Ok, I'm wanting to get a set of power pulleys. The question is, If i want to get an underdrive crank pulley, i should see or free up some power, correct? Well at Thunder Racing, they sell a package for crank and alternator pulleys, but the alternator pulley is an overdrive pulley. Now, am i mistaken, or would these not counteract themselves, and i would be better off just getting the crank pulley? Any opinions are always greatly appreciated !

 

Nope, all will work the way it is supposed to


Crank powers belt, smaller pulley makes it easier for the crank to turn belt because belt turns slower.

Pulley turns alternator, the bigger the pulley, the less force it takes to turn alternator, but the slower the alternator will turn.

So look at things in terms of what is happening at alternator.

pulley on crank slows belt and therefore slows alternator

pulley on alternator slows shaft rotation of alternator and alternator goes slower.

Slower turning alternator takes less power than fast turning one.

Make sense, or have I confused everyone?

John

 

So where does the "power increase" come from, The crank pulley or the bigger alt. pulley? Sorry, i should know this but it's late and i'm finishing up for a final. Thanks again !

 

how much hp increase would i get with just the underdrive pulley and how much am I looking to spend to get it installed? Are there any down sides? Is it worth it?

 

You can install it yourself with a couple of hand tools for free, not too hard. Only downsides i've heard of is the alternator might have charging problems, like if you have any extra lights or a big system. Just like anything else, some see a problem, some dont. But i think with the overdrive alternator pully, it will eliminate any problems that might otherwise occur. Hope this helps.

Ryan

 

Keith at ws6.com tested an U/D crank pulley, and made 0.7 peak HP, and 5.1 ft-lb torque. Yes... that would be 7/10ths of one HP. Average gains were a little better.

The LT1 pulley system isn't going to show the kind of HP figures you might get from the old SBC setups... the water pump is not belt drive, the AIR pump is not belt driven. You've got an idle/tension pulley, the A/C compressor, the alternator and the PS pump. None of those accessories sees a lot of load in a 1/4-mile pass, so the value of the U/D pulley is questionable.

The pulley slows down the alternator, and on many cars you get into charging problems. That's why they replace the alternator pulley with an O/D pulley in the March "Power & Amp" series.... to recover the charging capacity you lost at low RPM. Of course, it also eliminates some of the power savings.

March also sells a "Performance" pulley set that includes BOTH a U/D crank pulley and a U/D alternator pulley, for max power savings. But from personal experience, going U/D plus U/D on the pulleys isn't good for the charging system.

 

I've had the March 2-pulley UDs since day 1 and have never experienced any problems.

If you go with the 2-pulleys, advise that you have an impact wrench to remove and install the alternator pulley.

Probablyl good idea just to drop by your local garage when you get to the alternator pulley.

The rest is easy. JMHO

 

Do you have any kind of sound system (other than factory, such as amp and sub-woofer), and why do you suggest stopping by the local garage? Just curious.

 

Opps. Forgot to answer your question.

Theoretically, less parasitic loss should improve performance a hair. I believe (maybe in my head) that the pulleys improvee my throttle response.

All in all besides the biggies like heads, headers and cams and CAIs, all the little things like UDs, MSDs, perf. filters,air foils, etc. should enhance the overall performance.

Its the system, man. JMHO

 

I love my Underdrive pulley set. They are buy March Proformance. I have the alt and crack and alt accually charges a little better then it did before. One thing to watch out for is the bolt that come with the set are about 1/4 in too long so it pushes the opti vent off.. I ended up using shorter bolts. I think there is a diference in the hight RPM range. The crank pulley is ALOT smaller then the stock one! Didnt need and impact for the Alt. pulley.. Since you need a new belt I just grabbed the belt on the pulley with some channle locks and use a 1/2" drive and no problem.. Good Luck, I recomend it.. Its pretty cheep, not much HP but every little bit helps.. Key thing to remember.. 5 lbs of rotating mass is equal to 100 lbs of dead weight..

Craig

 

The thing about pulleys is they are one of those mods that work with other mods. On a stocker you won't see anything... If you haven't done a cam/headers you'll see the numbers ws6.com did, but of course if you manage to get into your internals the pulleys may make more of a differance overall. A note upon modding that shouldn't be forgotten. Just like cams put out better numbers with headers - the more there is on the system, the more you'll see overall. .. but I'm not willing to risk my charging for less than 1 ponie. A TB bypass is worth more overall...