Pulleys for power

[JAsher45]

this past week at work i was running some very powerful 6.5s on the dyno ... 5 in a row 190+hp and could not figure out why they were running so good. i got to looking closer and noticed that the pulleys were different on the water pump and crank... the were Aluminum alloy not steel.

i went to the production shop to check it out... they were coming off the tear down motors and they were light... wow light crank pully was close to 6 pounds lighter and the water pump pully was close to 4 pounds lighter.

So if you want to free up about 10-15 hp and 20-25 ft/lbs of torque keep your eyes pealed for these pulleys.. yes they are for HMMWV's but the only real thing you would have to change is the power streering pully since there is no step down like on our pullys

 

[84cucv1ton]

can you get them? i would buy some off you.

 

[ARMYMAN30YearsPlus]

My Suburban would love you if you found a pair for me too.

 

[M543A2]

JAsher45:
I found your post interesting. However, I am at a loss to see how the change in pulley material will affect power output at a set RPM given they are the same diameter for each material. Doesn't rotating mass only affect the wind-up time for an engine from lower RPM to higher, or how well it will maintain a given RPM if a sudden torque load is applied? In the case of increasing RPM, the lighter set-up will allow faster wind-up of the engine. In the case of a sudden torque load, the heavier set-up with its greater rotating mass will help maintain the current RPM longer. When checking engine horsepower at a given RPM setting, the rotating mass has no affect unless RPM is changed suddenly. Therefore, it should not affect horsepower reading at a set RPM to have aluminum or cast pulleys. Did you make sure of your conclusion by changing an engine back to cast pulleys and running another test to see if there is a difference? If I saw what you did, I would want to run that test to validate my conclusion.
We do not like aluminum pulleys for use in dirty conditions because the grooves are abraded out of shape by dust and dirt, then belt wear and the power transmitting ability is compromised. The cast iron pulleys will withstand the abrasion much longer. With that said, it is possible the aluminum pulleys have worn grooves, allowing belt slippage, which could cause a HP reading difference.
I am not intending to be critical of your conclusion, I just do not understand what is happening from my experience. Any further study and experimentation you could do and report on would reveal what is causing the increase you see. I would find it interesting to see any information you could give us from an "apples to apples" comparison. Most of usl do not have the excellent chance you have to check and verify things like this.
Regards Marti

 

[84cucv1ton]

i would think the less weight the motor has to spin the easier it would be?? i thinks