View Full Version : pulley question

04-24-2006, 01:47 AM
was curious as to which as to which setup is best 2.76 or 2.93 and 4# lower?

What exactly is the point of lower vs upper. Ive heard people say if you put a lower on you'll gain tq why is this? Will you not gain = amount of hp as well as tq?

Feel free to elaborate with any info on pulley setups that you may have. I have a brand new set of bf idlers snub idler and a 2.76 upper. I'm waiting to install it till I get my lfp heat exchanger but ive been reading about lower pulleys and people saying to get lower to gain tq.

I've been considering getting a ported blower to just waiting to see what the best options are.

04-24-2006, 07:00 AM
I have not pullied yet so my experience is nill. However, a lower pully will reduce paracitic losses as well as change the belt speed. Consider the lower and upper pully as a gear ratio and it takes a certain required amount of HP just to rotate the rotors of the supercharger. A smaller SC pully increases the load (less leverage) and to compensate by changing the lower crank pully to overcome that load increase. Considering the pullies, has anybody ever considered changing the other ones on the other belt? (typical ones changed with N/A motors, ie... water pump and the inner crank pully)

04-24-2006, 07:03 AM
You'll get varying opinions, but here is what has worked for us...

On an unported blower, the upper+lower combo is not very benefitial. Either one or the other works best. The upper only will most likely yield higher HP numbers, while the lower only will yield higher torque numbers. A 2.93 upper only will get you approx. 440-450rwhp, while the 2.76 approx 460-465rwhp.

On a ported blower the 2.93+4lb lower has seen the best results, but now Stiegemeire is saying not to run this combo, all though few have seen supercharger failures. This combo will likely yield 500+rwhp and close to 500tq :thumbsup:

04-24-2006, 11:11 AM
Since it is a ration of the two we have found the upper and lower combos to perform very strongly on ported and unported Eaton cars..for someone just starting to add boost it is important that you have a good foundation so you will see max performance from any mods you do..this is accomplished with a straight in air source CAI and aftermarket exhaust..I like to see guys who are just doing an upper to start with go with a 293..this is considered the sweet spot for the stock Eaton where it gives max performance and efficiency..it is also a good choice if you want to add a lower..you will not have to remove it and you can go with a larger lower that will do 2 things... it will give more belt surface for the belt to contact with thus helping to eliminate belt slip which causes boost drop and it gives better torque..the larger lower you can go with obviously will give you more belt surface but it will also give you more torque and it will come on sooner in the rpm bands and stay longer..using an ultra gripping surface blower pulley is also my recommendation and we only use the RR ultra grip pulley..it is the original patented pulley and anything else is just a copy that doesnt have all the benefits of the patent.

and as always having a tuner who has vast knowledge and experience doing your tuning goes a long way to acheiving your performance goal..Rick has many customers with just 293 pulleys running in the 11s

we have not seen any issues with our ported blowers when using a upper and lower combo or with running over 16# boost. our porting was designed to remove only enough materail that the structural integrity of the case is not compromised...we have seen very nice solid results with our port..high torque and HP