So i was curious, when replacing your crank pulley, i assume the power gains come from the differance in weight between the stock crank pulley and the lighter crank pulley. If the power gains come from less weight, why get the smaller, underdrive pulley if it has possible negative affects. Why not just get the same size pulley, but lighter and reap the benefits of the weight loss?

I have read tons of posts, i already know some people say the underdrive pulley doesnt negativley affect your car and some people say it does, so i am not asking that, just the reasoning behind getting the smaller underdrive pulley over just the lighter same size pulley.

 

i'd like to know too!

 

UR says you gain 15% hp more above and beyond the weight change, by driving your AC, power steering, and alternator at a lower speed- makes sense, because you exert greater leverage on the accessories, ie less power drain.

Love my pulley!!

 

So if you gain maybe 10 hp at the most from the standard lighter crank pulley, you might get 11hp by using the underdrive pulley. I think its a much more wise idea to not gain 1 hp and have absolutley no risk of messing up anything electrical or air conditioning related by underdriving your accessories, nor will you have that restriction on running additional electrical items in your car with the underdrive pulley.

I guess its up to the user, are you willing to increase your output by 1 measly horsepower for changing something like speed at which your accessories run, which could or could not have a problematic long term effect on your accessories. The possible risk definatly out weighs the 1hp benefit.

 

which is why I went with the stock diameter UR pulley.

Just to note, the whp/tq numbers for the UR pulley are from the underdrive crank pulley.

 

yeah okay, but is it similar numbers for the stock diameter one as well?

 

read post #3 and #4

 

ok.ummm . you answered your own question..

your avatar reminds me of Mikey Tuttel from Orange County Choppers..

 

Its some guy that was selling a mind reading machine on ebay...
I thought it was halarious.

 

well you must of bid, won and used it, because it read your mind....

 

I guess i just didnt understand the logic in reducing the speed of your accessories from stock to gain 1hp. Plus i am not an eleet mechanic so i didnt know if there is some alterior motive to underdrive your accessories besides the 1 hp gain. Maybe most people dont know that underdriving only gives you 1 hp. This might sway people to get the standard size pulley instead of underdrive, cause thats what i am going to do.

 

i still dont understand how you can gain hp with the stock diameter size crank pulley...............

 

because the unorthodox pulley is like 6 pounds lighter then the stock pulley

 

inertia..... mass// weight

example... why do people buy light weight rims???.. think about it...

This is why I find it SO funny when these idiots buy 24 inch rims and put them on their SUV and DO NOT upgrade the brake calipers/pads & rotors.. total disaster waiting to happen....

 

i would think smaller radius would have a greater effect..seeing as how moment of inertia for any object involves mass x radius squared. but that's purely from a physical standpoint..i dunno much about pulleys on the car

 

Correction, our stock pulley is 8.9 pounds, unorthodox is 2.0 pounds so you lose 6.9 pounds of weight on the crank. Unorthodox claims 2.7hp per pound lost from the crank, so theoreticly you should gain 18.63 hp from the lighter crank pulley.

If unorthodox's 2.7 hp/lbs includes underdriving then you would gain 15.8hp with the stock size unorthodox crank pulley and you would gain 18.63 on the underdrive unorthodox crank pulley. I am sure their 2.7hp/lbs is over exagerated, but you get the idea.

 

is it your helmet that helped you figure that one out?

 

i thought it was pretty good info to have....

thanks Mikey Tuttel.

 

I agree

 

Unorthodox's 2.7 hp/lbs does not include underdriving but rather from just the weight loss alone which account for only 85% of the gains. You have to add the additional 15% that you get from underdriving which would bring the total HP to 21.91 when underdriving giving you a whopping 3.28 hp difference. GIVEN THEIR INFLATED NUMBERS...

 

Actually, 18.63hp * 1.15 ~ 21.42hp and 21.42hp - 18.63hp = 2.79hp so theoreticly, you only get 2.79 hp by underdriving, and im sure they get the 2.7hp/lbs with the a/c off and only thing running is the engine. So realisticlly your probably only looking at 1hp or less gained with underdriving.

 

The aftermarket pulleys are a smaller for crank and larger for accesories diameter across. Think of a moutain bike and the different size teeth. The larger the sprocket, the easier to turn.

The con of pulleies is spinning your accessories slower, less amperage from alt.

 

That is where the horsepower gains are, not in weight...

 

u sure about that?

 

thats what I thought...

 

huh?

 

 

uh...i'm all confused. math never was my strong point. what next theories of universe expansion?

 

Not to be a dick, but can you NOT give people TOTALY INCORRECT information!?
Everyone please ignore his post and continue reading.

 

Huh, you got the equation wrong? I used this equation. 85/100 = 18.63/x
18.63 being 85% of the gains and X being the 100% equivalent of 18.63.

Let's not get too technical over 10ths of a hp, but seriously, all in all, if you're worried, don't underdrive, not worth the extra ~1-3 hp. If you're not worried and have tons of friends who've had no problem, underdrive the sucker!

Installing mine next week (underdrive that is) I'll definitely let you guys know if I run into problems!

 

Lighter rotating mass mey give you some tourque, but not horsepower. It would be the equivalent of lighter flywheel weight.

Thinking about it, the flywheel may be bigger on underdrive pulleys...with smaller accessory pulleys

 

I am running the UR underdrive pulley with no problems and improved performance. For various dynamometer graphs showing HP and torque gains, check their website(unorthodox racing). You may debate their accuracy, but in every case you apparently gain both with the underdrive pulley. Also, I have found their people to to helpful and responsive.

 

here's the real answer...the stock size UR is new....they only developed it for the super charger guys...but another benefit of the under drive s smaller diameter is moving the rotational mass inward also increase it's weight loss effect...

 

UR makes it underdrives to make power by not only lightening their weight but also by underdriving the accessories so that there is less parasitic drag. Therefore the lighter weight and the reduced drag created from running the accessories at peak creates more hp. Now the UR Ultra S Underdrive crank pulley will not affect anything adversely if you do not have a supercharger or a stereo system over 600 watts RMS.

- If you run the Ultra S underdrive pulley and your car is supercharged you could be suffering from a loss of boost (less psi) b/c the accessories are underdriven and a S/C runs off the belts.

- With a car with a large stereo system (over 600 watts RMS) there is a large draw on the alternator and electrical system. So your lights could dim somewhat b/c there is such a large amount of electrical current needed to run the stereo system and all the other accessories.

You do not need the Ultra Sc 12 Volt pulley designed for the stereo guys and the S/Ced guys. However if you want it is your choice.

 

so to get the gains mentioned above, you have to buy only the Ultra S underdrive crank pulley, the underdrive pulley set, or all of these together?

 

Horsepower is created through allowing air/gas mixture into the motor and exhausting that mixture.

Tourque is the ability/quickness of creating that horsepower. (i.e. the ease of the motor creating creating hosrepower)

 

yes, that is true. but it is also true that horsepower is unleashed by allowing more flow or decreasing resistance in many parts of the engine where otherwise you can't allow to happen cos of stock parts.

 

there is no such thing as hp...it is a calculation derived from torque

 

The bottom line is this:
The unorthodox underdrive pullies will give you 15% more horsepower then the unorthodox same size pullies, which as mentioned before equals 1-2 more horsepower.

 

u guys R pissing off Mikey Tuttel.....

I know you knew the answer, so I do not know why you put yourself through 2 pages of torture..