General SN Question

[JBeezy53]

Ok, first off I just got a SN92 that had been previously rebuilt that I will be putting on my 89 Mustang after I get smogged. For now I will stick with it but I'm sure I will upgrade to a VR4 soon after.

I have done a lot of research on the SN s/c and all I hear from people with newer s/c is that the SN series doesn't last that long and will break. I have though seen many people with SNs going 100K miles w/o a rebuild. I myself believe that the SNs are good and will last as long as you don't spin them past their capabilities.

So I guess my question is why do many people say that the Sn series s/c are crap?

[speedytang]

Because they put a 3" pulley on the unit and took the engine to 6k rpm and the unit failed. I have seen the Vortech units fail under the same conditions because of problems. I have combined mileage over 125k miles now on my units with no failures and I put out more power at lower engine rpm then those with a Novi 2000. If the unit is set up correctly you will get 8psi out of the 'SN' and 50k+ miles on a unit you can rebuild yourself.

[JBeezy53]

Thanks Speedy, thats exactly what I thought. How would I set it up to get 8psi? Also is there anywhere else I can get the VR4 upgrade besides Paradise? I talked to Craig and he said he won't mank anymore until theres more interest.

[speedytang]

If you have a modified engine list what you have engine,transmission and gears.

[JBeezy53]

Stock block
GT40P Heads
TFS Stage 1 Cam
Performer Intake
255 LPH pump
19lbs injectors (Not sure what I want to upgrade to yet)
All the usual bolt ons
T5
3:55s

[speedytang]

What size is the lower crank pulley for the blower

[JBeezy53]

6" Crank Pulley
6" Water Pump Pulley
4 1/4" and 4" S/C Pulley

[speedytang]

Get at least 36lb injectors and trash the FMU to get a good fuel curve. With a 6" crank your going to need a 3.75 blower pulley to get 8psi and shift at 5800 rpm.

[JPJP]

http://www.superchargerhelp.com/showthread.php?t=4907

SEE ABOVE THREAD FOR A HELPFUL SPREADSHEET AND CHANGE VALUES TO CALCULATE YOUR BLOWER RPM'S. THAT COMBINATION WILL PUSH YOU ABOVE 39,000 RPM's (STATED MAXIMUM RPM FOR A SN SUPERCHARGER). SHIFT BEFORE 5500 RPM (ENGINE) TO KEEP IT SAFE.

[speedytang]

With your Cam and Heads you must take it to 5800rpm to get the numbers(Horsepower)you will only be over spinning the unit for 3-5 seconds between shifts.

[Nutzy19]

I though I read somewhere that the max blower speed on the sn was 39k but later re-rated to 42 or 45k due to the 3 lip seal not tearing itself apart...