Finally done!!

[Nutzy19]

Well... its installed.....
I have a few last ?'s
I installed my sn89 kit on my mustang ..
timing is still 12-14 degrees BTDC ( havent changed it yet )
Plug gap is still .050 stock heat range.....
If it runs good should I still retard the timing???
Should I re gap the plugs and or go a heat range colder and why???
Its not as powerful as I hoped...only making 4.5 psi at 5000 rpm..... It takes forever to climb to 4.5 psi.. I definitely feels faster but I want the most boost I can get out of this little sn89 .. any suggestions (other than a new blower )

[F=MA]

If it works and doesn't detonate, then you don't need to retard the timing.

I use 10 degrees and .045 plug gaps but that's just what works for me. Colder plugs aren't needed and can foul at low load conditions.

It's a centrifugal blower, it needs rpm to work. 4.5 pounds sounds like it could use a little tweak in the pressure on the balls, it might be slipping a little.

Opening it up and inspecting it is really easy. Lots of experience with that here.

[speedytang]

Don't worry about plug gap unit your at WOT and the car jerks like a rev limiter then close the gap on the plugs because your blowing out spark. The 'SN' rating is 5psi at 5500 rpm on a Mustang with stock Paxton pulleys, so your in the ball park. If you can hear your engine and its not detonating check your plugs for spots if not your good to go. If your plugs have spots on the ceramic then go one range colder on plugs.

[Nutzy19]

how do I " tweak the pressure on the balls" ?? I think I have a line on an SN-93 to put in place of the SN 89...... What would I need then and how much more boost would I see? I think it would just bolt right up but would my FMU still be correct and would changing the fuel pump be immiediate or could I wait a few weeks till I have funds...

[speedytang]

The 2 units are the same except for the outer case change. Same boost and would be the same impeller unless it has been changed but probably not.

[Nutzy19]

ok heres the scoop.... Its and SN92 with a fresh rebuild on it ( still has Craigs tag on it ). My sn 89 has about 500 miles on it total in its life. I can upgrade to the sn 92 for nothing but I would have to swap pullies cause it was for a camaro and has a 3.25 pulley and I have a 4.25 pulley. What is the benefit of this and would you do it.....

[speedytang]

Really same unit.
If your interested in selling one of the head units let me know.
My son has a new project and maybe I will get him a 'SN' for his birthday.
PM me if you want to sell.
Thanks

[pavement pounde]

My son has a new project and maybe I will get him a 'SN' for his birthday.
Thanks

[Nutzy19]

It's a centrifugal blower, it needs rpm to work. 4.5 pounds sounds like it could use a little tweak in the pressure on the balls, it might be slipping a little.

How do I tweak the pressure.....

[F=MA]

To do it properly, you have to tear the unit down and reshim the races. It's less hassle than doing a jet kit on a bike, say, since there's really only one variable and you're likely to get it right the first time.

Good luck,

F=MA

[Nutzy19]

wow.... that was more vague than " tweak the pressure" ...lol

[Dirk Diggler]

I think pavement pound has a web site that shows you how to reubild the sn series.

[speedytang]

If you been reading the Forum for a while you will see that increasing the ball pressure to increase boost is not always a excellent option. The thing to remember is that impeller was designed for a certain boost range so spinning the blower harder may not give you the best boost. Example: You increase your boost from 6psi@180degrees intake temperature to 8psi@215 degrees intake temperature. Guess you got your 8psi but guess what, you just made your car perform like it has 4psi because of the density of the air and you also took a year of your superchargers life. Your better off putting a Water/Meth injection unit and run full timing and gain real horsepower without all the negatives of spinning a supercharger over its impeller boost design.

[Dirk Diggler]

you could get a VR4 upgrade, I know who has the last one:D

[speedytang]

Dirk Diggler has your only option other than going to a different supercharger if you want more boost. The VR4 pushes twice the CFM of air per psi of boost.