How to Turbo Your EZ30

[codyman]

Turbo EZ30 Bits and Bobs

This isn’t the definitive guide, but the way I did it and what I would do differently in my preface Spec B wagon. This post does not include the fabrication of the turbo manifolds or the intercooler intake side. That took most of the time and I’ll make a post on that in the future on how I made it equal length for those epic sounds. For now, this is just the bits and bobs you most likely won’t see covered in a YouTube build video, but can add weeks to a build as you wait for them to arrive. I am by no means an expert or a mechanic, just a bloke interested in modifying cars at home. Currently photos are not uploading into the post but I'll try fix that soon. If you could not care less about fabricating your own manifolds and would rather pay someone to do it then I know several people with really great work from https://www.facebook.com/geelongmotorsportfab

I started the turbo ez30 project throughout my last year at uni in 2022 in my spare time and in the end it took me around 5 months, but mostly due to unrelated issues with the ECU self-combusting mosfets. As of now I have been dailying the car turbo since mid-January and done over 2,500km’s with no major issues, only some small issues with idle and hot starts. The car is on stock head gaskets at 188,000km, stock internals and stock ECU. I had the motor out and pulled apart and it looked to be in excellent condition which was reassuring to add boost to it. Oil consumption is normal, and oil and coolant temps are great. Judging from injector duty cycle and grams of airflow from the MAF I would estimate the car is around the 250-260kw on 5.5psi, but that’s a rough estimate so take that with a pinch of salt, I need to get it on a dyno soon for real numbers. The car only runs on 98 due to ECU gremlins with E85 and E85 being hard to get near me and I’ve seen no issues, as I had heard “only turbo ez30 on e85 otherwise it will blow up” which is false. The car drives incredibly, the torque is so much more useable and fun compared to past turbo EJ’s I’ve owned. The driveability is so impressive, being able to crawl around everywhere in 3rd gear is lovely. Peak torque feels around 4500-5000rpm range, with full boost by 3800rpm. Boost and torque feel to drop off over around 5800rpm, but I suspect further fiddling with the boost controller can help to reduce this and a 1.01 A/R turbine housing could help. The tune on 98 is very healthy, with no knock that I've logged or seen, very good FLKC and a happy IAM.

Turbo:
I couldn't justify the cost of a Garrett and had seen a proven consistent track record with Pulsar turbos. Pulsar’s GTX range is based on the designs of a Garrett gen 2 GTX and after pouring over many compressor maps and matching my needs I decided on a GTX3576 with a 0.83 turbine housing. A G series would be an improvement sure but in the little difference at such low boost for my use I couldn't justify the step up. I have been told to not go any smaller than the GTX30 series, as any smaller and although considerable spool performance, torque down low has the tendency to noodle the toothpick stock rods. Furthermore, in the future If I do up the boost, this will only push the 3576 into increased efficiency islands. The 0.83 turbine housing A/R sits in the sweet spot for daily driving response, but I would be interested to see the difference a 1.01 A/R to see how considerably the top end improves.

Turbo Oil Feed:
There are several positions to get a consistent oil feed from on the motor, but I decided to go off the stock oil switch. Something to note is the oil switch is 1/8” BSPT which is not the same as 1/8” NPT. Almost but not. This allowed me the use of a 1/8” NPT to AN4 adapter to get my turbo oil feed to head into my Turbosmart Oil Pressure Regulator. Sure, this isn’t necessary, and you can use a restrictor but with the EZ30 at cold starts seeing over 130psi of oil pressure I felt the OPR was good insurance to ensure the turbo got a constant 40psi of oil pressure to save the seals. Now Turbosmart make a V2 OPR which is inline and return-less which would have saved the need to weld a AN4 fitting into the RH rocker cover. I also built and use my own Arduino oil pressure system to monitor both engine and turbo oil pressures, and the turbo gets immediate oil pressure when cranking over which is very reassuring.

Turbo Oil Drain:
The oil drain proved to be an absolute pain for me. Clocking the turbo at such an angle to get adequate water cooling (around 15 degrees) and getting my drain to get a decent drop was hard. I would recommend considering having the AN10 rocker cover drain in the back of the rocker cover, this would have made life much simpler than having it on the face. But alas we made it work, and I have had no drainage issues.

Cooling:
The stock radiator is flimsy and plastic top commonly cracks off in some form after enough heat cycles. The Kobe Motorsport alloy radiator works very very well, and I have noticed considerable temperature drops, with the car never getting into the too hot area. You could get away with the stock radiator, but the extra heat and load on the motor, and EZ’s tendency to overheat, warp heads and headgasket rip, it seems like common sense.

Turbo Water Cooling:
I ran the water cooling into the throttle body loop. From the output of the throttle body into the turbo low side, and then back into the stock system using 3/8” hose.

MAF and MAP:
The MAF is on a separate loom from the engine and with some new conduit it can be routed without soldering on extensions to sit around the throttle body. As the MAF also has an IAT sensor I wanted this as close to the throttle body, post turbo for accuracy. I ran 2.5” intercooler piping as this makes sense from an air speed and physics standpoint but causes some mild pain when having to rescale the MAF and would probably just go for 3” if I did it again, as this is also the size of the throttle body. As for MAP I ran a EJ255 MAP to read to something like 22ish PSI than the stock N/A MAP which bolts into same stock placement and the vacuum line fits no worries, just make sure to let your tuner know to adjust the scaling.

Fuel System:
This is something I was unsure about, as running the STI pink 565cc injectors with E85 would limit max power to around 300ishkw if I recall and around 330kw on 98. I currently run only on 98 and have no issues. If you did have easy access to E85, bigger injectors probably wouldn’t hurt. I put a Kobe Motorsport 340lph fuel pump in for head room and for the potential to run E85 in the future.

Reducing crankcase pressure:
Reducing crankcase pressure and letting the EZ breathe is key to motor longevity and optimal turbo drainage. LH rocker cover by default has a PCV and a breather hose which connects to the stock airbox but that is getting chucked. DO NOT leave the PCV hose connected to the intake manifold. Yes, the PCV is meant to act as a one-way valve letting pressure out of the motor, but over a few PSI of intake manifold (boost) will leak past the PCV and this will just pressurise the crankcase. Make sure to blank off this hole on the intake manifold underneath otherwise you will have a mega boost leak. I plugged both LH rocker cover hoses into a catch can system. The crankcase pressure system is connected on both banks of the engine, but reducing pressure in the RH side of the motor isn’t going to hurt, especially as that is close to the turbo drain. I used a 3/8” weld in aluminium fitting in the middle of the rocker cover (at an angle to keep the injector protector thing). I then ran a 3/8” hose into my catch can setup.

Brake Booster:
The brake booster hose from the brake booster to the intake manifold by default has a 1-way pill in it. Many people leave this, but my compressor housing was sitting very close to the stock brake booster bung on the intake manifold, using a 90-degree bent one allowed for more room and I have had no issues using the stock hose. Another option is to route the brake booster hose into the LH side, but I’m yet to see someone successfully remove the blocking bung.

Boost Control:
Alas having the 512kb SH7055 dweeb preface ecu meant no fun extra room to use the EVAP solenoid for boost control. Of course, you could just run a vacuum line from the compressor housing into the bottom of the wastegate, hope your wastegate spring works for you and call it a day. I went for electronic boost control using a 3-port solenoid and the GFB G-Force 3 electronic boost controller. It’s single din size means it fits neatly into the compartment in the centre and is handy as a boost gauge, although I find it reads a tiny bit higher than it should. The boost controller works well, adjusting the gain allows the gate to stay shut for longer and to build required boost. Running a 7psi spring and my duty cycle at 35% I see a max of 6.8psi in 6th gear, but I have only logged a max pressure of 5.6psi through the MAP sensor. The boost controller pressure reference is in a tee in the vacuum line going to the FPR.

ECU:
The stock ecu works really well, especially if you’re only running the stock ecu. 2 reputable tuners I know with considerable experience with turbo EZ30’s are Matt Mcleod and Sean from SickChips. Especially with the added memory of the 1024kb postface ECU’s, the stock ecu does the job well, and is far more capable than people think. I'm currently in the process of pulling apart and reverse engineering the preface SH7055 ecu in Ghidra to see what other cool things can be hacked into it.

Rough Parts List:
Pulsar GTX3576: $1000
Turbosmart GenV Hypergate 45mm: $600
1/8” BSPT Oil Pressure Tee: $12
Brass 90 Degree BSP Male to Female 1/8” x 10mm: $10
2x Raceworks Metric Male M14x1.5 to 3/8” Barb: $16 each
AN10 51mm turbo drain: $27
AN4 Aluminium Weld on fitting: $11
K&N Tapered Pod: $55
AN10 Aluminium Weld on fitting: $10
STI Pink Injectors: $400
Kobe Motorsport EZ Radiator: $550
Exedy Sports Tuff HD Clutch: $900
Turbosmart Oil Pressure Regulator: $200
AN4 Fittings: $200
AN10 Fittings: $80
Kobe Motorsport 340lph Fuel Pump: $240
EJ255 or any 3 bar MAP sensor: $60

Sum so far $4,400

Other Considerations
This list doesn’t cover the small parts which start to add up fast like vacuum lines, hose clamps, turbo blanket, intercooler and much more. As I think of more parts I will add it to the list, but yeah, it’s not cheap, and this doesn’t cover any fabrication costs or parts such as V bands, material, bungs and more. Having fabrication skills will save you money immensely but I’ll cover this further in another post. Also do note that preface and postface have several differences, including cylinder heads which are mostly cam shape, preface return vs postface returnless fuel systems, ecu and a few other small things. Preface stock also has a rising rate fuel pressure regulator (to what extent I’m not sure), whereas postface is static so you’ll need a proper FPR.

So should you do it?
Yes, the results really impressed me and I’m sure they will you too. The EZ30 longs for boost, and the great flow of the stock heads gives very impressive gains. Many are sceptical what difference does even 5psi really make and yeah it's rapid. The motor N/A is already plenty of fun, but adding boost just compliments it excellently. Be warned, this is a time-consuming project, issues always appear in any Subaru project, and this is no exception. My best piece of advice is to do your research, think things out beforehand, and expect to spend a lot of time reading through the depths of the factory service manual. But don’t let this turn you off from trying it, the learning, and people you meet along the way to boost your EZ are great. I am immensely proud of what I have created, and enjoying the fruits of my labour when it gets on boost is very rewarding. There is plenty of resources online if you do your research but there is agreeably a lot of bullshit which you need to do your due diligence on. I hope this post help to collect a lot of helpful information in one spot for people looking to do the same. I am always open to offer any help if I can.

So what's next?
New headgaskets and proper headstuds I would recommend. Maybe one day I'll build the motor properly but for now I'm enjoying it stock. I have a low km EZ36 on my engine stand which I have some intriguing plans and ideas for in terms of building and designing custom built internals for in the future. The idea of the the illusive built EZ32 would be the dream. Soon I'll get together a proper video of the car so you can all enjoy the sounds of the equal length headers. But for now I think I'll just continue to drive it and enjoy it.


People I owe great thanks to:
My Dad - For all his help and wisdom through the process and allowing to fill the workshop and yard with subaruparts
Matt Mcleod – For his immense help tuning and helping me to sort out all sorts of problems,
Josh Stokes – Providing many shipments of random EZ parts and one of the king of EZ knowledge
Connor Whelan – For my first proper ride in a turbo ez and for all his help
Hamish Boyd – For answering my many questions and his help
Bigbadbenny - For his methodical help and approach to successfully fixing several of the issues
The guys on the Romraider forums, espically Rimwall for his help with the ecu eeprom hacking

[nvmylh]

Nice write-up mate! Its almost spot on to what I've slowly been working on with my ez specB.

Did you flow test your injectors before using them? I've got 1 set of low-km 550 blues, just waiting on another (had some in japan but got stuffed around with shipping used injectors!).

My turbo is an xr6 3576, intenal gate and 0.8 rear housing so will be interesting to see how the internal gate goes.