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Old 09-27-2005, 12:43 AM   #1
cjfike
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Default EJ22T w/ SOHC 2.5 heads

Although the 22T block is built for turbo applications, there wouldn't be an issue with bolting on the 2.5 heads and intake manifold (additionally the other connections to the heads like exhaust...) and run this NA for a while.

Or would there?

From reading posts on not quite the same but very simillar topic, the ECU doesn't really care about the block, but it does care about the heads. What concerns me is the increased volume in the heads is going to mean lower CR. Although I read that this isn't a problem since the lower CR is easier to turbo, and then some addittional latitude with boost pressures. Those posts were a complete build all at once. Which would be wonderful, if I had the money to buy the turbo and TMIC at this moment also.

Any thoughts?
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Old 09-27-2005, 12:48 AM   #2
svek
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i dont think you would want to drop below the 8.0:1 CR of the ej22t. from what i understand 8.0 is a really good number...
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Old 09-27-2005, 12:53 AM   #3
cjfike
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I haven't gotten out my slide rule yet, I don't think the RS heads would go below 8.

Meaning it would be lower CR than the RS but not to a point below 8.
I remember seeing a post on this very topic, but I cannot find it

Last edited by cjfike; 09-27-2005 at 12:55 AM. Reason: clarification
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Old 09-27-2005, 01:07 AM   #4
poormansporsche
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You should talk to wedge...

http://forums.nasioc.com/forums/showthread.php?t=559449

I think he's pretty much the know-all end-all when it comes to this.

cheers

garrett
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Old 09-27-2005, 01:08 AM   #5
svek
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Quote:
Originally Posted by cjfike
I haven't gotten out my slide rule yet, I don't think the RS heads would go below 8.

Meaning it would be lower CR than the RS but not to a point below 8.
I remember seeing a post on this very topic, but I cannot find it
hmm you may be right...wheres monsoon when you need him
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Old 09-27-2005, 09:55 AM   #6
cjfike
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monsoon? where it rains heavily and constantly in eastern india? why would we want that? unless we convert a subie into a swamp racer!
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Old 09-27-2005, 12:17 PM   #7
cjfike
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Hmmm... I think my slide rule skills have gone from rusty to rusted shut. I come up with a CR of 9.74

However I will have to use a non-stock head gasket with a minimum diameter of 100mm so it is not unsupported. But I cannot remember how much the pistons will rise above the cylinder walls, therefore I cannot arrive at a definitive calculation.

Searching for this has brought me across some posts written by Monson, so I figured out the monsoon reference.

Once I find the measurement, then I can start looking into gaskets.
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Old 10-01-2005, 10:36 AM   #8
Matt Monson
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I was out sick for a few days and missed this thread. I only saw it this morning when was looking for another thread that had fallen to page 2...
I think you need to pitch your slide rule into the trash. Ej25 heads on an Ej22t block put you in the low to mid 7's:1 depending on if you use SOHC or DOHC heads. This is using the Ej22T head gasket, which is recommended. Remember, EJ22T pistons clear the deck, so you need a thick gasket with them.

Could you drive it for a while without boost? Sure. It would be a slug, but it would drive fairly normally. Since you have a '99, you have a MAF and it can compensate for the changes in displacement. If one were to do this on a MAP based car, it would run pig rich since the MAP takes no measurement of air volume, and would assume you still had the same displacement.
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Old 10-01-2005, 01:44 PM   #9
cjfike
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The heads are SOHC. The gasket was the only variable, the difference in the head volume for the SOHC is less than 1/2 of what the DOHC is. Unless I miscalculated there.
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Old 10-01-2005, 02:57 PM   #10
Matt Monson
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I don't know where you are getting your base numbers from, but DOHC and SOHC EJ25 heads only have 2cc's difference in combustion chamber volume between the two of them...
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Old 10-01-2005, 03:21 PM   #11
cjfike
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You are right. 7.72 CR with a .43 thickness gasket.
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Old 10-01-2005, 03:21 PM   #12
svek
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Quote:
Originally Posted by Matt Monson
I don't know where you are getting your base numbers from, but DOHC and SOHC EJ25 heads only have 2cc's difference in combustion chamber volume between the two of them...
lots of info about the different ej25 heads in my DOHC thread http://forums.nasioc.com/forums/show...highlight=dohc

but yah monsoon is right...


Quote:
Originally Posted by matt monsoon
Ej25 heads on an Ej22t block put you in the low to mid 7's:1
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