HOW TO - Install an Underdrive Pulley
Before you buy, read this: http://forums.probetalk.com/showthread.php?t=1701267006&highlight=underdrive
For £50 you can gain 5hp+ and get a nice shiney piece of metal to brighten up the bottom your engine bay. UDPs are light weight pulleys that have smaller diameters thus less energy is exerted to the alternator and power steering pump. Their reduced diameter decreases the weight the crankshaft has to rotate thus increasing response and hp.
Old broken pulley
How to Remove your old pulley
-Take off your front right wheel
-Take off the splash guard (approx 7 bolts)
-Slacken the alternator and powersteering belt tensioners until the belts can be removed (alternator first)
-Position your breaker bar as in the picture below. Use a 22mm socket. It is wedged into the ground perpendicular to the pulley
-Crank the engine briefly
-Be overjoyed at how easy that technique makes it
-You should now be able to hand loosen the bolt until it is off
-Pull on the pulley, you may need to wiggle it and use a screwdrive against the powersteering pulley to lever it a bit. I also gave it a few hammer taps
-Feel the weight of that? That's why we will see a small gain.
How to cut away the shroud for UDP clearance
-Your UDP will not fit on as the OEM part. You need to CAREFULLY grind away 5/8th" (14mm) of metal and plastic shroud.
-I used a dremel and many cutting disks to carefully remove the metal (blue) and plastic (green).
-Be VERY careful not to nick the timing belt or the crank position sensor(red). I covered up the sensor by wedging a bolt over the top of it. The dremel will inevitably slip, so just do it, cover it up.
-Cut away the metal gradually working around aiming to be flush with the cast webbing of the engine
-Smooth off any protruding rough parts with a grinder piece
How to install your new Underdrive Pulley
-Wipe away any metal fillings from the cutting (I also used compressed air)
-Put some copper/anti-sieze grease on the UDP or crank.
-Slide it on (if it doesn't use some fine sand paper to remove any corrosion)
-Tighten up to 116-122ft-lbs/157-165nm
-Give it a test spin with a ratchet to make sure enough metal was removed (it will sit out about 3mm due to the larger than OEM collar)
-Give it a test run in neutral to check it spins ok
-Put on new accessory belts (shorter - part# to follow)
-Tension up to correct settings in manual
-Put splash guard on then wheel
-Enjoy a cheap and easy mod :)
Where to Buy it: