Lightweight Pulleys

[McWatters]

I have been attending a automovtive tunning/ modding information confernce every sat and today they were talkin about Light weight pulleys. Apparently 20 percent of the engin power is used to turn belts, fans ect before going to the wheels, so if u were to get a lightweight pully, usually half the weight of stock ones, you can get 15+horsepower.. so does any one know about the e34's pulley??





J.McWatters

[RobPatt]

..don't know for sure about those numbers, sure the pulley's are lighter, but I'd guess that the primary load comes from the devices themselves, alternator, P/S pump, A/C compressor, water pump, etc etc.... I guess you'd see some power increase from lighter and (larger or smaller?) pulleys too....?

again I think it's going to that margin area of diminishing returns... could just pull belts (depends M20, M30, M50, etc) and only turn the water and alternator.... just don't hook up steering and a/c, but then get into drivability and comfort..?

guess if you have to replace the pulleys though, good opportunity to go for lighter ones.

I have been attending a automovtive tunning/ modding information confernce every sat and today they were talkin about Light weight pulleys. Apparently 20 percent of the engin power is used to turn belts, fans ect before going to the wheels, so if u were to get a lightweight pully, usually half the weight of stock ones, you can get 15+horsepower.. so does any one know about the e34's pulley??





J.McWatters

[McWatters]

I suppose it depends on the type of car as well.

thanks for the input



J.McWatters

[Jon K]

lawlz

Rotational mass is completely different from static mass.

Smaller pulleys "weigh less" when turning than large pulleys...

Besides, its not the pulleys that are heavy, its the things on the other end! Spin an alternator by hand, or a powersteering pump. Hell, take the pulleys off, its still hard as ****. Moving a compressor through a liquid....

[GAM]

I've got them on my 525i. In my opinion they weren't worth what I paid for them. No big hp boost although the engine did seem to rev up faster. They might provide more if my car was a manual verses an automatic. Also it isn't so much about the weight of the pulley's it's more about the size. They reduce the turn over rate of the alternator, a/c, etc. One thing I did notice that when my car's idling the lights are dimmer than when I'm driving.
http://www.unorthodoxracing.com/

[Bill R.]

compressors pump liquid... if they do you just lost a compressor..
Compressors only compress gases... but the only gain from these light weight pulleys is because the diameter is different so it has a different ratio to the driven device. Since the alternator/waterpump/compressor is turning slower with the smaller diameter it takes less horsepower to turn but also provides/ less power or less cooling to the engine or less cooling to the passenger compartment/ AC... Its a stupid tradeoff for a very small gain.

Edit, sorry GAM, i didn't notice that you had already said the same thing..

lawlz

Rotational mass is completely different from static mass.

Smaller pulleys "weigh less" when turning than large pulleys...

Besides, its not the pulleys that are heavy, its the things on the other end! Spin an alternator by hand, or a powersteering pump. Hell, take the pulleys off, its still hard as ****. Moving a compressor through a liquid....