Calculating 1/2UZ Compression Ratio

[RotaSpinna]

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

Read more: http://www.carcraft.com/techarticles/calculate_compression_ratio/index.html#ixzz1h4xhOCQc
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[RotaSpinna]

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

 

[RotaSpinna]

Cyl. Volume = 35.575ci
Clearance Volume = ?
Piston Dome = 1.7696873ci
Head Gasket Volume = ?
Chamber Volume = 2.6240191ci

 

[cribbj]

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]

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]

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]

7.0:1 CR

Gosh I hope that's not right haha

 

[RotaSpinna]

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]

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

 

[RotaSpinna]

That is calculating for the 1UZ crank shaft? Either way, 8.0:1 is still way too low :/

Thanks,

Andrew

 

[Paulwolf]

That is calculating for the 1UZ crank shaft? Either way, 8.0:1 is still way too low :/

Thanks,

Andrew

yeah, 3.25 stroke, great setup for twin turbos but :wink:

with those heads, I think you are going to need custom pistons, I am going the same route with a standard stroke 4.7

 

[RotaSpinna]

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]

Getting back into this little project...

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

Thanks,

Andrew