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I posted on different occasions the question concerning underdrive pulleys. Does anyone have any comments about using underdrive pulleys to increase hp/torgue. I haven't seen this topic yet in any of the archives.
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From: saramento usa
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I considered underdriving my pulleys for increased HP, but there are other consequenses to consider. You have your water pump, altenator, a/c, and power steering that you can underdrive. If you underdrive your accessories, you have to realize that you will probably run a little hotter, have lower altenator output, or steer a little harder. I don't know how much each affects, but I know there are folks who have underdrive pulleys and I would love to hear from them concerning their gains and also their loses.
Slik
Slik
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Slik,
I had heard the samething from someone else and wanted a second opinion. I haven't started any hp/torque improvements yet and was just making a list for where to start at. It sounds like I would be impressed with the catback and K&N air filter change and was going to start from there.
Thanks for your reply.
Steve
I had heard the samething from someone else and wanted a second opinion. I haven't started any hp/torque improvements yet and was just making a list for where to start at. It sounds like I would be impressed with the catback and K&N air filter change and was going to start from there.
Thanks for your reply.
Steve
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I would think long and hard before putting on an under drive set. Basicly it frees up some horse power because it takes less power to turn your accessories at a slower speed. But thats just it it turns them slower and reduces thier output. I don't think slowing down the water pump would be a big deal if your truck doesnt spend alot of time idleing in stop and go traffic. What scares me is slowing down the smog pump and the alternator. I've had hell with my EFI, and wouldn't touch anything on it if it was already working. Does anyone know if reducing the smog pump output would cause problems with the O2 sensor or the cat?
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From: Copley, OH
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There is no adverse effect on smog gear, or power steering with underdrive pulleys. There is a decrease in alternator output and cooling at idle, but not under running conditions.
If you are planning on either running low profile tires or changing your rear gears to 4.11 or 4.56 and not running oversize tires to compensate, then underdrive pulleys should be considered a mandatory part of the package to reduce the RPMs that all the accessories see at highway speed.
Pulleys will give you about 5-10 additional HP throughout the entire RPM range and reduce ET by 0.1 to 0.15. Mileage benefits are negligible
If you are planning on either running low profile tires or changing your rear gears to 4.11 or 4.56 and not running oversize tires to compensate, then underdrive pulleys should be considered a mandatory part of the package to reduce the RPMs that all the accessories see at highway speed.
Pulleys will give you about 5-10 additional HP throughout the entire RPM range and reduce ET by 0.1 to 0.15. Mileage benefits are negligible
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From: Montana
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I've used under drive pulleys for 20 yrs you don't notice the power gain or mileage.They were made to compinsate for the over reving of your accessories and it does take off alittle time on your et's. I've ran the on the street with the fiber fans no problem. The shop that does our electrical work says after a stock engine hits 1700 rpm the alternater will produce all it is capable of producing.
