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Old 03-03-2010, 10:32 PM   #1
WReXd
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Default ej207: best way to increase CR?

I’m planning to do a mild to moderate build and need some guidance. I’m currently running a v7 ej207 with a td05 20g, EWG, 50/50 meth/water injection, TMIC (though I’m considering front mount), and other supporting mods. The engine has ~30k miles and is running ok. My inquiry is primarily for future reference if/when I need/want to rebuild the engine.

Build requirements:
Displacement: 2.1-2.3L
Static CR: 9:1-9.5:1
Redline: 8-8.5k
Turbo: 44-50 lb/min
Power: 350 whp
Use: just my dd for now, will compete in the future
Budget: $2.5k (flexible)

Will do if my budget permits:
Cams: 264 duration, AVCS compatible (kelford and tomei my only choices?)
Heads: mild porting, valvetrain

The goal of this build is a broad powerband and response, not peak power. This is why my power goals are low. I don’t want to sacrifice longevity, so I’m more than willing to sacrifice power in its stead, even if that means spending more on quality work (balancing, blueprinting, etc.) instead of parts.

With all this in mind, what is the most cost effective path for reaching these goals? Should I keep my heads and sell the block for a different one? Keep the block and swap in a 2.5 crank? Will I need to upgrade the oiling system? Thanks in advance for your input.
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Old 03-05-2010, 12:40 AM   #2
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I think a 2.2l block with your 2.0L heads will get you in that compression range. And if its the 2.2lT block then it can handle the boost you want no problem. I agree with sacrificing a little power for longevity. Im plan on doing something similar in the far future.
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Old 03-05-2010, 08:13 AM   #3
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correct me if im wrong but i was under the impression that the subaru 2.2l block with wrx heads seriously lowerd compression i have scene numbers as low as 8. If you want a bump in compression the 2.5 sti block with wrx heads should work well ive scene them make alot of power.
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Old 03-05-2010, 08:27 AM   #4
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tossing a 79mm crank into your 2.0 engine will increase your displacement. also increases the height, which I believe, needs to be lowered.
IMO, custom pistons should do the trick.
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Old 03-05-2010, 10:28 AM   #5
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Quote:
Originally Posted by Nuke209 View Post
tossing a 79mm crank into your 2.0 engine will increase your displacement. also increases the height, which I believe, needs to be lowered.
IMO, custom pistons should do the trick.
+1

....just like that. You gain displacement and also get your desired compression ratio via custom pistons. You also keep your stock bore so you have cylinder strength.
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Old 03-05-2010, 11:50 AM   #6
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Pistons alone won't raise the displacement though, which is why I thought of getting a 79mm crank. The stock usdm sti crank should suffice, right? Would I need to cross-drill it to keep my redline?

Nuke, you also brought up a point that I've been thinking about... if the increase in height will cause the pistons to hit the head, and I get shorter pistons to alleviate that, won't the compression be low? How do they even achieve high compression on these things?
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Old 03-05-2010, 11:59 AM   #7
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With the pistons, you'll need a custom set, so you'll get any CR you ask for. Typically ~800 for a set depending on the maker.

There are some cheaper shelf pistons available for the 2.0 stroker, but I don't think any are available with the CR you're looking for.

With proper bearing clearances and oil pump/shims if necessary you should be able to do 8k redline. There should be a few folks with stroked 2.0's that can chime in on that.
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Old 03-05-2010, 12:00 PM   #8
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On custom pistons they can make the dish whatever shape you need to achieve your desired C/R.
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Old 03-05-2010, 12:52 PM   #9
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Quote:
Originally Posted by Nuke209 View Post
tossing a 79mm crank into your 2.0 engine will increase your displacement. also increases the height, which I believe, needs to be lowered.
IMO, custom pistons should do the trick.
yup, puts you at a 2.1 and some change. Will need custom pistons and then can change your CR.
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Old 03-05-2010, 01:16 PM   #10
WReXd
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Ah so it's the shape of the dish that keeps the pistons from hitting the head (or valves, I should say)...

For the pistons, what manufacturers and alloy would you guys recommend? For my power goals, would 4032 suffice?

Also, I'm curious why no one has brought up shorter rods and/or thicker head gaskets as options. I'm assuming they're not good ideas, but why? Based on some reading I've done, a 1mm gasket should get me into my CR ballpark and keep the pistons from hitting the heads without me having to replace them.
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Old 03-05-2010, 01:34 PM   #11
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all you need to have them do is...

diameter of your choice for the 2.0L bore 92mm / 92.25mm or 92.5mm
same dish shape as your 2.0L pistons or your shape
desired CR
EJ257 compression height for the wrist pin.

That's all... I got CP's for my build. The compression height is what's going to determine how much the piston comes to the surface deck.
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