pulley kit

[RayRay85]

Are these things any good http://www.summitracing.com/parts/BBK-15550/?rtype=10

 

[walnuts4x4]

have heard they are both good and bad.... but nothing I have ever thought about installing

 

[Idahokid]

I had one of those kits on a 5.0 mustang once.All it did was drain the battery during the summer when the a/c was on.Most bolt on items dont add up tp much.Just my 2 cents.

 

[Thermo]

RayRay, the underdrive pulleys are a sour sweet deal. Can they net you more power, of course. But, you need to understand how they net you more power.

First off, you are going to be spinning your accessory belt slower. The slower the belt moves, the slower the accessories move, therefore they require less power. But think about what the accessories are doing for you:

1) power steering pump: this is pumping up fluid to a pressure to help with turning the front wheels when you are stopped. Less fluid pressure (due to the pump not turning as fast) means you will have to turn on the steering wheel harder to get the tires to move. How much, can't say. I think it will be very dependent on how wide your tires are and what sort of rubber compound the tires are made with (more sticky rubber means harder time turning the steering wheel).

2) A/C compressor: like the power steering pump, you don't spin the compressor as fast, it doesn't pump up the freon to as high of a pressure. less pressure means less cooling. So, you can start reaching a point where on a hot summer day the compressor is not going to be able to keep you cool unless you start keeping the motor RPMs up above say 3,000 RPM (so much for mileage).

3) alternator: this is the one that most people have the biggest issue with and why they will pull the pulleys off. Keep in mind also that electricity wants a finite amount of power, regardless of how fast the alternator is spinning. A 55W headlight bulb is going to pull 55 watts. End of story. The only difference for an alternator with an underdrive pulley is the maximum power it can output. Yes, your alternator has different maximums based on engine RPM. With a stock setup, at idle (assuming you have the 130 amp factory alternator), you are limited to about 65 amps. If you need to pull above that, you are pulling that power out of the battery. Not until you hit say 1,500 RPM does the alternator become capable of outputting its maximum current. Above 1,500 RPM, the alternator can not output more current as you are hitting other limitations of the alternator and I won't get into that unless you want me to (this area is what I used to do for a living, but on a much larger scale). So, with the under drive pulleys, you are going to be spinning the alternator even slower. So, at idle, instead of having 65 amps at your call, you may be down around 50 or less (depends on what pulleys you get). Normally the answer I hear is "well then I will get an overdrive pulley for the alternator!!!!". Ok, then what have you truely gained then? You are just making the alternator spin as fast with a slower belt speed.

So, are you willing to potentially have issues with something that is really only going to net you 2-3 hp. Seems like a lot of risk for little gain. You would have a much better return by doing a switch over to say e-fans or something of the like.

If you need me to go into more detail about anything, just hollar. I can even break out equations and whatnot to help make the point.

 

[Brusky]

I have had those pulleys on my truck for about a year now and have had no problems, saw a noticeable gain in mileage and h.p., I also have a JL 300/4 running all 4 door speakers and the rear 8in sub and can sit at alight at night with headlights on and turned up as loud as it will go without distortion and the battery gauge doesnt move nor do the lights dim, its not much of a system but it is significantly more draw than factory stereo. the only thing i have noticed a change in is the ac, but after i tinted the windows it made up for the difference.

 

[whowey]

One of the other things I have seen done with the pulleys, is two guys split a set and each run only one or two of them. Both get some of the benefits and some of the downfalls. I have also seen someone run just the crank pulley to achieve the same idea.

 

[Brusky]

The only problem with that is the belt size would change, those once installed utilize factory belt size. As far as pulley sizes. The crank is smaller slowing all accessories down. Water pump is larger slowing it down and the alternator Is the same size as factory just aluminum.