Effectiveness of a Lightweight pulley

[DrifterX]

Oh and also, an argument could be made about it allowing the car to maintain torque a bit longer since the parasitic loss would be lowered, but to see any real effect you would probably need to do quite a bit of internal work as well.

[OrbitalEllipses]

Originally Posted by DrifterX

Oh and also, an argument could be made about it allowing the car to maintain torque a bit longer since the parasitic loss would be lowered, but to see any real effect you would probably need to do quite a bit of internal work as well.

A light pulley and a lighter flywheel are obviously the two easiest ways to achieve a lighter rotating assembly; often people say they have to practically relearn how to drive the car when they get a lighter pulley due to how much faster revs drop between shifts. Now lighter pistons, valves, valve springs, rods, and a billet crank will definitely make a difference...but who's going to do that.

[Dave-ROR]

Originally Posted by Dimman

You've mentioned that on a Mustang Dyno you can adjust the parameters and affect the indicated WHP. Now does this bump up the indicated gains, too? So we should look at the % instead?

Ie: on your example of 240 WHP baseline on an 'adjusted' MD, parts changed gain an indicated 12 WHP, but if the same dyno gets readjusted and baselines at 150 WHP, would the parts change indicate a 12 WHP increase (absolute increase) or 7.5 WHP (relative increase)?

I would imagine that if one played with the calibration or the parasitics, any gain would be a larger % than on an accurate dyno, but I have never tested the same part before/after two different dynos so I'm not sure.

[Dave-ROR]

Originally Posted by DrifterX

But the point I am getting at is, if it takes less energy to rotate the drivetrain, doesn't it cause the drivetrain to lose less power and thusly make a noticeable change in power being put down to the wheels?

I understand of course that changing anything in the drivetrain doesn't cause the explosions inside the engine to explode harder (I.E. more oxygen and fuel) resulting in 0 ACTUAL power gain, but the act of freeing up inertial mass in the powertrain should result in putting more power down to the wheels right?

Noticable? Not in my experience on ~200hp 4 cylinder NA cars. I've never seen more than fairly normal variance levels of change.. ie a couple of HP.

The claims we are talking about here are eliminating ~50% of the entire driveline loss through a pulley.

[Dimman]

Part of gains showing on a dyno depend on how the dyno is operated.

On a Dynojet you pretty much just do acceleration pulls, so you will a gain from ANY rotating mass reduction. They measure power based on the time it takes to accelerate a drum of known mass. Light wheels will show a gain. Flywheel will show a gain and pulley will show a gain. How much depends on the weight loss, where the weightloss is (outside of large diameter is better) and how much the part has to accelerate (pulleys and flywheels at engine speed take more than wheels which are slower because of gearing).

However on resistance or brake types that make the motor fight a resistance and hold rpms, you generally won't see rotating mass gains unless they are doing acceleration type pulls.

In real-world acceleration the lighter rotating mass will make an improvement from less power being wasted on accelerating the drivetrain.

[GTerran]

Originally Posted by Dimman

Part of gains showing on a dyno depend on how the dyno is operated.

On a Dynojet you pretty much just do acceleration pulls, so you will a gain from ANY rotating mass reduction. They measure power based on the time it takes to accelerate a drum of known mass. Light wheels will show a gain. Flywheel will show a gain and pulley will show a gain. How much depends on the weight loss, where the weightloss is (outside of large diameter is better) and how much the part has to accelerate (pulleys and flywheels at engine speed take more than wheels which are slower because of gearing).

However on resistance or brake types that make the motor fight a resistance and hold rpms, you generally won't see rotating mass gains unless they are doing acceleration type pulls.

In real-world acceleration the lighter rotating mass will make an improvement from less power being wasted on accelerating the drive train.

This is all very true.

Like what was said in the other thread, noticeable gains in the FIRST TWO GEARS. this is due to the eng accelerating the entire car at a high enough speed that the small weight change in the pulley has an effect on overall dynamics on acceleration. As you go higher in the gears the effects of the light weight pulley becomes marginalized to 0 as the acceleration of rotating mass becomes minimal.

[wu_dot_com]

Originally Posted by DrifterX

But the point I am getting at is, if it takes less energy to rotate the drivetrain, doesn't it cause the drivetrain to lose less power and thusly make a noticeable change in power being put down to the wheels?

I understand of course that changing anything in the drivetrain doesn't cause the explosions inside the engine to explode harder (I.E. more oxygen and fuel) resulting in 0 ACTUAL power gain, but the act of freeing up inertial mass in the powertrain should result in putting more power down to the wheels right?

Remember, drive tran mass lost performance gain is realtive. The pulley is a very small component in a massive assembly compairtive speaking, the 1 lb gain will not have a noticeable effect since te bulk of the mass is still here.

Hence any gain that is able to be pickup by the dyno will most likely be dismiss as test variation.

[wu_dot_com]

Originally Posted by CircuitJerk

I think it should be more like the fact that there is less rotational mass, that it allows it to spin up faster, not spin faster as a result. It would only reduce the work needed thus improving the time. Not the speed.

AMIRITE?

Very good point that people tend to miss. As I stated in te other thd. The gain by pulley and flywheel is your increase in angular acceleration, not velocity.

[wu_dot_com]

Originally Posted by OrbitalEllipses

Yes, that's more correct.



Read what others are saying, it may be more suited to your understanding. You MAY notice the revs climbing faster in gear, but you'll notice it way more when shifting. You're reducing a minuscule amount of drivetrain loss...as another poster said, you're not feeding more oxygen or anything like that; you're not MAKING more power. This mod is more about feel than performance, in my opinion.

There is no double a measurable performance gain. However you will not be able to verify it though the traditional measuring means like dyno.

The easiest way to see the gain is to go and rev someone else's car with this mod

[Obja]

So at the end of the day, what is the benefit of spending money on this?

[brichard0625]

im doing a dyno this coming sat on the lightweight pulley..going to a do a stock pull with visconti tune and then a pull with the pulley and visconti tune..we'll see if the pulley shows and it will be a on a mustang dyno

[Celica00]

Originally Posted by Obja

So at the end of the day, what is the benefit of spending money on this?

decreasing rotational mass and increasing throttle response.

[86KEEBS]

I think You'd feel the power more direct.. maybe gain 1lb/tq...

[CBR600RR]

Originally Posted by OrbitalEllipses

Read more carefully; if you are accelerating quicker it's not due to POWER it's due to being able to SHIFT faster due to a LIGHTER rotating assembly.

IMO the crank pulley being lighter should have nothing to do with being able to shift quicker... Shifting quickly stops at the driver, clutch peddle and the shifter.

If the engine can rev quicker it means the engine is accelerating faster and jens the car is accelerating/climbing the revs quicker. There is less power of the engine being robbed by having to spin up heavy parts - allowing more power transfer to the ground


Light weight wheels will do the same thing - plus a whole lot more to your suspension performance (less unsprung weight allows the shocks/springs to work more efficiently)