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King of the NA-T's
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4,044 Posts
According to my trusty slide-rule, it should be right around 18:1

:p
 

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SupraForums Manufacturer
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3,333 Posts
motorheaddown said:
Actually, it's more like 9:1. The TT hg compressed is 1.3mm; the additional clearance volume puts the C/R in the very low 9s.

-scott
What did you measure an uncompressed tt hg at? I got 1.3.... dunno about compressed.
 

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SupraForums Manufacturer
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3,333 Posts
5spd_sc300 said:
so a 2mm is somewhere around 8.6:1 ?
Pretty much right there....

Scott or anyone else,
Do you know the height of a compressed stock .3mm hg? Dish of the ge piston?

I estimated the dish to be around 6.4
 
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Discussion Starter · #12 ·
According to my calculations:

NA engine w/ TT 1.3mm HG = 9.52:1 CR
NA engine w/ 1.6mm HG = 9.26:1 CR
NA engine w/ 2.0mm HG = 8.94:1 CR

This is based on the following:

NA stock CR = 10.5:1
Stock NA HG = 88mm x 0.3mm (compressed) Area = 1.825cc
Total Clearance Volume = 52.58cc (this includes piston dish, any volume above the piston, combustion chamber volume, HG volume)
Stock Displacement = 2997cc (one cyl. 499.5cc)

~Brendan
 
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Discussion Starter · #14 ·
I originally thought the CR was 10:1 as well but after some searching around here I came up with 10.5:1.
~Brendan
 

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Thinking Person
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1,533 Posts
i'm very sure its 10.0:1 not 10.5... VERY sure
 
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Discussion Starter · #18 ·
Back by popular demand....

Here are CR's refigued for 10.0:1 CR stock:

NA engine w/ TT 1.3mm HG = 9.11:1 CR
NA engine w/ 1.6mm HG = 8.88:1 CR
NA engine w/ 2.0mm HG = 8.57:1 CR

All other figures remain the same.

mkivsoopra: You're right the stock bore is 86mm. However, the head gasket measures 88mm, instead of 86mm, to allow for cylinder honing and boring. In this case, you get about 1-2mm to work with.
~Brendan
 
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