2.3 hybrid build

AlaskanProtege · 10-20-2010, 11:21 PM

ok, i have a 02' ej2.5 sohc 90k miles..... and a 05' ej2.0 out of a wrx w/ 30k miles....... i wanna take the crank and bearings from the 2.0 and put them in the 2.5 block and use the 2.5 rods and pistons and stock 2.5 heads..... and run about 6-8 psi of boost. am i missing anything? i know its not the sti block or internals but it should be a large step up from this 1.8NA.....also when i split the case are the bolts reuseable? or torgue to yeld? also i plan on running head studs aswell hopefully prevent head gasket failure under load... besides new rod bearings piston rings and gaskets i should be set right? any in sight would be awesome!!

* Registered users of the site do not see these ads.

Homemade WRX · 10-21-2010, 11:02 AM

um, if you are just running stock rods and pistons, you're CR will be dropped so much you can run a fairly healthy amount of boost...

I'd opt for EJ257 off the shelf piston; that matched with the 131.6mm rod from the NA EJ25 will put your quench height (excluding headgasket) around .9mm lower than stock. Either way, compression is going to be low, so run the numbers really quickly for both options. JE does have a slightly higher CR model piston available off the shelf too.

AlaskanProtege · 10-21-2010, 05:01 PM

Quote:

Originally Posted by Homemade WRX

um, if you are just running stock rods and pistons, you're CR will be dropped so much you can run a fairly healthy amount of boost...

I'd opt for EJ257 off the shelf piston; that matched with the 131.6mm rod from the NA EJ25 will put your quench height (excluding headgasket) around .9mm lower than stock. Either way, compression is going to be low, so run the numbers really quickly for both options. JE does have a slightly higher CR model piston available off the shelf too.

hmmmmmmm... i need to find a way to build this de-stoker w/o dropping CR below 9.0:1..... i guess i dont really need to destroke it but i love the uniqueness... if i run a stock gasket with no major machineing to the heads any ideas how to figure that CR out? stock is 10:1 right? can i run the 2.0 rods to keep the quench up?

Homemade WRX · 10-22-2010, 09:18 AM

the NA EJ25 phase 2 rods you have are the longest OEM rods subaru has made. You'll have to crunch some simple numbers to see what your CR will be.

Any reason you can't go below 9.0:1? custom rods or custom pistons can help to correct everything (compression ratio and quench height).

I'd run the numbers but I don't have my massive subaru compression spreadsheet with me...so I don't recall the values of the cc's on your heads or the stock pistons (which IIRC are pretty much flat).

CKxx · 10-22-2010, 11:42 AM

Quote:

Originally Posted by AlaskanProtege

hmmmmmmm... i need to find a way to build this de-stoker w/o dropping CR below 9.0:1..... i guess i dont really need to destroke it but i love the uniqueness... if i run a stock gasket with no major machineing to the heads any ideas how to figure that CR out? stock is 10:1 right? can i run the 2.0 rods to keep the quench up?

I don't know the stats for your particular motor, but as an example an EJ257 block and heads, with std. compression pistons, and a 75mm crank will have a CR around 6.7:1.

You really need a set of +2mm rods and some higher CR pistons (higher than a stock STi set, again, I don't know your motor) if you want to be around 9.0:1.

Homemade WRX · 10-22-2010, 02:36 PM

well shooting form the hip, I'll say with the higher cr JE ej257 pistons and his motor, he'll probably be a high 7:1 area...simply because he will have 1.1mm more rod length thus helping to greatly reduce final volume.

a 133.6mm rod would be what you need if wanting to keep your NA EJ257 style piston. 132.5mm if going to an EJ257 piston.

10-20-2010, 11:21 PM	#1
AlaskanProtege Scooby Newbie Member#: 217112 Join Date: Jul 2009 Chapter/Region: AKIC Location: Fairbanks Alaska Vehicle: 1998 GC8 modified black and orange	2.3 hybrid build ok, i have a 02' ej2.5 sohc 90k miles..... and a 05' ej2.0 out of a wrx w/ 30k miles....... i wanna take the crank and bearings from the 2.0 and put them in the 2.5 block and use the 2.5 rods and pistons and stock 2.5 heads..... and run about 6-8 psi of boost. am i missing anything? i know its not the sti block or internals but it should be a large step up from this 1.8NA.....also when i split the case are the bolts reuseable? or torgue to yeld? also i plan on running head studs aswell hopefully prevent head gasket failure under load... besides new rod bearings piston rings and gaskets i should be set right? any in sight would be awesome!! * Registered users of the site do not see these ads.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
2.0 to 2.5 hybrid build question	mvcsk8r	Built Motor Discussion	1	07-01-2008 08:47 AM
2.5 Hybrid Build progress	Twiztidunreal	Texas Impreza Club Forum -- TXIC	24	07-08-2007 04:00 PM
My 2.5 hybrid build	quikie	Built Motor Discussion	9	07-04-2007 09:40 PM
Looking for help with 2.5 hybrid build in East TN.	kinada423	South East Region Forum	2	10-06-2006 11:55 PM
Question 2.5l Hybrids Builds What Turbos	dingobite	Factory 2.5L Turbo Powertrain	4	09-26-2006 02:49 PM

10-21-2010, 11:02 AM	#2
Homemade WRX Scooby Guru Member#: 33782 Join Date: Mar 2003 Chapter/Region: MAIC Location: 3MI Racing LLC Vehicle: 96 bastard child search FIRST, then PM!!!	um, if you are just running stock rods and pistons, you're CR will be dropped so much you can run a fairly healthy amount of boost... I'd opt for EJ257 off the shelf piston; that matched with the 131.6mm rod from the NA EJ25 will put your quench height (excluding headgasket) around .9mm lower than stock. Either way, compression is going to be low, so run the numbers really quickly for both options. JE does have a slightly higher CR model piston available off the shelf too.

10-22-2010, 09:18 AM	#4
Homemade WRX Scooby Guru Member#: 33782 Join Date: Mar 2003 Chapter/Region: MAIC Location: 3MI Racing LLC Vehicle: 96 bastard child search FIRST, then PM!!!	the NA EJ25 phase 2 rods you have are the longest OEM rods subaru has made. You'll have to crunch some simple numbers to see what your CR will be. Any reason you can't go below 9.0:1? custom rods or custom pistons can help to correct everything (compression ratio and quench height). I'd run the numbers but I don't have my massive subaru compression spreadsheet with me...so I don't recall the values of the cc's on your heads or the stock pistons (which IIRC are pretty much flat).

10-22-2010, 02:36 PM	#6
Homemade WRX Scooby Guru Member#: 33782 Join Date: Mar 2003 Chapter/Region: MAIC Location: 3MI Racing LLC Vehicle: 96 bastard child search FIRST, then PM!!!	well shooting form the hip, I'll say with the higher cr JE ej257 pistons and his motor, he'll probably be a high 7:1 area...simply because he will have 1.1mm more rod length thus helping to greatly reduce final volume. a 133.6mm rod would be what you need if wanting to keep your NA EJ257 style piston. 132.5mm if going to an EJ257 piston.