EJ25 Open Deck 500BHP Max Power Boost Strength Capabilities
 

Hi all,

New to the forum scene and would like some info on the EJ25 open deck engine in terms of strength.

I have a classic Subaru but with a forged EJ25, H-beam rods, arp bolts, quad gasket, rebuild heads, cosworth pump, billet steel nitrated crank, 1200cc injectors, turbo technics sc215 turbo (550BHP rated), 6 speed box etc etc all the goodies to hack 500 BHP.

BUT my question is now the engine has been run in; currently at 1.1 bar 401BHP, what's the max power the OPEN DECK EJ25 can take?

I was thinking of maybe 1.8 - 2.0 bar but local Subaru specialists are advising not to as the cylinder walls are too thin..?

What boost will I be able to push to before it causes problems as I know the closed deck engines are preferred..?

Any info on this would be much appreciated..

Thank You

Everything more than 450 will be pushing your luck (11mm ARP are the limiting factor as well).Also depends on rods used.

People have run 2.0 ODBs past 500 but i dont recally any one doing it on 2,5.
I would consider 2,5 cdb with 14mm head studs for that power.

I would side with the specialist here as the advice there giving you is from experience.You can get some good power from a forged 2.5 but the powers and boost that your thinking of running,you would be on borrowed time its the ODB's nature i'm afraid.SJ.

Even a scdb 2.5 would be near the limit at 450-480bhp, above 500bhp pining or closed deck insert is the only way.

Right thanks for all the replies guys.

Say I was to get the 14mm head studs and then go for a map what would you guys recommend in terms of max boost then?

Can I atleast push it to 450 bhp ?

CDB is the way but don't want to throw too much money at it after all of this..

Thanks again

Its not the headgasket I would be worried about, its more the ovalling of the bore, movement from the bore or splitting a bore. You are doing well as it is, unless you're willing to put some serious money into the engine I would leave as is.

+1,or sell block and start again with a CDB.SJ.

The engine would have to be dis-assembled for the 14mm stud conversion anyway, so you may as well go the whole hog and get the block pinned or CDB converted while you're about it.

This ^

I run over 500hp on a odb but it is a 2ltr so I believe these have thickets walls...

Much thicker bores, 92mm is standard on an Ej20 and its 99mm on an Ej25 so you have 7mm more material in the bore :thumb:

Assuming the specialists were either RCM or Api, my advise would be to follow their advise...

Just get the block sleeved or pinned , job done !

That's a how long is a piece of string kinda question, mate. Depends on how you're going to use it among other things. Put it this way My old 2007 Sti with a fully forged build and 11mm studs on the EJ257 block was at 470ish at 1.6 bar and that was as far as the engine builder or mapper suggested it be taken.

Bare in mind compared to some people, I drive like a complete p*ssy too! :D

The real question is can you afford to fix it if you turn up the boost and it goes pop! If not, leave it as is! :D

The 2.5 block is not safe above 450 hp - above that and its life will be severely shortened. Run 1.6 bar maximum.

If pinning or cdb'ing or any other trick made it work, us proper tuners would be shouting out loud from the rooftops.

We don't, none of us.

Sure some folks are ' getting away with it ' but professionally it would be suicide.

David APi.

^^^^^There you have it^^^^^.SJ.

api build on this car running 472bhp............

https://www.scoobynet.com/subaru-444...ld-470bhp.html

That's my old car :D And I'll have you know it was 473 ;) See the comment about boost. It just made good power for the boost. 450 isn't an exact cut off. The build was based on an SC46 (which is referred to as a 450+ capable turbo) at 1.6 bar they tend to produce a bit more than 450 with the right supporting mods of course!

Thanks to David (Merlin who built it) and Bob R who mapped it! :thumb:

BTW 4 years and it's still going strong :thumb:

Can't go wrong with an API build! If David says it's good, it's good! If he says don't, then don't ....... I learned that the hard way :D

PS I do miss that car - it was mental!!

its an awesome looking car mate

i am interested in this thread as my (possibly) next blobeye has an open deck 2.5 fully rebuilt by zen performance running a standard location garrett gt3071 turbo and is making 413bhp at the minute but i would like to know if its capable of more.

ive seen gt30's making well over 500bhp but i would be happy with 450 ish,im guessing with it being a 2.5 its the torque that matters :D

Well its not that huge amount....around 900£ for machin work and studs:)

2 bar I reckon ?

2.5 SCDB here, run 1.6 bar normally, 1.75 bar when I feel like it. 50k miles since the build, but it blew headgaskets 20k into that so went 14mm studs and a cossie headgasket then, and it's not missed a beat since.

When - not if - it goes again I will try a CDB insert and see what happens if I push the boost to 2 bar+ :D

ASperformance claim 600 bhp capable block.

I've still got mine,:D

Yep , I run 2.0 bar tailing down to 1.7 ish ! 530 bhp , no issues ! Sleeved block though and14mm

Sleeved block is another level (expensive) so wont be looking into that lol

Sweet then thanks for the replies will be going for the 1.5 bar level in terms of boost and see what the car makes..

Will update when done, hopefully next week

I thought all 2.5's were scdb or am I wrong?

Wrx and STI blocks are scdb.....maybe is out of NA car?

WRX are open deck if it is the 255 version

It is the 257 version that is scdb. Regardless of the scdb the liner walls are too thin to sustain high boost pressure and will crack.

We did a 2.5 years ago using "darton sleeves" a real pita to do But to my knowledge it is still going and regularly gets thrashed to death.

David

But then again Darton Sleeves don't come cheap..