STINick's S208 Twin Scroll VF58 Conversion
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270 Posts
This is not bad for the COBB Stage 1, much better than I'd imagine. Thanks for doing the testing and writing this up!
I have an OEM S208 downpipe for now. I want to do a "stage 1" comparison of the VF48 & VF58 first. I also live in California so it'll be helpful to have the OEM downpipe available.
As for aftermarket twin scroll downpipes, the Moore Power "TruDivorce" downpipe was the best design that I've found. I wish that there was a JDM equivalent COBB GESi downpipe because I really like their cast bellmouth and GESi cat, but I haven't found anything comparable. The other option is to buy an aftermarket single scroll downpipe and use the Kinugawa twin scroll "lost wax" cast bellmouth.
Turbo Dump Down Pipe Head For SUBARU WRX STI VF36 VF37 Twin Scroll 3" Spec C
shopping.kinugawaturbo.com
It may become harder to find downpipes (in general) with the recent EPA crackdown.
The downpipe flange is different between the two. It's possible to swap the twinscroll flange onto a single scroll downpipe with a bit of welding/fabrication depending on the downpipe. Mambatek & Kinugawa both make flanges:
Turbo Down Dump Pipe Flange For SUBARU GDB STI Twin Scroll VF36 VF37 VF42 SS304 | eBay
IHI VF36, VF37 VF42. MAMBA SUBARU GDB STI VF36 VF37 VF22 Twin Scroll Turbo Turbine Outlet / Down Dump Pipe Flange. Material: Stainless Steel 304 (SS304). SUBARU GDB STI Twin Scroll Turbo Dump Down Pipe.
www.ebay.com
For my goals, it would probably be easiest to buy a cheap aftermarket single scroll downpipe, the Kinugawa bellmouth, and a GESi cat to take to a fabricator.
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200 Posts
This is what I plan to do. I love the Cobb Downpipe with Gesi Cat. Having that visual EPA number on the cats may help get through visual inspection one day if needed. I am gunna buy a twin scroll bell mouth head and have it welded onto my Cobb DP. OR, see if I can just get away with cutting the flange off the cobb dp and welding on a TS flange.I have an OEM S208 downpipe for now. I want to do a "stage 1" comparison of the VF48 & VF58 first. I also live in California so it'll be helpful to have the OEM downpipe available.
As for aftermarket twin scroll downpipes, the Moore Power "TruDivorce" downpipe was the best design that I've found. I wish that there was a JDM equivalent COBB GESi downpipe because I really like their cast bellmouth and GESi cat, but I haven't found anything comparable. The other option is to buy an aftermarket single scroll downpipe and use the Kinugawa twin scroll "lost wax" cast bellmouth.
Turbo Dump Down Pipe Head For SUBARU WRX STI VF36 VF37 Twin Scroll 3" Spec C
shopping.kinugawaturbo.com
It may become harder to find downpipes (in general) with the recent EPA crackdown.
I think the flange swap may be easier. I think the COBB bellmouth is longer than the Kinugawa and may require adding some short length of pipe. But that's just my guess. Can't wait to see your build.
Joined
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200 Posts
Maybe one day n R205 downpipe will fall into our hands.
Added a bunch of parts to the "waiting to be installed" stock pile. Between it consistently being 100+ degrees out and having an overactive 1.5 year old.. there isn't much time or motivation to be in the garage sauna installing parts right now.
Most of these parts are to stiffen up the drivetrain to eliminate excess "slop" and improve the overall driving & shifting experience. I want the car to feel as connected & analog as possible without extreme NVH. I'll be sticking to rubber bushings rather than solid and/or polyurethane components where possible.
![63073]()
Cusco rubber front shift linkage bushing:
![63074]()
STI Group N rear shifter bushing:
![63075]()
Torque Solution rear diff bushing inserts:
![63076]()
Most of these parts are to stiffen up the drivetrain to eliminate excess "slop" and improve the overall driving & shifting experience. I want the car to feel as connected & analog as possible without extreme NVH. I'll be sticking to rubber bushings rather than solid and/or polyurethane components where possible.
- STI Group N Competition Transmission Mount ST410224S040 (stiffest version)
- STI Group N Competition Pitch Stop ST410404S000 (stiffest version)
- STI Group N Competition Cross Member Bushings ST41022ZR000
- STI Group N Rear Shifter Bushing B0220FG300
- JDM Cusco Rubber Front Shift Linkage Bushing - similar to Group N rubber as opposed to the typical aftermarket polyurethane bushings
- Torque Solution Rear Diff Bushing Inserts
- STI Red Silicone "Air Duct" Coupler ST2183066000 (TMIC > Throttle Body) - for when I install the VF58
Cusco rubber front shift linkage bushing:
STI Group N rear shifter bushing:
Torque Solution rear diff bushing inserts:
I also purchased replacement LED fog bezels. I upgraded from the older style (H4517VA417) to the newer '20+ style bezel. I've already installed these and will take some pictures soon.
INSTALL NOTE: Since the bezels were sold separately and the LEDs are the same size/shape, I mistakenly assumed that the old LED's were direct PNP. While the LED fits properly, it appears the LED mounting bracket has changed and the screw hole locations are slightly off. I got the LEDs to fit (albeit not perfectly), by bending the mounting bracket tabs to get 2 of the 3 screws in. The 3rd (middle screw) tab is just too far off to make it work. Overall, the LED fits fine, but it's not perfect even though an average person won't be able to tell. I'm sure it still fits better than aftermarket variants.
OEM JDM '20+ LED DRL bezels (H4517VA437):
![63077]()
![63078]()
![63079]()
I know ajsti24 has posted pictures comparing the older & newer style, so you can check his thread as well. You can see that the bezel grille itself is open (rather than the majority being fake vents on the older style). However, you would need to remove the back cover to really take advantage of this. The newer style would be great for building custom brake cooling ducts. Don't buy the new version expecting to have a noticeable improvement in cooling. I do think they make the front end look more aggressive though.
INSTALL NOTE: Since the bezels were sold separately and the LEDs are the same size/shape, I mistakenly assumed that the old LED's were direct PNP. While the LED fits properly, it appears the LED mounting bracket has changed and the screw hole locations are slightly off. I got the LEDs to fit (albeit not perfectly), by bending the mounting bracket tabs to get 2 of the 3 screws in. The 3rd (middle screw) tab is just too far off to make it work. Overall, the LED fits fine, but it's not perfect even though an average person won't be able to tell. I'm sure it still fits better than aftermarket variants.
OEM JDM '20+ LED DRL bezels (H4517VA437):
I know ajsti24 has posted pictures comparing the older & newer style, so you can check his thread as well. You can see that the bezel grille itself is open (rather than the majority being fake vents on the older style). However, you would need to remove the back cover to really take advantage of this. The newer style would be great for building custom brake cooling ducts. Don't buy the new version expecting to have a noticeable improvement in cooling. I do think they make the front end look more aggressive though.
Joined
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235 Posts
Where did you pick up the Group N stuff from?
JapanParts always has the best prices, even after shipping from Japan.
I was sad that I had to sell my @killerbmotorsport ELH when going the twin scroll VF58 route.
Luckily, I was able to pick up another quality product from them.. their new "Extreme Flow HARD Turbo Inlet"! I'm excited to give this a try, should be arriving early next week. It will either be paired with an OEM S209 intake or the COBB Redline CF Intake. It just depends on what happens first, whether I can find an used OEM S209 intake or if COBB receives their CARB certification for the new intake.
Some teaser pics of the turbo inlet from Killer B's development & production:
![63103]()
![63104]()
![63105]()
![63106]()
![63107]()
![63108]()
![63109]()
![63110]()
Luckily, I was able to pick up another quality product from them.. their new "Extreme Flow HARD Turbo Inlet"! I'm excited to give this a try, should be arriving early next week. It will either be paired with an OEM S209 intake or the COBB Redline CF Intake. It just depends on what happens first, whether I can find an used OEM S209 intake or if COBB receives their CARB certification for the new intake.
Some teaser pics of the turbo inlet from Killer B's development & production:
I finished working on my "Stage 1" ACN91 tune a while back and forgot to post the results. I'm very happy with my results. It took me way too many revisions, but I wanted it nearly perfect. Great drivability, retained the difference in throttle mapping between the drive modes, most power possible on ACN 91 "knocktane" without any significant knock, holding power to redline, tested in various ambient temps from ~50-105 degrees, fine tuned PID boost control, leaning AFR in cruise areas for improved fuel economy, etc.
Below is a comparison to the OEM & COBB Stage 1 ACN91 tunes. Don't focus on peak numbers (as they always vary between dyno runs), but rather the relative differences between the 3 tunes. Now I have a solid (and fair) baseline to compare the VF58 setup to....and then I'll start the flex fuel tune
![63115]()
And yes, the OEM tune made more power up top compared to COBB's more conservative ACN 91 stage 1 map. The OEM tune also relies a lot more on the knock correction system since it would encounter frequent feedback knock. I didn't observe any knock on COBB's OTS map while I was datalogging.
Below is a comparison to the OEM & COBB Stage 1 ACN91 tunes. Don't focus on peak numbers (as they always vary between dyno runs), but rather the relative differences between the 3 tunes. Now I have a solid (and fair) baseline to compare the VF58 setup to....and then I'll start the flex fuel tune
And yes, the OEM tune made more power up top compared to COBB's more conservative ACN 91 stage 1 map. The OEM tune also relies a lot more on the knock correction system since it would encounter frequent feedback knock. I didn't observe any knock on COBB's OTS map while I was datalogging.
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765 Posts
I gotta get me one of those!
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200 Posts
Love the attention to detail with your build. I plan to also send mine out to SoCal for the same treatment yours had. Anything to try and hit that 400whp mark....even though I plan to have power capped around 375/375. I worry the amount of torque that low in the RPM range wont play nice with the bottom end bearings.
Also, I saw SoCal offers porting services for the throttle body and the TMIC aluminum Y piece that mounts to the backside. Figured I would send those along to be ported and also have the Y piece coated to help keep the intake temps down.
Have you looked into Speed Density at all? I am on the fence about it. I know the Spec C's had an extra IAT sensor in the intake manifold that I am told helped make their AVCS tuning more agressive. Any insight on this?
Also, I saw SoCal offers porting services for the throttle body and the TMIC aluminum Y piece that mounts to the backside. Figured I would send those along to be ported and also have the Y piece coated to help keep the intake temps down.
Have you looked into Speed Density at all? I am on the fence about it. I know the Spec C's had an extra IAT sensor in the intake manifold that I am told helped make their AVCS tuning more agressive. Any insight on this?
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