[vex]

Originally Posted by RETed

Twins would give you the ultimate set-up, but getting the sizing right + increased cost / labor due to all the custom work might not be possible for you?
If you do have the resources to go individual twins, I wholeheartedly agree with that choice...

But since the title says just "turbo"...

My philosophy with turbo sizing is to always run as big of a turbo you can afford which will spool decently and keep the boost down.
You can run smaller turbos for better spool, but you end up jacking the boost up to compensate.
I'd rather keep the boost lower and run the larger sized turbo and just size down the turbine A/R if really needed.
For single turbo set-up's, I will not go anything smaller than a GT3582,

I set up a recent customer with an HKS cast collected turbo exhaust manifold, 60-1 / O-trim / 0.96 A/R turbine, Tial 44mm wastegate that had full spool by 3,800RPM.
Not the most responsive, but it does give us a baseline.
Yeah, the O-trim is considered small, but we were pleasantly surprised it ran a flat torque line all the way to 7kRPM at 12psi.
The numbers were 280 @ 12psi, 300 @ 15psi, 320 @ 18psi on a Dynapack, so this turbo will hit a true 350 @ the wheels at the edge of pump gas on a DynoJet.
Now, let's look into the spool portion of this set-up...
The HKS cast, collected turbo exhaust manifold is probably the worst flowing out of all the options out there.
Almost any tube turbo exhaust manifold will flow better, which means better spool.
Going with a more efficient flowing tube turbo exhaust manifold should drop the full boost spool down to 3,500RPM (or lower) easily.
Going with a full, divided set-up - i.e. keep front rotor versus rear rotor exhaust pulses separated through all the way to the turbine housing (divided turbine housing, twin wastegates, etc.) - and you're looking at low 3,000RPM...3,300RPM...3,200RPM full spool.

Having a manifold as described above I can tell you that I hit positive pressure as low as 2,500 RPM and can achieve my full boost pressure around 3,000 RPM (and this was on a horrible crappy tune). The only thing I would have done differently had I known about it would have been to re-orient the wastegate feed to be better flowing rather than what it currently is.

Add a BB CHRA, and you're looking at 3,000RPM full spool - i.e. GT3582R should be full spooling right at 3,000RPM if your system is efficient.
Drop the turbine A/R can possibly net you full spool in the 2,700RPM...2,800RPM range, but you might take the hit on losing some top end due to choking the exhaust down.

I'm close to this--but I think it might just have been the tune itself causing the issues. My turbo is a Turbonetics inc T60-1 with ceramic ball bearings.

Compressor options?
I can only give you opinions on Garrett models, since I'm most familiar with them.
60-1 is popular, and efficiency plateau centers around 0.7 ratio or about 10psi.
T04E "60 trim" is another option that compares very similarly to the above 60-1 but runs more efficient at higher pressures - efficiency plateau centers around 15psi.
GT-series is the evolution into the most current Garrett technology in terms of compressor (wheel) design.
GT3582 compressor wheel can support your power goals; you can go with a GT40 series compressor wheel and step up in size.
Problem is with GT-series BB CHRA's is the price!

I know the Borg Warner turbos have been getting popular and are economical, but I can't comment on their abilities cause I have zero experience with them.


-Ted