URD 2.2" Supercharger Pulley
As part of the upgrade path for Project SportRunner I wanted to install a slightly smaller supercharger pulley to add a few additional horses. I felt comfortable with this performance addition as I had the URD 7th injector installed to add fuel where needed. The stock TRD 3.4L supercharger pulley is 2.37". The standard TRD supercharger is claimed to add about 60 RWHP (75 crank horse power minus 20% drive line loss). The stock pulley produced right at 7 psi on my vehicle. That equates to roughly 9 RWHP per pound of boost added. The smaller 2.2" pulley will spin the supercharger faster producing more boost and thus more power. Based on the same calculation above the 2.2" pulley should add close to 20 RWHP with the 9.5 psi of boost that it shows on my vehicle. The 2.2" pulley is well below the RPM limit of the TRD supercharger.
For this modification you'll need:
URD 2.2" Supercharger Pulley
Strap wrench of fuel filter wrench
Torque wrench
Pulley puller
Copper anti seize
Blue Locktite
Installing the pulley is very straight forward. Using a 3/8 drive ratchet take the tension off the dynamic belt tensioner and remove the supercharger belt from the stock supercharger pulley. Using a strap wrench or fuel filter wrench hold the supercharger pulley stationary while removing the 18mm supercharger top nut. Once the nut is removed, use a pulley puller to remove the stock 2.37" pulley. DO NOT use an impact gun on the top nut as this can easily damage the supercharger nose drive.
Check the supercharger pulley shaft for any corrosion and remove with a scotch brite if necessary. My URD 2.2" pulley needed just a little dremel polishing in the shaft hole for it to fit. I've notified URD of this so yours may or may not need this polishing. I'm estimating I needed to remove about .001" of material. If you do need to polish your URD pulley just be sure to keep the hole round and use a fine grit sanding wheel test fitting often until the pulley fits over the supercharger shaft enough to allow you to start the top nut. Put a very small drop of blue Locktite on the nuts outer most threads and start the nut. Once the nut is started, use it to press the pulley on as you tighten it, again holding the pulley stationary with the strap wrench. DO NOT beat or hammer the pulley onto the supercharger as you could drive the pulley shaft back into the nose drive. Once the pulley is fully seated torque the top nut to 38 ft/lbs.
Put the supercharger drive belt back in place assuring that it is properly aligned and fire up the vehicle. Listen for any strange noises and watch the belt for proper alignment. Finally, tune the vehicle for the new boost.
I didn't think I'd notice a 20HP increase, but it was quite evident. Boost comes on sooner and the power is very apparent.
