Alright guys, some of you might have seen my thread on how im shooting for 400whp, and im only making 310 right now @ 13.5lbs of boost, and the consensus is that im gonna need a larger turbo, and i decided im gonna stick with precision.

Which one should i get? And which A/R ratio and Trim level? i have the precision SC50 right now, .63 A/R and 76-trim. Its not fully spooled till 5,500rpms. I was looking at the Precision SC44 which is rated to like 565hp (not sure which a/r and trim to go with)...would a smaller trim and a/r ratio (.48 a/r and 69 trim) spool a little faster? or should i go with the larger a/r ratio and trim level (.63 a/r and 76 trim).


Modified by B00STED Si at 6:56 PM 5/16/2005

 

Race gas and keep the turbo you have. DSM'ers have made close to 500 WHP on the turbo you have, theres no reason to go bigger.

 

well my problem is i want to stay at or under 17lbs in order to hit 400hp. i dont want to run anything more than 17lbs on stock heads, stock crank n stock sleeves.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B00STED Si &raquo;</TD></TR><TR><TD CLASS="quote">well my problem is i want to stay at or under 17lbs in order to hit 400hp. i dont want to run anything more than 17lbs on stock heads, stock crank n stock sleeves.</TD></TR></TABLE>

lol, why? The stock crank, for one, is used in tons of 600+ WHP setups, you have nothing to fear with the stock crank. Dump pure C16 in it and you don't have much to worry about on stock sleeves either. I have a friend running an LS motor at 8.6:1 and he runs 17-18 psi on the stock sleeves and 94 octane pump gas, and 28 psi on straight C16, with a T3/60-1 HiFi, that car sees lots of action on the street and the track with regularity. Keep in mind when the spark lights off in your cylinder you see 700+ PSI of pressure, do you think 10 extra PSI from boost makes any kind of a difference? ****, a 12.5:1 stock sleeve motor is hitting 250 PSI of cranking pressure, and your 9:1 motor definitely isn't going to hit 225 cranking PSI, so even using that comparison you have nothing to worry about. Don't worry about boost pressure, worry about horsepower. And just looking at horsepower, 400 WHP isn't a whole lot especially on race gas. Trying to make 400 WHP or more at 17 psi or less is only going to make you run a large turbo that sacrifices streetability. You're going to run race gas either way, so keep the 50-trim and have a nicer powerband.

 

yeah....youve got a point. What about heads tho? i hear past 17lbs of boost it gets pretty dangerous, at least with stock springs and retainers.... and how does running a larger turbo sacrifice streetability? just wondering, thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B00STED Si &raquo;</TD></TR><TR><TD CLASS="quote">yeah....youve got a point. What about heads tho? i hear past 17lbs of boost it gets pretty dangerous, at least with stock springs and retainers.... and how does running a larger turbo sacrifice streetability? just wondering, thanks.</TD></TR></TABLE>

It could be a problem at close to 30 pounds of boost, that is a fair bit of force pushing down on the valves. So get a set of new springs/retainers for &lt;300 bucks, done. Running a larger turbo sacrifices streetability because of more lag. A 50-trim spooling at 4000 is a lot more fun to drive than a T3/T67 spooling at 6000-6500, you get into boost quicker and you don't lose boost on shifts as bad.

 

The sc50 should be solid for your app, I plan on running one on my SOHC but with a 49a/r not 63. I fear if you go bigger you may even run slower at your target boost.
I would turn it up to 18-22psi on proper tune if I had that car of yours..

 

yeah, well i guess ill see how i do on the new ignition coil and then the gsr cams at 17lbs, then ill decide what i need to do.