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Old 07-03-2019, 10:22 AM   #1
whiterabbitrexy
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Default Gf8 v4 wrx ej20 heads ON a ej205 block stock ecu

Hi everyone i have a 1998 subaru Australian Wrx Gf8.....it has everything from factory stock beshides 3inch Tbe, vf22, fmic, and ecu is standard but soon will be fully tunable by installing a chipset and rom to turn it into a live standalone ecu......

The ej20 block Bottom end craprd it self long story short so i thought about installing a 2002 wrx ej205 for cheap.....i found one cheap for $300 aus, and now thininkg to myself my 1998 ecu parameters might be a bit diffrent fireing order compared to a ej205 block because of crank angle sensor might be off compared to my phase 1 ej20k block being suited to the factory harness and sensors?

Also notice somthing scarry the pistions come out complety FLAT to the top of the deck...my old block only had a ej20 wrx 75mm stroke and stoped a fair bit before the decking of the block.... will this mess with my timing and Valves hiting the pistons????

In all that said.....Block will bolt up perfectly with the ej205 oem gaskets.... i will use a ej205 harmonic balance Not my 1998 ej20k factory harmonic..... i want to play it safe i can run everything from Oil pump to cooling and block matting....so the rest im a little puzzled.

Please give us your advice on what u known i might be missing


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Last edited by whiterabbitrexy; 07-03-2019 at 10:36 AM.
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Old 07-18-2019, 11:39 PM   #2
whiterabbitrexy
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Here is a video of what I'm trying to explain and do

https://youtu.be/auiWy5QKM1A
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Old 07-19-2019, 08:33 PM   #3
ascendr
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A couple of points of clarification. The crank sensor picks up its signal from the crank pulley not the harmonic balancer. The sensor you are pointing to at 2:20 is the oil pressure sensor not the knock sensor. The knock sensor is the one you correctly identify at 5:35. I noticed that the differences you are pointing out like sensors, PCV, water crossover pipe, etc look similar to those we in the US need to change over to USDM when doing a JDM into USDM swap. There are several posts discussing this here, hopefully that will shed some light on what you will need to do.
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Old 07-25-2019, 07:57 AM   #4
whiterabbitrexy
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Quote:
Originally Posted by ascendr View Post
A couple of points of clarification. The crank sensor picks up its signal from the crank pulley not the harmonic balancer. The sensor you are pointing to at 2:20 is the oil pressure sensor not the knock sensor. The knock sensor is the one you correctly identify at 5:35. I noticed that the differences you are pointing out like sensors, PCV, water crossover pipe, etc look similar to those we in the US need to change over to USDM when doing a JDM into USDM swap. There are several posts discussing this here, hopefully that will shed some light on what you will need to do.
Oh gosh how embarrassing....yeah sorry that is the oil pressure sensor not the crank angle sensor.....i got confirmed by another member that i will need to change over all my sensors and use my Pcv..... anyone know what my compression ratio will be ? I think it will be somthing like 9:98 witch is scary stupid bad for weak wrx pistions
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Old 08-05-2019, 08:09 AM   #5
whiterabbitrexy
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Can somone please help me calculate my compression ratio? I cant find any info on volume of air for my v4 wrx cylinder heads.....also anyone know if this combo will work ? From what i know alot of people do add v6 ej207 shortblocks with good success....but this is a wrx ej205.... i think it should work ?
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Old 08-05-2019, 12:32 PM   #6
ascendr
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Using Jeff's spreadsheet I entered the following in a custom config:

EJ20G head volume (from Engine 1 on the sheet): 45.2 cc
Piston Dish Volume (EJ205 piston dish): 11 cc
Bore: 92mm
Stroke: 75mm
Gasket Thickness (EJ205 OEM): .8 mm
Piston Compression Height (EJ205): 32.7 mm
Rod Length (EJ205): 130.5 mm

Result: 8.85 Compression Ratio

Hopefully someone more knowledgeable can double-check and chime in but from the looks of it you would be running higher compression. As for the valve to piston clearance concern I was under the impression that the EJ205 piston clearance was more than the ej20g. I've had both blocks recently and the ej20g looked to be about flush with the deck where as the ej205 left some room. Again hoping someone more knowledgeable will chime in.
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