As i am seriously contemplating a twincharger system i thought i would pick everyone's minds on my possible directions of attack. After reading the successful implementation of a turbo only by rye and his observance that the m45 supercharger eats up "alot" of horsepower, even at stock speed, i wondered if you could put a larger pulley on the supercharger. I understand that the supercharger inturn runs the water pump, but what amount of difference in flow would the pump see with a 10% larger pulley in comparison to it at stock, and even running 19% smaller pulley? I mean, i know people were worrying about running the 19 because of caveatating, but that has never happened to me, in my style of driving. I guess my question is, if i was to make the supercharger spin more slowly when installing a turbo, would i benefit from unlocking those horsepower that would have otherwise been used to spin the SC? If i was to get a larger pulley, would it actually gain any efficiency? if i was to get a larger pulley, could i then change the gearing that would make the waterpump spin faster in comparison to the SC? would the pulley fit on the hub? Am i actually looking at this in the right perspective? Maybe just junk the SC and brave the troubleshooting and learning curve needed to build my own header, tubing, exhaust etc...
Any insight, from personal experience or even desk racers would be appreciated!

 

By going w/ the larger pulley you will reduce the amount of power the SC sucks away at peak rpm, but you will always have that engine drag as long as the SC exists. Larger pulley will lessen the effect so yes you are right in thinking that.

I wouldn't worry too much about going 10% oversize. Installing a cooler tstat will definitely help if there is an issue.

But remember you will never fully "gain" the HP lost by the SC even if you go oversize. That's the main benefit of the turbo-only system

 

I think that the Alta T/C kit has a larger s/c pulley. You could maybe buy one alone from them...

 

There are a few people here who have gone to a larger pulley I believe...