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Subaru EJ22T stroker hybrid engine for 2008 STI using dual AVCS cylinder heads

BACKGROUND

This engine we designed and prepared for a local Subaru tuner. Engine will be fitted to a 2008 Subaru Impreza STI using a Garrett GTX3076R ball bearing turbocharger, ID1000 injectors, and E85 fuel. Goal is reasonable street use response, thanks in part to a PRE-designed V-band turbine housing system, dual AVCS, and ECU calibration. Vehicle will also be use for road course racing locally in the Midwest. 450whp on “pump” fuel and 550whp on E85 are the goals which will soon be tested.

PARTS AND SERVICES

ENGINE BLOCK: Engine started out as an EJ22T closed deck block sourced half way across USA. Block was media blasted, cleaned thoroughly, deck milled, cylinders bored and honed as an assembly with two torque plates, and align honed. Block was mock-assembled numerous times checking bearing clearances and setting piston ring gaps. Each case half deck height was measured and milled different amount to be equal height.

CRANKSHAFT: Engine fitted with a brand new modified Subaru heat treated crankshaft. Crankshaft was machined to accept thrust at #3 position. Crankshaft was also performance balanced.

PISTONS: PRE-designed forged pistons are at the heart of this project. Strutted forging increased skirt and pin boss stiffness without weight penalty. Pistons designed in conjunction with Carrillo connecting rod pin end dimension. Narrow pin boss spacing reduces piston pin bending and actually work in double shear. Short piston pins reduce flex and weight. Piston pins made of tool steel and thick-wall design for heavy duty turbocharged application. Lateral gas ports for top compression ring utilize combustion gasses to aid sealing. Piston compression ratio depends on which cylinder heads used: this engine uses EJ257B W25 casting dual AVCS heads and final compression ratio is 8.4. If using single AVCS Ej255 D25 casting heads or EJ205 heads the compression ratio will be 9.0. Stay tuned for a another project using EJ22T stroker short block and D25 EJ255 heads. Piston compression height was designed for stock thickness head gaskets. We can design similar pistons for use with Cometic or Roger Clark Motorsports(RCM) head gaskets.

CONNECTING RODS: PRE uses Carrillo PRO-SA I-beam design forged connecting rods with WMC bolts. I-beam connecting rods were selected based on the low weight requirement while maintaining buckling stiffness. Connecting rod bearing ends and pin ends were measured and recorded. Connecting rods were weighed on the pin end, bearing end, and total weight. Connecting rods weight matched as a set to be within 0.5 grams. All our connecting rod bolts always tightened using a rod bolt stretch gauge. Torque wrench is not accurate enough and used for reference only.

BEARINGS: We use ACL Race series tri-metal connecting rod bearings and King XPG main bearings. King XPG main bearings offer superior profile and oil hole design.

CASE BOLTS: We use ARP case bolt kit for this engine. Block bearing housings were checked using stock and ARP bolts. The block was align honed using ARP bolts.

HEAD STUDS: We use a conventional ARP head stud kit for this engine. Block was bored and honed using two torque plates as an assembly using ARP case bolts and ARP head studs.

VALVETRAIN: Supertech valvetrain package was fitted to this engine after a radius valve job performed. Three angle valve job was performed as well. Valve seat protrusion and flow interference is a big issue on all Subaru engines; particularly intake ports. Our profile three angle valve job does a good job blending seat to port. To finish things off the seats are hand blended to the ports and all casting marks removed. Port velocity is more important than volume 😉 Supertech inconel exhaust valves and stainless steel intake valves fitted in stock size. Supertech dual valve springs and titanium retainer kit installed. Valve spring install heights measured, spring pressures measured, and shimmed as necessary to equalize all valves on intake and exhaust. Kelford camshafts fitted to these heads and camshaft followers adjusted to PRE spec.

LUBRICATION: Killer B oil strainer and baffle plate fitted inside OEM 2007+ STI oil pan. New oil pump is a high volume unit that has been disassembled, cleaned, gerotor clearances measured, casting marks cleaned up, and polished internally. Oil pump primed prior to reassembly with strategic use of thread locking fasteners.

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11 thoughts on “Subaru EJ22T stroker hybrid engine for 2008 STI using dual AVCS cylinder heads

  1. Who does your machining? I would like to build one of those 2.2 stroker motors.

    1. Hello David,
      Thank you for the inquiry. We are an engine builder and able to supply you either just parts or a complete engine. Please email with additional information about your engine, power requirements, car, and type of motorsports in which you will be participating. Email: [email protected]
      Thank you.

  2. what is the advantage to a stroker 2.2?

    1. As the saying goes: “There is no replacement for displacement.” There are no disadvantage of increasing stroke on an EJ22. EJ22 is an EJ20 75mm crankshaft with bigger bore than a 2 liter, thus making it a 2.2 liter. We fit an STI 79mm crankshaft in the 2.2 block making the engine 2332cc when matched with our set of 97.5mm pistons. Stroke increase improves engine torque. Increasing displacement also helps with turbo response. Don’t look at it from standpoint of increasing stroke of the 2.2 engine. Think of as decreasing displacement of the 2.5 engine and receiving a much more robust block and thicker cylinder sleeves in the process.

  3. I am doing a VERY similar build.

    Did they find that this setup worked well?

    1. Hi William,
      This engine combination works extremely well. This engine has been on the road for some time now and I have personally driven it at a track day at Gingerman Raceway in South Haven, Michigan. During that shakedown, the car was using the GTX3076R Gen1 turbo at 23psi on 93 octane “pump” gas. Full turbo spool was at 3400rpm and extremely responsive. After that track day, we put the car on a Mustang dyno and it made 454whp. Currently, this engine is running E60-70 mix, depending what fuel the local stations have, at least that is what the Cobb Accessport V3 Flex Fuel is reading, and it is running 30-31psi. The car is an absolute riot to drive! Let me know if you have any additional questions. Currently, we have four EJ22T engines we are building with similar specifications.

  4. Given that the EJ257 and EJ255 bores are larger diameter than he EJ22T bore, how does this affect performance? Also, do you have any dyno videos or driving videos of this setup? Thanks.

    1. Hello,
      Thank you for the interest. The bore of the EJ22T is 96.9mm. Our forged pistons are 97.5mm size. EJ255/257 bore is 99.5mm. Theoretically, this leaves a slight overhang of the EJ255/257 combustion chamber above the EJ22T cylinder bore, about 1mm per side, but in practice, the measured size of the EJ255/257 combustion chamber fits perfectly in the EJ22T head gasket. The combustion chambers of the EJ255/257 heads are not exactly 99.5mm and this is why this combination works.

      For example, fitting EJ205/207 head with the small chambers on the EJ255/257 block will hurt performance. We have done back-to-back dyno comparisons using stock EJ205 heads and then again with the same set of heads and modified combustion chambers enlarged to the 99.5mm size. Chamber-matched version of the same engine was able to take additional 3-4 degrees more ignition timing at peak torque.

      We can provide dyno graphs and track day videos of this setup at work. Please email us your contact information. We will post this additional information in the near future as well.

  5. Hello, this ej22t build is really impressive! I just purchased a 91 Subaru Legacy ss! I have always had big dreams of the 400hp mark! I was hoping you guys could point me in the right direction or do the machining of the heads. I was planning on doing something like STi Version 4 heads, EJ257 crank, Williams H beam rods, Mahle Powerpak 4032 stroker pistons, ARP headstuds, RCM headgaskets, Killer B Motorsport oilsump, pickup and baffle, Subaru JDM spec twinscroll headers, SC46 Billet twinscroll turbo, Link G4+ engine management, 850cc injectors, Turbosmart FPR-800 v2 fuel pressure regulator and a Walbro GST450 fuel pump. Any thoughts or a better build list from you guys would be amazing!!! The future goal is autocross and ripping up evening hill climbs. (I’m located in Kalispell Montana)

    Thanks!!!

    Gabe Miller

    1. Hello Gabe,
      Thank you for the compliments. Majority of the parts you mentioned will be good candidates for this project. Please check your email so we can discuss additional details.

  6. I am thinking about doing an EJ22T 2.35L stroker build in the near future. Pavel I can see that in both of the EJ22T builds you blogged about that you opted to keep the thrust bearing at #3 and machine the crank instead of machining the block for a #5 thrust bearing. Have these engines had later issues with crank walk? Is there a reason for doing it this way (other then saving money on machining costs)? Phase 1 Subaru cases with MTs are notorious for developing crank walk. In your experience would moving the thrust bearing to #5 have a meaningful effect on the life of the engine?

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