The real benefits of lightweight pulleys (quantified)

[SuperTom]

I look at the positives like this
-Cost ~$100 , mine I got $50 used
-Wont give more dyno captured HP but allows you to reach the higher RPM's quicker, which means you are at the higher HP levels of your motor quicker.
-5lbs off the nose the car (for full pulley kit) On a car that is front heavy

[Joesurf79]

Originally Posted by why?

The harmonics and vibrations are absolutely meaningless in any near stock engine unless you want to rev it too far beyond where the engine would explode due to its well known oiling issues.

This is 100% false, as evidenced by the engineers at Subaru putting a damper out on the end of the crankshaft of their internally balanced motor. Why would they then?


Spinning a motor's rotating assembly with an outside power source and balancing it in a fixture to not vibrate itself into oblivion is one thing. Easier on an opposed piston boxer motor than a 45deg or 60deg V motor for sure. But what happens when you add in the forces inherent in using that same rotating assembly in an engine block to produce power? Torsional vibration that flexes the crankshaft. Stock motor or not. Boosted or not. The big elastic steel crankshaft acts like (read: is) a big torsion spring when subject to combustion events as designed. The only thing that changes with boost is the amplitude and mode.


The damper from Fuji Heavy is a compromise, just like any other part in any well engineered, complex solution sold today. Things like Cost of production vs. Mean use case vs. MTBF vs. Risk vs. contribution to unit cost, etc...Most cars don't live at 5K+ RPM for most of their life, so there is no need to put a damper on the motor that will support abating the torsional vibes at 5K+ rpm, hours of exposure at a time. The majority of cars don't see that territory frequently enough for any collective main bearing damage to be an issue. The far easier, cheaper, and profit boosting thing to do is obviously to put a hollowed out aluminum disk there to drive the accessories - not a two piece elastomeric type damper - like they and most other manufacturers do.


Control the vibes well enough from idle to 5K rpm and call it a day. As long as the actual bearing warranty rates fall within the projected failure rates + tolerance, it's all good for the company. They account for a certain number of failures/replacements in the profit margin.


End Rant.


Carry on

[tomm.brz]

Originally Posted by why?

Besides I've never seen anyone say a simply pulley change is going to totally change your car, and if they did they are morons or lying.

People are taking this stuff far too seriously.

Be carefull lol.. Someone could get offended here

[gtengr]

Using a static speed and RPM to extrapolate the acceleration is very basic given the tools are readily available to perform a more thorough analysis. It's more precise to investigate the difference starting with a known time of acceleration between RPM1 and RPM2.

[Tcoat]

Originally Posted by why?

Besides I've never seen anyone say a simply pulley change is going to totally change your car, and if they did they are morons or lying.

People are taking this stuff far too seriously.

https://www.ft86club.com/forums/showthread.php?t=127548

[FRS Justin]

Originally Posted by why?

The harmonics and vibrations are absolutely meaningless in any near stock engine unless you want to rev it too far beyond where the engine would explode due to its well known oiling issues.

Besides I've never seen anyone say a simply pulley change is going to totally change your car, and if they did they are morons or lying.

People are taking this stuff far too seriously.

I disagree we had two cat motors in heavy machinery have the rubber fail in the harmonic balancers and beat the main bearing out of them and cat warrantied both motors. They were stock engines.

[wbradley]

Wish I could take the time to digest the physics, but at the very least it is true that in neutral there is a quicker response to throttle input therefore the lightweight pulley might allow for quicker rev matching.
Just agreeing with previous poster.

[weederr33]

Originally Posted by Tcoat

https://www.ft86club.com/forums/showthread.php?t=127548

[ls1ac]

Having worked with a speed shop with a dyno for years, we usually see butt dyno anticipated gains are in direct relation to the lighting of the wallet. Most are disappointed with the result.


When checking race engines it is best to use an engine dyno in a controlled environment room. And even then some changes are lost to background noise, but we "know" it must be better.


By the way a "good" dyno operator can change results by more than 10% by changing the setup, angle of straps and tension, tire pressure, cooling (fan position)and more.
[We regularly see charts brought in showing large gains from an air filter change.]

[nikitopo]

Originally Posted by why?

Besides I've never seen anyone say a simply pulley change is going to totally change your car, and if they did they are morons or lying.

People are taking this stuff far too seriously.

I agree with you. It doesn't totally change the car. It just makes the engine a bit more alive in 1st and 2nd gears and it can be an additive improvement to other lightweight related changes.

Originally Posted by Tcoat

https://www.ft86club.com/forums/showthread.php?t=127548

Can you read or just want to make an impression? The specific link you posted is not related just with a lightweight pulley kit change.

[Tcoat]

Originally Posted by nikitopo

I agree with you. It doesn't totally change the car. It just makes the engine a bit more alive in 1st and 2nd gears and it can be an additive improvement to other lightweight related changes.



Can you read or just want to make an impression? The specific link you posted is not related just with a lightweight pulley kit change.

Meh so it says "and other.." Close enough.

[nikitopo]

Originally Posted by Tcoat

Meh so it says "and other.." Close enough.

Again want to make an impression with the extra big bold letters? I've installed a pulley kit more than 2 years ago and I know what is the difference just with the pulley. About the "other mods" there is a detail list of them in the first post of the link you mentioned. Nice try.

[nikitopo]

Originally Posted by Subsonic

That link you posted, what is it from? It looks like a torque and power curve from an engine, showing two curves from different tests. Given the curves are showing such a large torque difference from one test to the next, it is obviously not supporting any claim that justifies a lightweight pulley at all. Benefits should be in single digit % if at all. If you’re going to use a dyno to demonstrate the benefits of a pulley, you’re either going to have to provide a lot more information (like the time base for the run), or GTFO.

The dyno is what it is. A before and after measurement of a vendor's pulley kit installation. A 2-8whp increase depending the rpm range is not a huge difference. You might feel it a bit, but it will not change totally the car as I mentioned already. If your model cannot explain the result there are the following options:


1. Vendor doing the dyno is lying and favoring a bigger difference
2. Theoretical model is incorrect


You invited me here and I was polite to reply. What is the GTFO acronym? Please explain ...

[86TOYO2k17]

Originally Posted by nikitopo

The dyno is what it is. A before and after measurement of a vendor's pulley kit installation. A 2-8whp increase depending the rpm range is not a huge difference. You might feel it a bit, but it will not change totally the car as I mentioned already. If your model cannot explain the result there are the following options:


1. Vendor doing the dyno is lying and favoring a bigger difference
2. Theoretical model is incorrect


You invited me here and I was polite to reply. What is the GTFO acronym? Please explain ...

If you had a 1000lbs atlas stone, and shaved 4lbs off, do you think you could even feel a difference. It’s still 99.6% same weight. That’s pretty much the equivalent to taking 4lbs off the crank pulley. Is it lighter sure, does it “technically” make an improvement sure. Is that improvement big enough that it would result in a noticeable, feelable, or measurable difference. Not at all.

Butt dynos have been proven time and time again to be off by the same ratio of the amount of money spent. Spend 100$ “feel” 100$ improvement even when there is none. Much like a placebo.