Pulley size effect boost?

[06Charger R/T]

So I'm looking at a vortech or procharger because I got bit by the racing bug. I replaced my under drive pulley on my 5.7 with the slp25% UD pulley. Will this effect the boost I create I remeber reading this somewhere but I can find it on the search if someone could post the link or answer my riddle. could i get a different size pulley for the supercharger or would that overheat or damage the supercharger? or would it be easier to get rid of my brand new slp and go back to factory? I want to run at the recommended 7 psi.

[Sjohalsrt8]

Im not 100% sure but I think the under drive pulleys make you gain boost the blower would produce more psi, not sure tho but I think that's the case

[nbookie]

if you know the pully size then use it with this calc. Impeller Speed Calculator | Vortech Superchargers

u can also call vortech with your pully size and they will be happy to add it up. I would think it would rase the PSI a bit.

[bozo4]

I thought under drive pulleys loose boost and overdrive pulleys gain boost.. Please correct me if I am wrong cos that's how I have always understood it...

[Vagabond]

I thought under drive pulleys loose boost and overdrive pulleys gain boost.. Please correct me if I am wrong cos that's how I have always understood it...

You are correct. An under drive pulley makes power by spinning the other pulleys and accessories slower. In this case your supercharger pulley will be spinning 25% slower than it would at stock speed. You can compensate for this by either removing the under drive or by putting a smaller pulley on the supercharger. The blower manufacturer should be able to provide the proper pulley size required.

[06Charger R/T]

I am pretty sure 99.9% it would have less boost. So if I put on a smaller pulley to make equal boost would it over heat or cause more strain on the blower?

[bozo4]

To give an idea.. I run a stock pulley with a 3.1 sc pulley and make 11psi.. at 25% less you would think I may achieve around 8.25psi.. So basically whatever the target psi of a pulley is you may as well drop a quarter off it.. You are going to have to get to the balance to pin it anyway.. in my oppinion you should either put the stock one back on or get yourself an overdrive one... But as far as spinning and heating the sc up it it more relative to the boost you will be making.. eg spinning it to 8psi with a 25% underdrive and a 3.1 pulley would be no different to spinning it with stock pulley and a 3.5 sc pulley.. Still making 8 psi just in a different way. Only thing to consider is your belt wrap on the much smalley pulley.. Hope this helps.