For over a year, I've been driving with the AC compressor by-passed. Not too long ago, I've upgraded my intake and exhaust system. I've been enjoying the benefits of such mods. However, since the triple-digit climate that we've been experiencing nationwide lately, I've decided to hook up the AC again. Although I enjoy not cooking in my car under such heat, I've experienced some loss of HP. So the question is....should I go with a UDP or not? Since the pulley is smaller, the engine gets to rev up a lot quicker and hopefully this will be the compensation I need.

What is your opinion? And if you all don't mind, for those with UDP, what UDP did you go for and what size of serpentine belt would I need?

Thanks.

 

I don't have PS or AC in my car, and i have the Unorthodox UDP. I didnt really feel any increase of power after putting the thing on...or any increase when i took my a/c and p/s off. I'm sure there was an increase, it was just so small that i didnt really notice it much. I say go for it if you find a nice deal for a used one, but i wouldnt pay $200+ for a new one.

 

save your money, its been debated on the forums for a long time, but the gains are either minimal or non existant.

 

The reason I ask is because it seems like its taking the engine longer to rev up at each gear. Before, it seemed to rev up a lot shorter probably because it wasn't driving an extra component.

Based on opinions from local org members, the UDP made the engine rev up quicker. Basing this on the principle of smaller pulley = bigger boost (on superchargers), I am thinking that it might help.

 

well there is no real HP gain its all in parasitic weight loss...same with light flywheels...they just allow for kwik revving....they will help overall efficncy of the motor and not make it work as hard...but the powerloss u are feeling is just from the hot humid air in the crazy heat of lately

 

When I installed a motostorm UDP on my car and I felt it pull a little harder, I also noticed a small increase in fuel economy

and BTW it revs quick as all heck

 

Comparing a lightened flywheel to an UDP isn't really valid. If you understand basic physics you understand that the inertia of a rotating body is directly proportional to its diameter and mass. The flywheel has a fairly large diameter and is pretty heavy, while the UDP is much smaller and lighter relative to the stock flywheel. The effect of lightening either component can't be compared. Lightened flywheel >>>>>>> UDP. Sure the motor will rev quicker in neutral with the UDP, but once in gear the car won't be any faster. Think about all the things the motor has to accelerate (rotors, wheels, axles, transmission, flywheel) and you'll see that the tiny loss of rotational inertia afforded by the UDP is negligible once the car is in gear.

My $.10

 

This makes a lot of sense.

 

a pointless mod, only semi reasonable if you are running nothing but the alternator and still makes very little difference. the gap in performance will be minimal and easily negated due to driving variability.

 

yep. Even differences in air quality will make more of a noticeable difference in driving than an Underdrive Pulley will. Honestly I cant imagine how the Underdrive Pulley lets you rev quicker - it makes the accessories spin slower, and may weigh less, but its really not that big of an item. Like nismology said, its inertia is relative to its diameter and mass, and its not all that large or heavy to begin with. You'd see tangible results with an ultralight flywheel, like I've done, and even more results with lightweight wheels. Even if you were trying to shave absolutely every pound off the drivetrain, you wouldnt start with a UDP.

amirite?