Effectiveness of a Lightweight pulley

[wbradley]

Originally Posted by Lantana frs

I will never use one again. Thank God Toyota didnt refuse my warranty because of it. Made the car snappier in lower gears.

Why?

[Lantana frs]

Toyota says it caused main bearing damage.

[wbradley]

Originally Posted by Lantana frs

Toyota says it caused main bearing damage.

Which may or may not have been the case. Tough to prove. I mean if you Google LWCP you will see every expert opinion, and there are tons.

Sure an LWCP takes away some of the smoothening flywheel effect on the engine, so what could be used to prove it damaged the main bearings?

[Lantana frs]

Toyota paid for a new motor. Ft86 club didn't. Google didn't. Perrin didn't. Ill accept Toyotas explanation.

[justatroll]

Here is a good (technical) read on the harmonic damping abilities of the various pulleys:
http://www.ft86club.com/forums/showthread.php?t=85527

Yes it is from a vendor, so that has to be taken into consideration but the technical explanation passes my engineer's 'sniff test':

"To measure the effectiveness and impact of the heavier Fluidampr performance damper (5.8lbs, 3.8lbs rotating weight), a comparative test was developed against the stock tuned elastomer style harmonic balancer (4.87lbs) and a leading lightweight pulley (1.195lbs) that provided torque, horsepower and crankshaft torsional vibration comparisons. Two data set speed sweeps at a rate of 30 seconds each were conducted on each unit for consistency.
The torque and horsepower results proved positive on the chassis dyno with the Fluidampr performance damper besting both the stock damper and lightweight pulley, providing consistent performance gains from 4000rpm to redline. Despite the weight disadvantage, the results show that the optimum damping ability of the Fluidampr performance damper unleashed lost power through vibration control even with only mild performance modifications. Diving deeper to understand the cause of the power differences in the target rpm range between the lightweight pulley and the Fluidampr performance damper, a torsional vibration analysis was conducted. Using a high resolution laser and specialized measurement equipment the speed fluctuation or torsional vibration of the crankshaft can be recorded up to four trillion times a second (4THz, 4 pico-seconds). Results of the test reveal the rotating assembly’s resonance frequency, peak twist in degrees and how many vibration events occur during each revolution through the rpm range. The goal is to diminish torsional vibration as effectively as possible to create durability and efficiency. The results of the analysis depicted in the torsional vibration magnitude diagram below shows the sharp contrast between the protection provided by a Fluidampr performance damper and a lightweight pulley at the point when horsepower began to drop off for the pulley.
Further analysis shows that installing this lightweight pulley shifted the resonance frequency of the rotating assembly to a point directly within the rpm range. The result was higher magnitude 5th order and 6th order vibrations at a potentially destructive 600Hz from 4500rpm through redline. Higher frequency vibrations, because they happen more often per crank revolution can create hazardous stress, excessive wear and potential failure of bearings and oil pump gears. Under this test, the stress level felt by critical internal engine components increased three times with a leading lightweight pulley."


This is the best argument for saying that LWCP actually produce LESS hp because they have less capability to dampen harmful harmonic vibrations.
Harmonic vibrations are well known to increase parasitic losses.
Therefore LWCP = higher amplitude harmonics = greater friction in the bearings = greater parasitic losses.

[wbradley]

Originally Posted by Lantana frs

Toyota paid for a new motor. Ft86 club didn't. Google didn't. Perrin didn't. Ill accept Toyotas explanation.

Considering they fixed it under warranty, I'd have been relieved, but not necessarily thinking I got a freebie

It does look bad when an OEM component fails that was directly connected/affected by an aftermarket part. It does make the pulley a prime suspect.

Still, there is no broad consensus that I have seen, that a LWCP will cause this on the FA20 engine. And, there are TONS of FA20's running for up to 4 1/2 years now using them

[wbradley]

Originally Posted by justatroll

Here is a good (technical) read on the harmonic damping abilities of the various pulleys:
http://www.ft86club.com/forums/showthread.php?t=85527

This is the best argument for saying that LWCP actually produce LESS hp because they have less capability to dampen harmful harmonic vibrations.
Harmonic vibrations are well known to increase parasitic losses.
Therefore LWCP = higher amplitude harmonics = greater friction in the bearings = greater parasitic losses.

Interesting argument, and I would tend to think that the harmonic vibration/resonance would occur more so with some engine designs and less so with others. I was of the impression that horizontally opposed 4 cyl engines like the FA20 produce far less vibration than most engines and that is why for example, they don't utilize balance shafts. There are still vibrations however, I believe on a plane that would somewhat cause the engine to "pan" back and forth if it could. Whatever resultant vibration takes place would be interesting to see analyzed using this laser scanner on our engines to settle the argument whether they can safely withstand/ not lose power from a LWCP. Even if there is no net power gain they do look good in the engine bay, reduce overall weight, and make the throttle feel more edgy when revving.

Too bad nobody will likely spend the time and money to test.

Buy at your own risk, kiddies. It looks like a *tiny* percentage might experience issues, potentially.

[Lantana frs]

I kinda believe that Toyota and subaru know a "tiny" bit more than us.

[Somerandom18]

Ordered a fluidampr last night to replace my perrin.. just don't feel like risking possible long term damage from a lwcp. Not with this car anyway.

Sent from my SM-N930V using Tapatalk

[new2subaru]

Originally Posted by Somerandom18

Ordered a fluidampr last night to replace my perrin.. just don't feel like risking possible long term damage from a lwcp. Not with this car anyway.

Sent from my SM-N930V using Tapatalk

Curious, if you were concerned about any pulley why not leave it stock. They could deny a warranty claim with the fluidamper on too, no?

[Somerandom18]

If the engine fails that's my only current mod. Would just tow it home abd put the OEM back on before getting warranty work done. Not a big deal. As far as the fluidampr that's better than stock at reducing harmonics so odds are bearing failure won't happen.

As far as I knew when installing the lightweight pulley boxer engines were balanced enough to not really need external balancing. Have done a bit more research since and have decided to replace it. Only 700-1000 miles with the lightweight on so not to worried.

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[churchx]

Somerandom18: boxers are very balanced, indeed, but as in ANY piston engine, there are torsional vibrations that need to be dampened. Firing in cylinders and pushing pistons slightly twist crank. Even with firings from both sides happening at same time there are still vibrations happening. Yes, boxers need way less heavy crank pulleys/flywheels then eg. some inline four, but they still need to dampen those vibrations. One can lighten stock flywheel or crank pulley, but better be reasonable with doing that and for example do just one of those, i recall EJ/FA bearing failures reported by tuning shops in some lightweight pulley related threads here after not that much of a mileage if both CP & FW were lightened. If it's own car, always better to err on safe side then going overboard, unless you are race team and since very beginning didn't expect for abused & beaten on track engine to last past 10K miles and have budgeted replacement.

[Captain Snooze]

Because internet.

[wbradley]

Originally Posted by Lantana frs

I kinda believe that Toyota and subaru know a "tiny" bit more than us.

Not sure what you mean by that. Their opinion regards to a warranty claim would be clearly biased.

I am sure there are engineers, probably several who read this forum that could better postulate as to whether they think a LWCP will test out to be destructive or inefficient on this motor. It might depend of the amplitude, frequency and direction of the vibrations that occur. Yes, an actual test is more conclusive but some things can be somewhat predicted by a qualified person.

Sometimes empirical proof can overturn that opinion too though.