In theory, lighter pulleys would be good for efficiency, since it reduces parasitic drag on the engine, and for the same reason improves HP. IIRC, Unorthodox Racing makes a set and they claim a WHP gain of 7-11 HP. All motor honda boys have been using UR's pulleys for years without issue AFAIK.
Since the engine will have to work that much less, I assume you would indeed save gas. Kind of a moot point to spend $200 on pulleys to save a dollar a month at the pump...
Since the engine will have to work that much less, I assume you would indeed save gas. Kind of a moot point to spend $200 on pulleys to save a dollar a month at the pump...
Well, it would obviously depend on how much gas mileage you save.
Say you get a 1 MPG savings. Also say you drive 20,000 miles a year and average 32 MPG with the old pulleys, and 33 MPG with the new pulleys.
At $2.50/gallon, your old fuel costs/year are $1,562.50. At the same $2.50/gallon, your new fuel costs/year with the new pulleys are $1,515.15. That's a difference of almost $50/year. After four years, they'd have paid for themselves.
Now, I don't have a clue how much gas mileage you might save. But if lighter pulleys have demonstrated a 10% gain in power, at the wheels, you might also reckon that there'd be a measurable gain in economy also, at least enough to offset the cost in a few years.
If lighter pulleys were all that it takes for increase in gas mileage, why wouldn't Toyota do it from the factory?
It's not only lighter but also different diameters (as in larger). If you spin the accessories slower, it takes less power. But the downside is reduced performance from those accessories. We did that on a '92 Mustang we had and the battery would die every now and then, because the alternator wasn't charging it enough (due to the slower speed it was turning). A/C performance might also be effected.
There is no free lunch. There will be a compromise.
That only apples if you don't overdrive the alternator pulley. Also, Aluminium pulleys are much softer than the steel ones used in the factory. Building an engine is all a compromise for reliability. They could have used a different cam spec, and gained more HP and mileage, but the wear and tear on the engine would be too much, and reduce the life of the engine. Even above efficiency, reliability is the primary goal of any OEM engine.
well the pulleys that you CAN buy are the same diameter as the OEM just a few pounds lighter....... which is alot considering thier size
i know the chance of comprimise using a lighter wheel, i got a friend who fabricates carbon fiber, i was thinking that could be an option if it could work, any advice?
There is a smart option, but you'd have to convince the right person to make your pulleys. MRZ Performance out of Quebec makes a pulley that is almost all aluminium, but uses steel on parts of the pulley that usually wear out on all aluminium ones. If you garner enough interest in a product, they'll produce and sell it. I've bought their stuff before, and it's top notch.
The problems I could see with CF are slippage and premature wear. It needs to be resin coated to hold together well, and resin isn't exactly a high friction surface. This would potentially cause slippage. The problem with premature wear would be the risk of fibers separating once that resin is worn. It could potentially be a great short term idea, but you'd be replacing them often. I wouldn't even try it on a good production engine with out lots of wear testing (at least a good month of straight testing on a high rpm electric motor in a separated closed space, constantly running). It would also have to be 100% flawless in build quality to work properly.
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