What are the drawbacks of underdriving your car with pulleys? Besides lesser voltage production which those of us without screens and amps wont use what else is there?

 

air conditioning seems to not work as well on some cars

 

Supposedly you can get dimming headlights on idle... electrical stuff doesn't get as much juice as before. But, I've had no issues at all with my 3 Piece Unorthodox Racing Pulley set an it's been on for close to 40k miles.

 

Why underdrive? You can get a KJR Lightweight Crank pulley that offers the same weight advantage as the underdrive pulley without the hassle of having to change belts. You still get the proper operation of the alternator, A/C, PS, etc.

 

Most people don't get underdrives for the weight advantage.

 

underdriving gives you something like 2.4 hp extra over the KJR

 

Keep in mind also if you ever want to do the Vortech or Procharger kit having underdrives will create less boost because the crank pulley will be smaller

 

Is this why my A/C does not turn on right away sometimes? It takes a few minutes or high rpms before it starts to blow cold. I never had this problem until after I installed my built motor with the UR pulley set.

 

I have the UR pulley and my AC works great. The lights don't dim at idle either. I do have a grounding kit, that may help.

 

the KJR pulley on a dyno gave 4.8 Torque and 7.9 Hp to the wheels on a dynapack dynamometer SAE corrected. Other things a lighter pulley give are quicker throttle response and when shifting the rms go down a bit quicker when you push the clutch in which helps with making quick shifts.

 

Probably true but according to UR's own website FAQ, the biggest gain is from the lighter weight.

 

Link to these KJR pullies?

I never heard of them before, then the last few weeks, I've been hearing bits and pieces of them.

I was planning to get the unorthadox pullies in a couple weeks, so now is the time to tell me about a new (and possibly better) product.

Keep coming with advantages/disadvantages too...I'm listening.

 

Our website is www.kjrperformance.com. You can get all the information you need from the site, including before and after dynos. You can also email us at sales@kjrperformance.com if you have any questions.

 

Interesting.

Is the KJR the same weight as the unorthadox pulley? If it is, it becomes a tradeoff:

Go unorthadox and get 15% more increase due to underdriving ("The rest of the gains are from underdriving, which accounts for about 15% of the total gains.") and more if you add the other underdriving pullies ("With the lighter accessory pulleys, as much as 15% to 30% more power can be found.")

-Quotes taken from unorthadox pully page on i-m-racing.com

OR

Go KJR and not have to worry about the under-driving effect and be able to maintain higher boost if you have a supercharger.

I guess those seeking higher NA- or turbo- power would be wiser to get the unorthadox set, and those with high end stereos or a supercharger would be wiser to get the KJR.

So...I guess the question that I have to ask myself is... do I want to stay NA, get a supercharger, or a turbo.....

 

The thing that steered me away from the underdrive pulleys was all the complaints I kept seeing about 1) not being able to find the right size belt 2) squeeking and squeeling of belts.

 

+1
agreed

 

You should probably decide now what your ultimate horsepower goals are. I've come to the decision that F/I is simply not for this motor and requires too much preparation and money to be reasonable. I am happy with the base power and a little boost with NA bolt ons, cams, and an ECU would be fine. I think you'd make the car "faster" simply by attending a driving school and getting some track runs under your belt as there is alot of power to handle in this beast.

 

I was planning on going with the KJR just to make things EZ, how much extra HP does that 15% add from the underdriving? I wouldnt see more than 2 hp right? I also wouldnt be able to handle underdriving causing noises, im a freak when it comes to rattles and squeeks!

 

Ok what if you were to leave all the pulleys stock but have an underdrive crank shaft pulley only. Would you still experience those common underdrive issues? Also, for an underdrive pulley, is it the lighter weight or the smaller diameter that has more of an impact in increase of performance?

 

Facts about pulleys
its been established that 85% comes from weight loss and 15% underdriving
there are 2 crank pulleys out
1 is underdrive UR
1 isn't KJR Performance
the accessory pulleys your talking about are only lighter no change in diamater

The smaller diamater crank pulley is what underdrives the rest of the accesories because for one revolution of the crank, the linear distance the belt travels is less.

I hope that answers your questions. I am an analogy freek so this may be a good example......
Take string and wrap it around your finger once, now pull the string off your finger notice when you let it straigthen out its about a inch and a half of string. Now wrap string around your wrist and mark the revolution point. Let the string loose and notice its about 9 inches in length. For one revolution around your hand you get 9 linear inches of string (belt) movement for your finger you get 1.5 inches of linear movement. That linear movement is what drives the pulleys.