Unorthodox Racing Underdrive Pulley Installed
Thread Starter
Junior Member
SL Member
Joined: May 2005
Posts: 12
From: Easton, PA
Unorthodox Racing Underdrive Pulley Installed
I just finished installing the UR Underdrive Crank Pulley on my xB. I weighed the stock pulley and the UR pulley so everyone could see just how much lighter the UR pulley is.
Stock Pulley
3 lbs. 11 oz.
UR Pulley
14 1/2 oz.
Installation should be easy, but it never is for me. I was worried about getting the crank bolt off and it was no problem. However, the bottom alternator bolt is pretty much impossible. The service manual lists the torque as 40 ft./lbs. It's probably more like 400 ft. lbs.
Needless to say, I never managed to loosen the bolt, but I did get the alternator to move enough to relieve the belt tension a little. Also, for those who don't know, since the UR Pulley is underdriven you'll need to pick up a smaller belt from your local auto parts store. UR provides the part number with the instructions.
As far as performance is concerned, I am very pleased. My butt dyno suggests that this part makes at least as much HP as my Injen Short Ram Intake. The best part is that you actually feel some gain in the lower RPM. Based on my first impression I would suggest this upgrade to anyone looking for a little extra kick.
Stock Pulley
3 lbs. 11 oz.
UR Pulley
14 1/2 oz.
Installation should be easy, but it never is for me. I was worried about getting the crank bolt off and it was no problem. However, the bottom alternator bolt is pretty much impossible. The service manual lists the torque as 40 ft./lbs. It's probably more like 400 ft. lbs.
Needless to say, I never managed to loosen the bolt, but I did get the alternator to move enough to relieve the belt tension a little. Also, for those who don't know, since the UR Pulley is underdriven you'll need to pick up a smaller belt from your local auto parts store. UR provides the part number with the instructions. As far as performance is concerned, I am very pleased. My butt dyno suggests that this part makes at least as much HP as my Injen Short Ram Intake. The best part is that you actually feel some gain in the lower RPM. Based on my first impression I would suggest this upgrade to anyone looking for a little extra kick.
I didn't know they finally came out with a pulley that was underdriven for the XB. I have a 20% underdriven piulley on my TC.
Thread Starter
Junior Member
SL Member
Joined: May 2005
Posts: 12
From: Easton, PA
According to Perrin's website, their pulley is 1.3 lbs. They also claim that this is a 4 lb. reduction over the stock pulley which seems to be a little optimistic considering that the stock pulley only weighs 3 lbs. 11 oz. 
Of course my scale could be off a little, but its probably not 1.5 lbs. off.
Of course my scale could be off a little, but its probably not 1.5 lbs. off.
Senior Member
SL Member
Joined: Apr 2005
Posts: 158
From: Winnipeg MB
Originally Posted by aireck
well are these beneficial for autos....??
would it help out an auto xb in anyway??
hopes that simplifies it!!
would it help out an auto xb in anyway??
hopes that simplifies it!!
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Scion Evolution
Joined: Dec 2003
Posts: 288
From: The Gold Coast
The perrin pulley is 575 Grams, which equals 20.25 ounces. doesn't seem like a huge loss, not even a whole pound. Hopefully I can get mine installed this weekend, and I can post the weight of my stock pulley as well. Maybe toyota have different runs, and the pulleys could have different weights.
Jason
Jason
Thread Starter
Junior Member
SL Member
Joined: May 2005
Posts: 12
From: Easton, PA
"Underdriven" means that the UR crank pulley is smaller than the stock unit. This causes the accessory pulleys that are driven by the crank pulley to turn more slowly and exert less parasitic drag on the engine. In this case, the alternator and the A/C compressor are underdriven and the power steering pump turns at the original speed.
