Contour Enthusiasts Group Archives Forums Modifications Zetec Performance Optimized Throttle Body

Originally posted by ZetecRacing:

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Originally posted by Paul Kienitz:

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I was also wondering if the figure of 8 ft-lbs of torque is really valid, because it seems improbable, but that's a separate question.

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do you want a copy of my dyno breakdown posted to make you happy?

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Originally posted by SleeperZ:

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Do you also question that lighter wheels allow a car to accelerate quicker?

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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:

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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.

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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.


I feel like Elyse on America's Next Top Model.

Originally posted by Kremithefrog:

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Ya'll hear that? Your dyno graphs and drag time slips are wrong!

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Originally posted by sosaudio1:

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Go here and read the difference between config one and config two.

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Originally posted by Paul Kienitz:

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Originally posted by Kremithefrog:

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Ya'll hear that? Your dyno graphs and drag time slips are wrong!

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I DIDN'T SAY THAT, GOD DAMMIT. Please review one more time the distinction between a lighter pulley and a smaller pulley.

Jeez, why the f am I even here.

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Originally posted by ZetecRacing:

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clearly you don't even know what a UDP is cause they are always lighter and smaller in diameter.

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Originally posted by Paul Kienitz:

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Originally posted by ZetecRacing:

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clearly you don't even know what a UDP is cause they are always lighter and smaller in diameter.

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<shaking head in disbelief...>

<contemplating quitting CEG in frustration at how hard it is to communicate simple ideas without them being turned upside down one minute later...>

Dude, didn't I say ALL ALONG that it's because you combined the lighter weight with the reduced diameter, that you can't credit lightened weight in itself for any dyno/ET gains?

This is not a rhetorical question. If you're going to give me crap like this "clearly you don't even know what a UDP is" line, you'd better be able to come up with SOME kind of justification for it. So go back and check if you have to. Is that, or is it not, what I said all along?

Now. What are we arguing about? What is the position we are disagreeing on? Once more, this is not a rhetorical question. I'd like a f'in answer. Can you tell me what the difference between my position and your position is?

ONCE YOU'VE GOT THAT STRAIGHTENED OUT, THEN WE CAN TALK. Otherwise this is a complete waste of time.




Okay, in case nobody wants to go back and actually look, I was disagreeing with a particular claim made by you, Sleeper, Kremit, and fingas: that lightening the pulley's weight frees up significant horsepower and torque, separately from any torque and horsepower freed up by reducing its diameter. THIS IS NOT a disagreement about whether a UDP does or does not give gains overall.

WHAT DOES IT TAKE to get you to pay attention to what I'm actually saying??????????????

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Originally posted by Paul Kienitz:

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Originally posted by sosaudio1:

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Go here and read the difference between config one and config two.

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I note that the HP and TQ gains are both about 5 there. This makes me suspicious that the oft-quoted numbers of 2 HP and 8 TQ really mean "2 plus or minus 3" and "8 plus or minus 3".

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