Effectiveness of a Lightweight pulley

[Kuzuri]

Originally Posted by Opposed

Post #3 shows pulley only...

my bad, the last time i saw that thread the post with JUST the pulley wasnt there. so, i didnt even look further down :P

[DrifterX]

Yeah I finally slugged through that whole thing and Perrin seems to feel super confident due to past H4 motors from Subaru. I might give it a try in the near future, if I do I will definitely post my experience up in the forum.

[OrbitalEllipses]

Originally Posted by Dave-ROR

It won't make the engine produce more power, but can show a little on a chassis dyno. However, the weight if VERY close to the centerline of rotating mass, and we aren't talking about a lot of weight so I do find a ~50% reduction in driveline loss under acceleration to be a bit unbelievable still from just a pulley. There are so many other components involved that I just find it very hard to believe.

I've seen lightweight pullies dynoed before, and have never seen any sort of WHP increase like Vivids.

That. The engine "feels" peppier and more alive simply because it can spin faster. You're not "making" hp as much as you're "unlocking" it in basic, unscientific terms. You should be able to feel a difference in the speed of revs falling/rising, not in acceleration or power. It might feel like you're accelerating faster, but you're just revving faster and shifting faster due to that.

[Dimman]

Originally Posted by Dave-ROR

It won't make the engine produce more power, but can show a little on a chassis dyno. However, the weight if VERY close to the centerline of rotating mass, and we aren't talking about a lot of weight so I do find a ~50% reduction in driveline loss under acceleration to be a bit unbelievable still from just a pulley. There are so many other components involved that I just find it very hard to believe.

I've seen lightweight pullies dynoed before, and have never seen any sort of WHP increase like Vivids.

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)?

[ruskymx]

Originally Posted by OrbitalEllipses

That. The engine "feels" peppier and more alive simply because it can spin faster. You're not "making" hp as much as you're "unlocking" it in basic, unscientific terms. You should be able to feel a difference in the speed of revs falling/rising, not in acceleration or power. It might feel like you're accelerating faster, but you're just revving faster and shifting faster due to that.

I've had a Perrin pulley on mine now for about a week and a half and can vouch for the car "feeling" peppier and it seems to rev quicker. I would describe it as not making any power as well, but instead of having a 15% drivetrain loss, it may now be a 13% loss. *DISCLAIMER* those are just random numbers and I have no scientific data to back it up. /DISCLAIMER

If anyone can offer a dyno, I'd be happy to drive, within a reasonable distance, and bring the stock pulley with to see if in fact there are any WHP changes. I do have Visconti's STG1 tune on my car, but the pulley would be the variable.

Ruskymx

[OrbitalEllipses]

Originally Posted by ruskymx

If anyone can offer a dyno, I'd be happy to drive, within a reasonable distance, and bring the stock pulley with to see if in fact there are any WHP changes. I do have Visconti's STG1 tune on my car, but the pulley would be the variable.

I think it depends on the dyno whether or not you see any changes. For example, lightweight wheels will show a slight HP advantage on inertial dynos; could be similar for this type of thing. All the consumer really needs to understand is that there's a heavy thing spinning and we made the heavy thing slightly lighter, thus it should spin faster. That should make sense to 99% of people.

[Kuzuri]

Originally Posted by OrbitalEllipses

That. The engine "feels" peppier and more alive simply because it can spin faster. You're not "making" hp as much as you're "unlocking" it in basic, unscientific terms. You should be able to feel a difference in the speed of revs falling/rising, not in acceleration or power. It might feel like you're accelerating faster, but you're just revving faster and shifting faster due to that.

i hope im not sounding stupid right now.... if the car is moving and its revving FASTER, it should mean that the car is accelerating FASTER as well... right?

[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.

[DrifterX]

Originally Posted by OrbitalEllipses

I think it depends on the dyno whether or not you see any changes. For example, lightweight wheels will show a slight HP advantage on inertial dynos; could be similar for this type of thing. All the consumer really needs to understand is that there's a heavy thing spinning and we made the heavy thing slightly lighter, thus it should spin faster. That should make sense to 99% of people.

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?

[Xanatos]

Think of the engine as having to put power to the crank pulley. Its heavy and the engine cant rev up and down as fast. With a lighter one the pulley has less rotational momentum so less power is required to get it up to speed. IE less power loss from the engine to the driveshaft.

[CircuitJerk]

Originally Posted by OrbitalEllipses

I think it depends on the dyno whether or not you see any changes. For example, lightweight wheels will show a slight HP advantage on inertial dynos; could be similar for this type of thing. All the consumer really needs to understand is that there's a heavy thing spinning and we made the heavy thing slightly lighter, thus it should spin faster. That should make sense to 99% of people.

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?

[Kuzuri]

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.

thats what im saying. but you were saying that you wont feel quicker acceleration with a pulley... im confused.

[OrbitalEllipses]

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?

Yes, that's more correct.

Originally Posted by Fancy

thats what im saying. but you were saying that you wont feel quicker acceleration with a pulley... im confused.

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.

[DrifterX]

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.

So, the end result is that you won't really get any appreciable amount of power freed up from this mod, however, when in neutral especially, your revs will build up faster. If we examine the rotating mass while the clutch is pushed in or the car is not in gear we see that it is likely fairly low. Something like 20lbs for the pulleys, 30 lbs for the flywheel assembly, and probably 40 lbs for the crankshaft and pistons. That is ALL that is spinning when the car is not in gear.

If we take the crankshaft pulley and reduce it from 4lbs 14 oz to 1lb 4 oz (Or whatever the specs were) we see a massive shift in mass while the car is not in gear. Losing 3lbs from a 90lb assembly is pretty darn good, and once more, it is from a part that is directly and always engaged. If I recall correctly, when the clutch is pushed in all you have rotating is the flywheel and the crank + any accessories, so with only the oil pump and alternator we are probably looking at more like a 60~ lb assembly which means 3 lbs is 5% improvement.

But if we look at the actual engagement, I.E. when we have the car in a gear and the engine is having to turn all of the components + move the weight of the car we realize it's only about 3 lbs in a 2600 lb contraption. That said, rotating mass is worth a bit more, but it would probably only be the equivalent of pulling 15~ lbs of static weight. (That is entirely based on a spitball effort and in no way should be used as gospel)

I think that sums up the discussion... /thread!