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Old 04-14-2013, 07:08 AM   #9
thstone
Certified Boxster Addict
 
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
Quote:
Originally Posted by particlewave View Post
The UD pulley is meant for cars that are tracked regularly and will sustain high rpm driving for long periods of time. The underdrive pulley reduces the RPM of the power steering pump, the water pump, and other accessories to lessen wear on them caused by sustained high rpm driving. During normal driving, this will cause accessories to spin at a lower rpm and therefore provide less power to them. Whether the effect is noticeable or not is debatable. However, the tiny bit of a horsepower you may gain by installing an underdrive pulley hardly seems worth the effort.

Again, it is meant for cars that are tracked and is for reduced wear on accessories in that situation, not for hp gain on street cars. Any hp gain would be minute...it is said that up to 5hp is gained at maximum rpm, but that would only be noticeable if you had an accelerometer in your butt. I have yet to see any before and after dyno results, but then I haven't looked either.
Not trying to bust your chops, just the facts from an engineer

Nothing wrong with installing it on your street car...until you are wondering why your AC isn't as cold as you'd like in the sweltering heat or why your car is running hot and dumping antifreeze.
That's just my opinion...and you know what they say about opinions

Personally, I trust the engineers at Porsche. At least, all except for the guy that designed the IMSB
The slight reduction in accessory speeds does not impact performance at all. I was extremely worried about this before installing an UDP in my car, but the reality is that the PS, water pump, alternator, and air conditioning all perform exactly like they do with the stock pulley. The A/C will be as cold as it ever was and your car will definitely not be running hot and dumping antifreeze.

In regards to horsepower, you are correct. There is certainly a small increase in HP but it is impossible to notice in daily driving. If fact, it is impossible to notice on the race track. BUT it is noticeable when running nose to tail against someone with the stock pulley when every hp counts.

Whether this is worth it to anyone driving exclusively on the street is up to the owner. Some will say "not worth the money" and some will say "I want every hp that I can get". Choose your poison.
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Last edited by thstone; 04-14-2013 at 07:10 AM.
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