I'm trying to understand this so help me out. Ok, when you change the underdrive pulley it says it slows accessories like the power steering, etc.. to give the engine more hp. How much does it slow the accessories, is it a good idea for a daily driver, does it make it harder to steer,etc..?? Also, how much hp does it add. I might sound like a total retard but i'm curious. Thanks

 

If I remember correctly, that pulley is a different size. It will run the accessories slower to devote more power running the car and less to powersteering, alternator etc.

 

Yes but how much does it effect these accessories?? Does it make the car harder to steer, alternator charge less, etc. or is it not noticeable?

 

Good Question. I was wondering the same thing, daily driver-wise. Did you try searching first? You can see gains of up to 30hp with the ASP Pullies for little work. I believe you can also purchase the Alt. pulley. You will need to change the ACC and A/C belts. They should give you a P/N and info for the belts where and when you buy the pulley. Cheap power, though.

 

I've had the underdrive pulley (crank pulley only) for a year now. on an automatic, you MIGHT get a slight dimming of the interior and exterior lights at idle and in gear (idle speed is like 600 rpm in gear). It's not severe though and once you come ANYWHERE off idle, it goes right back up to full charge.

ther'e aren't any steering issues or anything. if you're running a huge stereo it might be a little tough but i can blast my stock system, have my accessories on and it still works fine, just a LITTLE bit dimmer, but again ONLY in a warmed up idle.

 

i think the ASP pulley is somewhere around 25% underdrive.

it has no affect on the AC or powersteering. some people claim that it can prolong the life since they are turning that much less.

as for alternator, as stated it CAN affect charge at low idle situations but most cars are not at that speed very much. i have an M6 and notice not change in lights unless i bog the engine down to 6-700 when taking off in 1st.

the amount of power gained is arguable. company claims 10-15hp...but that is pretty exagerated. it is probably more like 5hp and 5# torque. some people also claim the engine revs faster, which i agree with, but that is pretty subjective.

here is a dyno graph for an underdrive pulley on an LT1. now granted the LT1 is a slightly different animal..but you get the idea.

if you are looking for easy boltons and don't mind the $225 price tag...it's a good mod. noticable on the street...not really....worth while in the end...i think so.

 

It's a good mod that's easy to do. I noticed that the engine does rev a little faster, but haven't noticed any accessory power loss. I've heard that if you are running a system in your car you might want to get and alternator pully as well.

 

Has anyone had problems with the belts slipping off? I was thinking about getting the UD pulley....SLP sells the pulley with "Extra-tall" sides to eliminate the thrown belt. Ideas..?

 

had a pulley on my 87 iroc with a TPI for 3yrs, one on my LT1 for 2 yrs, and i've had one on my LS1 for almost 2 yrs...

only thrown one belt...on the LS1...happened on start up one morning.

15mm wrench and 2 mins and it was back on...no problems since.

 

Do you have to get a different size belt since the pulley is smaller, if not will the belt slip after installing it?

 

yes you need a differnt belt...the directions tell you the size needed

 

for an LS1 i believe the number is 510K6 (or in other words a 51 inch, 6-rib belt).

 

Is it a noticeable gain like a lid installed or what? I was thinking about
maybe getting one this summer.

 

no...i didnt think so...

like stated, some feel like the engine revs quicker...but it's pretty subjective.

realize it's pretty unlikely you'll feel 5hp...

 

the pulley gained 7hp and 5 lbs of torque in this magazine article i was reading for the LS1. pully is 5 lbs lighter too.