into essentially what's a dyno mode.
There are other people I've heard of basically making jigs for the front wheel speed sensors on cars that they're tuning a lot and basically replicating the signal from the rear wheels but this is important to understand because it's likely that it's going to become a more common issue with two wheel drive cars and the only way to tune these is going to be to run them on a linked dyno. So we are seeing a lot more of the dyno manufacturers now put work into linked dynos where the front and rear rollers will operate together. Alright so I think we've probably covered off the main aspects there of our rolling road. Probably the pros and cons pretty well documented there. If you've got any questions, of course ask those and we'll get into those shortly.
Next one we're going to be talking about is the hub dyno. So I started with a hub dyno, we moved to a rolling road, in between, even while I owned my hub dyno, I was doing a lot of tuning overseas where I was using various types of rolling road so I was familiar with both types. And then of course now we have moved to our Mainline Prohub dyno as well. So a few considerations with the hub dyno, basically here from the purchase point of view, first of all they generally tend to be a little bit more expensive than a rolling road so that's a big consideration. You're also going to need a larger room than you probably think that you will need.
And I've actually seen a lot of people get themselves in trouble where they've designed and built a dyno cell which they think on paper seems more than adequate and then when they actually get into using the dyno, they find that there's not enough width in the dyno cell and the problem with this is that as we are working on the car, we need to be able to move the hub units away from the car, so we need enough room that we can actually move them back off the car. Generally I would suggest a good metre or metre and a half on each side, so we need to take into account the width of the car, the width of the hub units and then another metre, metre and a half on each side. So you actually end up with quite a big room. If you are stuck in a pokey little space where it's really difficult to work on, that's going to really take its toll on you over time, particularly if you are tuning a lot of cars so you really need to be able to be in a comfortable space to be able to work efficiently there. The advantage of course in terms of space is that when the hub dyno is not in use, you can roll the hub units out of the way, so clearing your workshop space, and this is why we'll see a lot of tuning shops which use a hub dyno, don't actually have a dedicated dyno cell for that, they'll just have them stored perhaps under a workbench normally and then they'll pull them out as required.
Goes without saying of course, no problems with wheel spin on a hub dyno. The wheels are physically locked to the, the axles or hubs are physically locked to the power absorber or a hub module so probably one of the key advantages. We also don't have the interference or contact patch between the tyre and a roller which can vary, as I already talked about, with different tyre compounds, tyre pressures and even heat which I didn't mention, heat in the tyre will affect your power reading. So because we're getting rid of that completely, what you're generally going to notice is that if you're comparing dyno figures, which is always fraught with potential for disaster, you're going to notice that most of the time a hub dyno will show you a higher power reading than a rolling road. I'll just take this moment just to touch on this a little bit because we always see people comparing dyno figures online, on Facebook groups et cetera and honestly it's about the most irrelevant thing you can do.
Every brand of dyno is going to give you a different reading for the same car and you'll also see that depending on how the particular operator straps the car down, for example on the rolling road, how they set up the car in terms of ramp rate, what gear they run it in, all of these factors can influence the power that the dyno will show. So don't try and compare your dyno figure, what you want to do instead is use a dyno that is repeatable and consistent, that's the most important part. And then you're just going to compare your numbers between different dyno sessions on that same dyno. And I'm not also going to get into the debate which is just as futile, on trying to convert between wheel horsepower or axle horsepower and flywheel horsepower. There's just so many factors in here, you can't possibly hope to go and apply a 20% factor to the wheel horsepower number and expect that that's going to work for every car, every engine at every power level, unfortunately life is just not that simple.
Let's get back into our hub dyno though. So because we've got no tyre contact patch, we've got no chance of wheel spin, one of the biggest advantages with a hub dyno is that they will show more repeatability and sensitivity than what we get with a rolling road. This is important, particularly if you are looking for really small improvements in power, I know that a test that I used to demonstrate on my old Dynapack dyno is that I'd run the car in steady state conditions and we would note the torque being measured by the dyno and we would turn the headlights on and off and we would actually be able to see the torque change as the alternator kicked in and out, drawing more power through the drive belt from the engine. So that's the sort of sensitivity that you'd probably struggle to replicate with a rolling road dyno but it is really important, what I want to do, again I don't really care so much about the absolute power number but I definitely want to know that if I do two runs back to back on the dyno, under the same atmospheric conditions with the same fuel, the same ignition timing, the same air temp, coolant temp et cetera, I wan to get the same results. If we're starting to see our power fluctuate by sort of three to five horsepower run to run when we haven't actually made any changes, it's going to make it very very difficult for us to be able to do the best job possible and be confident that the tuning changes we've got in there are correct and optimal.
So this is where the hub dyno really does come into its own, the advantage of being able to get that repeatability and that sensitivity. Downside, and this was my issue with my old Dynapack is that they do have a couple of limitations. First of all, they'll have a maximum torque limit. So everyone rates dynos in terms of their power handling, including some of the dyno manufacturers. It's really not specifically the power that's the important part, it's actually the torque handling capability because the dyno has to be able to provide sufficient load to basically counter the torque being produced at the hubs.
So with the Dynapack, there's a variety of different models but I got to a situation where on one very large capacity blown V8 drag engine with a high stall converter and an automatic transmission, basically the perfect storm of conditions for a Dynapack dyno. The high stall converter in particular has the effect of multiplying the engine torque. On that, with my Dynapack 4000 which took 4400 newton metres at the hubs, I could shut that dyno down just off idle at about half throttle so that gives you some indication. We found less issues if you're running a manual transmission with a clutch, you don't have that torque multiplication with the automatic transmission and the torque converter so that makes life a lot easier. But even then I tuned a turbocharged four rotor drag engine and that drag engine, I ended up basically balancing torque limit with hub speed limit, we ended up changing the final drive and I think off the top of my head, the most we could run it out to was about 1250 horsepower at the wheels.
That was at I think about 8800 RPM which was the hub speed limit and the power and torque were actually still climbing so we never got to see what that engine was capable of. This has become less of an issue these days with the likes of some of the prohub dynos as this is really where the development of the prohub came from. So again if we just jump across to my laptop screen. Mainline started producing these for a lot of the customers over in the U.S. market which were making more and more horsepower, couldn't hold the power on any rolling road and basically this is a quad retarded hub dyno.
So we've got one box here which we can see, sort of basically broken into two and it's got two eddy current power absorbers in each of those boxes. This is, I think off the top of my head, a nitrous drag car and if anyone's following any of FuelTech's videos on Facebook, you've probably seen, I think the highest number they've got at the moment is in excess of 5000 horsepower being measured on one of these dynos. That's been a game changer as well for those guys running the likes of Pro Mod because traditionally they haven't been able to dyno their engines and they've been tuning at the track and yeah that will get you so far but at the end of the day, particularly if you're doing engine development work at that power level, you're really going to be struggling to know exactly which direction you're going if you are limited to datalogging at the racetrack. So at least as far as the Mainline range of Prohub dynos go, they've basically got you covered just about no matter what power level you want to run. Alright we'll talk very briefly as well again about our engine dyno.
So the pros there, as I've mentioned, very easy to work around the engine. So let's just head back across to that photo of our engine dyno. So we can see that we've got complete access to here to all of the components on the engine. The other aspect, because the trolley that's at the base here that the engine is attached to, this is only bolted to the rest of the dyno. So particularly if you're in a situation where you are developing the same style of engine, what you can have is multiple trolleys and it can actually be a very quick job to swap between different engines.
Basically all it requires is the exhaust system and coolant system to be hooked up, maybe some of the electronics and then the driveshaft to the dyno. So yeah perfect for those people doing that level of engine development. Downside is a lot of infrastructure required for an engine dyno, particularly some of the water brake dynos, there's a lot goes into the plumbing, the water storage et cetera for that style of dyno and in most instances, other than the one I just mentioned, it is going to be quite time consuming to set an engine up on an engine dyno. Particularly if you've got a customer with a car where the engine is already in the car, the process of removing the engine from the car, replicating the electronics if it's EFI so you can actually run the engine on the engine dyno, it's not a small task at all and of course time is money so you need to factor that in. Accuracy and sensitivity of this style of dyno, obviously we've now removed the entire drive train from the engine, we don't have any effect from power loss through the transmission, through the differential, the hubs et cetera so this is really the only situation where you are truely able to see what the flywheel power is.
So if that's really important to you then by all means that's going to be the way of getting it. Alright so because the engine dyno, probably not suited to too many of our viewers here, I'm going to move on and I just want to quickly touch on power absorbers. I've already really mentioned the terms anyway but the power absorber, what I'm using there, that terminology means the way that the dyno is applying load to the engine. That's really important, I call this also a load bearing dyno, you may have heard me use that term before. So this is really important if we want to be able to steady state tune, the dyno has to be able to apply a variable amount of load to the hubs or the rollers, or straight to the engine in order to allow us to accurately move through each of the individual fuel and ignition cells, basically moving the throttle, applying more or less torque to the dyno and the dyno's going to apply more or less resistance in order to maintain that fixed speed.
So these power absorbers come in a few different varieties, I can't exactly say that these are all of them but they're the most common you will find. There's the eddy current which is basically an electrical style power absorber, that's what we are using in the Mainline dynos. Pretty common with a lot of chassis dynos. There is also hydraulic control which is how the Dynapack style dyno works. So what I'd sort of liken this to without really knowing exactly what's going on inside there, I haven't pulled a Dynapack dyno apart but essentially each of the hubs will spin a big hydraulic pump and the dyno will control a valve allowing the hydraulic fluid to escape out of the pump so by closing down that valve it applies more load, it makes it harder to turn the dyno, by opening that valve it allows the dyno to spin over more freely and that hydraulic control, one of the advantages of it is that it is incredibly fast to respond so I think it's probably actually a bit of an advantage with the Dynapack compared to an eddy current power absorber.
The eddy current power absorber, much larger in diameter, there's a lot more weight there, there's a little bit more latency in its control. So a sensitivity advantage there with the Dynapack, one of the downsides though with the hydraulic control, because there is almost no inertia in the system, makes it impossible for you to do any testing on aspects such as gear cut control, you can't really drive the car through the gears on a dyno, even if you've got a sequential or clutchless gearbox, they don't really work that well. We've had pretty good results doing exactly that on our Mainline Prohub, better again on the rolling road because you've actually got more inertia. And then of course I've also mentioned the water brake dyno. I think it would be fair to say that the majority of water brakes will be applied on engine dynos.
Not something that we would see, I don't think on a modern rolling road style dyno. Alright we are getting a bit long here so I see we've already got a few questions, I'm going to jump into those really shortly, if you have got any more, please feel free to ask those. I'll jump into those really shortly. The other couple of aspects I just want to briefly touch on is the software features and the type of control. And this is important to understand and particularly if you are looking at purchasing a dyno, just understanding that not all dyno software is created equal.
Particularly if you are doing a lot of development work, it's going to be powerful if you can do some more involved data analysis inside of your dyno. And this is actually one of the things that made me switch from the Dynapack dyno initially to the Mainline dyno. The Dynapack, at least the generation that I had and admittedly that was back probably seven or eight years ago now, was very limited in terms of bringing in additional inputs. So if we wanted to log things like fuel pressure, EGTs, multiple lambdas, all of the functions and parameters coming out of the ECU, we were very limited in what we could do there. On the other hand, Mainline with their DynoLog software, very very advanced and one of the features that I really like on the Mainline dyno, which if you've ever watched any of our webinars or lessons you would have seen me use the torque optimisation feature, which is really powerful for plotting the relationship between ignition timing and engine torque.
The dyno is obviously measuring torque, at least not engine torque it's measuring torque being produced at the rollers or at the hubs. And the Mainline dyno allows you to bring data in from the ECU via a simple two wire CAN bus. So if we jump across to my laptop screen here, you end up with something that looks a little bit like what we're seeing here. We've got torque on the vertical axis here and we've got our ignition timing coming from the ECU on the horizontal axis. The idea being that in this case we start at 10 degrees or whatever we want but generally a nice retarded ignition timing.
And we'll start the test and we'll hold the engine steady state in the cell that we're tuning and we'll sweep the ignition timing from 10 degrees all the way through in this case to 50 and the dyno shows us that relationship and it also shows us where abouts we are reaching MBT, in this case for whatever I was tuning at this point, we see that for that cell, that equalled 33 degrees, delivering us 103 newton metres. So that's a very powerful training tool, I will say that there's not way that you'd use that torque optimisation function for every cell. But I do find that it's a nice sanity check, might pick out a handful of cells in the map and go through and do a proper torque optimisation and just make sure that the trends that I'm seeing in between are making sense. Alright I think we'll leave the webinar there, as I say we've gone a little bit long already and I am expecting we're going to get quite a few questions so I'll jump into those questions and get started now. If you've got any more, please continue to ask them.
Smrodriguez has asked, do you have any experience with DYNO-mite dynamometers? No unfortunately that is a brand that I don't have any experience with so I can't help you there. JEM-Sport Jake has asked, do you have any suggestions or tips for budget-minded exhaust ventilation systems? I don't know about budget minded, it is a problem. So what we're doing here at HPA Labs, and we sort of started with this because we were intending to build a dyno cell. We've probably gone away from that idea just for simplicity. As you've probably seen, we just run the car vented straight out of our workshop and obviously that works well.
We also don't run our dyno very much and certainly if I was tuning a couple of cars a day, five or six days a week, I think we'd probably be starting to piss off all of the neighbours pretty quickly so you do need to be a little bit sensible about that. With my old shop, we built quite a sophisticated dyno cell and we used a couple of large fans to extract air out of the dynp cell and what we did to try and make sure that we extracted all of the exhuast gas is we actually ran some flexible tubing basically that went over, around the outside of the exhuast tip and then ran up the back wall of the dyno cell. I kind of had a false wall that came down probably about four feet off the ground and it was about two or three feet of the back wall and basically the extraction then made sure it was moving air down underneath the car. But there is a lot that goes into that, yeah I'm not a dyno cell design specialist but you do want to make sure that you are getting sufficient airflow through the dyno cell in order to evacuate all of the exhaust gases. It's going to improve the dyno tuning experience, you don't want carbon monoxide damaging your health as well over time, particularly if you are tuning a lot, that's a serious consideration, is your own health as well.
But sorry I can't really give you specifics on sizings of those fans, there's too many other variables that will play into that. Awsom Sauce has asked is it possible with a hub dyno to get misleading numbers due to an open differential? No it shouldn't. The way the hub dyno will work is that it's actually controlling axle speed or hub speed on each side. And yeah open differential or an LSD or even a spool, essentially we should be seeing almost matched hub speed. So that's important because otherwise, if the hub dyno can't get that level of control and there's significant differences in the hub speed left to right, then you do run into the risk of actually damaging an expensive clutch plate style LSD over the course of a dyno tyning session.
So first of all, no, the problem shouldn't exist in the first place and even if it does, what we're looking at is essentially the total of, sum of all of the measured torques from the different hub units so it really shouldn't have any effect, you shouldn't be getting a difference in your power. Marc Jackson says it sounds like the new tyres had less, that doesn't sound correct. Old tyres not flexing and power to heat? OK so what you need to understand, and this really comes down to a conversation I had with Todd from Mainline back fairly early on when we bought our rolling road, they actually travel around Australia going to car shows, the likes of Summernats et cetera and they at the time were providing rolling road dynos for their dyno competitions. So all of the guys there with their big power, basically generally turbocharged V8s, LS these days, were making more power than they could easily put to the wheels on a rolling road dyno. And the solution to getting as much power to the ground with less wheel spin was to actually run a large diameter wheel with a very low profile tyre and very very high tyre pressures.
So what we need to understand there is when we went from the old tyre, which was old, it was hard, it was worn, and we went to a new sticky tyre, obviously assuming that we weren't getting wheel spin initially, the sticky tyre, basically absorbs or reduces the power being delivered to the roller. So that is actually a problem if you go from a road tyre to a sticky slick tyre, you're actually going to find that the slick tyre costs you some power and will show a lower number on the dyno. JEM-Sport Jake has asked, could you comment on additional or necessary chassis dyno accessories? Any particular brands you suggest for these items? OK I mean a fan is the main one for cooling, obviously again I've already talked about it, we don't necessarily have a problem with exhaust extraction, that's a different thing. So there's two fans we really need to consider, there's the extraction fan that's moving air through the room and then an adequate cooling fan and I can't stress enough that bigger is basically always better when it comes to both of those aspects. The more air we can move through the room the better, the more consistent our temperatures in the dyno cell are going to be and likewise with a cooling fan in front of the car, this is going to become a real problem, particularly when you are running the car under sustained high load, if you aren't able to get enough cooling airflow through the radiator, you're going to end up having to stop frequently and allow the car to cool down.
Other aspects that you will need is a good quality wideband air/fuel ratio meter. I have always used a MoTeC PLM. I've basically had one of those when I purchased my Dynapack dyno, at the time that was what they were fitted with. And because I kind of got familiar with what sort of lambda values I could tune to for certain cars and I was confident and comfortable with the numbers that I was getting from the MoTeC PLM, I always stuck with it and I also got a Innovate LM2 that I use for road tuning. The Innovate LM2 reads exactly the same as the MoTeC PLM so I know that they're going to be consistent.
Now don't get me wrong, I'm not saying that the MoTeC PLM is the most accurate wideband controller in the world, it may very well not be. The important point is that I know that if I run a particular car at XX lambda or air/fuel ratio, then I know that's going to be safe. So I don't tend to swap too much between my air/fuel ratio lambda controllers, I've always stuck with the MoTeC PLM or lately LTCs, I've also found that they've been reliable. So that's the first one. Other aspect that you're probably going to want to consider is a knock detection system, probably getting a little bit out of the scope of dynos.
I use two, I use the Plex Knock Monitor, I also use the Link G4 + Knock Block, both of those are excellent, both have their own pros and cons. Touge Tuning has asked what cars have trouble on a prohub all wheel drive system? I don't actually know if I could say anything has trouble. You also need to understand that our usage of our prohub dyno is quite different to a professional tuning workshop in so much as we are not putting five or 10 cars across this dyno every week and the dyno will literally sit for a full week where it isn't used, generally it's the same cars, our own development and test cars that are going on and off the dyno so what I can say so far is that none of the cars that we have run on the dyno have been problematic. Actually I do tell a lie, we did have some issue with Taz's MX5 initially because it doesn't make very much power. The dyno, we need to understand that the dyno sensitivity, we can't expect a dyno that can comfortably read up, in our case, to 2500 horsepower in a rear wheel drive application.
Obviously if it can work all the way up to 2500 horsepower, it may also have sensitivity issues down at the other extreme and with Taz's MX5, Mazda Miata, I think originally it was putting out about 90 horsepower at the wheels. And what we found was that the dyno actually struggled a little bit initially, particularly higher in the RPM in a ramp run, it would tend to set up a bit of an oscillation. However we actually went back to Mainline and talked to them about this and they actually had a fix for it that improved the sensitivity with very light power cars. And since we've done that it's been really really good but I think it's fair to say that below about 100 horsepower we don't have the repeatability run to run to within sort of half a horsepower that we would see if we were running a 200, 400, 500, 800 horsepower car. OK so we actually did have another question there which was along the same lines from Cafego85 I think, what sort of dyno would you recommend for all wheel drive SUVs? Basically any of the four wheel drive dynos are going to work.
With SUVs I'm going to guess you're probably not chasing stupid power levels so probably a rolling road dyno would be more than sufficient. It just comes back to again if you've got a late model sophisticated SUV you may possibly be getting into the situation where they aren't comfortable or aren't too happy running on an unlinked system. Barry has asked, if you dyno test a car in third gear will it give a different torque or horsepower reading as opposed to doing the test in fourth gear? My assumption is that most third gears are torque multipliers and it would yield a different torque reading. OK so there is actually a really really good document that Mainline did on this just discussing the difference. What you need to understand is that yes the torque at the rear wheels as far as the car is putting out will change depending on whether we're in third or fourth gear.
Obviously the gearbox is simply multiplying the engine torque or a multiplier of the engine torque so yeah that's absolutely a given. What that's going to result in though is we also need to consider that there is, when we're looking at the calculation for power, the RPM comes into this as well. So the torque will be lower, may be lower or higher depending on what gear we're in, being measured by the dyno but at the same time the roller speed will also be different. So this takes out what most people think is the biggest consideration in terms of the torque multiplication running the car in a different gear. However we still can expect some minor variations in the power that the dyno will show depending on what gear we run the car in, again it's important if we're not chasing numbers and actually just want to use the dyno in a smart sensible way to make sure that we are consistent with the gear that we are using.
Right, let's see what we've got here. Gordo has asked... I'm not actually sure if that was a question or maybe an answer to someone else's question there. Seanno has asked, suggestions on dyno brand or type for a first time purchase, possibly to be rented out when not in use? Well hopefully all of the suggestions that I've just given throughout this webinar should be enough for you to kind of formulate a plan on what's going to be suitable. If you are looking at a first time purchase, and you are on a tight budget, probably the rolling road would be the cheapest option to get you into the market.
What I would suggest as well, 'cause I've tried here, obviously I've mentioned Mainline, I've mentioned Dynapack, the two dynos I've had the most experience with. I've tried to stay away from recommending particular brands and the reason I've done this is that the best brand or best option for you is going to depend on where abouts in the world you are and what I mean by this is you want to make sure that you can get good support for your dyno. This becomes an expensive tool and it's an expensive tool that we rely on to make our living every day when we're tuning cars so if we have a failure of a dyno component and it's out of action for weeks or months, obviously this is going to be a huge consideration. So probably just the consideration there around getting good support in your local area. Now that doesn't necessarily mean you're restricted to a local dyno, I know that Mainline currently are moving a lot of units out into both the Middle East as well as the U.S.
and we're in New Zealand, they're over in Australia, I get better support from Mainline than I did from Dynapack. At the time I was using my Dynapack, their workshop was literally 10km around the corner from me and yet I could get parts faster here in Queenstown from Mainline iin Sydney, Australia than I could from Dynapack just around the corner. So long winded way of just saying, make sure that you can get support. And basically that, coupled with what I've said already is probably the considerations you need to make. Savage has asked, could you shed some light on picking up a used dyno, all of my equipment would be based on two wheels, like what could be considered as a serviceable part? So I think in general it's fair to say that most of the dynos, there's not a lot of moving parts in them, we've obviously, with a rolling road we've got the rollers themselves.
On very high mileage dynos the knurling will wear on the roller, so this can cause traction issues. Basically it just wears down and results in sharp edges on that knurling which does affect the amount of traction available over time. These can be recut as well. What we'll learn is that there are a lot of dyno manufacturers that will actually refurbish old dynos, their own dynos or some dyno manufacturers also will refit competitor's dynos with their own control strategies or control systems. So it's a little hard for me to really go beyond that, I mean there's bearings involved in the dyno operation, these need to be serviced and maintained.
Beyond that yeah I'm not too sure what I could really tell you there sorry Savage. Zitro has asked, will you have a problem with an all wheel drive prohub dyno and the Nissan GT-R with the front clutch? I heard you will burn them out if they are not linked together and this is why they disconnect the driveshaft. Yeah I mean all of the guys that are running the big power GT-Rs basically for drag racing and top speed racing are all running them in rear wheel drive. Now I am not an R35 GT-R specialist so I can't really speak with too much authority on why this is. I remember talking to JR from ETS back at Texas 2K last year and he indicated that he way the GR6 transmission works, it tends to put out a limited amount of torque to the front axle regardless.
So it may be something to do with that. The other aspect why I think you probably see a lot of R35 GT-Rs being run on two wheel drive dynos is because it is simple for them to run them in two wheel drive and with these larger prohub dynos that most of them are using for their tuning now, there's really no need to go to four wheel drive, there's no advantage and in fact it's more... I think that would be more what it is as opposed to a problem with dyno control but again I'm not an expert on the R35 platform. Savage has asked, also speaking more about getting exhausting gas out, is it really that important due to it being inert so it could rob some power readings? I mean yes of course if you've got a lot of exhaust gas contaminating your dyno cell then the engine is not able to ingest fresh air, it's going to be reducing the oxygen content going into the cylinder so yes it can affect the power. I would say that that is probably a secondary concern to your own health though, making sure that you have clean fresh air to breathe while you're in the dyno cell.
You're going to be spending a lot of your time in the dyno cell and you don't want to complicate your health later on in life because you've been breathing a lot of nasty hydrocarbons and carbon monoxide et cetera. TheDamanrules has asked, I've been looking into a home built hub dyno using a truck hydraulic disc brake unit, what is your thoughts on using them as retarder? Yeah I don't think you're probably going to have too much luck with this. The reason for this is that, if my understanding is correct of what you're trying to do, what you're going to end up doing is creating a huge amount of heat very very quickly using a disc brake. As soon as you've got heat into the brakes, first of all the friction coefficient is going to change, meaning that basically your control strategy's going to be chasing a constantly moving target in terms of hydraulic pressure to load. Add ultimately you're going to put so much heat into the brake system that you're not going to be able to maintain control of the unit so I don't think that's going to work very well sorry.
Ktireman has asked, does the dyno selection make a difference in ECU choices for tuning on that system? No not really, I mean for the most part you can basically tune any ECU on any dyno. It doesn't really, the dyno doesn't care, it doesn't know what's actually going on. All it's doing is applying a variable amount of load to match whatever's coming out of the car so yeah the dyno doesn't really care. The only time that this might be a consideration is if you're in the likes of the Mainline software where you can communicate between the ECU and the dyno. In that case obviously you're going to want to have a supported ECU inside of your dyno but for the most part, not a consideration.
Alright some good questions in there. A bit of a long webinar, hopefully everyone has now got a better understanding of the better choices when it comes to dyno types, the pros and cons of each type and what considerations you may need to make when you are trying to decide on the correct dyno for your particular purposes and your application. As usual if there are any other questions that crop up after this webinar has aired, please feel free to ask them in the forum and I'll be happy to answer them there. Thanks for joining us and I look forward to seeing you next time. Now for those who are watching today on our YouTube channel, this is just a little bit of insight into what we put on every week for our HPA gold members.
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