The bottom line for me would be to recognise that the manufacturer put damping in there for a reason and that it will have cost them more money than a solid pulley. If it wasn't necessary they wouldn't have spent that extra money.
Switching from a harmonic balancer to an all-metal crankshaft pulley
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Excellent advice in the last paragraph!
By the way, I don't think that Fluidampr pulleys are lighter. They are made of steel: https://fluidampr.com/mitsubishi/
Indeed, but not all modifications have the same effect. Some could soon cause catastrophic failure and others could just cut the lifespan of the engine by a relatively small percentage.
Nope. Aftermarket parts are all over the map. They might engineer something to where it lasts for a while, but things like shattered oil pump gears probably only show up after some time, at which point they'll say something like 'you modified your car and it blew up, not our fault'
As someone who was responsible for developing the rubber compounds that were used to make the rubber strips that go into the crankshaft torsional vibration dampeners, I would not eliminate it. The rubber used in those is generally specific to the engine on which the damper is going to be used. The engineers know what frequencies of vibration that the engine is going to produce and that they'd like to dampen. So, the compounds are tuned so that the damper does damp the desired vibrations. If there is a damper on the engine, it's there for a purpose. The dampers are not inexpensive to make so if they weren't necessary, they wouldn't be on the engine. Anyway, I would not go without.
It’s not supposedly. They do damp crank vibrations.
They don’t do a whole lot of damping in terms of “q” factor, though. They aren’t dissipating energy (in the form of heat). If they did, that rubber would get brittle and crack.
Instead, what most of these “dampers” do is just add enough inertia to change the shape of the torsional sinusoisal vibration. Instead of a sharp tall peak, the damper will give lower, broader peaks.
This is important because a lot of things in the driveline are sensitive to the amplitude of that peak, especially in terms of metal fatigue. The wrong damper (or none at all) can have all kind of crazy effect that you wouldn’t expect— like hitting valve float 800 rpm sooner. (More torsional vibration transmitted to the cam). I’ve seen or heard of everything from crank noses cracked, crank noses snapped off (woodruff keys in a crank are asking for trouble IMO), thrust bearing failures, oil pump failures, accelerated timing chain wear, etc.
Crank damping is critical. If you want to upgrade to something with MORE damping, not less. Fluidampr is probably the best, but I’d consider the ATI to be a worthy contender also. There’s nothing else I’d consider running.
Well, if the difference is small, that would be OK. If the difference is huge, they could advertise their parts as suitable for race use only, for example, because in that case, rebuilding the engine is a more regular thing and performance has a higher priority than longevity.
I have two questions:
- How tough would it be to put rubber rings in lightweight pulleys? Aftermarket pulleys sold as OE replacements have the rubber, so why not the lightweight versions too?
- How difficult would it be to pick a rubber of the right stiffness? As I said, aftermarket versions of the pulleys are available. Is it safe to assume that they have a rubber ring with similar damping characteristics as the OE pulleys?
@Hohn
Yes, "supposedly" isn't the right word. I meant that they supposedly offer a benefit by damping vibrations. That benefit was what I questioned They do, of course, absorb vibrations, but what I was trying to find out is how critical it is to omit the rubber ring.
If I'm not mistaken, Fluidampr uses steel, so I assume their goal isn't to make lightweight pulleys. The goal of reducing weight is to minimize power loss. If I understand correctly, Fluidampr promises even fewer vibrations than OE pulleys, but I'm not sure how this affects power loss.
FLuidampr dampers use a silicone-based viscous fluid inside them. The damper converts vibration to heat using viscous friction, not too different from a shock absorber, just with much smaller amplitude and a much more viscous liquid.
The damper is not the place to save weight, nor does a lightweight one “add power.” They often will appear to add power because they might reduce rotational inertia, which allows the engine to rev slightly faster.
But it’s not adding power, per se. Look at the equation for horsepower and try to find the term for rotational inertia. There isn’t one. Power is torque times rpm divided by 5252, and that’s it.
The effect of a lighter or heavier damper is basically identical to going with a lighter or heavier flywheel. Or rather, a larger or small moment of inertia, because the distribution of the weight (MOI), not the weight per se is what matters.
This is why some small-clutch cars shift so much better than others with larger clutches— the lower rotational inertia of the smaller clutch makes the synchros act faster and the trans can shift much faster and more smoothly.
There are very few real world racing applications where the lower MOI of a lighter damper is a smart tradeoff because quite honestly the damper MOI isn’t much of a limit on how fast the engine can rev. It’ll show up at no load or perhaps even in first gear, but once you get any kind of engine load, the extra MOI of a more effective damper is moot.
The person buying a lightweight rigid damper is essentially saying they are operating a vehicle where they have plenty of traction in first gear, the rate at which the engine revs at little to no load is super important, and the tiny gain in MOI is totally worth the risk of breaking hard parts.
When you phrase it that way, you realize that almost everyone installing these “light” dampers is doing so in ignorance. There’s almost certainly a far more effective way to spend that money if the goal is going fast. Heck, losing 10# would make a bigger difference.
No. Any heavy spinning thing adequately held up by well lubricated bearings will keep spinning thanks to its inertia, and it will only take energy to change its speed.
That's not what it happens in real life though. In ideal conditions if friction was 0 that would be true. But in reality there is energy loss and you need to keep burning fuel for the vehicle to maintain its speed.
Yeah but they can account for the weight of the balancer when they spec the flywheel and take some off one end to give the other.
This is getting ridiculous. Weigh the rotational mass of the entire drivetrain, with and without the mod, then tell us that % difference.
Do you understand that imbalance creates it's own frictional increase, not just added wear and potential lifespan reduction?
Consider all the things automakers do to increase efficiency over the years, at significant cost increase, yet then it would be implied that they add dampening for giggles? You seem to want to equate it to performance, but in this context it would still be efficiency.
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Of course, but if you have money to spend you can upgrade many parts of the car to increase performance and handling and safety. Manufacturers have a target audience for each car and for that reason they keep its price within certain limits.
They could add damping to a lightweight pulley. Obviously the gain won't be huge, but certainly there is room for improvement and that's true for many parts of most cars. Cost is the restriction, otherwise all cars would have top notch technologies and materials.
By the way, I'm talking about the theoretical part of weigh reduction of drive train parts and the gain is not only less inertia, but less power loss too. I mentioned the power loss part, because till that point no one had mentioned it.
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Leave the OEM pulley alone. The EDPM rubber is specifically made for the engine to balance things out. My OEM pully was beginning to rust . Salt Belt again. I removed it, cleaned it up, and painted POR 15 on it. Good as new. Why are you trying to mess with something doing it's job ?
That's what I did: https://bobistheoilguy.com/forums/t...-metal-crankshaft-pulley.399750/#post-7367952
Many things do their job, but in some cases upgrades definitely do the job better. No doubt, modifications that are not well researched can do harm too.
for people wanting the "performance" benefits of a lightweight pulley, are there undersized pulleys available from fluidamper or ati?
@Jetronic
As far as I can see Fluidampr does not make any underdrive pulleys: https://fluidampr.com/find-your-fluidampr/
And I'm not sure if they are lightweight either. They are made of steel, so the answer is maybe not. What they claim to do is to offer better absorption of vibration than OE pulleys.
On the other hand, ATI seems to produce undersized ones:
As far as I can see Fluidampr does not make any underdrive pulleys: https://fluidampr.com/find-your-fluidampr/
And I'm not sure if they are lightweight either. They are made of steel, so the answer is maybe not. What they claim to do is to offer better absorption of vibration than OE pulleys.
On the other hand, ATI seems to produce undersized ones:
an undersized pulley could be an upgrade, if you don't spend a lot of time idling.
Yes, you are right! An undersized pulley delivers less energy to the components it drives, so definitely it means more power to the wheels.
