242 | Harmonic Dampers - Do You Need one?
The harmonic damper is possibly one of the most misunderstood items when it comes to a performance engine build. We’ll discuss what they are and why they’re used. We’ll also discuss the differences between factory dampers and aftermarket options such as the offerings from ATI and Fluidampr.
00:30 - Misconception of harmonic dampers
3:10 - Solid alloy front pulleys
4:45 - Internal vs externally balanced engines
7:05 - What is a damper and what does it do?
8:20 - Similar in its function to a suspension damper
9:40 - Effects of torsional twist
11:10 - Why do some stock engines not have dampers?
15:10 - Problems with factory dampers
18:55 - Aftermarket dampers
23:00 - Dampers and engine balancing
24:40 - Questions
- Welcome along to another one of our webinars and today we're going to cover a topic that I know there's a lot of misconception and confusion about. This is the topic of harmonic dampers and what they do, why you may or may not need one and how they could also potentially save your engine. So we're going to get into that and as usual, we're going to be having questions and answers as we go through so if there's anything that I talk about that you'd like to dive into in a bit more detail or anything related to the topic in general then please ask those questions in the chat and we'll jump into those at the end. Now to start with I think it's best to cover off one of the misconceptions about harmonic dampers and that is that if we've built our engine properly and we've had all the components inside of the engine balanced professionally, then we don't need a harmonic damper. And the reality is that balancing the engine and the harmonic damper, while there is some interrelationship between the two they are actually very different aspects and even a perfectly balanced engine still has the requirement for a harmonic damper.
And the problem with the harmonic damper or lack of harmonic damper is that if we don't have this, it's going to potentially result in some pretty nasty resonance inside the crankshaft and this can get out of control and result in failure of components, so we'll jump across to my laptop screen for a moment. And this is the result of exactly that, this is the front oil pump assembly on a Honda B18C turbo engine that I was tuning back through my old business, probably about 10 or 11 years ago now. This failure actually happened mid dyno run right up in the RPM range and because I'm always using audio knock detection when I am on a dyno tuning, I heard the gear basically fail, it actually smashed the front cover as well because there wasn't enough room for the broken oil pump gears so you can see that split running through the front cover there. Obviously as soon as this happens, the oil pressure dropped to zero. So generally this is going to result in an instantaneous or very very quick engine failure.
I was lucky enough to catch it quick enough and clutch in and shut the engine down, that it actually didn't end up destroying the rest of the engine. But you can understand that if that happened out on the street and you weren't listening for something like that, the oil pressure light on the dash is not going to be enough to save you so it can very quickly cause you costly amount of damage. So the reason for this is that the oil pump here, which we can see, first of all it is a relatively low grade material. Some of these pumps are better than others, we're seeing some aftermarket billet gears but essentially, in a way, at least as far as far as this situation is concerned, you could think of that as a bit of a bandaid for fixing the real problem which is getting rid of the harmonics that are occurring in the engine. Particularly because this is driven directly off the snout of the crankshaft, you can see there is a little flap there and a little flap there.
All of the harmonics that are transmitted into the crankshaft are then transmitted straight into the gears and yeah if that gets bad enough, this is the result. So this particular customer, as with a lot of people in the Honda tuning world, had decided during his build to replace the factory harmonic damper with a solid alloy front pulley. Obviously the idea behind this is it reduces the weight of the front pulley, it's also an underdrive gear as well so there can be some very small but measurable increases in performance by underdriving the accessories such as water pumps, alternators etc. That however is not really as important as keeping your engine together. So there you go, now the reasons for people going to these alloy solid front pulleys is there's multiple there.
There's a lot of companies selling them which is also quite scary. The first is that they're relatively cheap compared to the likes of maybe an ATI or Fluidampr aftermarket harmonic damper. Much cheaper, much much lighter as well, and the advantage with this, and I can't disregard this, having a light weight front pulley removes a lot of the rotational weight from the whole crankshaft assembly and this can actually show, often you'll actually feel an improvement in the acceleration response of the engine. Because there isn't so much inertia there, the engine crankshaft can actually accelerate faster so that's an advantage there in and of itself but again if your engine isn't going to last, the rest doesn't really matter. Alright so that's what can happen if we don't have a harmonic damper and we're going to get onto obviously why that happens, I just wanted to show you the results of when you get it wrong.
So the next aspect to cover is the difference between an internally an externally balanced engine and again this is where some confusion creeps in, people thinking that the harmonic damper is there to balance the engine. This falls back into what I was talking about there earlier with the fact that if you have got your engine balanced professionally, most people will think the harmonic damper is not necessary. So the difference between internally and externally balanced engine, there's a pretty big hint in the actual name there. Internally balanced engines, and most modern engines are internally balanced. The rotating assembly, so the weight of the pistons and the conrods is balanced out by the counterweights on the crankshaft so there's not need to add external counterweights or balancing weights onto the outside extremities of the engine in order to gain balance of those components.
Sometimes in some particular engines that are externally balanced, the harmonic damper may also include a counter balance, so this is where it starts to get a little bit grey but you'll see that they are two very different things still. So externally balanced engines, and I've got an example of this here which is our Mazda RX-7 out of our project car and we'll just get this under our overhead shot here. So this is the factory flywheel off the 13b engine, it's not really framed up particularly well. What you can see here is we've got his big offset weight on the crankshaft, on the flywheel here so this acts with the flywheel as an external balance for the engine. Got to be a little bit careful with these engines and this is what we've just gone through with that 13b.
We've removed the factory flywheel because we upgraded to a twin plate clutch. We're running an ORC twin plate clutch which comes with a conventional flywheel. It doesn't include this external balancing counterweight so if you want to do something like that, if you just replace the flywheel, you'd end up with a problem, the engine obviously wouldn't be balanced. So instead what we needed to do is start by fitting an external weight on the rear of the crankshaft, the eccentric shaft and then the new twin plate flywheel bolts onto that. So still retains that external balance.
Again, not the same as our harmonic damper. So what is the harmonic damper and what does it do? In short, it's designed to absorb and dissipate the harmonics that occur when the engine is running and again, this isn't about balancing the engine. Even in a perfectly balanced engine, what we are going to find is that when a combustion cycle occurs, when we have the fuel and air mixture burning in one of the cylinders, obviously that creates a lot of force on the top of the piston, transferred down into the connecting rod and finally into the crankshaft. Of course that's how the engine makes power and torque in the first place. Now what that does however is it actually creates a torsional twist in the crankshaft so even though the crankshaft, when we've got one on our workbench, they seem incredibly rigid, incredibly stiff, the reality is when they are subjected to the massive forces that are a result of the combustion process, it will actually create a twist in the crankshaft.
And over time, or as the engine is running, what this creates is torsional vibrations through the crankshaft and the harmonic damper's job is there to remove or dampen out those vibrations so that they don't become so great that they can cause catastrophic failures like what we saw. So a simple way of thinking about this is basically maybe the way a suspension system in a car works. So if we've got a damper and a spring, the damper is there to reduce the oscillations of the spring. So if we thought about a suspension system and we removed the damper out of the equation, normally most people can understand that if our car goes over a bump in the road, what's going to happen is that the car's going to continue to bounce because there's nothing to absorb the energy from the spring and it's just going to keep bouncing for a very long amount of time. Exactly the same thing happens with the vibrations in the crankshaft.
The other thing though, and this is where it becomes a little bit more dramatic is if we come back to our suspension analogy there, if we go over a single bump, we talked about what happens there, we find that the suspension will continue to bounce but where it gets even more dangerous is if we continue to go over a series of bumps at just the right frequency, what that will tend to do is magnify the amplitude of the oscillations, basically the car starts bouncing worse and worse. Exactly the same thing happens in our crankshaft if we haven't got a harmonic damper and we happen to be operating at just the right RPM. So that gets really dramatic and that's where we can get failures of things like our oil pump gears. There are a variety of other impacts that torsional vibration undamped can cause in our crankshafts though. So first of all, we've got component life, obviously the oil pump that I've just talked about but that's only one element there.
This sort of torsional vibration can basically beat up on all of the engine components. Not least of all the engine bearings. It also can beat up on your timing chain as well, can actually result in timing chain failure, they don't really like torsional vibrations being fed into them. You can also see this sort of effect as a result of bolts on the engine or components on the engine working loose and even electrical components can fail from those sorts of vibrations that are present. Another issue that we can end up having is a situation where we have timing inaccuracies.
So essentially the relationship between the crankshaft and the camshaft through the cam chain or cam belt, whatever you're using, can be affected by those torsional vibrations as well. The magnitude of those torsional vibrations obviously changes down the length of the crankshaft so there can be a subtle but real affect on the engine timing operations. And this actually adds up to, if we can get rid of those torsional vibrations in a situation where they were incredibly bad, this can actually show up a power gain on the dyno. So not that that's necessarily why we would be doing it. So also we've got the situation where we have a factory damper on most engines, definitely not every single engine and I think probably one of the questions that will come up from this webinar is how come some engines don't have harmonic dampers as stock and Porsche is one of the engines that often don't have a harmonic damper.
And those tend to work OK on the road however in some situations there have been failures occurring in those same engines when they are used on the racetrack and it comes down to the sort of RPM range that we are operating at. And it all comes down to trying to stay away from the RPM ranges that cause a resonant frequency. It's that resonant frequency that causes the large amplitude oscillations which undamped again can quickly result in a failure. So if you are operating the crankshaft at an RPM where it is at a resonant frequency, for a prolonged amount of time, that's where you can expect to see problems. And I'll relate this back to my own drag car and the old drag car I ran, our Mitsubishi Evo 3, and I'll just grab a picture of that in a second.
If we just switch over to my laptop screen for a second. So this is the 4G63 engine that I was running. This engine, in stock form was around about 300, 350 horsepower flywheel. We ended up modifying it to a point where it was producing around about 1160 wheel horsepower, running 54 psi of boost and revving out to 10,500 RPM. So a full 3000 RPM beyond the factory rev limit.
Despite this we did actually use a solid aluminium pulley on the front of this engine. And there's a few reasons why we did this, at the time the options available off the shelf weren't so great for import engines, bearing in mind that particularly here in New Zealand we were kind of at the forefront of 4G63 four wheel drive development. That was one thing, the cost of those options that were available was incredibly high. Now we need to factor that in with of course if you've got a $20,000 or $30,000 race engine, trying to save $1000, $1200, $1500 on a harmonic damper doesn't really make a lot of sense but the reason we could actually get away with using a solid front pulley on this particular engine is because of the way the engine operates. It never sat at one fixed RPM for any period of time.
It was constantly pulling through the rev range and because of this we don't have or don't see quite as much trouble with the harmonic dampers, running no harmonic dampers in some of these engines. That is not to say that I would recommend doing this now. I've sort of come a long way since we've developed that engine and certainly if I had my time again I would be putting a harmonic damper on the engine, I just wanted to explain why we can get away with that. So sometimes, depending on what RPM range those resonant frequencies occur at, we can actually get the worst situation in a road car. Let's say for example we've got an average road car which in fifth gear on the open road maybe 60 mile an hour, might be sitting at 3000 RPM.
If it just happened that one of the resonant frequencies was occurring at 3000 RPM, you could understand because you're sitting at that RPM range for such a long period of time so frequently it gets a big chance to do a lot of damage. Likewise with some of the racecars as I mentioned, Porsche, maybe when you're out on the racetrack and I'll be the first to admit I am not a Porsche specialist, I'm just passing on some information that's been forwarded to us, you're obviously going to be sitting in a higher RPM range and a narrower RPM range than what you would be if you're using that same car on the road and this is almost certainly what would exaggerate the failure rate of those sorts of components. So we've got a better idea of what's actually going on there. There are a few problems though, why we wouldn't necessarily want to just retain a factory harmonic damper. So the first aspect here is that the factory damper, designed by the factory engineers, understandably is designed to dampen out the harmonics or vibration that is expected or calculated to be in effect in a stock engine.
That's fine for a stock engine, however as we increase the RPM range the engine's going to run to, we increase the amount of power the engine's making, those torsional vibrations are not going to be the same as what was occurring in the factory. So we can expect in some situations, the factory harmonic damper can no longer protect a heavily modified engine. Again one of the examples that's been brought to my attention of exactly this is the late model Ford Coyote engine which is prone to failures related to torsional vibration with the factory damper in heavily modified examples. This was put down initially to failures of the oil pump gears because the gears weren't actually strong enough but further testing's resolved this that it's actually the torsional vibration that's the issue, not the oil pump gears. The way a factory harmonic damper works, and I've got one here that I just want to show you under our overhead and this is off one of our 3UZ engines.
So it's three piece, essentially this internal hub here which is also keyed onto the crankshaft, this is all one piece, this is cast, then, it's a little hard to see, but we have this outer ring of rubber here. So this is bonded to the inner and then we've got the outer part of the damper which obviously in this case has our belt drive for our accessory belt. And it's also, and quite importantly, got this mark here for our TDC marker. So again if we turn it over we can see there's that line where our rubber bonds between the inner and outer. So there are a few problems with these harmonic dampers.
First of all the rubber, just like a suspension bush, tends to deteriorate with age so particularly if you've got a high mileage engine, you can find that the rubber actually can crack, can fail and in worse case scenarios can actually end up with that outer ring actually parting way with the centre hub so obviously this is a major concern for safety and this is one of the reasons that a lot of racing classes, particularly common in drag racing, will not actually allow you to run in certain classes with a factory harmonic damper because of the chance of that damper failing and a part exiting the car and making it into the crowd so this is why, for a lot of those classes, you will actually require an aftermarket damper or a solid pulley that is SFI rated so that is a consideration there. The other aspect which I've actually experienced quite a few times with older cars, older engines with factory harmonic dampers is sometimes the failure or the debonding of that rubber is not initially obvious and what that does of course, when the inner and outer are no longer connected together, one of them's debonded, we can get this outer hub rotate relative to the inner. Now on face value that might not seem too important but again it comes down to our little timing mark here. So we're relying on that timing mark when we are setting our base ignition timing and if that timing mark has actually rotated relative to the crankshaft because the damper is no longer properly bonded together, it can give you a false sense of security on where your factory timing is and that can cause some pretty big headaches that can be quite time consuming to sort out when it comes to the tuning process. So I think we've covered at this stage why the factory harmonic damper may not be your best bet.
Of course if you have got a high mileage engine, you've got a damper that is in pretty poor condition, and you're only rebuilding that engine for stock performance, it may prove that just a replacement factory harmonic damper is your best most cost effective option. But for a lot of you watching, you'll probably be aiming to rebuild the engine with more power and this is where looking at an aftermarket damper really can come in. We're going to move into questions and answer really shortly so if you do have any, this is a good time to start asking them. We'll start by talking about what is available in terms of the aftermarket and there are a range of manufacturers, the two big names that keep popping are ATI with their Super Damper series, Fluidampr is another brand that I've personally used on some of our drag Evos with good results. They work on two different principles, the ATI damper uses elastomers which is essentially a rubber whereas the Fluidampr uses a silicon material.
So let's just have a quick look, some shots that we took when we were over at PRI, I think it was, maybe SEMA actually, of the ATI Super Damper. So that's the front, so obviously this is our crank bolt here. If we look at it sideways though, this gives you a better idea of the construction. So it is multi piece, you've got a central hub here which actually bolts directly to the crankshaft. The remaining components of the damper then bolt to that so in yellow here we've got the damper component itself and then in orange we've got basically just an accessory drive hub here for our belts.
And it's this part here that's really the key to the performance of the damper. We've got in red there highlighted, there's basically an inertial weight that's included inside of the damper. That inertial weight is supported to the outer shell there by a set of rubber elastomers so you can see that's what these little black things are, basically big o rings. And the way the ATI damper is designed is that they can change the number of elastomers included and they can also change the stiffness or hardness of the elastomers to tune the harmonic damper to suit a particular frequency that they're expecting vibration to be present in. So this gives them a lot of flexibility on designing a damper to suit your particular application.
Now a lot of this as well, most people aren't going to be doing anything too out of the ordinary so let's say you want to take a Toyota 2JZ turbo engine and you want to build it to make 1000 horsepower. Well that recipe's been done probably 10, 20,000 times by now, it's not particularly unusual and ATI know what's involved in that and will be able to provide you a damper that's going to be suitable pretty much off the shelf. But if you are doing something a little bit more unique, something pretty special, then they can actually develop the damper to suit your particular application. With the ATI damper as well, because they do include those elastomer o rings, they will age, they will wear out over time, they become brittle and hard so they are actually rebuildable as well so you can just replace all of those components that wear individually. The other option that I mentioned there, Fluidampr, they work on a slightly different principle, the Fluidampr uses a silicon fluid for its vibration absorption as opposed to those elastomers.
I can't speak specifically on the intricacies of the silicon style or Fluidampr style versus the elastomer, I've used both, I've had success with both, I definitely couldn't say that one was better than the other. However, it does appear that the Fluidampr style does tend to work over a wider range of frequencies as opposed to the elastomer which does need to be tuned for your specific application so there is that to think about. Now with these dampers as well it's really important to note that you don't want to fit that damper during the process of having your engine components balanced. So generally what we'll do is have the machinist balance the rotating assembly of our engine. And that'll generally start with the crankshaft on its own and that crankshaft will be balanced to whatever tolerance we're working to and then aspects such as the flywheel will be bolted on, clutch plate, sorry clutch cover, pressure plate, or flex plate, whatever you're running, and that will then be balanced to zero and then normally any front pulleys, the harmonic damper etc will be added in and those will then be balanced.
The idea behind this is that after that's done, if at a later point you need to replace your flywheel and clutch assembly or you swap to a different harmonic damper, then those components can be switched out, they can be balanced independently and you can then put them back together. So basically each individual component is balanced to zero, we don't need to pull the engine completely apart again to have the rotating assembly balanced. However, with these aftermarket harmonic dampers, the inertial weight, particularly in the likes of the ATI damper is not set, it can actually move, it can't come out, it is encapsulated but it will move. So what this means is that if you tried to balance the ATI damper on your engine, basically every time the machinist spins the crankshaft up in their balancing machine, they're going to end up with a very slightly different result. So you're not going to be able to sort that out so that's why ATI specifically say that you should not balance the damper on the crankshaft, it's going to be installed after the balancing has been completed.
Right we'll jump into our questions and see what we've got here. Boris Crump has asked, can we please touch on what dampers supercharged vehicles will need, I'm planning on supercharging my VE commodore L98, seven psi with a 2.9 litre Whipple supercharger. I've actually done this a number of times through my old business and from the best of my recollection, when you're doing something like that, the supercharger kits are designed to work with the factory harmonic damper. So that's one of those situations where the factory harmonic damper, particularly for a modified street car is probably more than adequate. It's one of those cases where it doesn't necessarily mean just because you're modifying your factory engine that you do have to replace the harmonic damper.
If you were building that for a race application, it was going to be constantly beat on out on the racetrack at constant high RPM, in that situation then yes, I might consider going to a harmonic damper but given that I've done this for street cars myself I know that the factory harmonic damper does work. When you are running a positive displacement supercharger like that, you do need to keep in the back of your mind as well that the boost that you're going to get is going to be a combination of the pulley size for the crankshaft or harmonic damper as well as the pulley size on the supercharger. So you do need to take that into account, otherwise you could end up with too much boost or insufficient boost depending on that ratio of sizes. Again all of these supercharger kits, particularly for the LS have been developed for a number of years, there's not a lot of combinations that haven't been dialled in and tested so your manufacturer and supplier will be able to tell you exactly what you're going to end up with there. Matthew has asked, any info regarding lightweight aftermarket crank pulleys? OK so yeah these are available from a range of different manufacturers and kind of as I touched on, the problem with them is they don't do anything to dampen any of the torsional vibration.
It's not to say that you're instantly going to suffer a failure, depending on your application you may be just fine but as I've also alluded to with the picture of the broken oil pump gear in the Honda B18C, it's a pretty big risk to take. Personally I stay away from lightweight solid alloy pulleys. The risk in my opinion certainly not with the reward and I'd like to keep a check on any torsional vibration that is occurring. Onalky87 has asked, do ATI balancers have a lifespan or can I just buy one used a few years old with no worries? They do have a recommended lifespan or, how would I put it, rebuild strategy and you can rebuild them pretty cheaply, depending on the number of elastomers in there. Talking to the guys from ATI back at SEMA last year, I think off the top of my head if it was just a case of replacing the elastomers you're looking at under $100 USD so pretty cost effective to rebuild as long as the outer shells are in good condition, those are replaceable as well, then yeah you can rebuild them.
So it'd be a little bit hard to know with one that's a few years old what condition it's going to be in but pretty cheap insurance to rebuild it anyway. Kelvin has asked, can we talk about vibration transferred through blower belts? Yeah this is probably getting a little bit outside of my own realm of experience. You do see, particularly if you've got a supercharged engine on a dyno, you're going to see again there will be certain RPM ranges where you do have harmonics occurring in that belt. Particularly if you've got a hydraulic tensioner pulley, you're going to see, at certain RPM ranges that thing will be bouncing all over the place. So whether or not that's going to actually do damage to your engine components though, particularly in a street driven application, that's probably pretty unlikely, again as I was talking in the answer to that earlier question,.
The off the shelf supercharger kits for the likes of the LS, just to one example, I have got no idea what particular engine you're talking about, they're pretty well developed so you're unlikely to have any real issues with that. Probably where that starts to get a little bit more of a concern, and again outside my realm of experience, when you're starting to look at purpose built drag engines running really big blowers with massive wide belts, I could see that being more of a potential issue but again I can't really speak too much from personal experience I'm sorry. Brian's asked, with balancers for equal quality and type of construction, is bigger just better within obvious space constraints or does the law of diminishing returns apply? And also Brian's asked, does the drive train with some flexing and a bit of give from the tyres help with damping harmonics at the other end? OK so I'm actually going to answer your last question first. So in terms of the drivetrain, this shouldn't really be a consideration in terms of the crankshaft harmonics. The reason for this is, if you've got an automatic transmission, then any harmonics etc, that's going to be taken out essentially and eliminated through the torque converter.
Likewise if you've got a manual transmission, you're going to have normally in a street driven or modified vehicle, probably a sprung centre clutch. Even with a solid centre clutch, there's still some amount of play so very very unlikely that the drivetrain really plays into a part of this, you can consider it just the engine itself. Coming back to the other part, in terms of quality, type of construction, is bigger better? Again this comes down more to the design of the damper itself. I do not design dampers, if I wanted to buy a damper, I would be going to the likes of ATI or Fluidampr and having them specify what I needed for my particular given application. We're not sponsored by either of those companies either, those just happen to be two of the companies that I've used products from.
So there is quite a lot that goes into this and again well and truely beyond the scope of both my personal knowledge as well as the scope of this webinar. But ATI for example, we did do an interview with one of the guys from ATI at SEMA. They've got some torsional vibration testing equipment, they're installing a dyno as well for doing vibration testing in house. So from their own back catalog of knowledge, given that they've been doing this for decades now, plus being able to calculate what's, sorry not calculate, measure what's happening with the design of a factory harmonic damper, they've got a pretty good indication of what needs to be done for a particular increase in power, increase in RPM etc and can design their damper to suit your application so definitely not a case of bigger is better, it's a case of matching it to your application. Cmelle has asked, do aftermarket vendors such as ATI publish an estimate of the rubber liner lifetime? Yeah I'm pretty sure that they do.
Again this is something that did come up in conversation with JC from ATI and perhaps if you do want to learn a little bit more, because I know we covered that topic, after this, check out on our YouTube channel, search for ATI damper, you'll find that interview and JC and will be able to answer that more accurately than I can right now. Ken Tireman's asked, on the SR20DET the main pulley does not have anything that appears to be a damper, is that correct in your experience or am I mistaken? No definitely the SR20DET does in fact have a factory harmonic damper. Unfortunately I don't have a photo of one now but given that we've got an SR20VE now in our 350z, we rebuilt that engine and definitely they do run a stock style harmonic damper, much like the one that I showed earlier. Manitou Black's asked, can you discuss the benefits or drawbacks of a fluid damper verses a rubber elastomer damper? So again, I've used both, I could not pick an advantage between one or the other. Both in my own personal experience have worked perfectly.
This can come back down to considering the cost of one versus the other, I couldn't actually tell you right now which is more expensive. As I mentioned in the webinar itself, my personal understanding talking to the likes of ATI and Fluidampr is that the elastomer style damper that ATI use, has to be tuned for a relatively specific frequency range whereas the silicon fluid in the Fluidampr style works over a wider frequency range so doesn't require tuning as such. I guess if anything, that makes the Fluidampr probably a safer bet over a wide range of likely harmonics. Newbie23 has asked, I know I need a damper if I'm shooting for 700 horsepower but which damper do I need for drag racing in mind? Again, this webinar is not about go and buy this particular damper, it's about giving you the knowledge so you know why you need a damper, how they work. From here for your specific application I would suggest that you talk to one of those companies I have listed and they'll be able to help you.
Given that you've mentioned 700 horsepower, but absolutely no information about the sort of engine that you're using, it's impossible for me to really give you much more information there. Masoud has asked, what's the advantage of an aluminium crank pulley with a smaller diameter for a four cylinder race engine? So the idea with these is twofold, and I've really touched on these already, first of all a solid aluminium pulley, you're going to be reducing the weight of the rotating assembly and this can allow, because it's reducing the inertia, can allow the engine to change RPM quicker on a transitional RPM change, yep, think that probably makes sense. The other aspect is by designing the pulley to under drive your accessories such as the alternator, this can free up a little bit of extra power, generally relatively minor but it is measurable. Deathrodcustoms has asked, is there a way to know the wrong resonance before it goes boom? I wish I could tell you, I certainly couldn't predict it on that Honda B18C. The problem with it is that the resonant frequency can do some really really dramatic damage but it depends on how long you're spending at that particular RPM range and short of having an engineering degree and going through and actually calculating that out, for most of us mere mortals, we're not going to know where those resonant frequencies lie.
We're abouts in the RPM range they lie so it's a bit of a gamble really and again, one that I'm not prepared to play. Eduardo has asked, will a lightweight flywheel affect the damper? No the, I say no, so the overall, when you're designing, when the likes of ATI, I'll try and get this all out in one sentence, when the likes of ATI are designing a damper for a particular application, the overall rotating assembly weight will be one of the inputs that they factor in. So I said no, to a degree yes the overall rotating assembly weight is an important factor. Generally it's not that sensitive though that if you take a factory flywheel off and you replace it with a lightweight flywheel that you're going to need to go and replace your harmonic damper. Vitesse Motorsport's asked, is there a way to find any dangerous vibrations so I can decision...
OK so we're pretty much getting the same question, answer there I've already given. Pai Ern Joody has asked, can you use lightweight alloy pulleys for accessories like power steering, water pump etc? Yeah if you're talking about just the driven pulley on the power steering pump and the water pump, yeah absolutely, that's a not a consideration, it's only the crankshaft pulley that we're really worried about. Ken has asked, would you recommend changing the stock damper on over 400 horsepower on an SR20? From my own personal experience, no. We've run many SR20 turbo engines beyond 400 horsepower at the wheels with no problems with the factory harmonic damper. So it's not a necessity, obviously assuming that your factory damper is in good condition and you aren't in one of those classes where you are restricted to an SFI damper.
Scott has asked, at what level of modification do you suggest looking beyond the stock damper, or harmonic balancer? That's actually a good question Scott and I mean the answer here is probably going to depend on the specific engine and the usage. So for a street car, if I was looking at getting up towards maybe just under two times the factory power, so I'm just using my 4G63 experience here as a bit of a guide, so factory 300 horsepower engine, probably not quite two times. If I was pushing much above about 500 horsepower, or I was wanting to extend the RPM much beyond about 500 RPM above stock, that's about the point that a harmonic damper might make a lot of sense but it is going to be very much dependent on the specifics of your engine that you are dealing with. There are a lot of things, I hope you can understand, that go into this and the specific power level is just one of those elements. Next question, my engine is at stock power but switched to a fluid based damper, any negatives in doing this? Only negative really to your bank account there, definitely no negatives in terms of engine performance and if anything going to be a lot more reliable than stock.
Obviously at stock power level, definitely not an essential though. Next question, does mounting type play a big difference in the quality of damping? For example, the 4G63 has press fit and keyed style versus the standard fluid damper bolt on types. So not specifically, so I mean ultimately the way the damper actually fits to the crankshaft, that's going to be an element of the engine's design, there are a variety of them. The most common of course would be something that is keyed to the crankshaft or the bolt holding it on. Often the aftermarket pulleys like the ATI which we looked at, they'll include a central hub which basically replicates the factory style, so the keyway, the interference fit to the crankshaft etc, and then they will have a bolt pattern where the outer hub bolts together and this is more to do with the fact that the ATI damper is something that's rebuildable.
Bruce has asked, big power RB30s don't have a great reputation for smooth power at high RPM, would a good quality damper improve the usable RPM range and make it rev more like its little brother the RB26? A lot of this is actually down to the design of the RB30 crankshaft. So if you start looking at some of the aftermarket kits that include a fully counterweighted aftermarket crankshaft, the likes of Nitto produce, you're going to get an engine that's been well and truely proven, now the RB30s, easily able to make massive power, pull high power RPM smoothly and reliably. Alright that has got us through our questions, there's a bunch in there so great to have all of those from everybody, hopefully everyone's got a better idea of what harmonic dampers are and what they aren't now and hopefully we won't see too many more smashed oil pumps needlessly damaging or destroying expensive race engines. As usual, for our HPA members, if you've got any questions after this webinar has aired and it's in the archive, please ask those in the forum and I'll be happy to answer them there. Thanks for joining us and look forward to seeing you in our next one.