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1996 Legacy Lx Sedan
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5 Posts
Discussion Starter #1
Ej18 block, ej15 crankshaft. Has this been done before? What would be the pros and cons to this if possible.

Ideally I would like a higher rpm, low CR (for turbo) EJ18. This isn’t aiming for super high hp or ever longevity, just a bit of dumb fun for someone that’s not a gearhead but an aspiring one!

Cheers for any and all replies. Much appreciated :)
 

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1995 EZ30 Coupe
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867 Posts
The ej15 (and ej16) uses a 65.8mm stroke! Super short compared to the bigger engines. Should come out to about 1.66 liters. I'm getting a rod-stroke ratio of about 1.99.
 

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2000 RSTi
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916 Posts
I am only semi familiar with the destroker builds, but don't you need custom height pistons for it to work? Going the other direction, my stroker ej22/2.34L pistons are a different height than normal ej22 ones.
 

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1995 EZ30 Coupe
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867 Posts
Well, you're SUPPOSED to use either hight adjusted pistons or longer/shorter rods... Depending on stroked or destroked...
I'm gonna be assembling an ej25 destroyer (I hope, meant that to be destroker) with an ej205 crank and STI rods/pistons. The pistons won't quite reach normal hight and will affect the quench and drop the compression ratio. I'm keen to see what it can do anyway.
 

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1996 Legacy Lx Sedan
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5 Posts
Discussion Starter #6
I am only semi familiar with the destroker builds, but don't you need custom height pistons for it to work? Going the other direction, my stroker ej22/2.34L pistons are a different height than normal ej22 ones.
In all honestly I have little to no idea, I’m extremely new to modding. (maybe 3-4 months of research but nothing physical yet) Which is exactly why I thought I’d try my luck out here given that a solid 20% of what I know as it is was read from here haha, as mentioned above this isn’t supposed to last for long it’s just a first project to get my hands dirty, wrap my head around engine components and what I can do with them!

Anybody know if pistons not meeting normal height is bad? What’s your take SoCo? You seem to know a thing or two haha.

That Ej25 project sounds like it’ll be fun! I’ll be making sure to follow along with that!
 

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1995 EZ30 Coupe
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867 Posts
The top of the piston is meant to reach a certain height in the cylinder/combustion chamber. That's why mike-tracy's pistons are different than stock, I'm guessing they're shorter.
Naturally, a shorter stroke means the piston won't travel as far, up or down, from it's mid-stroke position. When the piston doesn't reach it's full height, the quench area is affected. Basically it's the shape and size the combustion chamber is meant to achieve to help improve the efficiency of combustion. Altering the quench area can prevent all the fuel from being burned, or even cause the motor to be prone to knocking.
That's why you see people machine out the combustion chambers of ej20 heads to match them to the ej25 bore. This is to maintain a proper quench area, as the heads will technically bolt up and run without machining.
I recapped here:

All that said, we're certainly not the first people to say screw the quench. My own inspiration comes from reddevil's 1990 Legacy wagon. Besides supercharging and twin charging, he had a few frankenmotors in there and it makes for an entertaining and informative read.
 

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2000 RSTi
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916 Posts
Reddevil can and did rebuild his engines in an evening. Frequently ;)
 
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White Lwag
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1,081 Posts
How about a 65.8mm crank with +6mm rods on a 2.0L bore NA build with ported heads and long duration cams? Maybe 14,000rpms? Dream of mine.

I say do it.
 

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White Lwag
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1,081 Posts
Not overly sure what turbo would work well?
Internals would need to be balanced to a T.
Sounds like fun. Dream big. Do it. Report back.
 
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