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Autech
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Discussion Starter · #1 ·
As above.

My thoughts have been making me do a lot of calculations. I am concerned some of the figures thrown around for n1 pistons are wrong - in regards to their compression they create in a 2.0 VE engine.


Heres my maths and rational.


Stock N1 Engine specs.

86 x 68.7 - Bore X stroke.
11.56 CR
87mm head gasket - 1.2mm thickness.

We all know the N1 head is shaved (apparently 1mm). Also assuming deck height of 0.4mm. When calculating this must be -0.4mm.


Now to get 11.6/11.5 CR we will assume chamber volume is close to 42cc. We are now left with a rought piston dome CC volume of 8cc.

This equates to 11.3:1 CR.

If we substitute with 6.8cc piston dome = 10.9CR
If we substitute with 6.8cc piston dome and 40cc chamber volume = 11.5CR

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Now throwing the above specs into a 2.0 regular VE engine with STOCK head.

86x86
87mm 1.2mm gasket
44cc chamber volume
Pistone dome CC = 8
deck height -0.4mm

CR now equals 13.2

How is this possible? Im simply substituting values.

If we use 6.8 CC piston dome = 12.9
If we use 6.8cc piston dome and 41.8cc chamber volume =13.5



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Calcs assuming VET gasket is used in 2.0 regular VE engine with STOCK head.

86 x86
86.5mm 1.6mm
44cc chamber volume
8cc piston dome volume.
deck height -0.4mm

Calculated CR: 12.6:1

If we use 6.8 CC piston dome = 12.29
If we use 6.8cc piston dome and 41.8cc chamber volume = 12.8


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Does anyone have any idea or thorughts to add? Im trying to get my head aroud what is what and what is and isnt correct. I know the N1 has deeper notches, so maybe my Piston CC is wrong? If my piston CC is wrong, and is in fact lower - it means factory N1 cylinder head has to have a higher CC chamber volume.

Remember im trying to work off the original N1 info - so it all has to correspond and substitute.

other supporting info -
VET metal gasket is 86.5mm diametre.
Stock Graphite gasket is 87mm diametre.
None of these include piston clearance inside the bore. This is the sapce from the crown to the bore, and depth of the first compression ring.
 
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