Calculating 1/2UZ Compression Ratio

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RotaSpinna

New Member
Messages
63
Location
Spring, TX
I've been trying to figure out what the compression ratio of a 2UZFE with 1UZFE heads would be after de-stroking with a 1UZFE crank. Seeing that the 2UZ go past the deck at TDC, the 1.5mm difference in the 1UZ crank stroke should make that irrelevant.

So, I need some help filling in the blanks! :)

2UZ bottom end w/ 1UZ crank and heads...

Compression Ration =
Cylinder vol. + clearance vol. + piston Comp. vol. + gasket vol. + chamber vol. divided by Clearance vol. + piston vol. + gasket vol. + chamber vol.


Thanks,


Andrew

 

RotaSpinna

New Member
Messages
63
Location
Spring, TX
So far, some specs I've found are...

1UZ Head Chamber - 43cc
1UZ Crank Stroke - 3.25"
2UZ Bore - 3.7"
2UZ Piston Dome - 29cc

Chime in and verify these finds if you know!

Thanks,

Andrew
 

cribbj

"Supra" Moderator
Staff member
Messages
4,794
Location
Houston, TX
These are figures we took on my 1st 1UZ with Wiseco pistons & Cometic head gaskets:

Cylinder Volume: 502.3
Chamber Volume: 43.5 (measured)
Deck & gasket: 6.2
Piston dome volume: 8.5

Total: 560.5

Chamber, deck & dome: 58.2

CR = 560/58.2 = 9.63:1
 

RotaSpinna

New Member
Messages
63
Location
Spring, TX
Cyl. Volume = 35.575ci
Clearance Volume = 1.4719626ci
Piston Dome = 1.7696873ci
Head Gasket Volume = ?
Chamber Volume = 2.6240191ci

Since the 2UZ piston goes past the deck stock(I believe -.05" at the 3.31" stroke), where will the piston be at TDC with the 3.25" stroke?

.01"?! If so, you really wouldn't need to get custom pistons when you go NA 1/2UZFE!

Clearance volume would be
 

RotaSpinna

New Member
Messages
63
Location
Spring, TX
Cyl. Volume = 35.575ci
Clearance Volume = 1.4719626ci
Piston Dome = 1.7696873ci
Head Gasket Volume = .0548357ci
Chamber Volume = 2.6240191ci

Went with standard bore and compressed gasket thickness for the head gasket volume(3.7" and .051").

IF all these numbers are correct...
 

RotaSpinna

New Member
Messages
63
Location
Spring, TX
I guess that isn't too far off if the factory 2UZ compression is 9.6:1 and you add cylinder volume by de-stroking it...hmmmm...

Any suggestions/comments/opinions?

Thanks,

Andrew
 

Paulwolf

New Member
Messages
11
Location
Rockhampton, Qld
Checking your calculations whilst doing my own motor, your clearance vol is wrong

i get 0.108 ci for your clearance vol

which puts your compression at 8.0:1

Paul
 
Last edited:

RotaSpinna

New Member
Messages
63
Location
Spring, TX
I'm wondering if just using a thicker headgasket may work if using the 2UZ crank with 1UZ heads. Compression may be the same 9.6:1 or higher using the 43cc 1UZ heads with .02 thicker 2UZ head gasket. Hmmmm...
 

RotaSpinna

New Member
Messages
63
Location
Spring, TX
Getting back into this little project...

Anyone have more to offer as far as more recent/updated info, experience, etc.?

Thanks,

Andrew
 
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