Moddiction

I'm curious to what rpm some of the high boost sc guys are going to with the 1200 blower.

I'm planning to upgrade my vortech s trim to si which is the same as the 1200. I'd like to go down to a 3.2" pulley from 3.6(vortech uses larger crank pulley than sos) I'd imagine that would get me to about 17-18 psi or so. I'm running water/meth and 93 pump.

It seems these blowers do a good job when being overspun!

CoolGuy094

Calling 99SH, S2000Junky...

RAIN H8R

Some guys have run a 2.8in. Im curious as to how the blowers are holding up

Moddiction

Do you know what the 2.8 spins to blower to?

I know the vortech uses a larger crank pulley so a 2.8 on a vortech would be crazy overspinning it and would blow I would imagine. I was thinking maybe a 3.2" I could go down to but not sure if it would last as I am already overspinning it slightly with a 3.6" pulley at 9k. This is with S trim not si(1200)

RAIN H8R

I have a chart that tells you blower speed by crank pulkey dia. Send me a pm with your email address.

For paxton....n1220 can spin faster than a 1200. The impeller blades on a n1200 extend out farther than n1220. That is why the rpm limit is lower than a 1200.

I would imagine this is true for the impellers you have with vortec units.

Moddiction

Isn't it usually the bearings that give the rpm limit for the blowers? I know on a bunch of domestic cars they overspin these blowers and say the blowers love to be overspun.

s2000Junky

Faster spin = more heat = quicker bearing failure. There may be some association with the blade size/shape having an effect on heat, maybe with more air cavitation? But that’s just a guess. Besides, you want to push cooler air, not hot over spun air into the motor, or there is little benefit. I was too afraid to over spin my 1200. So I just ran it up to the limit, which was the standard Comptech 5.45" crank with 3.2" pulley, revving to 8350/8400rpm. I never took it past that. On my lower 9.6:1 comp motor I was seeing 16-17psi during the hot months, and 18-19psi during the cold days at sea level. I didn’t feel the need to push it any more and risk the blower health. There may be more in it to spin faster, as some have reported, but I don’t have any experience in that arena.

Moddiction

I'll probably go with something around the 3.2-3.4" pulley with the 6" crank pulley in the vortech kit. I have water/meth injection so I'm not worried about iat's as they are instantly cold with the water/meth which is really nice.

99SH

I've been overspining my blower for about 3 years now (track only) and have had no issues. Like s2000Junky noted heat is one of the biggest factors to consider. The faster you spin it, the most boost you make, the hotter [compressed] air comes out. Your aftercooler setup must be up to par to keep IAT temps in control. Also, as you overspin the blower you'll be operating in a less efficient region of the compressor map. You can see this on the dyno as you approach redline (HP starts to flat line as CFM output is choked).

The Novi 1200 is rated at 52,000 MAX RPM. To figure out where you are use the formula below:
Blower rpm = (Crank pulley size/Blower pulley size)*Motor RPM*3.61

I'm currently running a 8" crank pulley and 4" blower pulley which puts me at 61370 RPM at 8500 engine RPM (overspin by 18%)

Now, consider the amount of time you spend above the Novi redline and you'll see it's not significant. In my example above, at 7202 engine RPM is where I hit the Novi 52k redline. Plot below. Dashed green line is 52K RPM.



Given this, you're not overspinning the blower at full duty-cycle so it's not as bad as it seems. The time you spend above 7202 RPM is minimal and the early torque at low end is a nice addition on the track for corner exits.

Moddiction

Thanks for the info. Looks like I'll try the 3.2" pulley out with si trim and see if my motor is healthy enough for upper 400whp. 422 right now on 3.6" pulley with S trim blower.

Found this link for checking blower speed with vortech kits.

http://www.vortechsuperchargers.com/page.php?id=33511