MelloYellow

What is the rule of thumb with overspinning blowers past their stated redline?

I believe 5-10% was ok last time I talked to Vortech. They noted that all SC's have belt slippage, so even at 5-10% over on paper you are not achieving those blower RPM's due to minor slippage.

Any thoughts?
Am considering going 4-7% over my T-Trim Redline (55k).

TIA.

P.S. FWIW, my S-Trim made peak power at 4-5% past Redline (50k).

gator's 99TA

iTrader: (2)

on the old s-trim, we were truning it to 54K rpms and never had a problem for a couple of years it was on there. this new YSi trim we are going to turn to 58K rpms ( but it is rated to 62). i personally wouldnt overspin a blower more than 5-7K over its max.

i also agree that most people dont account for the 10% slipage at top rpm if using an 8 rib.

MelloYellow

Good note on the 8-Rib.
FWIW, I'm running a 6-Rib w/Secondary Cog.

Will have to have ASP custom make the new Cog I need to gain more psi/rpm's.

Pro Stock John

iTrader: (34)

Big dog YSi guy told me that I should factor in 10% slippage to my setup.

MelloYellow

Cool.
So 10% rule holds for both 6-Rib and 8-Rib slippage?

Pro Stock John

iTrader: (34)

I would think so, but what is a secondary cog?

MelloYellow

It's the belt setup for the C5 Vortech kits.

Primary drive is a 6-Rib serpentine. There is a 3.60" SC Jackshaft pulley on the 6-Rib serpentine. There is a jackshaft that goes thru the Vortech SC bracket. On the rear is a 32 Cog Pulley attached to the same jackshaft the 3.60" 6-Rib is on. The Supercharger itself has a 28 Cog pulley. Cog belt between the 32 and 28.

If something is going to slip it will be the primary 3.60" 6-Rib in our setup.

MelloYellow

Not my car, but here are some pics:

1st Pic = Belt wrap around 3.60" 6-Rib w/loose cog belt in background.
2nd Pic shows Cog Side view.

Schurters LT1

iTrader: (2)

How do you do the math again to fig out the blower rpm

NA$TY-TA

iTrader: (21)

crank divided by blower pulley size X the step up ratio of the blower X the max RPM you shift at.

like my old setup
7.25" crank pulley divided by my 3.4" blower pulley= 2.132
2.132 X 4.1 steup of the blowers internal ratio= 8.742
8.742 X 6600 RPM shift point= 57,701 RPM's

Kyle

MelloYellow

Calculator for a C5 Vortech setup is here:
http://www.vortechsuperchargers.com/...edv-2jack.html

greentahoe

iTrader: (2)

Im wanting to try a smaller pulley on my S trim. Right now Im shifting at 5800 and seeing almost exactly 50K. Id like to go to a 2.95 pulley and spin to 6200, at that point Id be seeing 56,7XX not factoring in slip.

MelloYellow

You'll make a bit more power and also shift your powerband down a little maybe.

greentahoe

iTrader: (2)

So the S trim would be alright spinning almost 7K over its max RPM, of course not factoring in belt slip?

MelloYellow

I believe Vortech said it was ok to go up to 10% over due to belt slippage, but you could call. I know they shipped S-Trim pulleys to me that spun the blower to 56k as the highest they made/supported even tho that carried no warranty. Past that the didn't really advise spinning much more.

I made max S-Trim power at 52500rpm. Power started falling off fast at 55000rpm, I believe due to heat and inefficiency. Max efficiency is at 45000rpm I think. Not factoring in belt slip.

greentahoe

iTrader: (2)

Thanks. That was what I was looking for. Im pretty sure I be near the 52500 if I raised my shift points to 6200. I guess I'll see where I am after the cam swap and see what kind of power it makes with the higher shift points. Thanks.
One more..... I seem to remember someone saying that the upgrade to the T trim hybrid was $900. Does that seem about right? Thanks alot.

gator's 99TA

iTrader: (2)

the trading in never seems to add up. esp for what you can sell your head unit on line. as for overspining, i think it is ok to overspin by 10% as long as you 1) account for overspin 2) it depends if it is not a daily driver. if you put 10 thousand miles + on your blower a year, then it is going to adversely affect your blower as compared to the weekend warrior.

greentahoe

iTrader: (2)

I wasnt going to trade it in. The program for that is absurd. It would end up costing me almost 2K to do a trade in. There is a program where you can send in your blower (S trim) and have it upgraded with a T trim impeller and some other stuff. Another guy on here did it. If I remember correctly, it was around $900.
Thats one of my problems. This is my daily driver. I dont want to worry about th blower seizing up on me. I may just bide my time and get some other stuff done and see where Im at. For $900 though, that seems like a pretty good deal.

MelloYellow

Ya, the trade in for a T-Trim is $950 or so.
They make a quiet SQ T-Trim Hybrid if you ask for one.

gator's 99TA

iTrader: (2)

oh ok. for 900 dollars, getting the T trim is worth it. more efficient boost is awesome. for the money, definately worth it if you are at the end of the S trims capability.