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770 Posts
I am sure you will like the TS VF58 on EJ257 and the extra top end above the VF56 is a welcome addition.

Perhaps you can ask ASEL to calibrate your ECU since they have a lot of experience with this turbo.

I myself is currently about to get a new ECU calibration since I am relocating the IAT to the intake manifold using Spec C IAT sensor and re-purposing the rear 02 sensor for wideband. This time by a German tuner. And this time Aquamist will be utilized as part of the tune.

770 Posts
Sorry, it's been a while since I last posted.. so here's a quick sneak peak..

A huge thanks to Giorgio @ Advanced Sports Engineering for this rare, beautiful, engineering masterpiece.. I almost feel that it better belongs in a museum glass case rather than under the hood of my STI.

JDM STI S208 IHI VF58 turbocharger.. twin scroll, ceramic ball bearing, billet compressor wheel, TiAl (titanium aluminide aka Gamma-Ti) turbine wheel & shaft, and custom CAD/CNC machining & porting.

The legendary VF58 that few know exists.. let alone have ever seen.

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Custom profile 6+6 billet compressor wheel w/ extended tips:

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The TiAl (titanium aluminide) 9-blade turbine wheel & shaft:

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Optional big port (gasket matched) twin scroll turbine housings available:

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More OEM S208 goodness:

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I look forward for your review!

770 Posts
Me too 😁 Thanks for your inspiration for this build!

I've yet to decide on a downpipe.. I'm leaning towards the HKS or Moore Power TruDivorce downpipe. I'd love to find a high flow R205 downpipe that's not $1500-2000+ USD 🤣

I wish I could just use COBB's new GESi catted downpipe.
The only reason I bought the HKS is the dual cats. Don’t bother with oem downpipe.

770 Posts
Sorry to disappoint! I have all of the parts now, just need to order the wideband O2 for tuning. I plan to do the install in two phases:
1) Install the turbo & tune on stock injectors (will max out IDC).
2) Upgrade injectors & install flex fuel kit for E85.

I plan to do the first round of calibration myself via road tuning. I will rent some dyno time once I upgrade to E85 for torque optimization since I won't be knock limited.

I also plan to do a "lag torture" test with the VF48 & VF58 to measure the lag time to peak boost & torque.
Ahahaha. Is alright man.

Well we look forward for the results!

770 Posts
I'm happy to say that my VF58 twin scroll conversion went to good homes.

The new owner of the VF58 received it yesterday. He'll be using it for a twin scroll conversion on his '18 Type RA. His first comment upon receiving the turbo was "this thing is beautiful".. it's truly a work of art.
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And of course Jeff (Archer1.8) received the rest of the twin scroll conversion parts for his ASEL VF58+ build. He'll be finishing what I started and sharing his amazing Type RA build with the forum. I can't wait to see the outcome. The main difference is that his turbo uses ASEL's "SUPERCORE" which utilizes a higher flowing (larger) 9-blade Inconel turbine wheel & shaft. Its blade profile also differs from the TiAl turbine wheel. The VF58+ SUPERCORE should be capable of higher peak power output than my VF58 at higher RPMs.

I've had quite a few people ask me for a list of parts required for the twin scroll conversion. Below are the parts that I personally chose for my conversion. Hopefully Jeff will be able to update it with anything new that he finds that may be missing/required.
  • OEM S208 VF58 turbo (Part # ST14411ZR010)
    • Rebuilt & upgraded by Advanced Sports Engineering Lab
    • Forge Motorsport Upgraded Wastegate Actuator
    • Ported & ceramic coated by SoCal Porting
  • OEM S208 twin scroll header (Part # 44610AA801) & uppipe & (Part # 44614AA061)
  • OEM S208 catalyzed twin scroll downpipe (Part # 44622AA000) & resonated front pipe (Part # 44106FG000)
  • OEM twin scroll turbo stay bracket (Part # 14421AA091)
  • PTP Lava turbo blanket & Grimmspeed ceramic coated black turbo heat shield v2 (Part # 092007) - better heat retention than OEM heatshield
  • OEM twin scroll header to uppipe gasket (Part # 44011FE060)
  • OEM twin scroll uppipe to turbine housing gasket (Part # 44011FE040)
  • OEM twin scroll downpipe gasket (Part # 44011FE050)
  • OEM downpipe to front pipe exhaust joint gasket (Part # 44165AG000)
  • Grimmspeed exhaust header to engine gasket (Part # 020001) - higher quality than OEM
  • Grimmspeed downpipe to catback donut or regular gasket (depending on downpipe) - higher quality than OEM
  • OEM ball bearing turbo oil restrictor (Part # 15194AA130)
  • OEM twin scroll ball bearing turbo oil feed line (Part # 15192AA470)*
  • OEM turbo oil feed bolt washers x2 (Part # 803910050)
  • OEM twin scroll water coolant outlet house (Part # 99078AA341)
  • Reuse or purchase new OEM VF48 turbo oil drain hose (Part # 807515712)
  • Reuse or purchase new OEM VF48 turbo water coolant inlet hose (Part # 99078AA710)
  • Misc OEM nuts, bolts, studs, etc. as needed
*The oil feed line was the hardest to source and it was the only part # that I wasn't 100% positive on because it was really hard to find any info on. I also purchased an aftermarket oil feed line as a backup just in case the OEM didn't fit during the install:

For the OEM gaskets, PartSouq had the best prices and shipping. For other JDM OEM parts you can't find there, JP-carparts had good prices as well.

My VF58+ turbo build details:
  • OEM S208 IHI VF58 twin scroll turbocharger purchased from Japan.
  • Inspection, rebuild & upgrades performed by Advanced Sports Engineering Lab (ASEL) in Italy:
    • Upgraded Ceramic Dual Ball Bearing CHRA (compared to OEM steel bearings - improved durability, reduced friction & lower inertia yielding improved boost/transient response & reduced spool/turbo lag/time-to-boost)
    • Upgraded Forged Billet Aluminum 6+6 Compressor Wheel w/ Extended Tips (Reducing rotational mass while also improving strength and flow compared to OEM curved nickel compressor wheel)
    • OEM Titanium Aluminide (TiAl aka Gamma-Ti) 9-Blade Turbine Wheel & Shaft (Significantly reducing rotational mass while improving flow, spool, transient response)
    • Ported/Polished Compressor Inlet
    • Forge Motorsport Billet Aluminum IWG Actuator (Improved durability and wastegate control/response along with higher boost levels)
    • Parts cleaned via sandblasting, ultrasound & solvents (REM Chemical isotropic superfinishing process which significantly reduces friction, reducing heat & providing better inertia which is particularly helpful for the turbine shaft.)
    • Reused components were x-ray, laser & pressure tested to verify integrity
    • Reconditioning & balancing of whole CHRA assembly on Schenck & TurboClinic machines
    • Machine work performed via 5-axis CAD/CNC
  • Work performed by SoCal Porting:
    • Turbo inspection
    • Ported Turbine Housing Inlet Scrolls (gasket matched). Ported from ~40.4mm to 43.6mm (~2980 mm^2). This results in a ~16% larger cross-sectional flow area improving spool and top-end performance.
    • Cerakote Ceramic High Temperature Coating applied to the Turbine Housing (Retaining the heat, maximizing exhaust gas energy, improving spool and reducing under-hood temps & IATs)
The VF58 is the final/ultimate/best/rarest OEM turbo made by IHI for the EJ powered STI. It was only available on the JDM S206, S207, Type RA-R & S208. It's considered the "holy grail" for us diehard JDM Subaru enthusiasts that love rare OEM+ parts.

No expenses were spared when rebuilding & upgrading this turbo. Only the best parts were used.. Twin Scroll + Ball Bearing + Titanium Aluminide (TiAl) Turbine Wheel & Shaft. I took it a bit further and upgraded to a Forged Billet Aluminum Compressor Wheel, Ceramic Dual Ball Bearing, Ported Compressor & Turbine Housing, Ceramic Coating, etc... It’s essentially a twin scroll EFR turbo with OEM fitment & reliability. Perfect match for a Type RA or S209.

All measures were taken to provide maximum efficiency & boost response (aka spool) while also increasing the flow rate for the larger displacement EJ257. Durability and heat retention were also top priority. This far exceeds OEM quality, output, durability, tolerances, etc. The turbo will spool faster than the VF48 with significantly better part throttle & transient response. The top-end should be comparable to (or slightly better than) the S209's HKS turbo or the new IHI VF48 HF as the compressor wheels are similarly sized between all of the turbos and the VF58's 9-blade turbine wheel is less restrictive. Depending on the mods, fuel & dyno.. this turbo should easily be capable of ~350-400 whp. However, this turbo was designed for maximum efficiency and response (area under the curve), peak power gains are a secondary benefit. It's a rare engineering masterpiece for us Subaru enthusiasts. It's the modern turbo setup that Subaru should have given the EJ257, especially the S209. Twin scroll, dual ceramic ball bearing, forged billet aluminum compressor wheel, titanium aluminide (TiAL) turbine wheel, ported, ceramic coated… Meanwhile even the S209 stuck with the ancient, inefficient UELH, single scroll, journal bearing turbo setup.

If anyone has any questions about the conversion or needs help sourcing a turbo, just let me know! I hope that this thread will server as an inspiration and good reference for others interested in the future. I'll be sure to post an update once I have dynos from the new owners ;)

I can’t wait to see for the result!
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