Discussion: Lightweight Crank Pulley

[willssss]

Drawn in by the allure of increased horsepower, throttle response, and relatively low cost, I installed an ECS lightweight crank pulley and chucked the old pulley, aka dead weight, into the trash. I've now started to read of the concerns people have of increased torsional vibration and engine wear potentially causing engine internals to fail.

Naturally, I've come to the hivemind to settle the debate by offering opinions, and first hand experience. Did you make the switch to a lightweight pulley, has it had a negative impact on engine durability? Did you choose not to, why not? Have I made a huge mistake?

Thanks for the input in advance!

[oVeRdOsE]

mmm, I've asked the same question few months ago , since CTS lightweight pulley was around 100$ on sale, with the belt.

I had around 4-5 replies stating to get far from this mod, since there's more cons than pros.

One of them was that the pulley is badly/lightly crafted and can crack and break. Vibration was also mentioned.

This has been said, I did NOT get any feed back from user. Just like blowoff valve, I read tons of bad thing about blowoff on fsi, but people that I personally know with blow off, never had any issue with in 10x 000 + km.
Same with oiled cone filter, tons of net hate, no issue on use, and I use oiled filters...

So wait for proper feedback.

[EvolutionArmory]

I chose to go the opposite direction. I added a pulley that was physically twice the weight of the stock pulley, adds a few HP but actually helps balance the motor at all RPM’s 😀

Fluidampr.

[EvolutionArmory]

I had a lightweight crank pulley on my old Jetta GLI. It didn’t really do anything.

Lightweight mods don’t really do much on their own. It’s when multiple lightweight mods are added up that you really notice.

The exception is with wheels. The difference with those are easier to feel right away because they can free up a good amount of power by themselves.

A crank pulley might free up a HP or 2. A little more depending on the power the car makes but don’t ever expect much.

[willssss]

mmm, I've asked the same question few months ago , since CTS lightweight pulley was around 100$ on sale, with the belt.

I had around 4-5 replies stating to get far from this mod, since there's more cons than pros.

One of them was that the pulley is badly/lightly crafted and can crack and break. Vibration was also mentioned.

This has been said, I did NOT get any feed back from user. Just like blowoff valve, I read tons of bad thing about blowoff on fsi, but people that I personally know with blow off, never had any issue with in 10x 000 + km.
Same with oiled cone filter, tons of net hate, no issue on use, and I use oiled filters...

So wait for proper feedback.

Yeah, I get the physics and why that might cause issues, but I can't really find anything about it. Have you installed one?

[willssss]

I had a lightweight crank pulley on my old Jetta GLI. It didn’t really do anything.

Lightweight mods don’t really do much on their own. It’s when multiple lightweight mods are added up that you really notice.

I definitely noticed the difference, not huge but I could feel it. That said, I feel it more when my engine shakes the car at idle. Not trying to have that unneeded vibration wreck my engine.

[EvolutionArmory]

Get a Fluidampr. It’s twice as heavy as the OEM pulley but while spinning, the substance inside it is suspended so that weight isn’t fully resting on the crank.

[Kevin C]

For some insight into what the factor engineers saw or were concerned with look at the changes from the 1.8T to the 2.0 direct injection turbo. On the 2.0T they went to a forged crank, oval shaped timing belt pulley pulley with two extra bolts on the flange to the damper. They also added a diamond coated washer to increase friction between the belt pulley and the crank snout.


Why? The pressure rise on the direct injection engine with a turbo is sharper and increases the amount of crank deflection. That's also why they added a sprung friction mechanism to the balance shaft drive (decoupled drive chain sprocket). It's not a bad thing, it's why you have more low end torque.

http://www.volkspage.net/technik/ssp/ssp/SSP_337.pdf

So the obvious thing is if you replace the factory damper with a light weight pulley you increase the amplitude of the crank oscillations. For the crankshaft, that in itself shouldn't be an issue, on a four cylinder there are no harmonics in any reasonable rpm range and the crank is pretty strong. What will happen is the balance shaft drive and its friction damper will get worked harder. It's a part that's already known to fail and a lightweight damper will increase its stress level.

If I was changing thing, I agree with previous posters the fluid damper is a better bet.

Also. while the forged steel crank is stronger ( and has tougher journals) it doesn't damp oscillations as well as a cast crank.

[AudiB720TS]

The pulley that would be replaced by an aftermarket lightweight pulley (this thread) is perfectly round. I have just measured it's outside and inside diameter compared against a perfect circle. All three lines are on top of each other. It's very very round.
Now the toothed pulley that sits underneath it might be oval (I have looked at it several times and it looks round also, but sure could be a tiny bit oval), but it doesn't matter for this discussion.

For what it's worth I also put the pulley on a scale: 1675 grams (3 lbs something).


I will put a lightweight pulley on at some point and dyno it. Will be at least until mid next year though.

[Kevin C]

The pulley that would be replaced by an aftermarket lightweight pulley (this thread) is perfectly round. I have just measured it's outside and inside diameter compared against a perfect circle. All three lines are on top of each other. It's very very round.
Now the toothed pulley that sits underneath it might be oval (I have looked at it several times and it looks round also, but sure could be a tiny bit oval), but it doesn't matter for this discussion.

For what it's worth I also put the pulley on a scale: 1675 grams (3 lbs something).


I will put a lightweight pulley on at some point and dyno it. Will be at least until mid next year though.

No one said anything about the belt pulley not being round.

The timing belt pulley has a 3mm (.12") difference in diameter (66mm largest OD, 63mm at the smaller).

I would say it matters since its an indication how far the factory went to control torsional vibration.

[aluthman]

The timing belt pulley was made oblong to reduce strain on the timing belt to increase belt life. It has nothing to do with vibration. I’ve been running a Fluidampr for about 6 years now and you couldn’t pay me to swap it with a lightweight pulley.

[willssss]

The timing belt pulley was made oblong to reduce strain on the timing belt to increase belt life. It has nothing to do with vibration. I’ve been running a Fluidampr for about 6 years now and you couldn’t pay me to swap it with a lightweight pulley.

Sounds like the Fluidampr is a good alternative, if things are being changed out. I wish it werent such a pain to take the entire front end off....

[AudiB720TS]

Sounds like the Fluidampr is a good alternative

If your goal is to reduce vibrations, sure. That is not what you asked for starting this thread. You have a problem with vibrations? Or you want horsepower?
These are positioned as performance dampers, not because they add performance, but because they are used on modified cars (which tend to have more vibrations).
Not saying they are bad (from what I hear they are great at reducing vibrations), but decide on what you want.

[willssss]

If your goal is to reduce vibrations, sure. That is not what you asked for starting this thread. You have a problem with vibrations? Or you want horsepower?
These are positioned as performance dampers, not because they add performance, but because they are used on modified cars (which tend to have more vibrations).
Not saying they are bad (from what I hear they are great at reducing vibrations), but decide on what you want.

Well, I was speaking more generally. But you are right, it depends on the overall goal. For me, the best thing to do (and cheapest) is to go grab an OEM harmonic damper off ebay or a parts yard and put it back on. My goal is to maintain engine longevity, and not compromise engine internals for a couple horsepower.

[Kevin C]

The timing belt pulley was made oblong to reduce strain on the timing belt to increase belt life. It has nothing to do with vibration. I’ve been running a Fluidampr for about 6 years now and you couldn’t pay me to swap it with a lightweight pulley.

According to Audi it was adopted to deal with vibration. Go back and read SSP_337. The oblong pulley that was adopted for this engine reduces camshaft rotational vibrations caused by changes in the speed of the crankshaft as the cylinders fire, while it does improve belt life it also improves the accuracy of the cam timing. Why was it added? To deal with increased torsional deflection (vibration) of the crankshaft from the increased cylinder pressure of the new engine. BTW, even Audi's description has an error in it but it's close enough to get the idea across. Working stroke is the term for the cylinder firing, a higher pressure working stroke increase the the crank speed for part of the stroke ( rotational vibration / deflection). Evening out the belt speed with an oveled pulley reduces the magnitude of belt vibration at the drive systems resonant frequency.

I agree that the Fluid Damper is a good choice. My point of this is that the engineers at Audi recognized this as an issue so why make it worse with a lightweight puller that eliminates the damper?



belt.JPG

[Charles.waite]

The pulley that would be replaced by an aftermarket lightweight pulley (this thread) is perfectly round. I have just measured it's outside and inside diameter compared against a perfect circle. All three lines are on top of each other. It's very very round.
Now the toothed pulley that sits underneath it might be oval (I have looked at it several times and it looks round also, but sure could be a tiny bit oval), but it doesn't matter for this discussion.

For what it's worth I also put the pulley on a scale: 1675 grams (3 lbs something).


I will put a lightweight pulley on at some point and dyno it. Will be at least until mid next year though.

He's talking about the crank sprocket, the toothed pulley, not the crank dampener pulley. And it is, in fact, ovaled.

[Charles.waite]

I would argue that smoothingout the belt movement was also a priority because of how the cam adjusting mechanism works. Since its attached directly to the cam, oscillations could cause it to be a bit inaccurate or make the n205 work harder to keep the cam position constant. The 1.8t had a more simple statically mounted adjustment mechanism that was easier to keep the timing value constant, but didn't allow for as fine/quick adjustment as the 2.0t mechanism.

I've come to really appreciate how smooth and vibration free the 2.0t is compared to my 1.8t and doing things to eliminate the smoothness seems counterproductive to me, especially since the gains aren't really documented. And butt dyno results really don't count.

A fluidamper offers the best of both worlds, increased power (this has been documented) and reduced vibration. Other than the price, I see no reason to get anything different.

[willssss]

A fluidamper offers the best of both worlds, increased power (this has been documented) and reduced vibration. Other than the price, I see no reason to get anything different.

Do you have links to this documentation? I am curious, as it doesn't seem to make sense that both a lighter, and heavier crank pulley make more power. Increasing inertia on a crank pulley would seem to reduce the amount of available power, but hey what do I know...

[EvolutionArmory]

USP Motorsports did a dyno before and after on a VR6 Golf. Did a run on the stock damper, changed to a Fluidampr while the car was still strapped to the dyno and ran it again. There were HP gains.

The Fluidampr works as advertised. It helps the engine run smoother and adds power. The only thing that’s really debatable is if the gains in smoothness and the extra HP is worth 400 bucks. 😀

[Charles.waite]

USP Motorsports did a dyno before and after on a VR6 Golf. Did a run on the stock damper, changed to a Fluidampr while the car was still strapped to the dyno and ran it again. There were HP gains.

The Fluidampr works as advertised. It helps the engine run smoother and adds power. The only thing that’s really debatable is if the gains in smoothness and the extra HP is worth 400 bucks.

Yup. The benefits are proven, the issue is the price. It’s a large sum to drop on such subtle benefits.

[EvolutionArmory]

Here’s a 340 HP 1.8T Fluidampr making 11 extra HP up top because of a Fluidampr. Some extra TQ too.

https://www.google.com/amp/s/forums....f4421682&amp=1

[i3oricua]

To answer your question a little more directly I ran one for about 3 years or so before switching to a Fluidampr and had zero problems. I thought I felt a slight increase in power with it but those small gains are hard to feel sometimes. It felt "peppier" on throttle to me.

[willssss]

To answer your question a little more directly I ran one for about 3 years or so before switching to a Fluidampr and had zero problems. I thought I felt a slight increase in power with it but those small gains are hard to feel sometimes. It felt "peppier" on throttle to me.

Ran a lightweight crank pulley? Who knows, maybe it's fine, but I can't shake the thought that my engine is shaking itself to bits internally. I think Ill go back to OEM for peace of mind...

[i3oricua]

Ran a lightweight crank pulley? Who knows, maybe it's fine, but I can't shake the thought that my engine is shaking itself to bits internally. I think Ill go back to OEM for peace of mind...

Yes. A lightweight crank pulley. Don’t believe the myths. You won’t feel a thing. If you’re curious enough I have one I can sell you for cheap. I bought it used many moons ago so I don’t know the brand.

Either way

Edit: I see you have one installed. Do you feel some sort of wild vibrations?


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[willssss]

Edit: I see you have one installed. Do you feel some sort of wild vibrations?

Not especially, on occasion at idle, if at all. But the nagging feeling that I might be doing lasting damage is definitely vibrating my soul.

[Charles.waite]

I think the idea of doing actual damage is unlikely. But it’s more that the vibrations are annoying and the actual benefit is minimal-to-nonexistent.