Let’s talk about dampers. Not the usual suspects that keep the car planted to the road, but the dampers that keep your engine from snapping its crankshaft.
We’ll go into some detail about the overall theory here but the focus is going to be around high performance 4 cylinder engines, like turbocharged MX5/Miata engines. This is one of those parts that is an absolute must-have in highly strung race engines as well as heavy machinery – as we start to push what the drivetrain of the MX5 is capable of we start to need to look at how we can keep the engine alive.
So, what is a harmonic balancer (or damper), and why are there even aftermarket parts available?
To understand that, we’ll have to talk about torsional vibrations – or rather, twist – that the crankshaft experiences. Throughout the running of the engine, the crankshaft is being loaded up on each ignition event, trying to twist the crank and causing it to take on a vibration. Just like a ringing bell or a wine glass you’ve just tapped.
Just like a wine glass, it has a resonant frequency and while this example isn’t entirely relevant, it’s possible to have those items ring and hit that resonant frequency and in doing so they rip apart and explode, we’ve all seen the videos of the opera singer breaking the wine glass with just their voice.
The reason the glass breaks is it’s trying to return back to its normal state and the further away from normal it gets the more violently it pulls back, much like a spring. Eventually, the force is so great that the part simply fails.
Segueing into crankshafts, consider that there is always a piston pushing down on the crankshaft while at the same time an opposing piston resisting the downward force, causing a twist across the crank, this force will spring back and in some engines can become out of control, especially as RPMs increase – eventually something will give.
The job of a harmonic balancer is to dampen these vibrations, the twist, going back to the wine glass example if you were to touch the glass it will cease to vibrate, this is due to the effective resonance being changed due to your finger being now involved – but irrespective, that’s the job of an external damper.
How does it do this?
There are a few ways of achieving this damping effect and let’s start by talking about how the OEMs do it, or at least the non-performance oriented OEMs. They use rubber, sandwiched between two surfaces of the pulley, one part attaches to the crank snout and then the next is bonded to it via rubber, typically using an inner and outer ring.
In this image you can see the 3 rings on the front face, the outer most is metal, the middle is rubber and inner is metal again. This rubber soaks up an amount of the vibrations, for generally a quite specific frequency range – never above OEM rated rev limiter. It does a reasonable job on OEM power engines while new, but as with everything made of rubber it deteriorates – and one of the worst parts of this is that the timing marks are on the outer ring, these can and do slip as the rubber wears.
ATI operates a similar but more technically sound solution, they use rubber O rings tuned to a specific rev range, often higher than standard OEM rev limiters. In the case of the MX5 engines, these are press fit to the crank pulley which can make installation quite painful, these units are rebuildable and have seen incredible success in all racing disciplines.
The next and frankly the reason for the post is Fluid Dampers or ‘Fluidampr’. These use an incredibly viscous silicone fluid inside the damper body and an internal weight, this type of damper works regardless of rpm as the fluid is able to absorb the vibrations, dampen the spring effect and transmit that energy into heat and out of the body of the unit, self-tuning in real time. This technology is used in racing, performance OEMs as well as heavy machinery where a failure of the system would result in incredible knock-on effects and costs.
Unlike the ATI / Rubber dampers they do not require rebuilding and work at any RPM range,
they are attached to the crank pulley via 4 12.9 grade bolts in the same way the stock damper is and while is often considered a point of failure, those bolts are 8.8-grade stock and are consumable items. Note the versions that we sell / new version now uses the crank bolt to attach the same way as stock. It also features a 10% underdrive pulley for the water pump, which ensures the pump isn’t being overworked at high RPM as well as minimising cavitation of the coolant.
So, let’s take a step back here – I’ve never heard of anyone snapping a crankshaft in an MX5, so why is this product getting an entire post to talk about its benefits?
Because what does break is Oil Pumps and they break because of the crankshaft flexing and vibrating at the nose. These break consistently with 7k+ rpm, shock loading or just very high horsepower, which is why we also offer the industry standard Boundary Oil Pumps and gears. What the vibrations also do is put stress on your bearing surfaces and rob your engine of genuine horsepower potential.
What also breaks, which perhaps isn’t given as much attention as it’s more specific to supercharged applications – is the crank keyway. The constant load back and forth on that keyway will wear it down, destroying the crankshaft. This problem is exacerbated by the additional load on the snout of the engine via the supercharger.
Appreciating that any time a retailer starts suggesting this ‘bolt-on part’ will add horsepower, make you a better track driver and in general improve your life beyond measure – people start to switch off. There has been genuine tests, not conducted by us as our R&D budget isn’t quite that high just yet, tests done by the likes of Greg Peters at the CarPassionChannel, indirectly mind as well as direct testing done by the manufacturer and motoIQ.
Is this going to turn your 280hp MX5 into a 300HP MX5? No, it’s not, but what it will do is protect your engine, your oil pump, smooth out the engines overall operation and it will net some improvements under the curve, how much? We simply don’t know, but wouldn’t be surprised if you picked up a 1-2% increase.
At the end of all this, you might be looking or have heard of ‘lightweight’ or ‘billet’ front pulleys, in higher horsepower applications these will be a contributing factor to engine failure. They have no place in a 4 cylinder engine and the free-revving nature they may provide is made irrelevant by the loss in power and added wear to the engine without the torsional forces being adequately dampened.
If you’re looking at purchasing a Fluidampr, ATI damper or otherwise and are turned off by the price – take a look at your stock damper, it’s highly likely it needs to be replaced anyway and these typically retail for £150-200 and are only designed to operate at OEM power levels, they are often listed as ‘Crankshaft Pulleys’.
OEM Crankshaft Pulley Engine Damper