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csweston
04-03-2011, 09:14 PM
If I understand correctly from what ive read putting the SOHC on an EJ25 with DOHC will up the compression ratio. However the SOHC don't flow as well. So would the end result be more power or would you end up losing power?

mike-tracy
04-03-2011, 09:45 PM
The sohc ej25's actually flow better than the phase I ej25D heads. The problem you'll run into is electrical - specifically the cam and crank sensors and triggers (you'll need the sohc 25 intake manifold as well). I believe there is an oem parts solution (I looked into doing this a few years back, can't remember exactly) involving ej18 parts, but the combination isn't ideal - the reason I was interested is because getting cams for the sohc is half as much as the dohc heads.

rougeben83
04-03-2011, 11:50 PM
SOHC shifts the torque curve towards the middle a little, but I think this has more to do with the OEM cam timing...both are capable of roughly the same peak HP though. It's not until you start taking advantage of the inherent properties of DOHC in the higher revs would you really start to see a difference IMO.

csweston
04-04-2011, 12:08 AM
Id like to find out the combination to make this run, also the electrical aspects. Get a E-manage piggy back and tune for e85 :)


What about using phase 1 EJ22 SOHC? Would that still bump the compression ratio?

Huffer
04-04-2011, 06:55 AM
Sohc shortblock plus dohc heads = bump up in compression

prodriver1
04-04-2011, 09:15 AM
what about changing pistons? do any of the engines have higher comp pistons or longer rods? I used to be into hondas and you could build a 12.5:1 compression engine with stock OEM honda parts. and in VW and Nissan land they have forged cranks in some of the stock engines (passat 1.8t and some of the SR20's) any subies have that?

StatGSR
04-04-2011, 11:00 AM
Id like to find out the combination to make this run, also the electrical aspects. Get a E-manage piggy back and tune for e85 :)


What about using phase 1 EJ22 SOHC? Would that still bump the compression ratio?

yes this does bump up the compression (this is generally referred to as a high comp Frankenstein engine in the subaru community). It is NOT an upgrade from an originally stock DOHC or SOHC EJ25. it is an upgrade for someone with a SOHC EJ22 though (most of the gain is seen by the displacement increase and eliminates having to do any wiring changes as the heads still match the car)....

If you want to increase the CR on an EJ25 buy pistons

rougeben83
04-04-2011, 11:43 AM
The EJ205 and EJ255/7 have forged cranks I think...they are also interchangeable with the late model n/a ej25's (I think the ej25d isn't one of them though).

csweston
04-04-2011, 12:14 PM
Dang, i was just looking for an easy option if i had to replace my head gaskets.

Huffer
04-04-2011, 12:22 PM
Hang on now.

If you just simply take the short block from the SOHC EJ25, and apply the heads from a DOHC EJ25, you will effectively bumped the compression up to around 11.1. This may require the use of 89 octane fuel to avoid pinging, but it will make the engine more lively.

This was a build I was going to undertake but eventually had to sell the shortblock due to a lack of funds.

StatGSR
04-04-2011, 12:28 PM
^ i got no objections to that swap, just need to look into what thickness head gasket you can/need to run.


found some decent info here....

http://forums.nasioc.com/forums/showthr ... =sohc+dohc (http://forums.nasioc.com/forums/showthread.php?t=901904&highlight=sohc+dohc)
http://forums.nasioc.com/forums/showthr ... =sohc+dohc (http://forums.nasioc.com/forums/showthread.php?t=1672854&highlight=sohc+dohc)

mike-tracy
04-05-2011, 12:38 AM
Ben, they all have forged cranks, lol. The earliest STI's shared the same crank and rod part numbers with the ej18, lol. Aka, nothing special. But you're right, to use a phase II crank he'd have to have his block machined for a thrust bearing on position #5, and an ej251/3 crank any non ej25D rods (the lengths are the same on all ej rods except for the ej25d). For some more build fun the ej18/20/22 crank and ej251/3 pistons would create a destroked 2.35L motor. Happy reving fun!

But methinks the best/easiest solution would be to put a phase II '25 n/a block as mentioned above, using the thicker ej25d head gaskets.

prodriver1
04-05-2011, 09:06 AM
Ben, they all have forged cranks, lol. The earliest STI's shared the same crank and rod part numbers with the ej18, lol. Aka, nothing special. But you're right, to use a phase II crank he'd have to have his block machined for a thrust bearing on position #5, and an ej251/3 crank any non ej25D rods (the lengths are the same on all ej rods except for the ej25d). For some more build fun the ej18/20/22 crank and ej251/3 pistons would create a destroked 2.35L motor. Happy reving fun!

But methinks the best/easiest solution would be to put a phase II '25 n/a block as mentioned above, using the thicker ej25d head gaskets.
so are the EJ25d rods longer? and what about strength, are any of the thrusty bits stronger on any particular engine? someone in the subaru world has to have all this info in a forum somewhere.

Grafton
04-05-2011, 10:38 AM
time for the compression guy to chime in...

you best bet @ an all oem compreesion bump is the phase 2 short block inbetween you heads it grants you an approx 10.7:1 compression ratio if you use sti thickness headgaskets

the 2.2/2.5 hybrids are ment for people with a 2.2 to start with no wiring changes ftw

rougeben83
04-05-2011, 04:21 PM
Ben, they all have forged cranks, lol. The earliest STI's shared the same crank and rod part numbers with the ej18, lol. Aka, nothing special. But you're right, to use a phase II crank he'd have to have his block machined for a thrust bearing on position #5, and an ej251/3 crank any non ej25D rods (the lengths are the same on all ej rods except for the ej25d). For some more build fun the ej18/20/22 crank and ej251/3 pistons would create a destroked 2.35L motor. Happy reving fun!

But methinks the best/easiest solution would be to put a phase II '25 n/a block as mentioned above, using the thicker ej25d head gaskets.
so are the EJ25d rods longer? and what about strength, are any of the thrusty bits stronger on any particular engine? someone in the subaru world has to have all this info in a forum somewhere.

Yeah ej207, pretty much has all forged internals...also balanced to spin up to 8000 rpm.

But in all seriousness, you don't really need drop so much money and effort on an NA build. Go with what everyone is already telling you with the Phase 2 shortblock and DOHC heads with the valve work and cams thrown in. Run 89, or even 93 octane.

prodriver1
04-06-2011, 09:07 AM
But in all seriousness, you don't really need drop so much money and effort on an NA build. Go with what everyone is already telling you with the Phase 2 shortblock and DOHC heads with the valve work and cams thrown in. Run 89, or even 93 octane.[/quote]


effort is free and fun to use in the garage, and $? used engine parts from junkyard cars is not expensive.

prodriver1
04-06-2011, 09:17 AM
I was looking for something like this: 95' civic lx 4 door with the stock D16Y7 (non V-TEC 1.6l) put in D16Y8 V-TEC head from a 97' CRX Si, use the pistons from a D16A1 (88-89 integra) and the combo gives a 12.6:1 CR. I would love that! but not a honda though, I dont like engines made from rubber bands wrapped in aluminum foil LOL :D

StatGSR
04-06-2011, 09:21 AM
^ i hope you were just trying to make an example because none of that made any sense (all your vehicle to engine references are incorrect except the first gen integra)

and yea, d-series engines are arguably much tougher and more reliable than most subaru engines.....


i guess its a good example in that building an NA d-series is about as silly as building an NA EJ

prodriver1
04-06-2011, 10:08 AM
^ i hope you were just trying to make an example because none of that made any sense (all your vehicle to engine references are incorrect except the first gen integra)

and yea, d-series engines are arguably much tougher and more reliable than most subaru engines.....


i guess its a good example in that building an NA d-series is about as silly as building an NA EJ


the engine built was done by a honda expert and it worked great Omniman I think is his name, you should look it up as it is correct. honda joke was just that, a joke, I have said many times I love hondas. and as far as silly goes that was a huge ass hole statement, are you fucking calling me "silly"? piss off dude! silly is putting work into a project that will never be, silly is putting a honda tach as your avatar on a subaru forum, silly is ONLY having shitty attitude comments on every post, you act like mr.fuckingknowsitall. now you have a shitty comment, feel good?

Huffer
04-06-2011, 10:41 AM
prodriver, cut it out, or expect a ban. Member-abuse is not tolerated around here. Understood?

StatGSR
04-06-2011, 11:01 AM
the engine built was done by a honda expert and it worked great Omniman I think is his name, you should look it up as it is correct.

I know of omniman, hell i have his coilovers on my integra. my point was that a 95 lx civic does not have a d16y7 (it has a d15b7, d16y7 is from a 96-00 CX/DX/LX), a 97 crx si doesn't really exist (i consider it a stretch to refer to a del sol as a CRX at least in this country), and the d16y8 is from 96-00 civic EX's and 96-97 Del Sol Si's

don't take it so personal dude, I just don't see the value in dumping thousands of dollars into building NA EJ25's and D16s for that matter. yes a few hundred here or there is one thing, and trying a creative approach to getting a little more out of the engine while in the middle of a rebuild is another, but a bottom to top build just because seams like a waste to me.

Sorry if i come like a know it all, i just know how to use the internet to find information i want to know. i just like get to the point so i can help people help themselves instead of running in circles asking questions that have been answered 100 times...

btw, I've had that avatar since 2003 on all my car forums, its not going anywhere.

prodriver1
04-06-2011, 12:37 PM
I know of omniman, hell i have his coilovers on my integra. my point was that a 95 lx civic does not have a d16y7 (it has a d15b7, d16y7 is from a 96-00 CX/DX/LX), a 97 crx si doesn't really exist (i consider it a stretch to refer to a del sol as a CRX at least in this country), and the d16y8 is from 96-00 civic EX's and 96-97 Del Sol Si's
I had a civic lx with the 1.6... I do make the mistake of using euro facts but thats my familiar source of info is formula monkey and thebox.bz hell I even type tyre and colour when I talk cars.
don't take it so personal dude, I just don't see the value in dumping thousands of dollars into building NA EJ25's and D16s for that matter. yes a few hundred here or there is one thing, and trying a creative approach to getting a little more out of the engine while in the middle of a rebuild is another, but a bottom to top build just because seams like a waste to me.
the whole point of asking about OE upgrades IS to save thousands of $. that civic build was done for cheeeeeeeeeeap.
Sorry if i come like a know it all, i just know how to use the internet to find information i want to know. i just like get to the point so i can help people help themselves instead of running in circles asking questions that have been answered 100 times...
the only OE hybrid build I have seen with any sort of info is just a block head swap, I just want to see if its possible to go further
btw, I've had that avatar since 2003 on all my car forums, its not going anywhere.[/quote]
I don't actually care about any of the things I said negatively to you, I was just illustrating my point of hurtful comments being rubbish, this is a free country feel FREE to say anything to anyone and have whatever opinion you want its a beautiful thing and if anyone tries to keep that from you... well I think theirs a constitution they need to read

Huffer
04-06-2011, 12:40 PM
I don't actually care about any of the things I said negatively to you, I was just illustrating my point of hurtful comments being rubbish, this is a free country feel FREE to say anything to anyone and have whatever opinion you want its a beautiful thing and if anyone tries to keep that from you... well I think theirs a constitution they need to read

Well done. You just got this thread locked.

Maybe you should READ the rules of this forum because you obviously don't understand them - you're allowed an opinion, but when you start bashing someone for questioning what you post, and insulting them, you lose all your rights and respect.

viewtopic.php?f=49&t=1863 (https://sl-i.net/FORUM/viewtopic.php?f=49&t=1863)

Well done.

Airgne
04-06-2011, 10:40 PM
nice. this is not nasioc or rs25. take that crap over there.