Does having the UDP offset the loss of power when riding with the AC on?

 

Maybe a little. The easiest way to offset your power loss from having the AC on is to FLOOR IT!! There is a switch that'll cut off the AC while the fun pedal is planted.

 

Well, I don't stomp it a lot, but good to know.

I figure the UDP has got to help some, it seems logical to me. I mean the reason you lose power is because the engine has an extra accessory to run, so if the pulley that runs those accessories is lighter, than the engine has to work less to run the accessories, right? Isn't that the whole point of the UDP?

 

Actually the opposite, b/c the udp is smaller in diameter it will underdrive the AC (lowering the speed of the compressor and this can be noticable at idle). The reason the pulley is reduced in diameter, is to furthure reduce the weight of the pulley. The gains we see from a UDP is mainly due to the weight reduction and only partly from under driving the accessories.

You can clean your IACV if the engine does not idle high enough. There is a solenoid that is called AAC auxillary air control and that steps the engine idle up around 100rpm (so long it is not plugged with carbon, which is why I suggested to clean the IACV).

Or you can simply raise the base idle during summer months 50-100rpm.

 

I don't know about this specific case (maxima A/C pulley) but I'm pretty sure that most UDP's are larger in diameter mainly designed because as engines rev higher the accesories can't handle the rpms plus they are spinning faster (not slower) as is the case with a supercharger pulley (do the research if u don't believe. smaller pulley = faster rpms for accesory/supercharger) and draining power exponentially as the speeds increase. In English, one would expect something to draw power as the speed rises, eg for every 2000rpm more it draws (just a eg) 10lbs-ft torque. With the accesories the first 2000rpm might draw 10lbs-ft but the second might be 20lbs-ft the next 2000rpm 30lbs-ft and so on. (Remember this is just an arbitrary example grossly exaggerated)
They are called underdrive pulleys because they were designed to stop accesories from being overdriven (powersteering being the primary culprit necessary for robbing power)

And the moral of the story is...
UDP's are usually larger in diameter, not smaller, which is why most of them are made from lighter materials with "holes" cut in them to reduce weight.
Concerning the original question, I don't think that u will see/feel a drastic difference in power once the UDP's are installed or a major reversal of the power loss with the A/C on but all rivers start with one molecule of H2O...

 

Umm, no. UDPs are smaller. Your theory is correct, but a smaller pulley will turn slower at a given speed. Look at your crank pulley when the engine is idling. It's turning pretty quick right? And that's at 700rpm or so. Now, think of a ferris wheel. Imagine that thing spinning at 700rpm. People would be flying off into outer space! The longer the arm (distance unit) is on a rotational path, the faster the tip will be travelling. This is why propellers on aircraft are so loud. The tips of the props are spinning quite near the speed of sound, even though the engines are turning 2500rpm or so. Can you tell I teach this stuff for a living?

 

Hey, that's an idea! Maybe NASA should hear about this alternative method of sending people into space!

 

Basically that means the accessories are given less power than normal with the UDP. Does that have any negative effects on the AC, Power Steering, etc?

 

 

OK, let's see now....

In order to "underdrive" an A/C compressor (or P/S pump, etc) one must either put a larger diameter pulley on the compressor, OR put a smaller diameter pulley on the end of the crankshaft. Either way will slow down the driven device for a given drive device (crankshaft) speed (rpm).

My understanding of UDPs is that the overwhelming advantage comes from less parasitic loss by underdriving the accessories NOT from any weight gain from a lighter pulley.

My newbie question is - when the aftermarket speaks of underdrive pulleys, are we generally refering to a crank pulley, or a host of pulleys for the different driven accessories?

Kirk

 

umm, I think newbies should: 1)Ask permission to speak. 2)Ask permission to think. 3)Search the WEB before posting.

http://www.unorthodoxracing.com/faq_pulleys.html

2) "How do Unorthodox Racing pulleys give me more power?"
Weight loss is the most critical factor in HP production, each lb. of mass taken off the crank/eccentric shaft is worth approximately 2.7 HP and the figure increases with forced induction, nitrous, VTEC and increased RPM's. Only 15-20% of the gains seen from our pulleys comes from the underdriving. We achieve the maximum gain for each application/model by the singular use or combination of reduced diameter ("underdriving") and weight loss versus the OEM crank pulley/s. This principle allows us to maximize the HP gain without causing any adverse effects in the general function of the vehicle.

The diameter of each of our crank pulleys is reduced specifically (from 20-30%) to the vehicles accessory needs. In other words we maintain all accessory minimums: air conditioning efficiency, power steering feel, and voltage (minimum allowable voltage 12v) even at idle with everything electrical on in the car. There are no adverse effects from the use of our pulleys whether Ultra S, Ultra R, or Ultra SS pulley sets are used. Bolt them on and forget about them, then just follow your vehicles normal maintenance schedule.

 

Thanks, Eric. That's the answer I was looking for.

 

hahaha... lol - thanks, needed a good chuckle...

<waiting for caffination>
Matt