Originally posted by SleeperZ: Do you also question that lighter wheels allow a car to accelerate quicker?
Of course they do, to some mild degree. But four large wheels are a lot more significant than one small pulley. To return to the half ton sled analogy, that's like adding or removing a hundred pounds on top instead of adding or removing one pound.
Originally posted by SleeperZ: Its the same priciple. The less rotational mass of the item, the less energy is being wasted to rotate the item. BASIC PHYSICS.....find a high school science book and read it.
Yes, it is the same principle. Just as the two cases of the hundred pounds on the sled vs. the one pound on the sled are the same principle. By taking off one hundred pounds and seeing it speed you up, you can prove that taking off one pound also speeds you up. It's the same principle... but that doesn't mean you can expect results from both.
Do you understand how to factor in the car's overall weight as effective rotational mass? The engine cannot distinguish between the inertial load of the actual rotating mass and the inertial load of accelerating the car forward. To the engine, it all looks like one big rotational mass.
We can put some rough actual numbers on this. The stock pulley has a rotational mass of maybe one foot-pound ("pound" here used as a unit of mass, not force), since its effective radius rotational-mass-wise is well under three inches (it's less than the real radius by an amount depending on how much of the weight is closer in to the center -- two thirds of the real radius for a disk of uniform thickness). The accessories are probably more, because they spin faster -- the alternator alone is probably more than the pulley. The four wheels probably have a total rotational mass of at least one hundred foot-pounds, but from the engine's point of view that has to be scaled according to the gear ratio, which reduces it by a factor of from three to fourteen, depending on what gear you're in. The drive train and engine internals are hard to estimate -- it varies with crankshaft position -- but one can at least say it's somewhere between 5 and 50 foot-pounds. The torque it takes to actually accelerate the car forward adds an effective rotational mass at the axles of somewhere between 3000 and 3500 foot-pounds (because the tire radius is a bit over a foot), which at the engine is divided by the same ratio that the wheel mass is.
So if your wheels and tires had no weight at all that might make a performance difference of five percent or so, but if your pulley had no weight at all this would make a difference of at most half a percent in first gear, less in second gear, still less in third, etc. What I'm telling you is not that it has no effect at all, just that you're not going to see any verifiable difference in your ET from that small of a change. (On the other hand, it might save some wear on your clutch during shifts.)
Now, if you followed all that and can find anything wrong with it, feel free to lecture me on basic physics.
