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'94 gx impreza - ej18 swap to ej20

ej18 ej20 swap impreza gx

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11 replies to this topic

#1 blaksam

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Posted 09 April 2014 - 07:45 AM

bought a write off 96 model .. suby with a working ej20 Na engine from and 5spd manual transmission and awd drivetrain ... and I already have a 94 gx impreza with an ej18 5spd fwd with a blown water pump and a really bad knock in the block from overheating due to blown water pump.... given that i paid $90au for the entire wreck i figure i might as well do the swap to the 2 litre...instead of a rebuild(to fix the knock which is most likely rod end bearings) .. so would swapping the engine be fairly straight forward?

Edited by blaksam, 09 April 2014 - 08:10 PM.


#2 blaksam

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Posted 09 April 2014 - 08:15 PM

if there's an existing thread with this swap please refer me i can't find one

#3 Gloyale

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Posted 09 April 2014 - 08:31 PM

You might not get alot here.......

 

We didn't get EJ20's here in US.....

 

BUt if both use the same SOHC heads......I would just swap the EJ20 longblock in with the existing EJ18 intake.



#4 blaksam

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Posted 10 April 2014 - 01:30 AM

the 18 is sohc but Im not sure about the ej20 til i pick it up owner couldn't tell me... anythings possible to achieve its just weather its cost effective... also i was planning on doing that eventually but don't have the money atm... was hoping it would be a fairly simple swap given i have everything from the other suby as well...

#5 Bushwick

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Posted 10 April 2014 - 11:51 PM

It'll fit if that's what you mean. 94 is OBDI correct? 96' will be OBDII, so there will be differences with the sensors, ECM, etc. if you try and swap the entire engine. The ej18 was essentially built off the ej20. Putting an ej25 block on an ej22 top-end, is a common cross breed here in the US and provides a nice bump in output from a base ej22 since it raises the compression ratio slightly plus the larger bottom end. Might want to look into an ej18 top-end on the ej20 bottom-end deal to avoid messing with the sensors. I'm pretty sure you'd get a similar bump in performance. Both of your engines are non interference, so that's a plus. Also, I know Australia has strict auto laws, but if you leave the top-end alone and just swap the block over, it should fly well under their radar. Try searches for "frankenbuild Subaru" or "frankenmotor Subaru" and see if others have done this with those 2 engines easily.


Edited by Bushwick, 10 April 2014 - 11:56 PM.


#6 blaksam

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Posted 11 April 2014 - 07:42 AM

yeah that's what I intended for the future I just dont have the money for new parts (for swapping heads and such) only doing it for a cheap repair atm, given that i have all the parts from both cars.

are the transmissions different for an AWD? like how does it work? mine being fwd at the moment, and the ej20 being AWD ...can you just use the gearbox without converting mine to awd or would i need to use the old gear box? ... i suppose a simpler way of putting that question would be whats the difference between a fwd and awd impreza... mechanically... is it just a lack of rear drivetrain? or?



#7 Bushwick

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Posted 11 April 2014 - 04:14 PM

You can buy an inexpensive head gasket and manifold gasket kit online for cheap. Since the cylinder heads only share 2 pistons each, I consider them to be SUPER easy to deal with considering they are light and compact. If you have some muscle or friend, you can pull the entire top end by yourself, then unbolt the block and lift out of the donor. With the donor engine out and sitting, you can trial fit everything from your car onto it and see if there will be gasket issues and/or bolt hole issues or not with your intake manifold and heads (take care not to gouge the head mating surface and unbolt the heads in a proper manner). Also, degrease donor engine FIRST (oven cleaner works G-R-E-A-T). Probably want to use an ej20 head gasket kit while making sure every coolant passage matches up with the ej18 heads, but I'm shooting from the hip here so you'll have to investigate more, especially with the final compression ratio (10.5:1 is the highest cr you want for a daily driver on premium 93 octane pump gas; 10:1 would be better and can tolerate 91 octane). IF the donor is DOHC, you'll need to find out if the crank pulley is balanced differently or not i.e. the weight of the balance and if the outside diameter is different. Ideally, you'll want to use whatever your engine has and attach to donor. I'm not sure if Subaru changed that up or not between different blocks or not? If you are wrong, it'll create an imbalance and a rumble that'll destroy the bearings and seals. Since the 94' is an OBDI? getting the sensors to work, etc. will be a potential headache on the newer engine, hence swapping the full donor block would be fairly straight-forward assuming there's nothing goofy about it. If you are intent on just swapping the engine as-is, you need to swap the entire engine harness from donor over and get it powered up. Lot of work, and you'll be down on HP.

 

 

Focus on the block swap and getting it running (I mean do your research and make sure everything will work out OK). Unless you want to go off road, I wouldn't mess with the AWD swap as it's pretty pointless in lower HP engines on dry pavement, PLUS trying to get AWD from a different year working in a non AWD car won't be fun. 

 

If you are low on funds, you can EASILY make quick cash parting out the donor's stuff you won't use, just don't tell them what you paid for it or else they'll think you should "give" them the stuff for nothing  ;)


Edited by Bushwick, 11 April 2014 - 04:17 PM.


#8 blaksam

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Posted 12 April 2014 - 10:03 PM

Yeh Im going to sell what i don't need so i can do the block swap then.... makes for more parts to sell as well... and ill stay away from awd was only thinkin about it.... btw i found out... its an ej20e sohc ;)

#9 blaksam

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Posted 12 April 2014 - 10:04 PM

also donor engine and gearbox is already out of the car..

#10 Bushwick

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Posted 12 April 2014 - 10:52 PM

Cool. Did you already pull it that quickly? If it was already yanked by previous owner, check it over thoroughly (make SURE it's even the correct motor).

 

Your ej18 is roughly around 85 kw (114hp); that ej20 should be 99 kw (132hp -but the numbers are all over the place from different sources so might be a tad less). If the compression ratio wasn't a factor, you can probably expect roughly an 18 hp bump minimum assuming the combustion chambers are the same between the two engines. I can't find the cr for an NA ej20, but the ej18 is either 9.5:1 or 9.7:1. If I were you, I'd visually inspect the combustion chambers in both engine's heads and see if the area is smaller in the ej18. If it IS smaller, you'll definitely be somewhere in the 10's as the smaller combustion chamber from the ej18 should bump you up. To play it safe, you might want to browse what's available for that engine and not get the thinnest head gasket set to avoid being overly high. I have NO idea what you guys have available at local gas stations there as far as octane ratings go, but if you guys get more than 93 oct you might be able to get away with a higher 10 to 11 range and not have it overly temperamental. In V8's, going from 9:1 to 10:1 can bring roughly 20hp. Given the smaller pistons in the ej20, maybe an extra 5-8 hp if you can go from 9.5:1 to 10:1 or 10.5:1. It's just a rough guess. But swapping the block over might net you 17-19 kw (22-25 hp) which should be pretty noticeable. Not to mention the extra torque :)

 

Please bookmark and update with how this goes as it's apparently not very common as most just jump up to an ej22 or ej25. I'm definitely interested in hearing about the progress in the future and hope it goes smoothly for you, good luck!


Edited by Bushwick, 12 April 2014 - 10:52 PM.


#11 blaksam

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Posted 13 April 2014 - 02:50 AM

Yeh it was already pulled out .. and he couldn't figure out what engine specifically it was but i checked it and researched and its an ej20e sohc... ffigured that out from vin and engine codes.. (then verified with pics of other ej20e engines cuz i know it couldve already been swapped out) ...
i did notice a missing coil pack in the pics so Im gonna hit him up about what else is missing.. most of everything is there though... and in good but dirty condition... thanks for all the input and info it helped heaps... will deaf keep this updated cuz it was way hard to find info on.....

also on a side note... here we have e85 .. 91..93..95...98.... depends on what service stations you use

#12 Bushwick

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Posted 13 April 2014 - 07:12 PM

Yeah, I thought I remembered an Aussie in the Saab forums saying they get higher octane, but I couldn't remember how high it went. Wish we got 98 easily here, but I'm guessing even if available it'd be $5-7 a gallon. WE used to be able to get higher octane at a very few select gas stations, but I don't believe it's the case anymore. Hell, 25-30 years ago you used to be able to pull up to a local, small-plane airport and get "jet fuel" at a pump LOL. My mom dated a guy in the mid 80's that had an original (pretty sure it was a 67') Corvette with a 427. Think he had 11:1 in it and would fill it up at the airport gas pump. 

 

Well, if your build pings a bit on 91, you have options ;)


Edited by Bushwick, 13 April 2014 - 07:13 PM.






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