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myztery
23-12-2008, 07:22 PM
how can you determine the compression ratio of a motor without taking the head off...
VTi_b0i
23-12-2008, 07:38 PM
the way they checked mine, im not 100% sure but they:
*moved the piston to TDC ( Top Dead Centre) then filled it with a liquid to a certain point and measured the amount it took then did some maths LOL i hope some one can clear this up?
OR
http://www.zealautowerks.com/
myztery
23-12-2008, 07:54 PM
isnt that with the head off??? thats how i got taught to check it
myztery
23-12-2008, 07:55 PM
the way they checked mine, im not 100% sure but they:
*moved the piston to TDC ( Top Dead Centre) then filled it with a liquid to a certain point and measured the amount it took then did some maths LOL i hope some one can clear this up?
OR
http://www.zealautowerks.com/

wouldnt it be bottom dead centre to know how much fluid goes in
VTi_b0i
23-12-2008, 07:56 PM
lol im sure it was TDC. and it was with the head on, just did it through the spark plug (without the spark plug in obviously...)
myztery
23-12-2008, 07:59 PM
lol im sure it was TDC. and it was with the head on, just did it through the spark plug (without the spark plug in obviously...)

sorry your right tdc not bdc lol if you measure bdc then you get cylinder volume...lol
VTi_b0i
23-12-2008, 08:00 PM
lol! true... now make with the PQ points HAHAHA no one ever gives me any :p
myztery
23-12-2008, 08:06 PM
i would if i knew how to, i cant even get one...lol

now back to the subject, i heard that there was a tool, you place it in the spark plug hole, wind the motor over and is read on a dial????
bennjamin
23-12-2008, 08:30 PM
now back to the subject, i heard that there was a tool, you place it in the spark plug hole, wind the motor over and is read on a dial????

......that is called a "compression tester". It give the maximum compression in PSI of each cylinder when hot. Higher compression ratio will yield a higher number.
myztery
23-12-2008, 08:49 PM
......that is called a "compression tester". It give the maximum compression in PSI of each cylinder when hot. Higher compression ratio will yield a higher number.

cheers...
delsol9000rpms
25-12-2008, 01:20 AM
...... Higher compression ratio will yield a higher number.

this is not true as a compression tester shows the dynamic compression of the motor and not the "compression ratio" which is the static compression. larger duration cams with more overlap will read less on the compression tester.. a engine could hav a 13:1 comp ratio but still read 200psi in the cylinders due to having high duration and overlap cams
bennjamin
25-12-2008, 09:17 PM
this is not true as a compression tester shows the dynamic compression of the motor and not the "compression ratio" which is the static compression. larger duration cams with more overlap will read less on the compression tester.. a engine could hav a 13:1 comp ratio but still read 200psi in the cylinders due to having high duration and overlap cams

Correct to a degree , then again so is my statement.I am aware it does not show the compression ratio , simply that a engine with a higher compression ratio can give a higher read out per cylinder , that another engine with the same capacity but lower compression. Bring in standard engines and cam specs vs high lift cams as you say and there is a billion combos of compression per cylinder ;)