Multiple Hybrid Equations.

[Alucard]

Let's fix this and repost the data so that the readers of this forum can have what they need to utilize what they have or want to build.

We will start with applications for the naturally aspirated 2.5.

EJ25E Version 1:
1990-1998 EJ22E heads on 1997-1999 EJ25D w/Cometic hybrid head gaskets.
Chamber cc: 41.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -14.5cc.
Deck clearance: 0.3mm.
Compression ratio: 10.4:1.
Compression ratio: 10.7:1 w/1mm head gaskets

EJ25E Version 2:
1990-1998 EJ22E heads on 1996 EJ25D block w/Cometic hybrid head gaskets.
Chamber cc: 41.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -8cc.
Deck clearance: 0.3mm.
Compression ratio: 11.4;1
Compression ratio: 11.9:1 w/1mm head gasket.

EJ25E Version 3:
1990-1998 EJ22E heads on 1999-2004 EJ251 w/custom Cometic head gaskets.
Chamber cc: 41cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -6cc.
Deck clearance: -0.3mm
Compression ratio: 11.3:1
Compression ratio: 11.7:1 w/1mm head gaskets.
Compression ratio: 12:1 w/0.8mm head gaskets.
Compression ratio: 12.4:1 w/0.6mm head gaskets.
(The EJ25E is the hybrid people formerly knew as "Frankenmotor.")

This kicks off the DOHC versions.
EJ25D Version 1:
1996 HLA EJ25D heads on 1997-1999 EJ25D block/OEM EJ25D head gasket.
Chamber cc: 56cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -14.5cc.
Deck clearance: 0.3mm.
Compression ratio: 8.6:1.
Compression ratio: 8.9:1 w/1mm head gasket.

EJ25D Version 2:
1997-1999 EJ25D heads on 1996 EJ25D block w/OEM EJ25D head gasket.
Chamber cc: 46.6cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -8cc.
Deck clearance: 0.3mm.
Compression ratio: 10.5:1
Compression ratio: 10.9:1 w/1mm head gasket.

EJ25D Version 3:
1996 EJ25D heads on 1999-2004 EJ251 w/OEM EJ25D head gaskets.
Chamber cc: 56cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -6cc.
Deck clearance: -0.3mm.
Compression ratio: 9.5:1
Compression ratio: 9.8:1 w/1mm head gasket.
Compression ratio: 10:1 w/0.8mm head gasket.
Compression ratio: 10.2:1 w/0.6mm head gasket.

EJ25D Version 4:
1997-1999 EJ25D heads on 1999-2004 EJ251 w/OEM EJ25D head gaskets.
Chamber cc: 46.6cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -6cc.
Deck clearance: -0.3mm.
Compression ratio: 10.75:1
Compression ratio: 11.1:1 w/1mm head gasket.
Compression ratio: 11.4:1 w/0.8mm head gasket.
Compression ratio: 11.8:1 w/0.6mm head gasket.

EJ25D Version 5:
1997-1999 EJ25D heads on 1999-2004 EJ254 w/OEM EJ25D head gaskets.
Chamber cc: 46.6cc.
Bore: 99.5mm.
Stroke: 79mm.
Head gasket thickness: 1.3mm.
Piston cc: -3cc.
Compression ratio: 11.2:1
Compression ratio: 11.7:1 w/1mm head gasket.
Compression ratio: 12:1 w/0.8mm head gasket.
Compression ratio: 12.3:1 w/0.6mm head gasket.

That concludes the 2.5 N/A hybrids.

[Alucard]

I'm going to start this off with the Phase 1 SOHC EJ22E's.

EJ22E Version 1 (90-96 EJ22E block).
Chamber cc: 41.
Bore: 96.9mm.
Stroke: 75mm.
Head gasket thickness: 1.3mm.
Piston cc: -14.5cc.
Deck clearance: 0.03mm
Compression ratio: 9.52:1.
Compression ratio: 9.82:1 w/1mm head gaskets.

EJ22E Version 2 (97-98 EJ22E block)
Chamber cc: 41.
Bore: 96.9mm.
Stroke: 75mm.
Head gasket thickness: 1.3mm.
Piston cc: -12cc.
Deck clearance: 0.03mm
Compression ratio: 9.86:1 (This is stock even though Subaru claims 9.7:1!).
Compression ratio: 10.2:1 w/1mm head gaskets.

EJ22E Version 3 (EJ22E head/EJ221/2/3 bottom. This is a hybrid that is not factory).
Chamber cc: 41.
Bore: 96.9mm.
Stroke: 75mm.
Head gasket thickness: 1.3mm.
Piston cc: -3cc.
Deck clearance: -0.03mm
Compression ratio: 11.27:1 w/1.3mm head gaskets.
Compression ratio: 11.71:1 w/1mm head gaskets.
Compression ratio: 12.03:1 w/0.8mm head gaskets.

The DOHC EJ22 hybrid approach is a bit more difficult with nomenclature as Subaru used different letters than "E" for each of it's 4 camshaft cylinder heads.
Though there were early EJ20 heads with pentroof chambers, we will be using the equations for the 46.6cc clover chamber heads since they are more plentiful and will be easier to obtain.
The EJ20 heads that possess the 46.6cc clover chambers are the following: Version 2 EJ20G (NOT to be confused with Version 2 WRX), EJ20H, EJ20R, EJ20K, Version 2 & 3 EJ20D, and USDM Version 2 & 3 EJ25D (along with Version 2 JDM EJ25D).
That being said, the Phase 1 head stage of DOHC EJ22 hybrid equations will be called "Stage 1 EJ22D" to keep things simple.
However, said particular hybrid can also be called "EJ22D, EJ22G, EJ22R, EJ22H", and so on to identify the heads being used on the EJ22 block if you want to go into detail within conversation.
Also, to keep things clear, no one should be using Version 1 (1996) EJ25D heads on an EJ22 block, as the chambers have a 99.5mm circumference vs the EJ22's 96.9mm bore.

EJ22D Version 1 (90-96 EJ22E block):
Chamber cc: 46.6.
Bore: 96.9mm.
Stroke: 75mm.
Piston cc: -14.5cc.
Deck clearance: 0.03mm
Compression ratio: 8.7:1 w/1.5mm head gaskets.
Compression ratio: 8.85:1 w/1.3mm head gaskets.
Compression ratio: 9.1:1 w/1mm head gaskets.

EJ22D Version 2 (97-98 EJ22E block):
Chamber cc: 46.6.
Bore: 96.9mm.
Stroke: 75mm.
Piston cc: -12cc.
Deck clearance: 0.03mm
Compression ratio: 8.92:1 w/1.5mm head gasket.
Compression ratio: 9.13:1w/1.3mm head gasket.
Compression ratio: 9.41:1 w/1.0mm head gasket.

EJ22D Version 3 (EJ221/2/3 block):
Chamber cc: 46.6.
Bore: 96.9mm.
Stroke: 75mm.
Piston cc: -3cc.
Deck clearance: -0.03mm
Compression ratio: 10.08:1 w/1.5mm head gasket.
Compression ratio: 10.3:1w/1.3mm head gasket.
Compression ratio: 10.6:1 w/1.0mm head gasket.
Compression ratio: 10.92:1 w/0.8mm head gasket.

This concludes Stage 1 EJ22D setups.

[nepbug]

You should throw in the 255/257 head gasket too. It's a thinner MLS version of the 251, I've seen both 0.6 and 0.7mm mentioned as the thickness.

Sent from my VS985 4G using Tapatalk

[Alucard]

Ooooh, good call. I'll add in the turbo Phase 2.5 blocks as well. It may take a while to create a lot of that data, since I lost a nice chunk of my original stuff, but it'll work out. I'll input the data a bit later.

[Alucard]

.

[Reason]

EJ22E V1-V2 heads/EJ25D V1 block = 11.4:1 with 1.3mm custom head gasket, but thinner 1mm head gasket yields 11.8:1

That's me!

Good thread, this will be a sticky.

[BDAlex95]

My compression is as follows:
Cylinder Bore: 97mm
Piston Stroke: 75mm
HG Diameter: 98mm
HG Thickness: 2.032mm
Combustion Chamber Vol: 46.6cc
Piston Dish: -12mm
Deck Clearance: -.0012
Final CR: 8.4979

I have the v2 25D heads and v1 22E block. Is my compression lower than I calculated since I'm using a 2mm headgasket?

[Alucard]

My compression is as follows:
Cylinder Bore: 97mm
Piston Stroke: 75mm
HG Diameter: 98mm
HG Thickness: 2.032mm
Combustion Chamber Vol: 46.6cc
Piston Dish: -12mm
Deck Clearance: -.0012
Final CR: 8.4979

I have the v2 25D heads and v1 22E block. Is my compression lower than I calculated since I'm using a 2mm headgasket?

Yes. You're actually closer to 8.3:1.

[BDAlex95]

Yes. You're actually closer to 8.3:1.

What did I do wrong then? I went here http://www.csgnetwork.com/compcalc.html to calculate the compression. Are my inputs off or is the calculator off?

[Alucard]

What did I do wrong then? I went here http://www.csgnetwork.com/compcalc.html to calculate the compression. Are my inputs off or is the calculator off?

I just tried that same combo of parts on that same calculator and got 8.52:1, which is the same as what I came up with when using the EJ22T head gasket. So, either that calculator is being crazy, or you have gotten 22T head gaskets.

[Alucard]

It's also telling me that the total displacement volume is 70cc? LOL, what? I'm getting 2217cc, which is about 135ci.

[BDAlex95]

I just tried that same combo of parts on that same calculator and got 8.52:1, which is the same as what I came up with when using the EJ22T head gasket. So, either that calculator is being crazy, or you have gotten 22T head gaskets.

That calculator is broken then. I got the EJ22T style gasket, but got custom .08in thickness cause I remember we were trying to get as close to 8.5:1 as we could. Wish we would have caught this when I was building the motor Oh well, 8.3:1 just means more space to fill with air.

[Thomistopheles]

From what I've read, EJ251 is .65mm and 255/257 is .56mm.

[Alucard]

From what I've read, EJ251 is .65mm and 255/257 is .56mm.

I've read the same. Subaru has changed head gasket thickness on the Phase 2 EJ25's quite a bit. I have anywhere from 0.6mm to 1mm as the EJ251/3 head gasket. The thickness availability between the EJ20's, for example, is ridiculous. The revisions will make one's head spin.

[Wiscon_Mark]

EJ22E V1-V2 heads/EJ25D V1 block = 11.4:1 with 1.3mm custom head gasket, but thinner 1mm head gasket yields 11.8:1

That's me!

Good thread, this will be a sticky.

I've added it to the newly minted "threads of note" for this forum.

[Alucard]

.

[Alucard]

Bump thread for updated and correct compression ratio data.

[Alucard]

Keep in mind the difference between Phase 1 & Phase 2 bottom end ends when it comes to piston clearance.
Phase 1 pistons can come up above the deck anywhere from .3mm to .4 (from rod stretch or JDM pistons).
Phase 2 pistons come up under the deck by about 0.3mm.

Also to note, the head chamber cc for the following heads:

Phase 1:
EJ18E - 41.
EJ20D V1 - 56.
EJ20D V2 & V3 - 46.6.
EJ20E - 41.
EJ20G V1 & V2 - 56.
EJ20G V3 - 46.6.
EJ20H V1 & V2 - 46.6
EJ20J - ? (This exists!)
EJ20K V1 & V2 - 46.6.
EJ20R V1 & V2 -46.6.
EJ22E - 41.
EJ22G - 46.6.
EJ22T - 41.
EJ25D V1 - 56.
EJ25D V2 & V3 - 46.6.

Phase 2:
EJ201 - ?
EJ202 - ?
EJ203 - ?
EJ204 - 49.
EJ205 - 49.
EJ206 - 49.
EJ207 - 49.
EJ208 - 49.
EJ20X - 49.
EJ20Y - 49.
EJ251 - 51.
EJ252 - 51
EJ253 V1 & V2 - 51.
EJ254 - 49.
EJ255 - 51.
EJ257 - 56.

(V1, V2, V3 refer to versions.)

[Alucard]

Turbo EJ25 hybrids:

EJ25T Version 1.
EJ22T heads on EJ257 block:
Chamber cc: 41.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -24cc.
Deck clearance: -0.03mm
Compression ratio: 9.15:1 w/1.3mm head gasket.
Compression ratio: 9.41:1 w/1mm head gasket.
Compression ratio: 9.6:1 w/0.8mm head gasket.
Compression ratio: 9.8:1 w/0.6mm head gasket.

EJ25T Version 2.
EJ22T heads on EJ255 block:
Chamber cc: 41.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -22cc.
Deck clearance: -0.03mm
Compression ratio: 9.37:1 w/1.3mm head gasket.
Compression ratio: 9.65:1 w/1mm head gasket.
Compression ratio: 9.84:1 w/0.8mm head gasket.
Compression ratio: 10:1 w/0.6mm head gasket.

EJ25D+T Version 1.
1996 EJ25D heads on EJ257 block:
Chamber cc: 56.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -24cc.
Deck clearance: -0.03mm
Compression ratio: 7.8:1 w/1.3mm head gasket.
Compression ratio: 8:1 w/1mm head gasket.
Compression ratio: 8.1:1 w/0.8mm head gasket.
Compression ratio: 8.23:1 w/0.6mm head gasket.

EJ25D+T Version 2.
1996 EJ25D heads on EJ255 block:
Chamber cc: 56.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -22cc.
Deck clearance: -0.03mm
Compression ratio: 7.95:1 w/1.3mm head gasket.
Compression ratio: 8.14:1 w/1mm head gasket.
Compression ratio: 8.27:1 w/0.8mm head gasket.
Compression ratio: 8.40:1 w/0.6mm head gasket.

EJ25D+T Version 3.
1997-1999 EJ25D heads on EJ257 block:
Chamber cc: 46.6.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -24cc.
Deck clearance: -0.03mm
Compression ratio: 8.6:1 w/1.3mm head gasket.
Compression ratio: 8.8:1 w/1mm head gasket.
Compression ratio: 9:1 w/0.8mm head gasket.
Compression ratio: 9.13:1 w/0.6mm head gasket.

EJ25D+T Version 4.
1997-1999 EJ25D heads on EJ255 block:
Chamber cc: 46.6.
Bore: 99.9mm.
Stroke: 79mm.
Piston cc: -22cc.
Deck clearance: -0.03mm
Compression ratio: 8.8:1 w/1.3mm head gasket.
Compression ratio: 9:1 w/1mm head gasket.
Compression ratio: 9.2:1 w/0.8mm head gasket.
Compression ratio: 9.35:1 w/0.6mm head gasket.
The 46.6cc clover chambers also include the EJ20G, EJ20H, EJ20R, EJ20K, EJ20D, and EJ25D heads that have them.
Will do 2.0 bottom as soon as I am able.

[Alucard]

It's been a few years since I was last in here but I thought to come back and do some work.
Update to compression ratio numbers to Phase 1 engines and hybrids using Phase 1 heads.
This section is incomplete as it takes time to jot down data from my notes but I will complete it.
For now, the compression ratio numbers are correct, given the data from OEM components.

[mike-tracy]

Have you seen Marnix's old compression matrix pdf file?

[Alucard]

Have you seen Marnix's old compression matrix pdf file?

I have not. I have done this with specs and a compression calculator. Is there a link to the compression calculator file? I thought it disappeared years ago!