I want to had boost to my 300 rwhp combo. A friend have a YS-trim kit for sell, but im not sure if its not a bit to bit for me. Is it possible to make around 8 psi with this blower with out probleme ? Or its made for big boost only ?
I read an article in one of the mustang magazines the other day. They took a Y-SI blower and pulley'd it to make some high boost numbers...like 18 or something crazy like that. Then they put a vacuum controlled wastegate/boost controller on it set to like 12 psi. This allowed the blower to spin up really quickly and make more boost lower in the rpms. Once it saw 12 psi it dumped pressure. Unlike a bypass valve thats either open or closed a vac operated wastegate can partially dump pressure. This gave the car almost turbo like torque and HP curves. It was really an interesting article....perhaps you should look into it a little more.
The idea is excellent for street cars who dont want to spin to 6500 rpm just to get decent boost. They did a before and after comparison...and the difference in the power/tq curves was astonishing...especially below 4k rpm.
If you can get a good deal on the Y-SI then i would say go for it...and spend a couple hundred bucks on a nice boost controller/wastegate setup.
I don't think it will go that low even if you tried. If it did, it will be very unefficient. The size of that unit is going to take quite a bit of power just to turn it. It was never intended to be put on a 300rwhp motor. They've also been known to flex the brackets and toss belts more common than most blowers. The T and YS/YSi trims have always been known as belt throwers.
Even on a high flowing motor you'll only get the YS down to maybe 12-14psi with the largest blower pulley and a small crank pulley. That specific kit shoudl make 18psi easily, most run in the 22 range. Pulleying it down will really make that blower lazy and very, very innefficent as mentioned above, you will not be happy. It takes about 80hp to turn that blower