I tried a quick search but didn't find what I was looking for. on the Vortech website I saw a 7 inch crank pulley and 2.75 inch blower pulley = about 52,500rpm at 6000rpm engine speed. The compressor map only goes to 50,000, so I'm guessing that would overspeed the blower? Anyone else running this combination? Is it safe or not? I'm only seeing about 8lbs on a 7in/3.33in combo but wanted to ask before I swap things out. Thanks.

 

What intake tube are you running? If it's the stock Vortech flexible line, that's probably limiting your boost. I'm seeing 10# of boost with a 7"/3.3" combo through the Vortech Aftercooler with a Brad Brand solid intake tube @ 6,000 rpm.

 

I've researched this quite a bit when I was considering overspinning my T-trim. From what I can find, the blower is mechanically sound to overspeed, but the efficiency drops fast. The Renegade cars waaaaay overspeed theirs, but I'd bet money they don't have the factory Vortech impellers. They probably convert them to a turbo-style impeller that is efficient at very high compressor speeds.

Mike

 

Thanks to OBE1 and Mike for your replies. I'm still unsure so I thought I'd offer more info and maybe ask another question or two.

I have a Brad Brand pipe but don't have it installed right now. It's a steady 8lbs and I sprayed a little "belt prep" just to see if it was slipping (same boost, no slip). I agree the convoluted "drier" pipe isn't the best. I plan to upgrade a few things at once. I have ported MAF ends (will keep my stock ones if tuning becomes an issue), the Brad Brand pipe, and the 2.75 inch blower pulley. It's running well (11.8AFR at WOT) and isn't knocking, this on crap gas (91/93 mix) a mild/safe tune on a warmish day. One small reason boost might be a little lower is the home ported heads (stock valve sizes though) and a minor blower cam maybe? I've also gone with a 58mm TB and it's a very sound car mechanically (no boost leaks, tuning issues). Drives like a stocker until you step on the gas, then it's a whole different animal. Do you think the bypass valve (blow off valve?) may be venting my excess boost? It's the stock vortech plastic part. Doubtful, I know. Just thought I'd throw out as much info as possible.

Back to the overspeed, if I'm reading the compressor map right is 52,500rpm around 63% (in)efficient? Not good but I do have alky injection which would hopefully drop intake temps a little. Am I reading things right? Should I hold off on installing the pulley? Maybe some of the other members (rkrause, etc) could offer some advice as well. Thanks again for your time and help.

 

I recently upgraded my stock Bosch bypass valve with a Bailey DV30 (learned about it from the turbo crowd); didn't see any difference in performance. The stock valve is prone to ripped diaphrams that cause a vacuum leak, but when healthy will support 10 psi.

 

Thanks OBE1, I kinda thought the stock valve was fine. So will 52,500rpm be a bad idea? Too many rpm, too much intake heat or am I reading things wrong? I'm seeing 8psi now, thought the mods would net maybe 10psi? I know it's hard to predict but how are others getting 12-15+ psi, swapping to a T or YS trim? Thanks.

 

When comparing a T to an S trim, keep in mind that the T won't make any more boost, but it will have a higher efficiency.

 

Asked the same question to a rep at vortec, he told me the calculations dont allow for belt slip (8- 10 %) and the head unit was safe for at least 10 % overspeed as long as I had a bypass that could deal with the high volume of air so the input bearings would not get damaged.

John

 

Just how much are you willing to bet?

 

If they don't then I have a great idea on how they could pick up some compressor efficiency.

 

but that would be against the rules. These guys do get torn down and it is checked .
I overspin my YSI at least 10% with cogs, so no belt slip .

 

how do you do the math to fig in the belt slip...I no if you go to the Vortech page and enter all the info it give you blower rpm but! then do you - by 10%

???

 

Just skimming through the Renegade rules, I don't see where it outlaws changing the impeller in the blower.

http://www.worldfordchallenge.com/rules_renegade.html

According to Jim Reichard (www.reichardracing.com), the Renegade guys are spinning those YS's to 75,000 rpm (15% overspeed) and making 35 psi boost without Cog belts or intercoolers.

According to the YSi and T-76 compressor maps, at 75000 rpm and, say, 80 lb/min, the YSi is somewhere around 60% efficient (though it's hard to predict since it's way off the map) while the T-76 is around 70%.

 

we run factory unmodified YSi impellers... the impellers are CAST, not BILLET so its not simple to just carve a different impeller up.. I have been running the same YSi (first one made) since August of 2003 with zero probs.. I spin my blower about 70k THEORETICALLY with a 8rib serpentine... I have measured about 10% belt slippage..

BTW, that Max RPM is an efficiency max... it will make more power above that but with a rise in air charge temp.

 

You can overspin the s/c but make sure your bov is able to vent the VOLUME of air you are pushing.


DAYUM!
What's the flyin_hawaiin doing on a Chevy board ???
It's nice to have a competitive Renegade racer offering help on these boards!
DonB.

Guess you heard what's going on with your old X-trim.