(EDIT 7/3/2013: Added new link with detail on IHI turbos, includes VF36 airflow rating!)
To go along with my Engine build thread here at viewtopic.php?f=5&t=52205, this will be the thread for discussing and selecting an appropriate turbo to match the power goal of 450-500+ WHP while maintaining some level of daily drivability / streetability and at or near stock reliability.
I have a VF36 twin-scroll ball-bearing turbo with the titanium compressor wheel and shaft that is good for up to 400HP, destined for my 1994 SS with a RobTune.
This thread is for selection of an appropriate turbo to match my 1991 SS's upcoming build, which will involve full forged internals.
I have gathered some good links with info on reasonably-available turbochargers below for reference, which is what I've been reading lately.
There are a couple reasons I'd like to stick with a Subaru turbo for this build, mainly the reliability factor, but that may not be feasible for the power levels I desire. I briefly researched Garrett T3/T4 turbochargers during the period when I was turbocharging my '99 Saturn SC2 (ended up with a T3 on a custom manifold before it got wrecked), and have looked into some TD05 Mitsu turbo options (maybe an 18G? 20G?) as well... but the actual selection of the turbo is proving to be quite difficult with all these options.
I'd like to try and save money on this build but I have a feeling I'll have to go with some new or custom parts in the turbo category. Or is there a widely-available used turbo model out there just waiting for my build?
As I am currently undecided on how I will go with compression ratio on the engine build, I may end up with a higher-than-stock CR to help make up for the turbo lag, but this warrants more research.
Any comments or thoughts or criticism would be greatly appreciated; as in my other thread, board consensus is important to me and will greatly drive the direction my build goes. It's hard to argue with the huge collective experience on here where consensus exists...
---------------------TURBO REFERENCE LINKS--------------------------
Info on VF36
Ver.8 STI spec C Turbo
IHI Turbos - specs & faqs - incl VF36
2ndHand Subaru TurbosVF36
Roller bearing version of the twin scroll VF37, also has a titanium turbine and shaft for even quicker spool. Same compressor housing as VF30/34, however twin scroll P25 exhaust housing provides slightly better top end output due to reduced exhaust pulse interference. This turbo is good for 400HP and used on JDM STI Spec C from 2003 onwards.
Turbos (incl. VF36)
(430cfm, 250-325whp, Modification Required)
This is the standard equipment turbocharger used on the JDM V8-V9 Subaru Impreza WRX STI Spec-C Type RA. The VF36 is a twin-scroll turbocharger that utilizes a ball bearing design, a P25 exhaust housing, and Titanium (possibly TiAl?) compressor wheel for improved spool. It is essentially a fast spooling VF34.
Expect to achieve full boost with the proper mods and a quality tune between 2800-3300rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles.