PCT/CTR piston and compression ratio

[vTec[Rock]]

from the very limited sources i have (omniman, c-speeds compression calc, and various HT users) there seems to be a rather large difference of opinion on the effective compression ratio's of CTR pistons in blocks other than the b16b
personally the range of difference is the problem. to me .2 or .3 difference wouldnt bother me, but recently people have been talking of 1+ point differences in the compresion calcs available online today!

i really trust omnimans opinion, i have spoken to him once about a particular head he ported, and the #'s he achieves speak for themselves.

i woul like some help in getting to the bottom of this. i have a set of of overbore ctr pistons available to measure if anyone can point t me what needs to be measured.

 

[vTec[Rock]]

Pic...
PCT and CTR piston

 

[vTec[Rock]]

:(

 

[vTec[Rock]]

:(

 

[vTec[Rock]]

PCt

 

[vTec[Rock]]

Topics copy from Honda-Tech.hope will nop angry all.
i'm really interest about compresion ratio.let talk here........Yooooooo

 

[vTec[Rock]]

may I know,who can help me calculate my engine compression ratio?Pm me.i will send engine spec and piston sheet pls help me calculate.thanx!

 

[D16Y6]

Originally posted by vTec[Rock]@Mar 21 2005, 19:02
may I know,who can help me calculate my engine compression ratio?Pm me.i will send engine spec and piston sheet pls help me calculate.thanx!

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hey tiong koh ask xenix lar.... last time he got make the format.. mayb not i forgot :P

 

[vTec[Rock]]

erm...................ok!
I try.yooooooooo

 

[D16Y6]

brother tiong maybe this will help you :) search from internet
http://www.dunegoon.org/compression.html
:P

 

[vTec[Rock]]

Thanx.
brother!

 

[399]

ah chung can do it on the spot.

 

[D16Y6]

Originally posted by vTec[Rock]@Mar 22 2005, 18:07
Thanx.
brother!

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dont mention it bro :D

 

[basahboy]

sori to bother this already dead topic but nevertheless we are always engulf with compression ratios and forged pistons...

CR can be calculated based on a number of factors (u can get it in the net lah)...so no need to explain...however, it is not always necessary to have the CR in direct correlation with horsepower...

BUT the rule of thumb is that for every 1 pt increase, the relating increase in HP is only 3% AND that is mostly the rule of thumb for compression ratios for 9+ and abovelah....

so, if your current engine is having...say 170bhp with comp of 10.6...and you put in the forged pistons n bump the comp to 12.0...the hp increase will only be to about 177bhp or about 4.2%...hmmm not much considering the amount to time and money spent...

THEN AGAIN.....this is only the rule of thumb..of course many other factors can take into consideration like cams, etc....so in most likelyhood, changing pistons should not be a priority...the airflow should be the no.1 priority i.e. the intake manifold, exhaust manifold and the HEAD...all must jive because any turbulance in the flow of the air will cause the engine to loose power...

ADIOS....