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    Dirt Tech / Vendor Reuben's Avatar
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    Lightbulb So you've bought youself a JDM twin turbo eh?

    I'm seeing a lot of TT's starting to pop up stateside now, I've helped out a couple of the boys out in the pacific northwest with theirs, but there's more and more entering the states now that they've hit that sweet 25. SO. This thread is for those that just got their own TT, and now have the joy of working on them... There's going to be tips and tricks, pitfalls, and work arounds. Don't worry, there's only a small bit of devil magic in these engine bays, otherwise they are pretty straight forward!!! I will be updating this thread as it progresses, and adding Q+A's into this first post.

    Working on Subarus Sequential Twin Turbo.

    Pictured, an 1996-1998 BG5B GTB

    Working on a twin turbo is very similar to signle turbo, only a bit more shit. As far as removing turbo's, playing with exhausts, this should all be like USDM stuff... But when it comes to vac lines, it's easy to get yourself in trouble.

    Tip Number ONE: DO NOT PULL THE VAC LINES OFF THE BLACK BOX. On top of the black box is a 10mm bolt, securing down a fork shaped clamp. The fork shaped clamp is holding in up to 4 vacuum plugs, that have up to 4 vac lines on each plug. These plugs are numbered, and keyed, so it is impossible to fuck it up. The intercooler has it's own plug, the secondary turbo has it's own plug.... knowing this one fact will help you not fucking up your vac system!!!
    The black box (of Death)(Aka BBoD), is the muscle of the twin turbo operation. Inside the black box is multiple solenoids, as wll as your map sensor. Like sinlge turbo, you have a pressure select solenoid inline before the map sensor, and you have a boost control solenoid. Important to note is the boost solenoid inside the black box is not actually controlling boost, it's actually the secondary turbo exhaust valve. The cars boost control solenoid lives in the left (passenger side) fender. Also in here are solenoids to control your secondary boost bypass valve, your intercooler secondary butterfly valve, and some other random shit. You won't ever need to know this stuff cause it's just not part of any maintenance or repair you'll ever do. I work with these cars on a semi profesional basis, and I never have had to go into the guts of a BBoD, any boost issues are normally outside of this box, usually because muppets have fucked with something in the engine bay and broken it.

    Here's a video on how to remove and re-fit the intercooler properly!!! This is the easiest way, trust me, I've only done it 100 times.

    Another issue you will likely face, is a TT that isn't performing right. Sometimes if they perform so poorly, they can throw the dreaded code 66! Never fear, code 66 is widely missunderstood. In all my dealings with it, it's never been major, it's always been some vac line someone has changed, or that has snapped. Though I have read of people who have needed to clean out their BBoD to sort it. Put simply, code 66 is the ECU figuring out that yo car aint boosting proper! that's it. Unlike the other 60 codes, it's not linked to a specific solenoid or sensor. It usually comes on when you've got the engine loaded, that is, say, going up a hill, but the primary isn't coming on boost. The last 66 I solved a few months ago was a customer who had just bought a GT VDC, but it looked as though the engine had been replaced with a non VDC engine, and the mechanics who had put it in had done the vac lines up following a non VDC vac diagram. I corrected the vac lines, and presto, primary started to boost proper and code 66 went away. I've also seen 66 in cars where people had replaced their vac lines with silicone. Don't be that guy, you're just opening yourself up a world of hurt. Code 66 can also come on when your primary turbo dies. And yes, primary turbo's dying is a way of life for twin turbo's. I wouldn't say it's as prevelant as EJ25's blowing headgaskets by a long way (nothing is), but it is common still. You can still buy primary turbo's new though! (Update: From where I don't know, the guys in NZ who were importing them have stopped) So if you get code 66, check ALL of your engine bay vac lines against the CORRECT vac diagram. Keep reading to see how to identify what vac system you have.

    ECU Error codes are listed at the end of the thread, including the 60 series of TT codes.

    Now to the engine bay... Now this is where I tell you there's actually 4 different types of black box, and associated vac line setup. You have BG5A, BG5B/C, BH5A/B/C and BH5D, And for bonus points, BH5A/B/C WITH VDC (twin vac line BOV's anyone?). Online you will find BG5A, BH5A/B/C and BH5D info, but curiously you wont find BG5B/C. I plan to change this is the near future as I am sick of not having diagrams of the vac system for BG GTB's. - EDIT, done, created a B/C rev BG vac line layout, posted below! You're welcome!
    Some of the big differences are for example, BG5A has a wastegate on the secondary turbo, but B/C does not. BH is different again, and Rev-D's simplified things a bit. BH's are much more confusing than BG's, lots of tee pieces around the BOV/primary side for some reason...

    Engine/Model Identification:

    Engine identification... What twin turbo have I, and why does this vac line pic I found on the googles not resemble my engine bay in any way... So a big part of knowing twin turbo, is knowing what type you are dealing with. As mentioned above there's 4 (5) types of vac line arrangement, but it goes much deeper than that. Spanning the 10 year life of TT was multiple engine generations. We started with hydraulic lifter engines like USDM 96 outbacks, and ended int he bug eye generation with phase-III top feed injector goodness. Here's the break down

    2nd Gen legacy, Pre facelift 1993-1996
    Chassis: BD5A, BG5A.
    Engine generation: Phase-I
    Engines: EJ20H
    Power: 250ps/246hp/183kw
    Valvetrain: Direct HLA
    Compression EJ20H - 8.5:1
    Quick id: Rocker covers have lines embossed, 6-bolt.
    USDM part commonality: EJ25D '96
    JDM single turbo part commonality: Ver. 1/2

    Interesting notes: All pre facelifts have the same engine, auto or manual. All engines are hydraulic lifter (Inside the bucket, we will call this Direct HLA, rather than roller rockers like in the BC5's), these engines are common with your first year EJ25D, found in the 96 outback, that odd one that has lines on the rocker cover... Why did the US only get that engine for one year? well that just happened to be the last year of production for hydraulic DOHC engines, this generation engine had been in production from 92 till 96 in japan.

    2nd Gen Legacy, Facelift. 1996-1998
    Chassis: BD5B, BD5C, BG5B, BG5C
    Engine generation: MASTER-4 (Phase-I)
    Engines: EJ20H, EJ20R B-Rev, EJ20R C-rev
    Power: EJ20H 260ps/256hp/191kw
    Power: EJ20R 280ps/276ph/206kw
    Valvetrain: Solid lifter, shim over bucket
    Compression: EJ20H - 9:1
    Compression: EJ20R B-Rev - 8:1
    Compression: EJ20R C-Rev - 8.5:1
    Quick id: Smooth rocker cover, 6-bolt. EJ20H grey injectors, EJ20R yellow injectors.
    USDM Part commonality: EJ25D '97+
    JDM single turbo part commonality: Ver. 3/4

    Interesting notes: Facelift introduced the GTB. The GTB is not a "B-spec", it's a GTB (B-spec started with 4th gens). There was a divergence in the engine types from this point on, and we get 190kw engines, and 206kw engines.
    EJ20H: This is the 190kw engine. This is a different engine to the pre facelift. this engine has solid lifters with shim over bucket, these engines are like the late 25D's, and EJ20K's (V3/V4 STi motor) etc. EJ20H's of all forms come with grey top injectors.
    EJ20R: Physically looks identical to the smooth cover 20H, same rocker covers etc. Camshafts are different, compression ratio is different, turbo's are different, air flow meter and injectors are different. Power is a glorious 206kw. These engines are the twin turbo version of the EJ20K. The only difference from the 20K is there's an extra hole bored in the left head for the primary turbo, shim over bucket, unlike the 20K which is shim under bucket, and cast pistons, unlike 20K's forged pistons. Piston crown is the same design, camshafts are the same, head castings are the same. Interestingly with the EJ20R, the B-rev was 8:1 like the 20K, C-rev was 8.5:1... EJ20R's have yellow injectors and orange air flow meter like the 20K.
    EJ20R's are found only on MANUAL GTB's (and RSB). Auto GTB's got the 20H. GT's got the 20H.

    WARNING!!! Mechanics who don't know this shit, and who don't give a f*ck, have been working on these cars for 25 years by the time you get your mits on them, there is no gurantee that just cause you got a manual GTB, that you have an EJ20R in your car! I have seen hydraulic engines in GTB's, I have seen grey top smooth 20H's in GTB's. Mechanics here when they get a GTB with a blown engine usually have no idea that the EJ20R is any different to an H, and will slap whatever twin turbo they get their hands on in the hole. So yeah. enjoy. and also, sorry.

    3rd Gen legacy, Pre facelift. 1998-2000
    Chassis BE5A, BE5B, BH5A, BH5B
    Engine generation: Phase-II
    Engines: EJ206 A/B-rev, EJ206 A/B Rev with VDC, EJ208 A/B-rev
    Power: EJ206 260ps/256hp/191kw
    Power: EJ208 280ps/276ph/206kw
    Valvetrain: Solid lifter, shim over bucket.
    Compression: EJ206 - 9:1
    Compression: EJ208 - 8.5:1
    Quick id: Smooth rocker cover, 8-bolt. Intake manifold has flat runners on passenger side (where the coil pack would sit on an WRX of the same year)
    USDM Part commonality: None
    JDM single turbo part commonality: Ver. 5/6

    Interesting notes: Engine design starts to converge again. Still EJ206 in GT's and Auto GTB's, EJ208's in manual GTB/RSK's. Now all motors have same air flow meters, and yellow injectors (larger body than the older injectors, these are the same fitment as EJ25D red top injecotrs funny enough). Much like the smooth cover EJ20H vs R, there's no way to tell these engines apart visually, and it's especially hard since they both have yellow injectors (at least 20H/R had grey/yellow). There's nothing much to say about these engines. They are Phase-II DOHC, you didn't get this type of motor in the states, since they killed the 25D and went to EJ251's, blegh. They are more similar to the Phase-III motors you're used to seeing in the bug eys, same manifold bolt pattern, fat cam seals and all that jaz. In japan this is when the EJ204 and EJ254 DOHC AVCS Non turbo's were introduced, so they have common parts with AVCS engines such as cam seals and rocker covers etc. They are a little odd, cause they are like an AVCS head, but have no AVCS.
    The VDC (Vehicle Dynamics Control) equipped cars have a different vac layout, as there's an extra solenoid to control the BOV, and the BOV has two ports. VDC could solenoid open up the BOV to kill your power as a form of traction control. These cars are hilariously bad when fitted whith shitty chinese tyres, as they will wheel spin in first, VDC will traction control you and kill the power, then the auto gets confused by what's going on and shifts and bogs you down. Yaaaaaaay. Do not buy VDC cars when they become available stateside, they are shit to drive, and shit to work on. If you end up with one, buy good quality tyres, only buy them in sets of 4. Do not modify your engine in any way shape or form, the ECU will have a FIT if you touch anything in the engine bay, they are really really tricky to work with, in essence, VDC cars are unmodifyable.

    3rd Gen Legacy, Pre facelit 2000-2001
    Chassis BE5C, BH5C
    Engine generation: Phase-II
    Engines: EJ206 C-rev, EJ206 C Rev with VDC, EJ208 C-rev
    Power: EJ206 260ps/256hp/191kw
    Power: EJ208 280ps/276ph/206kw
    Valvetrain: Solid lifter, shim over bucket.
    Compression: EJ206 - 9:1
    Compression: EJ208 - 9:1
    Quick id: Smooth rocker cover, 8-bolt. Intake manifold has high rise runners both sides
    USDM Part commonality: None
    JDM single turbo part commonality: Ver. 5/6

    Interesting notes: Kind of an oddball car these. They are mostly the same as the other pre-facelift, still have yellow injectors, still phase-II, make same power etc. The intake manifold design changed, no longer did they have the flat half, both side runners go high. EJ208 got a compression ratio bump to 9:1, now the same as EJ206.

    3rd Gen Legacy, Facelit 2001-2003
    Chassis BE5D, BH5D
    Engine Generation: Phase-III
    Engines: EJ206 D-rev, EJ206 D-Rev with VDC, EJ208 D-rev
    Power: EJ206 260ps/256hp/191kw
    Power: EJ208 280ps/276ph/206kw
    Valvetrain: Solid lifter, shim over bucket.
    Compression: EJ206 - 9:1
    Compression: EJ208 - 9:1
    Quick id: Top feed pink injectors
    USDM Part commonality: GDAA, "Bug-eye"
    JDM single turbo part commonality: Ver. 7

    Interesting notes: Phase-III is here, enter the modern age! These engines are common with bug eyes in almost every way, except AVCS. Manifolds though are very similar design to the C-rev, only now they have pink top feed injectors like JDM EJ207 bug eys. These engines have all the short block goodness of the bug eyes too, gone is the big end bearing unreliability of the old phase-I and phase-II engines. (And don't laugh, you guys think big ends in USDM turbo subies are unreliable... they are not, they have got NOTHING on the unreliability of the EJ20R and EJ208, NOTHING I SAY). These cars are somewhat sought after here, as the twin turbo system in them is PHENOMINAL compared to the older ones, they actually do what you think they should. They are pleasing to drive, and reliable. Subaru essentially after 8 years perfected twin turbo... Only to drop it 2 years later with the introduction of twin scroll turbo's on the 4th gen.

    Conclusion on engine differences. As you can see it can be very hard to identify the difference between them. EJ206's and EJ208's of the same year appear identical on the outside. So yeah, good luck. Your only hope is to pray that the engine in your car is original, and that you can rely on the vin plate.

    Part info coming later.

    Technical Docs
    Here's a link to my google drive that has pinouts for all the JDM models I can find, and wiring diagrams for all the models I can find. Of not is the absence of BG wiring diagrams. Never found one, not in 15 years. The Impreza V3/4 wiring diagram is 90% applicable, with the USDM outback wiring diagram filling in another 5% missing stuff. But no joy on the TT specific wiring.

    Pinouts are in their own folder. Wiring diagrams are in the chassis specific folders with the rest of the FSM's

    But Reuben, how does TT actually work?
    Like... How does it actually chooch? Why does it have a dead spot at 4000rpm?

    CEL Error codes:
    (Yes these work on JDM BH/BE models)

    11 - Crank Angle Sensor
    12 - Starter Switch
    13 - Cam Angle Sensor
    14 - Injector 1
    15 - Injector 2
    16 - Injector 3
    17 - Injector 4
    21 - Water Temp Sensor
    22 - Knock Sensor
    23 - Air Flow Sensor / MAF Sensor
    24 - IACV / Idle Control Valve
    31 - Throttle Position Sensor
    32 - o2 Sensor (Pre cat)
    33 - Vehicle Speed Sensor (In instrument cluster for BG/BD)
    35 - Evap Purge Solenoid
    41 - A/F Learning Control
    42 - Idle Switch
    44 - Boost Control Solenoid / Wastegate Duty Solenoid
    45 - Manifold Absolute Pressure Sensor / MAP Sensor
    45 - Pressure Select Solenoid (The wee solenoid between the manifold and MAP sensor)
    49 - Improper MAF detected
    51 - Neutral Switch (MT)
    51 - Inhibitor Switch (AT)
    52 - Parking Switch
    58 - Vacuum leak detected by ECU

    TT Specific codes:

    61 - Air Suction Control Solenoid Valve (BBoD Solenoid - Controls vacuum to the vacuum cannister?)
    62 - Exhaust Valve Control Solenoid - Negative side (BBoD Solenoid)
    63 - Supercharging Relief Valve Control Solenoid Valve (Primary) (Main boost solenoid in passenger side fender)
    64 - Supercharging Relief Valve Control Solenoid Valve (Secondary) (BBoD Solenoid - A-rev BG only, NOT the main duty solenoid in the BBoD)
    65 - Differential Pressure Sensor (On firewall)
    66 - Twin Turbocharger System(H)
    66 - Twin Turbocharger System(S)
    66 - Twin Turbocharger System(T)
    66 - Two Stage Twin Turbocharger System
    67 - Exhaust Valve Control Solenoid - Positive side (BBoD Solenoid)
    68 - Exhaust Valve Duty Solenoid - (BBoD Solenoid - Main duty solenoid in BBoD)

    Code 66 is used by the ECU is something is fuckey with the vac lines and it detects the car is running like shit. It's not related to a specific solenoid, rather the overall health of your vacuum layout. It can crop up when the vac lines are put back together wrong, like what happens where someone fucks around and uses the wrong diagram, or if a hose has snapped/fallen off somewhere for example. More on this above in the "Working on Subarus Sequential Twin Turbo" section.


    LINE 10 MOD

    Line 10 mod bad, no do.
    Also it can only be done to BH's, but it thrashes the primary, I've replaced a few primary's for customers now, who had the line 10 mod, normally about a $1200 job if yah unlucky and are paying full retail ($400 in time, $600 for the turbo at wrecker prices in NZ). I've also seen people try do it to BG's, but you can't... so naturally that goes about as well as you'd expect... So yeah, fucking forget the line 10 mod.

    Onto more positive things.


    Sometimes you own a BG5A/BD5A, and ya turbo's fuck out, or they just aren't boosty enough for yah... So you go chuck on the big boys off a BH D-rev... WELL, if you look at the above diagrams real close you'll note the BG A-rev's have quite a different vac system... there's a heck of a lot more vac lines... and yup, that's a wastegate on the secondary turbo in ya A-rev... Well WTF are you gonna do about the vac lines for that!? Simple, turns out only two lines need to be delt with.

    Line 16 is the duty solenoid positive pressure reference (Only has positive pressure once secondary is online, and the intercooler valve is open).
    Line 8 is the duty solenoid to wastegate line.

    Remove line 8, it's useless now.
    Block line 16 at the junction tube thing above the secondary pre-spool releif valve, and remove the line to the BBoD if you want. Or if you wanna get real fancy, replace this junction pipe with one from a facelift or BH, it will only have one vac port, not two!
    Well done, you now have a Secondary-sans-gate running in yah A-rev.

    If you do not do this, every time you hit secondary, the ECU will be opening up the solenoid, and suddenly you have a pretty modest vacuum leak. With 16 blocked, no more leak, and the solenoid will just chooch away on it's own affecting nobody.

    So this is a work in progress, that took me 2 hours to write, I now have to proof read it, flesh it out, format it, take photo's and find photo's online. Please ask questions, I want to add as much info in here as possible for you poor cunts. Welcome to the world of twin trubo f*ckers, enjoy your stay!!!

    Change Log:
    Added BBoD Diagrams
    Added modifications section
    Updated all vac layout images, now they are common with each other.
    Added Rev-D vac layout image
    Added link to my video showing the correct pocedure for removing and fitting the intercooler
    Added CEL codes, including 60 series codes for TT.
    The NZ suppler of new primary turbo's (I think they had VF 13's and 26's) has stopped importing them. They no longer list them on their website - It was turbochargersNZ
    Added link to my google drive with the pinouts and manuals I have.
    Last edited by Reuben; 03-30-2021 at 06:16 AM.
    Single turbo conversion, "How to" can be found here
    JDM 1998 BG Legacy GTB Limited, EJ20K STi swapped
    JDM 1990 BC Legacy Ti type S, EJ25D swapped
    JDM 1995 BG Legacy 250T, EJ20D swapped
    JDM 1989 BC VZ-R, Stock - Dead now

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