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Discussion Starter · #1 · (Edited)
Hi ppl! I'm starting a project, a mini-me with a D14 and needed to figure out some number's that weren't available, like CR for a d16Z6 head bolt to a D14. Measured my own stuff and ended up with these calcs. This info suits all engines but here is exemplified my own to better illustrate the calcs. I know there are CR calculators but not every engine is available (like D14 isn't) and every engine has it's own milled head, valve wear, milled deck, that results will differ from others similar ones. Hope this info serves someone and if you have any doubts, please ask, i'll explain as much as i can.


..::My calculations::..

Formulas
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CR=CV+CCV
CCV

CR=Compression Ratio
CV=Cylinder Volume
CCV=Combustion Chamber Volume
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V=PIx(DxD)xH
4000

V=Volume
PI=3,1416
D=Diameter
H=Height
(result=CC - no conversion needed)
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Notes and Instructions

CV is the engine capacity in cc divided by the number of cylinders;
CCV is made up of the head combustion chamber volume, plus the volume caused by the thickness of the head gasket, plus the volume of the dish if dished pistons are used, or minus the amount displaced by high top pistons if this are fitted, plus piston's valve cut-outs volume, if they exist;
There are two more variables, the deck clearance, and the volume of piston/cylinder gap and top piston ring case; About this last one nobody seems to talk about but may play a major role at the final result. The first time i measured The piston's top volume (let's call it that) it ended up being 13,5cc, the last time i measured it was only 11cc. Yes i measured it wrong...first i used a very thick oil to do that, ended up to be very difficult to fill up the space as air bubbles wouldn't come out and it spilled out a couple of times, second, after doing that i read a tip in a book about sealing the piston edge with some kind of grease, so that the liquid wouldn't fill up the space below piston's crown till top ring's case, including piston to cylinder gap; this space can add up to 2cc or 3cc, or even more according to engine's health, bore, and piston's crown to first ring distance.

This measures i made aren't 100% accurate but are enough to have an idea about swaps and possible gains related to them.

For instance, i played with numbers and added 2cc for piston's gap and ring's case, and a deck clearance of -0,4mm (as i read if piston is above deck must use (-)). The result was 9,37 CR, almost the same as without considering this. Adding just 2cc for piston's gap and ring's case without considering deck clearance the result was 9,02 CR. By achieving a result near the Honda's official numbers without considering those, dicided to ignore them as my goal is to compare the before and after results.
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D14A1

Head combustion chamber volume = 37,5cc
Head gasket volume [1,2mm smashed)= 5,37cc
Piston's valve cut-outs volume = 2cc
Piston's dome = 3,37cc

CCV = (37,5+5,37+2)-3,37=41,50cc

CR=CV+CCV=349+41,5=9,41
.. CCV .... 41,5
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D14Z6

Head combustion chamber volume = 34,5cc
Head gasket volume (1mm D16Z6 metal gasket)= 4,47cc
Piston's valve cut-outs volume = 2cc
Piston's dome = 3,37cc

CCV = (34,5+4,47+2)-3,37=37,60cc

CR=CV+CCV=349+37,60=10,28
.. CCV .... 37,60
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..::How to achieve these numbers::..

Head combustion chamber volume

Clean up a cylinder head combustion's chamber and with valves closed and head leveled, aplly a thin layer of sylicon sealant over it's edge and place an acrylic plaque over it;
Press it hard against the head's face and across an hole previously drilled fill up the space below with liquid using a graduated syringe (petrol, alchool...) subtracting the final volume from the inicial one we achieve head's combustion chamber volume.
(Like i did with the cylinder pictured below, same procedure for the Head)

Head gasket volume

Measure head gasket cylinder's ring diameter and thickness and calculate it using the above volume formula.

Valve cut-outs volume

Fill up the holes at piston's top with liquid using a graduated syringe; subtracting the final volume from the inicial one we achieve valve cut-outs volume.

Piston's dome

Place one piston at a determined height and measure it from piston's top till engine deck and find that space volume using the above volume formula;
Fill up the space between piston's edge and cylinder wall with grease to prevent liquid from filling up that space and mess up calcs;
do as for head combustion volume procedure and see pictures described below;


1- cleaned piston's top and sylicon sealer ready to receive the acrylic plaque; 2- plaque placed ready to receive the oil; 3- space surrounding the piston filled with oil and volume achieved

Subtract valve cut-outs volume from volume above piston's top (achieved with a graduated syringe)
subtract the achieved value from piston's top till engine deck volume (achived using the volume formula)
The result will be piston's dome volume

Example: D14A1 numbers

cylinder's diameter 75mm
piston's top till engine's deck distance (determined by me) 2,8mm
(Atention, when filling up cylinder with liquid, piston must be at the same point as it was when measured for achieving volume using the above formula)
Cylinder's volume from piston's top til engine deck - 12,37cc
Cylinder volume from piston's top till engine's deck (filling up with liquid) - 11cc
Valve cut-outs volume - 2cc

12,37-(11-2)=3,37

Cheers
If any innacuracy found, please point it out, even english ones, as it isn't my mother language and i try hard to write it wright.


 
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