A-trim install on 95 Cobra

[David1969]

I'm preparing to install an A-trim on my 95 Cobra. I'll be using a 2.95"/7" combo. Question is: How fast will the blower be spinning and what is the max it will spin at? I do not want to overspin the blower and cause it to fail prematurely. I am uncertain how to calculate this value.

Secondly, i have been informed that i will NOT need an FMU, bypass valve or BTM for the A-trim install. Is this correct?

Thanks in advance,
David

[5LVENOM]

If you are making over 6psi(which you probably will with those pullies), you will need some sort of FMU and BTM and bypass valve. The vortech website will show you how fast you'll be overspinning that A-trim. www.vortechsuperchargers.com

[midnight]

The formula for calculating sc speed is Crank pulley Size (7") times stepup( "A"= 3.45)times rpm shift point(say 6K) divided by the supercharger pulley size(2.95) So 7x3.45x6=144900 divided by 2.95=49119..The "A" trims max efficiency is 40k & max impeller speed is 45k & yes u can over spin, but not going to gain anything but poss detonation due 2 heat.Further u r going to have 2 have at least an fmu or bigger inj's....

[David1969]

Thanks for the help. I was able to plug in all the data at vortech's support site to determine impeller speed. If i choose the 5500 rpm as a shiftpoint, I get the speed of 45025.42 on vortech's calculator. If i keep the 7.00"/2.95" combo, i assume it will be ok to just shift at 5500 to avoid overspinning the blower. Is that correct?..or should i go with a 3.12" crank pulley so i can take it to 6k rpm's?

I will be running a 12:1 FMU with the system so i should be ok with the FMU and my 24lb'ers.