Summary of the USDM EJ.
When it comes to EJ22s, there are 3 Phase 1 variations here in the USA.
They are also all SOHC as the USA did not get a DOHC version. Ever.
All have the same bore, stroke, & forged internals (rods, crank) with slight differences.
These engines have open decks, SOHC, & dual exhaust ports per head.
Pretty problem free for the most part of they're taken care of.
They share rods w/Phase 1 EJ20s & EJ18s & generally produce about 130-135bhp.
Compression ratio is about 9.5:1 max.
The 2.2 engine was further upgraded with higher compression, molybdenum coated pistons.
They also received valvetrain changes in the cylinder heads to reduce friction & single exhaust ports per head.
The block is open deck, the same as the first EJ22E.
The piston crowns in these engines are different than those in the earlier variations.
The compression ratio in this variation is about 9.7:1 max.
It produced 135bhp but there were a few dual ports produced in 1996 as Subaru was overstocked w/EJ22s @ the time of mass production.
The only turbocharged variant of USDM Phase 1 EJ22s.
These have closed decks, piston oil squirters, deeper dish pistons, slightly thicker rods, & their heads are drilled/tapped for turbo.
The camshaft has a profile that's set up for turbocharging & the valves are smaller than that of the 22E variant.
These are very strong but like all other things, can & will be destroyed if they are put under too much stress.
Now onto the EJ25D.
We got 3 variations of these in the USA (the last variation actually being a cross between Phase 1/Phase 2) & they produce 155-165bhp.
They have larger bores & higher strokes than the EJ22 along with thinner piston rods that are NOT forged.
As such, they naturally produce more power & tq but are not nearly as reliable due to their habit of blowing head gaskets like its their job.
The cylinder heads are variations of JDM heads but have lower RPM limits & lesser valvetrains.
These came equipped in 1996 Outbacks, GTs & LS/LSi & were bolted to an automatic only.
They could not be had any other way.
The 25D of this year had 9.5:1 compression, domed head chambers which were cut to the bore of the block, & high compression pistons.
These did blow head gaskets but not nearly as much as their later variations.
The cylinder heads had hydraulic lifters & larger intake ports than its later variations.
This engine made peak tq @ 2800rpm, which I personally think is awesome.
The peak bhp was 155 max.
This engine recieved changes to its valvetrain, Subaru got rid of the hydraulic setup to produce more power at higher rpms but lost the ability to produce peak tq @ low rpms.
The chambers are cut into clover shapes & are not domed as the earlier variant was.
The intake ports are larger than that of the 96 DOHC heads.
The pistons are also deep dish & square cut.
Rods & crank are the same as the 96 variant.
These were prone to head gasket leaks, which would lead to compromised & destroyed internals.
These were now in autos or manual transmission equipped cars.
Peak bhp is 165 max.
The factory "hybrid."
It has Phase 1 1997-1999 heads on a Phase 2 block with 1996-1999 internals (pistons) but the crank is Phase 2.
Came in auto or manual transmission equipped cars.
This engine produced the same power as the variant before.
Peak bhp is 165.
All EJ22s have 52mm rod journals & all EJ25Ds have 48mm rod journals.
This is the gist of what you're working with when you're dealing w/Phase 1 USDM EJ engines.
This is all of the general info that I have been able to gather from personal experience as well as others who have worked w/Phase 1 Subaru EJs. Don't let the horizontally opposed architecture of the engine surprise you. It's actually a really simple concept. Just another 4 stroke engine with an extra cylinder head. That is all it is.
I also request that this bit of information be stickied so that it is easily accessible at all times so the new guys know what they've been introduced to. I'll get onto hybrids in a short while.
I've noticed that there are many questions regarding hybrid engines & while I'm not going to go into full detail, I am going to explain the hybrids that I know will work with the stock Phase 1 ECUs that we have here in the United States. If anyone has more info on their hybrid builds, please feel free to chime in. Also, the use of different sized head gaskets will determine the end ratio. I'm just explaining the different types of hybrids on stock head gaskets & head gaskets MUST AT ALL TIMES match the bore of the block. If you have an EJ22 block, the EJ22 head gasket must be used & so on.
Dual Overhead Cam EJ22:
Done by installing EJ25D heads on an EJ22 (E or T).
There is no need to change sensors on the heads of the block since they are the same.
This hybrid has lowered compression (Es have 9:1 while Ts have 7.5:1) from it's original SOHC variant & is better for turbocharging, since it has pretty deep chambers combined with dished pistons.
The DOHC 22Es can be used as they produce a little more midrange power than the SOHC 22Es but the 22Ts should not EVER be used without turbocharging.
The best DOHC heads to use are the 97-99 heads as the chamber is enclosed in the bore of the EJ22's cylinders while the 96 25D chambers are cut to the bore of the 25D & should not be used on any EJ22 block.
This engine can be safely run on 87 octane.
Any Phase 1 ECU will run DOHC heads, even the first generation Legacies.
"Big Valve" EJ22T:
This is done by bolting EJ22E heads on an EJ22T block.
The compression ratio doesn't change much but the 22E heads have bigger valves, so this helps out w/tq delivery as a little more air is brought in to be compressed.
The heads are essentially the same as the turbo heads but they have to be drilled & tapped for turbocharging.
You must also use the 22T camshafts in this build as they have profiles for the turbocharger.
The 22T computer will run these heads without an issue.
Single Overhead Cam EJ25D:
This is any 25D block w/EJ22 heads on it (the EJ22 heads have small chambers, which contributes to the high compression).
Again, no need to change sensors.
However, the compression ratio increases tremendously (approaching 11:1), which necessitates 91+ octane be used at all times to keep detonation at a minimum to zero.
There are reports of this hybrid produces 180+bhp & nice tow-end tq.
This would probably be an engine good for rock climbing, mudding, rallying, & "dirty" situations.
The 97-99 25D block provides a lower compression than the 96 block, which has flat top pistons designed for max compression.
Using a 96 25D block may cause some issues with compression being TOO high & require more depth of control, like installing a stand alone ECU.
High Compression DOHC EJ25D:
This is made by installing 97-99 25D heads on a 96 25D block.
Compression is about the same as the SOHC 25D variant & it must be run on 91+ octane also.
The powerband is pretty much an exaggerated version of the 97-99 EJ25D.
This hybrid can run on the stock ECU.
Low Compression DOHC EJ25D:
This is made by installing 96 25D heads on a 97-99 25D block.
Compression is lowered to about 8.8:1/9:1 & makes this engine good for turbocharging but on the flipside, the heads do not allow very high revs.
Power produced is more or less that of a 96 25D.
This engine can run safely on 87 octane & on the stock ECU.
I only have pictures of my DOHC EJ22E hybrid but I have seen the hybrids I have mentioned (haven't seen a 96 25D SOHC yet) & they all seem to work well but the SOHC 25Ds grant the most power & low-end tq out of all the builds & are easier to maintain, since they have the simplicity of the SOHC design.
Hope this helps anyone who wants to have general info on EJ hybrids.
I am also going to explain this.
When using 2.2 heads on a 2.5 block, MAKE SURE that they are ported & polished (at the very least ported) or you will not be able to get the power you're expecting from the high compression combo.
Good info. Thanks!
Regarding the "Big Valve" 22T, I haven't personally done this, but apparently you can install 22E valves on 22T heads.
That is good stuff man, I may be ridiculous for asking this:
Ever heard of a ej18/ej22t hybrid? My thinking is along the the same lines as the honda mighty mini build of the d16y8 block with d16b1 non-vtec heads, low compression for turbo application.
I don't know the ins and outs of the boxer motor, but if the 2.2t heads and 2.2t internals go into the 1.8 block it would have low enough compression to sustain good boost pressures.
i think the 96 GT came with 5 speed or auto trans.
at least the parts manuals show it did.
the LSi was auto trans only, 96 - 97, and then discontinued.
it was never available with a manual trans.
i'm not sure why the 96 outback manual trans was ej22.
For you BD owners w/Phase 2 EJ22s (99s only):
If you wanted to make a high compression EJ251/3 (11.5:1), you would take the EJ222 heads/sensors, & put those onto your 251/3 block.
Your could also swap cams between the heads & see what kind of performance you come up with since the cams have different profiles.
The heads of the 18E are very similar to those of the 22T/E to the point where you cannot tell the difference between them externally. Internally, the 18E heads would be suitable for boost if they were drilled & tapped & had 22T cams in them. Other than that, there is no need to change heads, IF your head gasket is thick enough.
I believe that the 18E heads have a lower cc than that of the 22E/T heads. I'll have to double check on that.
The REAL question is whether or not one can put DOHC heads on an 18E block, like 25D heads or 20K heads, for example. That would be a great upgrade for 18E blocks.
If the block and heads are basically the same then the the rods and stroke are probably just shorter, said the rods aren't forged in the 1.8. though,That would be a good dual cam turbo motor. That means the exhaust mani and downpipe from ej22t would work too (in theory. ...kinda sounds like a crazy little build.
Nice gathering all this. Over the next while I plan to read this, i love learning
18E heads on an 22E will raise compression on that combo. The oil ports will line up just fine & the coolant ports will be fine since the open deck design will allow good passage from head to block.
Whatever head gasket you get would need to match the design on the heads to withstand the internal combustion pressures without worry.
The exhaust will fit since the 18E is dual port just like the 22E & 25D. They even have the shared benefit of header options.
Bad ass, I wonder what the compression is on the 18/22e block, I like the bulletproof 22e but I want it to pull all the way through the gears at least a little. I like n/a power, even though its expensive and fickle. I thought about eg33/bd swap but I hear for the trouble and cost the performance difference isn't worth it.
Good info again btw..
I have a few sets of extra 22T heads, 22T intake mani, downpipe, and VF11 that I am hoarding in case I ever get a Brat or a beater Legacy for a cheap turbo build. Some have safely run 5 psi without any engine management.
great read thanks for this information
the ej25d heads on the ej18 block may be limited, will be limited by the diameter of the ''fire ring''? and the cylinder bore.
the ej18 and the ej22 blocks are the same except for the bore.
so if there is the 25D heads fit on the ej22 they should fit on the ej18.
As for the EG33 swap, that's much better than swapping in any turbo EJ.
It puts out about 240bhp, it's 6cyl, 3.3L, is completely compatible w/any EJ22 piston or rod, has 3 exhaust ports, TQ pull all over it's RPM range, & is a very sturdy, well built, & reliable engine. It's a wiring nightmare but nightmares don't last for long. It can bolt up to any of our 5/6spds or autos.
For JDM turbo engines/205/255/257 swaps, we have to go through the same kind of wiring hell for engines that are not nearly as reliable as the EG33. If I were looking for power & extra potential, we don't have anything that beats an H6 swap. Linear pull, linear power, & a VERY Porsche-like sound is amazing.
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