Thinking of buying a UR underdrive pulley... Some questions and concerns..

[ken240sx]

sorry, meant to say circumference.

[DaniMike]

I have been just sitting here and watching peoples replies... Anyways to turn this into useful information let me break it down for you because me and a friend of mine thought about it more and figured it out, Basically visualize the pulleys in your head... on the ka there is the Alternator pulley, Water pump pulley, power steering pulley and the Crank pulley.So hypothetically speaking im just going to say the Crank pulley is 4 inches in diameter The alternator pulley is 1 inch in diameter the water pump pulley is 2 inches in diameter and the power steering pump pulley is 1 inch in diameter.

Ok so if the crank pulley rotates one time it rotates the alternator and the power steering pump pulley 4 times, and the water pump pulley 2 times.

If you were in fact going to decrease the Crank pulley size to (hypothetically) 3 inches in diameter while leaving the other pulleys the same size with one rotation of the crank pulley it would rotate the alternator and power steering pump 3 times and the water pump 1.5 times. So that is how the Smaller underdrive pulley actually UNDERDRIVES the accessories in a way that is so minor for the accessories that they will still function as they normally should but its alot less work for the engine to do. Which is why it gives you more horsepower/torque.

On another note i have the lightweight flywheel already, The 11lb fidanza, Pulley sets and light flywheels are both really good for power, Any weight taken off the crank is good and noticable, I remember driving my friends 240 with a DE that was completely stock besides catback and mishimoto radiator and that pulley was installed and WOW it was noticable so you people saying its not noticable need to leave and stop spreading useless information... Also You dont really have to worry about it messing up the engine because import motors are INTERNALLY BALANCED which means that what you do to the outside such as the crank pulley isnt going to really hurt it.. Unless the pulley is not balanced and or is wobbling everywhere then you have some serious issues.

You people really need to stop talking about SEARCH SEARCH SEARCH... Do you really think i would take the time to post a thread about something without searching first? Give me a break do us all a favor and reset your post counter so us people who actually post threads look like we know what we are talking about, I could easily post whore by going in to every thread telling people to search. Did you try searching yourself and find anything useful? If so please direct me and slap my A$$.

I know this is late as hell but I must get this cleared up!!! This is for anyone like me looking for information and stumble upon this...not all of this is true. The KA IS NOT INTERNALLY BALANCED. It uses an external HARMONIC BALANCER and the crank shaft is NOT fully balanced.

There. I am a year late but I had to get that off my chest.

[TWO 40 SX]

Hey Bro Dont worry go with the pulleys i install OBX pulleys on mine 240sx she runs great just make sure you change your front seal is ok to use a impact tool i used one to take off the stock crank and to install the new light wight under crank and my 240 is auto so theres no hassle at all about the water pump there was a small change in cooling car warms up faster than before but temp gauge dose not move beyond the normal point to make sure i would upgrade to a two core ridiator but stock ridator should be fine